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BIOLOGY REVISION AND EXAMINATION TIPS Main reasons why Students Perform Poorly in the Biology Subject Confusion of biology concepts and terminologies. Inability to recall ideas about the subject content (subject matter). This could be attributed to lack of interest and concentration in class and poor study habits hence the meaning of the content is never grasped. Use of poor vocabulary-lack of good English command to express ideas e.g. the relaxation of erector pili muscles cause the hair to fall down instead of lie flat on the skin surface Assuming too much. This leads to giving sketchy, ambiguous, half answers or giving more information than asked which in most cases is irrelevant. Not following simple instructions and guidelines in answering questions (examination techniques) particularly graphical and structured questions. Students need to know that most structured questions require a deeper understanding of the concepts behind the question/experiment. Furthermore, most of the answers in the various subsections are tied i.e. the student has to get the first part of the question right first to guarantee him/her a correct response in the subsequent subsections of the question. Possible Remedies During study sessions, ensure that you understand adequately the subject matter for every topic. This calls for a lot of reasoning, comparison, application, relation, evaluation, analysis and observation. These are core science-process skills that make science therefore Biology a unique discipline. Understanding can be enhanced through having interest in what you are reading (have a positive attitude towards the subject having understood its relevance in your future career as well as individual life and community development); planning and organizing yourself by knowing what to do, where, when and for how long (prepare a realistic study schedule/timetable and follow it); concentrate by being attentive and alert in class; be determined; never give up and have a dream or vision that will help you look into your future. Thorough revision or study ensures information is securely fixed in the long-term memory of the brain (principle of consolidation). The best method is ensuring you review notes right after class. Large chunks of information can be summarized through use of pseudo codes, mnemonics or use of concept maps (schematic mapping). Arrive in class and examination room in time. This will enable you gather all the verbal and written concepts taught and boost confidence and reduce pre-exam stress respectively.
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Large chunks of information can be summarized through use of pseudo codes, mnemonics or use of concept maps (schematic mapping). Arrive in class and examination room in time. This will enable you gather all the verbal and written concepts taught and boost confidence and reduce pre-exam stress respectively. This can also be enhanced by conferring with other students to predict what might be in the test prior to the start of the examination. Read through each question at least three times before you decide to write down your answer. Use grammatical clues within a statement as hints for the correct answer. Underline the key words in the question to help you know exactly what is being asked. If you go blank on any of the questions, skip it and go to the next but remember to spare some time later to answer the skipped question (s). Believe in yourself. Do not try to be perfect; instead try to balance your work by giving the best. Never be in a hurry/panic. The time allocated for each paper has been pretested to be adequate for every student’s level of achievement (intelligence) and it only requires proper planning and approach to fit within the allocated time and even have time to review your work. Budget your time according to what is required of you in each question. Answer questions in a strategic order starting with the easy ones to help you build confidence and familiarize yourself with the vocabulary and concepts that you will deal with, then answer the more difficult questions. Write your answers neatly, accurately and precisely. Start by writing the points you are sure of first. This is because in Biology, only the first required correct responses are awarded. Any extra point beyond the required is just acknowledged but not awarded even if it is also or is the only correct one yet the earlier stated ones are wrong or not all. Use proper English and avoid confusing concepts. English is the medium of instruction (lingua franca) of the Biology subject matter and therefore a correct and clear command of the language is paramount to passing the subject. Remember to write exhaustive answers as half answers and ‘hanging’ statements are never awarded in any Biology examination e.g. for each structure or process, mention the function or reasons respectively depending on how the question is framed. Concentrate on the unique or distinguishing features or characteristics and avoid obvious things e.g.
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Remember to write exhaustive answers as half answers and ‘hanging’ statements are never awarded in any Biology examination e.g. for each structure or process, mention the function or reasons respectively depending on how the question is framed. Concentrate on the unique or distinguishing features or characteristics and avoid obvious things e.g. if asked for the adaptations of the gills in fish to gaseous exchange, don’t expect to be awarded for mentioning that they are moist yet it is obvious that fish are aquatic animals found in water (moist) bodies. Strive to answer the questions as they are stated but not to memorize the content read e.g. you might be tempted to state all the adaptations of gaseous exchange structures you know including the structures having a dense network of capillaries…yet the question asked is specifically asking for the adaptations of plant structures. Therefore, get to understand the question asked first before attempting to answer. Avoid canceling your work by being sure before writing down. Canceling can also be a point of suspicion for cheating. Neatness of the answers also encourages the examiner and implies keenness, clarity and being sure, all being the expected attributes of a modern scientist. Write all scientific names and technical words/phrases according to the rules of the binomial nomenclature and correct spellings respectively. Avoid using abbreviations, short codes and symbols as most are not conventional (not universally used/accepted by the body of scientists) hence you risk being penalized for their use. Never add information in brackets if you are not sure e.g. red blood cells (leucocytes). This will not be awarded as it shows confusion of concepts which is penalized. All diagrams drawn should be clear, neat and proportional sketches (not artistic impressions) and must be true representations of the object/specimen. Follow the simple rules: Labeling lines should not cross each other; the labeling line should touch the structure in question but not hang; use lines not arrows to label, arrows only show direction; do not shade the drawings but use dots or crosses within the part if you want to show the difference; lines must be continuous and not broken; no two structures should have the same name; for cross-sections and plan diagrams, remember to use double outer lines (outline) and only show key/few features avoiding unnecessary details.
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This will not be awarded as it shows confusion of concepts which is penalized. All diagrams drawn should be clear, neat and proportional sketches (not artistic impressions) and must be true representations of the object/specimen. Follow the simple rules: Labeling lines should not cross each other; the labeling line should touch the structure in question but not hang; use lines not arrows to label, arrows only show direction; do not shade the drawings but use dots or crosses within the part if you want to show the difference; lines must be continuous and not broken; no two structures should have the same name; for cross-sections and plan diagrams, remember to use double outer lines (outline) and only show key/few features avoiding unnecessary details. For essay questions, choose the option you are sure of and comfortable with in terms of raising the maximum points possible. Write down key words as they are fresh in your mind; use the first paragraph as an overview of your essay; when time is up for one question or part of the question, stop writing, leave some space and begin the next question or part of the question. The incomplete answers can be completed later during review. However, remember six incomplete answers will receive more credit (marks) than thee complete ones, so don’t waste time. Compactness, completeness (exhaustiveness) and clarity of a well-organized answer is what is important in essay questions. This can be achieved by ensuring that every sentence earns you at least 2 marks hence a 1-1½ pagelength (A-4 paper/foolscap) essay is more appealing than 3 pages of verbal irrelevancies. Remember also that to know a little and present it well is superior to knowing much and presenting it poorly. Allow yourself time to review your work. Review allows you to ensure that you have answered all the required questions, not skipped any relevant question, not made some simple mistakes and also gives you time to complete any uncompleted questions as well as correcting the wrongly answered ones.
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Remember also that to know a little and present it well is superior to knowing much and presenting it poorly. Allow yourself time to review your work. Review allows you to ensure that you have answered all the required questions, not skipped any relevant question, not made some simple mistakes and also gives you time to complete any uncompleted questions as well as correcting the wrongly answered ones. Rules for graphical questions may vary from time to time (year to year) but currently the following apply: Use a thin (well-sharpened) pencil to draw thin clear curves for accuracy; all graphs should be curves drawn using continuous lines regardless of the number; the graph should occupy at least ¾ of the grid/graph paper provided, achieved through appropriate scales; state the title and scale at the top of the graph clearly and avoid using abbreviations (remember to include the given units); ensure the Cartesian plane (X and Y axes) has arrows at the ends to show continuity; use dots/small crosses for plotting; do not extrapolate the curve unless asked for a point beyond the plotted ones; label the axes and curves; be neat; if the range of the data is so wide, break the affected axis/axes but don’t force the curve to begin from the 0 point. Commonly Used First Statements in Biology Questions and their Meanings State/What -This requires the student to present the said concept in a brief and clear form. If it is an adaptation, then it must be given fully i.e. structure, modification and function. Explain- Give reasons why something/anything happened or will happen. Describe-Give a detailed or graphic account of the issue or phenomenon showing all features and characteristics e.g. if it is a structure and function question (adaptation), you are expected to correctly name the structure or feature, explain how it is modified and give the function (s) of the structure. Sketchy explanations are penalized or earn least marks. So give as many detailed points as possible. Define-Give a precise meaning of a word/phrase normally in one sentence. Illustrate-Use a figure, diagram or any non-text form as an example to explain or make something. Name/Give/Mention-Give points only, no explanations Why-Give clear reasons supported by an argument. Outline-Give the main features in a sequential manner.
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Illustrate-Use a figure, diagram or any non-text form as an example to explain or make something.
Name/Give/Mention-Give points only, no explanations Why-Give clear reasons supported by an argument.
Outline-Give the main features in a sequential manner.
Distinguish between-Define the terms to clearly bring out the differences in their meanings.
You only earn a full point (s) or mark (s) when both definitions are correctly given.
Account for-Such questions need a two-prong approach: The first part is to give the trend/situation as it is e.g.
the volume increases (d) rapidly/gradually with increase in temperature.
The second portion of the answer involves giving the explanation/reasons for the situation/trend e.g.
because the molecules/particles gain kinetic energy, moving/vibrating more rapidly hence occupying more space (hence raising the volume).
These questions are common in the Paper 2; Section A structured questions and the compulsory question in Section B of the same paper.
The questions assume prior knowledge in either one or a number of the Biology topics.
Differentiate/Give the differences-Use either a table for the differences or use connectors such as the word ‘while’.
Make sure the responses rhyme to earn a mark e.g.
an artery has a narrow lumen while the capillary has a wide lumen not an artery has a narrow lumen while a capillary’s wall is thin.
Compare (and Contrast)-Outline both the similarities and differences between the given terms/processes.
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FORM ONE BIOLOGY
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell
Cell wall
Cell membrane
Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate
diffusion in liquids
diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:
Osmotic pressure
Osmotic potential
Isotonic solution
Hypertonic solution
Hypotonic solution
Turgor pressure
Hemolysis
Wall pressure
Plasmolysis
Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether
Carbon (IV) oxide is necessary for photosynthesis
Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on
Starch
Reducing sugars
Non-reducing sugar
Lipids
Proteins
Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on
Effect of temperature on enzymes
Effects of enzyme concentration on the rate of a reaction
Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beings
Introduction To Biology
Biology derived from Greek words-BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE.
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FORM ONE BIOLOGY
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell
Cell wall
Cell membrane
Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate
diffusion in liquids
diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:
Osmotic pressure
Osmotic potential
Isotonic solution
Hypertonic solution
Hypotonic solution
Turgor pressure
Hemolysis
Wall pressure
Plasmolysis
Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether
Carbon (IV) oxide is necessary for photosynthesis
Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on
Starch
Reducing sugars
Non-reducing sugar
Lipids
Proteins
Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on
Effect of temperature on enzymes
Effects of enzyme concentration on the rate of a reaction
Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beings
Introduction To Biology
Biology derived from Greek words-BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE. Biology means "life knowledge".
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FORM ONE BIOLOGY
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell
Cell wall
Cell membrane
Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate
diffusion in liquids
diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:
Osmotic pressure
Osmotic potential
Isotonic solution
Hypertonic solution
Hypotonic solution
Turgor pressure
Hemolysis
Wall pressure
Plasmolysis
Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether
Carbon (IV) oxide is necessary for photosynthesis
Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on
Starch
Reducing sugars
Non-reducing sugar
Lipids
Proteins
Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on
Effect of temperature on enzymes
Effects of enzyme concentration on the rate of a reaction
Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beings
Introduction To Biology
Biology derived from Greek words-BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE. Biology means "life knowledge". It is the study of living things/organisms.
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FORM ONE BIOLOGY
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell
Cell wall
Cell membrane
Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate
diffusion in liquids
diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:
Osmotic pressure
Osmotic potential
Isotonic solution
Hypertonic solution
Hypotonic solution
Turgor pressure
Hemolysis
Wall pressure
Plasmolysis
Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether
Carbon (IV) oxide is necessary for photosynthesis
Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on
Starch
Reducing sugars
Non-reducing sugar
Lipids
Proteins
Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on
Effect of temperature on enzymes
Effects of enzyme concentration on the rate of a reaction
Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beings
Introduction To Biology
Biology derived from Greek words-BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE. Biology means "life knowledge". It is the study of living things/organisms. Branches of Biology
Botany - study of plants.
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Biology means "life knowledge". It is the study of living things/organisms. Branches of Biology
Botany - study of plants. Zoology - study of animals. Microbiology - study' of microscopic organisms. Morphology - study of external structure of organisms. Anatomy - study of internal structure of organisms. Physiology - study of the functioning or working of the cells or body. Biochemistry - study of the chemistry of materials in living organisms. Cytology - study of cells. Genetics - study of inheritance. Ecology- study of the relationship between organisms and their environment. Taxonomy - sorting out of organisms into groups. Histology - study of fine structure of tissues. Virology - study of viruses. Bacteriology - study of bacteria. Entomology - study of insects. Ichthyology - study of fish. Importance of Biology
One learns about the functioning of the human body. One understands the developmental changes that take place in the body. It contributes immensely to improved life. It enables one to enter careers such as:
Medicine,
Nutrition,
Public Health,
Dentistry,
Agriculture
Environmental Studies. Teaching
Characteristics of Living Things
Life defined through observations of activities carried out by living things;
Nutrition –
Nutrition is the processes by which food/nutrients are acquired/made and utilized by living organisms. Green plants and certain bacteria make their own food. All other organisms feed on complex organic materials. Respiration –
This is the breakdown of food to provide energy. The energy released is used for various activities in the organism. Gaseous Exchange –Process throw which respiratory gases(CO2&O2) are taken in and out through a respiratory surface. Excretion –
Excretion is the removal of metabolic wastes from the body. Substances like urea, carbon dioxide (Carbon (IV) oxide). These substances are poisonous if allowed to accumulate in the body. Growth and Development –
Growth means irreversible change in size. All organisms increase in size that is, they grow. Development is irreversible change in complexity. As they do so, they also become differentiated in form. Reproduction-Reproduction is the formation of new individuals of a species to ensure continued existence of a species and growth of its population. Irritability –
The ability of organisms to detect and respond to changes in the environment. This is of great survival value to the organism.
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Reproduction-Reproduction is the formation of new individuals of a species to ensure continued existence of a species and growth of its population. Irritability –
The ability of organisms to detect and respond to changes in the environment. This is of great survival value to the organism. Movement –
Is the progressive change in position from one place to another. Some organisms are sessile (i.e. fixed to the substratum). The majority of plants move only certain parts. Collection and Observation of Organisms
Biology as a practical subject is learnt through humane handling of organisms. Materials needed for collection of organisms:-
Knives to cut portions of plant stem/root or uproot. Polythene bags to put the collected plant or specimens. Insect collecting jars. Insect killing jars. Hand gloves. Sweep nets
Pooters
Traps
Observation of Organisms
Observe the plant/animal in its natural habitat before collecting. Identify the exact place -on surface, under rock, on tree trunk, on branches. What does it feed on? How does it interact with other animals and the environment? How many of that kind of plant or animal are in a particular place? Plant specimens placed on the bench and sorted out into;- seeds/stems/roots/leaves/fruits. Animal specimens may be left inside polythene bags if transparent. Others (killed ones) are put in petri dishes. Use hand lens to observe the external features of small animals. Presenting the Results of Observations
Organisms are observed and important features noted down: colour, texture hard or soft; if hairy or not. Size is measured or estimated. Biological Drawings - It is necessary to draw some of the organisms. In making a biological drawing, magnification (enlargement) is noted. Indicate the magnification of your drawing. i.e how many times the drawing is larger/smaller than the actual specimen MG=length of drawing/length specimen
How to Draw
Several drawings of one organism may be necessary to represent all features observed, e.g. Anterior view of grasshopper shows all mouth parts properly, but not all limbs. Lateral (side) view shows all the legs. Collection, Observation and Recording of Organisms
Collection
Plants and animals collected from the environment, near school or within school compound using nets, bottles and gloves. Animals collected include:-arthropods, earthworms and small vertebrates like lizards/chameleons/ rodents.
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Lateral (side) view shows all the legs. Collection, Observation and Recording of Organisms
Collection
Plants and animals collected from the environment, near school or within school compound using nets, bottles and gloves. Animals collected include:-arthropods, earthworms and small vertebrates like lizards/chameleons/ rodents. Place in polythene bags and take to the laboratory. Stinging/poisonous insects killed using ether. Other animals are observed live and returned to their natural habitat. Plant specimen collected include:- leaves, flowers and whole plants. Observations are made to show the following:-
Plants have roots, stems, leaves and flowers. Animals have legs, hair, hard outer covering, feathers, eyes, mouth, limbs and other appendages,
The differences between animals and plants collected. Comparison Between Plants And Animals
Classification I
Introduction
Classification is putting organisms into groups. Classification is based on the study of external characteristics of organisms. It involves detailed observation of structure and functions of organisms. Organisms with similar characteristics are put in one group. Differences in structure are used to distinguish one group from another. The magnifying lens is an instrument that assists in the observation of fine structure e.g. hairs by enlarging them. Using a Magnifying Lens
A specimen is placed on the bench or held by hand,
Then the magnifying lens is moved towards the eye until the object is dearly focused and an enlarged image is seen. The magnification can be worked out as follows:
length of the drawing
Magnification = length of the specimen
Note: magnification has no units. Nececity/need for Classification
To be able to identify organisms into their taxonomic groups. To enable easier and systematic study of organisms. To show evolutionary relationships in organisms. Major Units of Classification (Taxonomic Groups)
Taxonomy is the study of the characteristics of organisms for the purpose of classifying them. The groups are Taxa (singular Taxon). The taxonomic groups include:
Species: This is the smallest unit of classification. Organisms of the same species resemble each other. The number of chromosomes in their cells is the same. Members of a species interbreed to produce fertile offspring. Genus (plural genera): A genus is made up of a number of species that share several characteristics. Members of a genus cannot interbreed and if they do, the offspring are infertile. Family: A family is made up of a number of genera that share several characteristics.
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Genus (plural genera): A genus is made up of a number of species that share several characteristics. Members of a genus cannot interbreed and if they do, the offspring are infertile. Family: A family is made up of a number of genera that share several characteristics. Order: A number of families with common characteristics make an order. Class: Orders that share a number of characteristics make up a class. Phylum/Division: A number of classes with similar characteristics make up a phylum (plural phyla) in animals. In plants this is called a division. Kingdom: This is made up of several phyla (in animals) or divisions (in plants). It is the largest taxonomic unit in classification. Kingdoms
Living organisms are classified into five kingdoms;
Monera,
Protoctista,
Fungi,
Plantae
Animalia. Kingdom Fungi
Some are unicellular while others are multicellular. They have no chlorophyll. Most are saprophytic e.g. yeasts, moulds and mushrooms. A few are parasitic e.g. Puccinia graminae. Kingdom Monera (Prokaryota)
These are very small unicellular organisms. They lack a nuclear membrane
do not have any bound membrane organelles. Hence the name Prokaryota. They are mainly bacteria, e.g. Vibrio cholerae. Kingdom Protoctista
They are unicellular organisms. Their nucleus and organelles are surrounded by membranes (eukaryotic). They include algae, slime moulds - fungi-like and protozoa
Kingdom Plantae
They are all multicellular. They contain chlorophyll and are all autotrophic. They include; Bryophyta (mossplant), Pteridophyta (ferns) and Spermatophyta (seed bearing plants). Kingdom Animalia
These are all multicellular and heterotrophic. Examples are annelida (earthworms), mollusca (snails),athropoda, chordata . Example of Arthropods are ticks, butterflies. Members of Chordata are fish, frogs and humans. External Features of Organisms
In plants we should look for:-
Spore capsule and rhizoids in moss plants. Sori and fronds in ferns. Stem, leaves, roots, flowers, fruits and seeds in plants.
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External Features of Organisms
In plants we should look for:-
Spore capsule and rhizoids in moss plants. Sori and fronds in ferns. Stem, leaves, roots, flowers, fruits and seeds in plants. In animals, some important features to look for are:
Segmentation, presence of limbs and, number of body parts, presence and number of antennae. These are found in phylum arthropoda:
Visceral clefts, notochord, nerve tube, fur or hair, scales, fins, mammary glands, feathers and wings. These are found in chordata. Binomial Nomenclature
Organisms are known by their local names. Scientists use scientific names to be able to communicate easily among themselves. This method of naming uses two names, and is called Binomial nomenclature. The first name is the name of the genus: (generic name) which starts with a capital letter. The second name is the name of the species (specific name) which starts with a small letter. The two names are underlined or written in italics. Man belongs to the genus Homo, and the species, sapiens. The scientific name of man is therefore Homo sapiens. Maize belongs to the genus Zea, and the species mays. The scientific name of maize is Zea mays. Practical Activities
Use of Collecting Nets, Cutting Instruments and Hand Lens. Forceps are used to collect crawling and slow moving animals. Sweep nets are used to catch flying insects. Cutting instrument like scapel is used to cut specimen e.g. making sections. Hand lens is used to magnify small plants and animals. Drawing of the magnified organism are made and the linear magnification of each calculated. Collection and Detailed Observation of Small Plants and Animals
e.g. moss, ferns, bean. Look for the following:
Moss plants: Rhizoids and spore capsules. Fern plants: Rhizomes with adventitious roots; large leaves (fronds) with Sori (clusters of sporangia). Seed plants: Tree/shrub (woody) or non-woody (herbs) e.g. bean. Root system - fibrous, adventitious and tap root. Stem - position and length of interrnodes. Type of leaves - simple or compound; arranged as alternate, opposite or whorled.
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Root system - fibrous, adventitious and tap root. Stem - position and length of interrnodes. Type of leaves - simple or compound; arranged as alternate, opposite or whorled. Flower - colour, number of parts, size and relative position of each:
Fruits - freshy or dry; edible or not edible. Seeds - monocotyledonous or dicotyledonous. Small animals e.g. earthworms, tick, grasshopper, butterfly, beetles. Observe these animals to see:
Number of legs. Presence or absence of wings. Number of antennae. Body covering. Body parts. THE CELL
Introduction
The cell is the basic unit of an organism. All living organisms are made up of cells. Some organisms are made up of one cell and others are said to be multicellular. Other organisms are made of many cells and are said to be multicellular. Cells are too little to see with the naked eye. They can only be seen with the aid of a microscope. The microscope
The microscope is used to magnify objects. Magnification
The magnifying power is usually inscribed on the lens. To find out how many times a specimen is magnified, the magnifying power of the objective lens is multiplied by that of the eye piece lens. If the eye piece magnification lens is x10 and the objective lens is x4, the total magnification is x40. Magnification has no units. It should always have the multiplication sign.e.g.x40
Microscope parts and their functions
To View the Object
Turn the low power objective lens until it clicks into position. Looking through the eye piece, ensure that enough light is passing through by adjusting the mirror. This is indicated by a bright circular area known as the field of view. Place the slide containing the specimen on stage and clip it into position. Make sure that the specimen is in the centre of the field of view. Using the coarse adjustment knob, bring the low power objective lens to the lowest point. Turn the knob gently until the specimen comes into focus. If finer details are required, use the fine adjustment knob. When using high power objective always move the fine adjustment knob upwards. Care of a Microscope
Great care should be taken when handling it. Keep it away from the edge of the bench when using it. Always hold it with both hands when moving it in the laboratory. Clean the lenses with special lens cleaning paper.
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Keep it away from the edge of the bench when using it. Always hold it with both hands when moving it in the laboratory. Clean the lenses with special lens cleaning paper. Make sure that the low power objective clicks in position in line with eye piece lens before and after use. Store the microscope in a dust-proof place free of moisture. Cell Structure as Seen Through the Light Microscope
The cell as seen above has the following:
Cell membrane (Plasma membrane):
This is a thin membrane enclosing cell contents. It controls the movement of substances into and out of the cell. Cytoplasm:
This is a jelly-like substance in which chemical processes are carried out. Scattered all over the cytoplasm are small structures called organelles. Like an animal cell, the plant cell has a cell membrane, cytoplasm and a nucleus. vacuole. Plant cells have permanent, central vacuole. It contains cell sap where sugars and salts are stored. Cell wall:
This is the outermost boundary of a plant cell. It is made of cellulose. Between the cells is a middle lamella made of calcium pectate. Chloroplasts;
With special staining techniques it is possible to observe chloroplasts. These are structures which contain chlorophyll, the green pigment responsible for trapping light for photosynthesis. The Electron Microscope (EM)
Capable of magnifying up to 500,000 times. The specimen is mounted in vacuum chamber through which an electron beam is directed. The image is projected on to a photographic plate. The major disadvantage of the electron microscope is that it cannot be used to observe living objects. However, it provides a higher magnification and resolution (ability to see close points as separate) than the light microscope so that specimen can be observed in more detail. Cell Structure as Seen Through Electron Microscope
The Plasma Membrane
Under the electron microscope, the plasma membrane is seen as a double layer. This consists of a lipid layer sandwiched between two protein layers. This arrangement is known as the unit membrane and the shows two lipid layers with proteins within. Substances are transported across the membrane by active transport and diffusion. The Endoplasmic Reticulum (ER)
This is a network of tubular structures extending throughout the cytoplasm of the cell. It serves as a network of pathways through which materials are transported from one part of the cell to the other. An ER encrusted with ribosomes it is referred to as rough endoplasmic reticulum.
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The Endoplasmic Reticulum (ER)
This is a network of tubular structures extending throughout the cytoplasm of the cell. It serves as a network of pathways through which materials are transported from one part of the cell to the other. An ER encrusted with ribosomes it is referred to as rough endoplasmic reticulum. An ER that lacks ribosomes is referred to as smooth endoplasmic reticulum. The rough endoplasmic reticulum transports proteins while the smooth endoplasmic reticulum transports lipids. The Ribosomes
These are small spherical structures attached to the ER. They consist of protein and ribonucleic acid (RNA). They act as sites for the synthesis of proteins. Goigi Bodies
Golgi bodies are thin, plate-like sacs arranged in stacks and distributed randomly in the cytoplasm. Their function is packaging and transportation of glycol-proteins. They also produce lysosomes. Mitochondria
Each mitochondrion is a rod-shaped organelle. Made up of a smooth outer membrane and a folded inner membrane. The foldings of the inner membrane are called cristae. They increase the surface area for respiration. The inner compartments called the matrix. Mitochondria are the sites of cellular respiration, where energy is produced. Lysosomes
These are vesicles containing hydrolytic enzymes. They are involved in the breakdown of micro-organisms, foreign macromolecules and damaged or worn-out cells and organelles .. The Nucleus
The nucle s is surrounded by a nuclear membrane which is a unit membrane. The nuclear membrane has pores through which materials can move to the surrounding cytoplasm. The nucleus contains proteins and nucleic acid deoxyribonucleic acid (DNA) and RNA. The chromosomes are found in the nucleus. They are the carriers of the genetic information of the cell. The nucleolus is also located in the nucleus but it is only visible during the non-dividing phase of the cell. The Chloroplasts
These are found only in photosynthetic cells. Each chloroplast consists of an outer unit. membrane enclosing a series of interconnected membranes called lamellae. At various points along their length the lamellae form stacks of disc like structures called grana. The lamellae are embedded in a granular material called the stroma. The chloroplasts are sites of photosynthesis.
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At various points along their length the lamellae form stacks of disc like structures called grana. The lamellae are embedded in a granular material called the stroma. The chloroplasts are sites of photosynthesis. The light reaction takes place in the lamellae while the dark reactions take place in the stroma. Comparison between animal cell and plant cell
Cell Specialisation
Cells are specialised to perform different functions in both plants and animals. Example;
Palisade cells have many chloroplasts for photosynthesis. Root hair cells are long and thin to absorb water from the soil. Red blood cells have haemoglobin which transports oxygen. Sperm cells have a tail to swim to the egg. Multicellular organisms cells that perform the same function are grouped together to form a tissue. Each tissue is therefore made up of cells that are specialised to carry out a particular function. Animal Tissues- Examples of animal tissues
Plant Tissues
Example of plant tissues
Organs
An organ is made up of different tissues
e.g. the heart, lungs, kidneys and the brain in animals and roots, stems and leaves in plants. Organ systems
Organs which work together form an organ system. Digestive, excretory, nervous and circulatory in animals and transport and support system in plants. organism
Different organ systems form an organism. Practical Activities
Observation and Identification of parts of a light microscope and their functions
A light microscope is provided. Various parts are identified and observed. Drawing and labelling of the microscope is done. Functions of the parts of the mircroscope are stated. Calculations of total magnification done using the formula. Eye piece lens maginification x objective lens rnaginification. Preparation and Observation of Temporary Slides of Plant Cells
A piece of epidermis is made from the fleshy leaf of an onion bulb. It is placed on a microscope slide and a drop of water added. A drop of iodine is added and a cover slip placed on top. Observations are made, under low and medium power objective. The cell wall and nucleus stain darker than other parts. A labelled drawing is made. The following are noted: Nucleus, cell wall, cytoplasm and cell membrane. Observation of permanent slides of animal cells
Permanent slides of animal cells are obtained e.g, of cheek cells, nerve cells and muscle cells. The slide is mounted on the microscope and observations made under low power and medium power objectives.
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The following are noted: Nucleus, cell wall, cytoplasm and cell membrane. Observation of permanent slides of animal cells
Permanent slides of animal cells are obtained e.g, of cheek cells, nerve cells and muscle cells. The slide is mounted on the microscope and observations made under low power and medium power objectives. Labelled drawings of the cells are made. A comparison between plant and animal cell is made. Observation and Estimation of Cell Size and Calculation of Magnification of Plant Cells. Using the low power objective, a transparent ruler is placed on the stage of the microscope. An estimation of the diameter of the field of view is made in millimeters. This is converted into micrometres (1mm=1000u)
A prepared slide of onion epidermal cells is mounted. The cells across the centre of the field of view are counted from left and right and top to bottom. The diameter of field of view is divided by the number of cells lying lengthwise to give an estimate of the length and width of each cell. Cell Physiology
Meaning of cell physiology
The term physiology refers to the functions that occur in living organisms. Cell physiology refers to the process through which substances move across the cell membrane. Several physiological processes take place inside the cell.e.g. respiration. Oxygen and glucose required enter the cell while carbon (IV) oxide and water produced leave the cell through the cell membrane. Structure and properties of cell membrane
The cell membrane is the protective barrier that shelter cellular contents. Movement of all substances into and out of the cells takes place across the cell membrane. It is made up of protein and lipid molecules. Lipid molecules have phosphate group attached to it on one end. They are then referred to phospholipids. The phospholipids are arranged to form a double layer. The ends with phosphate group face outwards. the proteins are scattered throughout the lipid double layer. Some of these proteins act as carrier molecules that channel some material in and outside the cells. The cell membrane allows certain molecules to pass through freely while others move through with difficulty and still others do not pass through at all. This is selective permeability and the cell membrane is described as semi-permeable. Properties of cell membrane
Permeability
The cell membrane is semi-permeable. it allows small molecules that are soluble in lipid to pass through with more ease than water soluble molecules. this is due to the presence of the phospholipids double layer.
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Properties of cell membrane
Permeability
The cell membrane is semi-permeable. it allows small molecules that are soluble in lipid to pass through with more ease than water soluble molecules. this is due to the presence of the phospholipids double layer. Polarlity
The cell membrane has electrical charges across its surface.it has positive charged ions on the outside and negatively charged ions on the inside.this property contributes to electrical impulses sent along nerve cells. Sensitivity to changes in temperature and pH
Very high temperatures destroy the semi-permeability nature of the cell membrane because the proteins are denatured by extreme pH values have the same effect on the membrane permeability. Physiological processes
Some of the physiological processes include diffusion, osmosis and active transport. Diffusion
Diffusion is the movement of molecules or ions from a region of high concentration to a region of low concentration aided by a concentration gradient.. diffusion continues to occur as long as there is a difference in concentration between two regions (concentration gradient). Stops when an equilibrium is reached i.e., when the concentration of molecules is the same in both regions. Diffusion is a process that occurs inside living organisms as well as the external environment.. Does not require energy. Factors Affecting Diffusion
.~ -
Concentration Gradient
An increase in the concentration of molecules at one region results in a steeper concentration gradient which in turn increases the rate of diffusion. Temperature
High temperature increases kinetic energy of molecules. They move faster hence resulting in an increase in rate of diffusion, and vice versa. Size of Molecules or Ions
The smaller the size of molecules or ions, the faster their movement hence higher rate of diffusion. Density
The denser the molecules or ions diffusing, the slower the rate of diffusion, and vice versa. Medium
The medium through which diffusion occurs also affects diffusion of molecules or ions. For example, diffusion of molecules through gas and liquid media is faster than through a solid medium. Distance
This refers to the thickness or thinness of surface across which diffusion occurs. Rate of diffusion is faster when the distance is small i.e., thin surface. Surface Area to Volume Ratio
The larger the surface area to volume ratio, the faster the rate of diffusion. For example, in small organisms such as Amoeba the surface area to volume ratio, is greater hence faster diffusion than in larger organisms.
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Rate of diffusion is faster when the distance is small i.e., thin surface. Surface Area to Volume Ratio
The larger the surface area to volume ratio, the faster the rate of diffusion. For example, in small organisms such as Amoeba the surface area to volume ratio, is greater hence faster diffusion than in larger organisms. Role of Diffusion in Living Organisms
Some processes that depend on diffusion include the following:
Gaseous exchange: Movement of gases through respiratory surfaces is by diffusion. Absorption of materials into cells Cells obtain raw materials and nutrients from the surrounding tissue fluid and blood through diffusion, e.g., glucose needed for respiration diffuses from blood and tissue fluid into cells. Excretion: Removal of metabolic waste products like carbon (IV) oxide, and ammonia out of cells is by diffusion. Absorption of the end-products of digestion from the intestines is by diffusion. Osmosis
Osmosis is the movement of water molecules from a region of high water concentration to a region of low water concentration through a semi-permeable membrane. Osmosis is a special type of diffusion that involves the movement of water molecules only and not solute molecules. Osmosis takes place in cells across the cell membrane as well as across non-living membranes
e.g. cellophane or visking tubing which are also semi-permeable,
It is purely a physical process. Factors Affecting Osmosis
Size of solute molecules-
Osmosis' occurs only when solute molecules are too large to pass through a semi-permeable membrane. Concentration Gradient . Osmosis occurs when two solutions of unequal solute concentration are separated by a semi-permeable membrane. Temperature ,. High temperatures increase movement of water molecules hence influence osmosis. However, too high temperatures denature proteins in cell membrane and osmosis stops. Pressure
Increase in pressure affects movement of water molecules. As pressure increases inside a plant cell, osmosis decreases. Roles of Osmosis in Living Organisms
The following processes depend on osmosis in living organisms:
Movement of water into cells from the surrounding tissue fluid and also from cell to cell. Absorption of water from the soil and into the roots of plants. Support in plants especially herbaceous ones, is provided by turgor pressure, which results from intake of water by osmosis. Absorption of water from the alimentary canal in mammals. Re-absorption of water in the kidney tubules.
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Support in plants especially herbaceous ones, is provided by turgor pressure, which results from intake of water by osmosis. Absorption of water from the alimentary canal in mammals. Re-absorption of water in the kidney tubules. Opening and closing stomata. Water Relations in Plant and Animal Cells
The medium (solution) surrounding cells or organisms is described by the terms hypotonic, hypertonic and isotonic. A solution whose solute concentration is more than that of the cell sap is said to be hypertonic. A cell placed in such a solution loses water to the surroundings by osmosis. A solution whose solute concentration is less than that of the cell sap is said to be hypotonic. A cell placed in such a solution gains water from the surroundings by osmosis. A solution which has the same solute concentration as the cell sap is said to be isotonic. When a cell is placed in such a solution there will be no net movement of water either into or out of the cell. Osmotic Pressure
The term osmotic pressure describes the tendency of the solution with a high solute concentration to draw water into itself when it is separated from distilled water or dilute solution by a semi-permeable membrane. Osmotic pressure is measured by an osmometer. When plant cells are placed in distilled water or in a hypotonic solution, the osmotic pressure in the cells is higher than the osmotic pressure of the medium. This causes the water to enter the cells by osmosis. The water collects in the vacuole which increases in size. As a result the cytoplasm is pushed outwards and it in turn presses the cell membrane next to the cell wall. This builds up water pressure (hydrostatic pressure) inside the cell. When the cell is stretched to the maximum, the cell wall prevents further entry of water into the cell. Then the cell is said to be fully turgid. The hydrostatic pressure developed is known as turgor pressure. Plasmolysis
When a plant cell is placed in a hypertonic medium, it loses water by osmosis. The osmotic pressure of the cell is lower than that of the medium. The vacuole decreases in size and the cytoplasm shrinks as a result of which the cell membrane loses contact with the cell wall. The cell becomes flaccid. The whole process is described as plasmolysis.
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The vacuole decreases in size and the cytoplasm shrinks as a result of which the cell membrane loses contact with the cell wall. The cell becomes flaccid. The whole process is described as plasmolysis. Incipient plasmolysis is when a cell membrane just begins to lose contact with the cell wall. Plasmolysis can be reversed by placing the cell in distilled water or hypotonic solution. However, full plasmolysis may not be reversed if cell stays in that state for long. Wilting
The term wilting describes the drooping of leaves and stems of herbaceous plants after considerable amounts of water have been lost through transpiration. It is observed in hot dry afternoons or in dry weather. This is when the amount of water lost through transpiration exceeds the amount absorbed through the roots. Individual cells lose turgor and become plasmolysed and the leaves and stems droop. The condition is corrected at night when absorption of water by the roots continue while transpiration is absent. Eventually, wilting plants may die if the soil water is not increased through rainfall or watering. Water Relations in Plants and Animals
Haemolysis
Haemolysis is the bursting of cell membrane of red blood cells releasing their haemoglobin. It occurs when red blood cells are placed in distilled water or hypotonic solution. This is because the cell membrane does not resist further entry of water by osmosis after maximum water intake. Crenation
Takes place when red blood cells are placed in hypertonic solution. They lose water by osmosis, shrink and their shape gets distorted. Animal cells have mechanisms that regulate their salt water balance (osmoregulation) to prevent above processes that lead to death of cells. An Amoeba placed in distilled water, i.e. hypotonic solution, removes excess water using a contractile vacuole. The rate of formation of contractile vacuoles increases. Active Transport
Active transport is the movement of solutes such as .glucose, amino acids and mineral ions;
From an area of their low concentration to an area of high concentration. It is movement against a concentration gradient and therefore energy is required. As such it only takes place in living organisms. The energy needed comes from respiration. Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins. The shape of each type of carrier protein is specific to the type of substances conveyed through it.
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The energy needed comes from respiration. Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins. The shape of each type of carrier protein is specific to the type of substances conveyed through it. It has been shown that the substance fits into a particular slot on the protein molecule,
As the protein changes from one form of shape to another the substance is moved across and energy is expended. Factors Affecting Active Transport
Availability of oxygen
Energy needed for active transport is provided through respiration. An increase in the amount of oxygen results in a higher rate of respiration. If a cell is deprived of oxygen active transport stops . Temperature
Optimum temperature is required for respiration, hence for active transport. Very high temperatures denature respiratory enzymes. Very low temperatures inactivate enzymes too and active transport stops. Availability of carbohydrates
Carbohydrates are the main substrates for respiration. Increase in amount of carbohydrate results in more energy production during respiration and hence more active transport. Lack of carbohydrates causes active transport to stop. Metabolic poisons
Metabolic poisons e.g. cyanide inhibit respiration and stops active transport due to lack of energy. Role of Active Transport in Living Organisms
Processes requiring active transport:
Absorption of mineral salts from the soil into plant roots. Absorption of end products of digestion e.g. glucose and amino acids from the digestive tract into blood stream. Excretion of metabolic products e.g.urea from the cells. Re-absorption of useful substances and mineral salts back into blood capillaries from the kidney tubules. Sodium-pump mechanism in nerve cells. Re-absorption of useful materials from tissue fluid into the blood stream. Practical Activities
1.Experiment to Demonstrate Diffusion
Various coloured substances such as: dyes, plant extracts and chemicals like potassium pennanganate are used. Potassium manganate (VII) crystals are introduced to the bottom of a beaker filled with water using a glass tubing or drinking straw which is then removed. Observations are made and the disappearance of the crystals and subsequent uniform colouring of water noted. 2.Experiment to Demonstrate Osmosis Using a Visking Thbing
A strip of visking tubing 8-10 cm is cut and tied at one end using strong thread. About 2 ml of 25% sucrose solution is put inside and the other end tied with thread. The tubing is washed under running water and then blotted to dry.
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2.Experiment to Demonstrate Osmosis Using a Visking Thbing
A strip of visking tubing 8-10 cm is cut and tied at one end using strong thread. About 2 ml of 25% sucrose solution is put inside and the other end tied with thread. The tubing is washed under running water and then blotted to dry. It is immersed in a beaker containing distilled water and left for at least one hour or overnight. It will then be observed that the visking tubing has greatly increased in size and has become firm. A control experiment can be set up using distilled water inside the visking tubing in place of sucrose solution. 3.Experiment to Show Osmosis using Living Tissue
Irish potato tubers are peeled and scooped out to make hollow space at the centre. Sucrose solution is placed inside the hollow, and the potato tuber placed in a beaker or petri-dish with distilled water. A conttrol is set using a boiled potato. Another one using distilled water inside hollow in place of sugar solution. The experiment is left for 3 hours to 24 hours. 4.Experiment to Demonstrate Turgor and Plasmolysis in Onion Epidermal Cells
Two strips of onion epidermis are obtained. One is placed on a slide with distilled water while the other is placed on a slide with 25% sucrose solution and a coverslip placed on top of each. The mounted epidermis is observed under low power microscope and then left for 30 minutes. After 30 minutes, observations are made again. The cells in distilled water have greatly enlarged. Cells in 25% sucrose have shrunk. Nutrition in Plants and Animals
Structure of the Leaf
External Structure
The external structure of the leaf consists of a leaf stalk or petiole and a broad leaf blade or lamina. The lamina has a main vein midrib from which smaller veins originate. The outline of the leaf is the margin and the tip forms the apex. Internal Structure of the Leaf
Epidermis
This is the outer layer of cells, normally one cell thick. It is found in both the upper and lower leaf surfaces. The cells are arranged end to end. The epidermis offers protection and maintains the shape of the leaf. It is covered by a layer of cuticle which reduces evaporation.
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The cells are arranged end to end. The epidermis offers protection and maintains the shape of the leaf. It is covered by a layer of cuticle which reduces evaporation. Leaf Mesophyll
Consists of the palisade layer, next to upper epidermis, and the spongy layer next to the lower epidermis. Palisade Mesophyll Layer
The cells are elongated and arranged close to each other leaving narrow air spaces. These contain numerous chloroplasts and are the main photosynthetic cells. In most plants, the chloroplast are distributed fairly uniformly throughout the cytoplasm. In certain plants growing in shaded habitats in dim light, most chloroplasts migrate to the upper region of the palisade cells in order to maximise absorption of the limited light available. Spongy Mesophyll Layer
The cells are spherical in shape. They are loosely arranged, with large intercellular spaces between them. The spaces are airfilled and are linked to the stomatal pores. The spongy mesophyll cells have fewer chloroplasts than the palisade mesophyll cells. Vascular Bundles
These are made up of the xylem and the phloem tissues. The xylem transports water and mineral salts to the leaves. The phloem transports food manufactured in the leaf to the other parts of the plant and from storage organs to other parts. Adaptations of Leaf for Photosynthesis
Presence of veins with vascular bundles. Xylem vessels transport water for photosynthesis. Phloem transports manufactured food from leaves to other parts of the plant. Leaf lamina is thin to allow for penetration of light over short distance to reach photosynthetic cells. Broad lamina provides a large surface area for absorption of light and carbon (IV) oxide. Transparent cuticle and epidermal layer allow light to penetrate to mesophyll cells. Palisade cells are close to the upper epidermis for maximum light absorption. Presence of numerous chloroplasts in palisade mesophyll traps maximum light. Chloroplast contain chlorophyll that traps light energy. Spongy mesophyll layer has large intercellular air spaces allowing for gaseous exchange. Presence of stomata for efficient gaseous exchange (entry of carbon (IV) oxide into leaf and exit of oxygen). Mosaic arrangement of leaves to ensure no overlapping of leaves hence every leaf is exposed to light.
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Spongy mesophyll layer has large intercellular air spaces allowing for gaseous exchange. Presence of stomata for efficient gaseous exchange (entry of carbon (IV) oxide into leaf and exit of oxygen). Mosaic arrangement of leaves to ensure no overlapping of leaves hence every leaf is exposed to light. Structure and Function of Chloroplasts
Chloroplasts are large organelles (5 um in diameter) found in the cytoplasm of green plant cells. They are visible under the light microscope. They contain chlorophyll, a green pigment and other carotenoids which are yellow, orange and red in colour. Certain plants have red or purple leaves due to abundance of these other pigments. Chlorophyll absorbs light energy and transforms it into chemical energy. The other pigments absorb light but only to pass it onto chlorophyll. The wall of chloroplast consists of an outer and an inner membrane. The two make up the chloroplast envelop. Inner membrane encloses a system of membranes called lamellae. At intervals, the membranes form stacks of fluid filed sacs known as grana (singular granum). Chloroplast and other pigments are attached to the grana. In between the lamellae is a gel-like stroma, that contains starch grains and lipid droplets. Enzymes for the dark stage reaction (light independent stage) are embedded in the stroma. Enzymes for the light dependent stage occur in the grana. Functions
• .Absorption of light by chlorophyll and other pigments. Light stage of photosynthesis occurs on the grana. (transformation of light energy to chemical energy.)
Carbon fixation to form carbohydrate takes place in the stroma which has enzymes for dark stage of photosynthesis. Process of Photosynthesis
Photosynthesis involves a series of chemical reactions, all of which take place inside chloroplasts. A general equation for photosynthesis is:
Carbon (IV)Oxide+Water light energy---Glucose+Oxygen
chlorophyll
6CO2+6H2O light C6H12O+6O2
chlorophyll
The reaction occurs in two main phases or stages. The initial state requires light and it is called the light dependent stage or simply light stage. It takes place on the lamellae surfaces. Its products are used in the dark stage. The dark stage does not require light although it occurs in the light and is called light independent stage.
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It takes place on the lamellae surfaces. Its products are used in the dark stage. The dark stage does not require light although it occurs in the light and is called light independent stage. Light-Stage
Two reactions take place that produce raw materials for the dark stage:
Light energy splits the water molecules into hydrogen and oxygen. This process is called photolysis. The hydrogen is taken up by a hydrogen acceptor called Nicotinamide adenine dinucleotide phosphate (NADP) while oxygen is released as a by-product. 2H2O(l) light energy4H+O2
photolysis
Light energy strikes the chlorophyll molecules and sets in motion a series of reactions resulting in the production of a high energy molecule called adenosine triphophate (ATP). Dark Stage
This stage involves the fixation of carbon i.e. the reduction of carbon (IV) oxide by addition of hydrogen to form carbohydrate. It uses the products formed during the light stage. ATP
Carbon + Hydrogen --- Carbohydrates
(IV) oxide
The synthesis of carbohydrates does not take place in a simple straight line reaction as shown in the equation above. It involves a series of steps that constitute what is known as the Calvin cycle. Carbon (IV) oxide is taken up by a compound described as a carbon (IV) oxide acceptor. This is a 5-carbon compound known as ribulose biphosphate and a six carbon compound is formed which is unstable and splits into two three-carbon compounds. Hydrogen from the light reaction is added to the three carbon compound using energy (ATP) from the light reaction. The result is a three carbon (triose) sugar, (phosphoglycerate or PGA). This is the first product of photosynthesis. Glucose, other sugars as well as starch are made from condensation of the triose sugar molecules. The first product is a 3-carbon sugar which condenses to form glucose (6-C sugar). From glucose, sucrose and eventually starch is made. Sucrose is the form in which carbohydrate is transported from the leaves to other parts of the plant. Starch is the storage product. Other substances like oils and proteins are made from sugars. This involves incorporation of other elements e.g. nitrogen, phosphorus and sulphur. Factors Influencing Photosynthesis
Certain factors must be provided for before photosynthesis can take place.
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This involves incorporation of other elements e.g. nitrogen, phosphorus and sulphur. Factors Influencing Photosynthesis
Certain factors must be provided for before photosynthesis can take place. The rate or amount of photosynthesis is also influenced by the quantity or quality of these same factors. Carbon(IV) Oxide Concentration
Carbon (IV) oxide is one of the raw materials for photosynthesis. No starch is formed when leaves are enclosed in an atmosphere without carbon (IV) oxide. The concentration of carbon (IV) oxide in the atmosphere remains fairly constant at about 0.03% by volume. However, it is possible to vary the carbon (IV) oxide concentration under experimental conditions. Increasing the carbon (IV) oxide concentration up to 0.1 % increases the rate of photosynthesis. Further increase reduces the rate. Light Intensity
Light supplies the energy for photosynthesis. Plants kept in the dark do not form starch. Generally, increase in light intensity up to a certain optimum, increases the rate of photosynthesis. The optimum depends on the habitat of the plant. Plants that grow in shady places have a lower optimum than those that grow in sunny places. Water
Water is necessary as a raw material for photosynthesis. The amount of water available greatly affects the rate of photosynthesis. The more water available, the more the photosynthetic rate, hence amount of food made. Effect of water on photosynthesis can only be inferred from the yield of crops. It is the main determinant of yield (limiting factor in the tropics). Temperature
The reactions involved in photosynthesis are catalysed by a series of enzymes. A suitable temperature is therefore necessary. The optimum temperature for photosynthesis in most plants is around 30"C. This depends on the natural habitat of the plant. Some plants in temperate regions have 20°C as their optimum while others in the tropics have 45°C as their optimum temperature. The rate of photosynthesis decreases with a decrease in temperature below the optimum. In most plants, photosynthesis stops when temperatures approach O°C although some arctic plant species can photosynthesise at -2°C or even -3°C. Likewise, increase in temperature above the optimum decreases the rate and finally the reactions stop at temperatures above 40°c due to enzyme denaturation. However, certain algae that live in hot springs e.g.
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In most plants, photosynthesis stops when temperatures approach O°C although some arctic plant species can photosynthesise at -2°C or even -3°C. Likewise, increase in temperature above the optimum decreases the rate and finally the reactions stop at temperatures above 40°c due to enzyme denaturation. However, certain algae that live in hot springs e.g. Oscilatoria can photosynthesise at 75°C
Chlorophyll
Chlorophyll traps or harnesses the energy from light. Leaves without chlorophyll do not form starch. Chemical Compounds Which Constitute Living Organisms
All matter is made up of chemical elements, each of which exists in the form of smaller units called atoms. Some of the elements occur in large amounts in living things. These include carbon, oxygen, hydrogen, nitrogen, sulphur and phosphorus. Elements combine together to form compounds. Some of these compounds are organic. Organic compounds contain atoms of carbon combined with hydrogen and they are usually complex. Other compounds are inorganic. Most inorganic compounds do not contain carbon and hydrogen and they are usually less complex. Cells contain hundreds of different classes of organic compounds. However, there are four classes of organic compounds found in all cells. These are: carbohydrates, lipids, proteins and nucleic acids. Carbohydrates
Carbohydrates are compounds of carbon, hydrogen and oxygen. Hydrogen and oxygen occur in the ratio of 2: 1 as in water. Carbohydrates are classified into three main groups: monosaccharides, disaccharides and polysaccharides. Monosaccharides
These are simple sugars. The carbon atoms in these sugars form a chain to which hydrogen and oxygen atoms are attached. Monosaccharides are classified according to the number of carbon atoms they possess. The most common monosaccharides are:
Glucose - found free in fruits and vegetables. Fructose - found free in fruits and in bee honey. Galactose - found combined in milk sugar. The general formula for these monosaccharides is (CH2O)n where n is 6. They have the same number of carbon, hydrogen and oxygen molecules i.e. C6H12O6. Properties of Monosaccharides
They are soluble in water. They are crystallisable. They are sweet. The are all reducing sugars.
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They are crystallisable. They are sweet. The are all reducing sugars. This is because they reduce blue copper (II) sulphate solution when heated to copper oxide which is red in colour and insoluble. Functions of Monosaccharides
They are oxidised in the cells to produce energy during respiration. Formation of important biological molecules e.g. deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Some monosaccharides are important metabolic intermediates e.g. in photosynthesis and in respiration. Monosaccharides are the units from which other more complex sugars are formed through condensation. Disaccharides
These contain two monosaccharide units. The chemical process through which a large molecule (e.g. a disaccharide) is formed from smaller molecules is called condensation and it involves loss of water. Common examples of disaccharides include sucrose, maltose and lactose. Disaccharides are broken into their monosaccharide units by heating with dilute hydrochloric acid. This is known as hydrolysis and involves addition of water molecules. The same process takes place inside cells through enzymes. Sucrose+water_--hydrolysis-----------------glucose+fructose
Properties of Disaccharides
Sweet tasting. Soluble in water. Crystallisable. Maltose and lactose are reducing sugars while sucrose is non-reducing sugar. Sucrose is the form in which carbohydrate is transported in plants:
This is because it is soluble andjchernically stable. Sucrose is a storage carbohydrate in some plants e.g. sugar-cane and sugar-beet. Disaccharides are hydrolysed to produce monosaccharide units which are readily metabolised by cell to provide energy. Polysaccharides
If many monosaccharides are joined together through condensation, a polysaccharide is formed. Polysaccharides may consist of hundreds or even thousands of monosaccharide units. Examples of polysaccharides:
Starch - storage material in plants. Glycogen is a storage carbohydrate in animals like starch, but has longer chains. Inulin - a storage carbohydrate in some plants e.g. Dahlia. Cellulose - structural carbohydrate in plants. Chitin - forms exoskeleton in arthropods.
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Dahlia. Cellulose - structural carbohydrate in plants. Chitin - forms exoskeleton in arthropods. Importance and Functions of Polysaccharides
They are storage carbohydrates - starch in plants glycogen in animals. They are hydrolysed to their contituent monosaccharide units and used for respiration. . They form structural material e.g. cellulose makes cell walls. Cellulose has wide commercial uses e.g. Fibre in cloth industry. Cellulose is used to make paper. Carbohydrates combine with other molecules to form important structural compounds in living organisms. Examples are:
Pectins: Combine with calcium ions to form calcium pectate. Chitin: Combine with (NH) group. Makes the exoskeleton of arthropods, and walls of fungi. Lipids
These are fats and oils. Fats are solid at room temperature while oils are liquid. They are made up of carbon, oxygen and hydrogen atoms. The structural units of lipids are fatty acids and glycerol. Fatty acids are made up of hydrocarbon chain molecules with a carboxyl group (-COOH) at one end. In the synthesis of a lipid, three fatty acid molecules combine with one glycerol molecule to form a triglyceride. Three molecules of water are lost in the process. This is a condensation reaction and water is given off. Lipids are hydrolysed e.g. during digestion to fatty acids and glycerol, water is added. condensation
-
Glycerol + 3 Fatty hydrolysis Lipid + Water acids
Properties
Fats are insoluble in water but dissolve in organic solvents e.g. in alcohols. They are chemically inactive, hence used as food storage compounds. Functions of Lipids
Structural materials - as structural material they make up the cell membrane. Source of energy - they are energy rich molecules. One molecule of lipid provides more energy than a carbohydrate molecule. Storage compound - They are stored as food reserves in plants. In animals e.g. mammals, all excess food taken is converted to fats which are stored in adipose tissue, and around internal organs such as the heart and kidneys. Insulation - They provide insulation in animals living in cold climates. A lot of fat is stored under the skin e.g. blubber in seals. Protection - Complex lipids e.g.
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A lot of fat is stored under the skin e.g. blubber in seals. Protection - Complex lipids e.g. wax on leaf surfaces protects the plant against water-loss and overheating. Fats stored around some internal organs acts as shock absorbers, thus protecting the organs. Source of Metabolic Water -:-lipids when oxidised produce metabolic water which supplements water requirements in the body. Desert animals e.g. the camel accumulate large quantities of fat in the hump which when oxidised releases metabolic water. Proteins
Proteins are the most abundant organic compounds in cells and constitute 50% of total dry weight. Proteins are compounds which are made up of carbon, hydrogen, nitrogen, oxygen and sometimes sulphur and phosphorus. The structural units of proteins are amino acids. The nature of a protein is determined by the types of amino acids it is made of. There are about 20 common amino acids that make up proteins. Essential and Non-Essential Amino Acids
Essential amino acids are those which cannot be synthesised in the body of an organism and must therefore be provided in the diet. There are ten amino acids which are essential for humans. These are valine, leucine, phenylalanine, lysine, tryptophan, isoleucine, methionine, threonine, histidine and arginine. Non-essential amino acids are those which the body can synthesise and therefore need not be available in the diet. There are ten of them. These are glycine, alanine, glutamic acid, aspartic acid, serine, tyrosine, proline, glutamine, arginine and cysteine. Proteins are essential in the diet because they are not stored in the body. Excess amino acids are deaminated. Formation of Proteins
Proteins are made up of many amino acid units joined together through peptide bonds. When two amino acids are joined together a dipeptide is formed. The chemical process involved is called condensation and a molecule of water is eliminated . When many amino acids are joined together a polypeptide chain is formed. The nature of a particular protein depends on the types, number and sequence of amino acids from which it is made. Functions of Proteins
As structural materials proteins-
Are the basic building structures of protoplasms. Proteins in conjunction with lipid form the cell membrane.
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The nature of a particular protein depends on the types, number and sequence of amino acids from which it is made. Functions of Proteins
As structural materials proteins-
Are the basic building structures of protoplasms. Proteins in conjunction with lipid form the cell membrane. Examples of structural proteins include:
Keratin (in hair, nails, hoofs, feathers and wool)
Silk in spider's web. Elastin forms ligaments that join bones to each other. Protective proteins. Antibodies that protect the body against foreign antigens. Fribrogen and thrombin are involved in clot formation, preventing entry of micro-organisms when blood vessel is cut. As functional chemical compounds. Examples are hormones and enzymes that act as regulators in the body. Respiratory pigments. Examples are haemoglobin that transports oxygen in the blood and myoglobin that stores up oxygen in muscles. Contractile proteins - make up muscles, i.e. myosin and actin. Proteins combine with other chemical groups to form important substances e.g. mucin in saliva. Source of energy. Proteins are a source of energy in extreme conditions when carbohydrates and fats are not available e.g. in starvation. Enzymes
Enzymes are biological catalysts that increase the rate of chemical reaction in the body. They are all produced inside cells. Some are intracellular and they catalyse reactions within the cells . Others are extracellular and are secreted out of the cells where they work. e.g. digestive enzymes. Properties of Enzymes
Enzymes are protein in nature. Enzymes are specific to the type of reaction they catalyse. This is referred to as substrate specificity. Enzymes work in very small amounts. They remain unchanged after the reaction. They catalyse reversible reactions. They work very fast (high turnover numbers) e.g. the enzyme catalase works on 600 thousand molecules of hydrogen peroxide in one second. Naming of enzymes
Enzymes are named by adding the suffix -ase to:
Name of substrate that they work on e.g. carbohydrates - carbohydrases e.g.sucrase. Starch (amylose) - amylase
Protein - proteinase (protease)
Lipids -lipases
Type of chemical reaction catalised e.g.
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Naming of enzymes
Enzymes are named by adding the suffix -ase to:
Name of substrate that they work on e.g. carbohydrates - carbohydrases e.g.sucrase. Starch (amylose) - amylase
Protein - proteinase (protease)
Lipids -lipases
Type of chemical reaction catalised e.g. Oxidation - oxidase
Reduction - reductase
Hydrolysis - hydrolase
Factors Affecting Enzyme Action
Temperature
Enzymes are sensitive to temperature changes. Generally, the rate of an enzymecontrolled reaction doubles with every 10OC increase in temperature. However, temperatures above 40°C do not favour enzyme reaction. This is because enzymes are denatured by high temperatures. pH
Every enzyme has a particular pH range over which it works best. Some enzymes work best in acidic media while others function better in alkaline media. Many enzymes function well under neutral conditions. Enzyme Concentration
Under conditions where the substrate is in excess, the rate of an enzyme-controlled reaction increases as the enzyme concentration is increased. Substrate Concentration
If the concentration of the substrate is increased while that of the enzyme remains constant, the rate of the reaction will increase for sometime and then become constant. Any further increase in substrate concentration will not result in corresponding increase in the rate of the reaction. Enzyme Inhibitors
These are substances that either compete with substrates for enzyme active sites or combine with enzymes and hence they inhibit the enzyme reaction. e.g. certain drugs, cyanide and nerve gas. Co-factors
Most enzymes require the presence of other compounds known as co-factors which are non-proteins. There are three groups of co-factors. Inorganic ions - e.g. iron, magnesium, copper and zinc. Complex organic molecules known as prosthetic groups are attached to the enzyme
e.g. flavin adenine dinucleotide (FAD) derived from vitamin B2 (riboflavin). Co-enzymes e.g. coenzyme A is involved in respiration. All co-enzymes are derived from vitamins. Nutrition in Animals=Heterotrophism
Meaning and Types of Heterotrophism
This is a mode of nutrition whereby organisms feed on complex organic matter from other plants or animals. All animals are heterotrophs.
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All co-enzymes are derived from vitamins. Nutrition in Animals=Heterotrophism
Meaning and Types of Heterotrophism
This is a mode of nutrition whereby organisms feed on complex organic matter from other plants or animals. All animals are heterotrophs. Their mode of feeding is also said to be holozoic to distinguish it from other special types of heterotrophic nutrition namely:
saprophytism
parasitism. Saprophytism/saprotrophysim- occurs in most fungi and some forms of bacteria. Saprophytes feed on dead organic matter and cause its decomposition or decay. Parasitism is a mode of feeding whereby one organism called the parasite feeds on or lives in another organism called the host and harms it. Modes of Feeding in Animals
Animals have developed various structures to capture and ingest food. The type of structures present depend on the method of feeding and the type of food. Carnivorous animals feed on whole animals or portions of their flesh. Herbiverous animals feed on plant material. Omnivorous animals feed on both plants and animal materials. Feeding in Mammals
The jaws and teeth of mammals are modified according to the type of food eaten. Mammals have different kinds of teeth. Each type of teeth has a particular role to play in the feeding process. Feeding in Mammals
The jaws and teeth of mammals are modified according to the type of food eaten. Mammals have different kinds of teeth. Each type of teeth has a particular role to play in the feeding process. This condition is described as heterodont. The teeth of reptiles and amphibians are all similar in shape and carry out the same function. They are said to be homodont. Types of Mammalian Teeth
Mammals have four kinds of teeth. The incisors are found at the front of the jaw. They are sharp-edged and are used for biting. The canines are located at the sides of the jaw. They are pointed and are used for tearing and piercing. The premolars are next to the canines and the molars are at the back of the jaw. Both premolars and molars are used for crushing and grinding. Teeth are replaced only once in a lifetime. The first set is the milk or deciduous teeth. These are replaced by the second set or the permanent teeth.
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Teeth are replaced only once in a lifetime. The first set is the milk or deciduous teeth. These are replaced by the second set or the permanent teeth. Dentition refers to the type of teeth, the number and their arrangement in the jaw. A dental formula shows the type and number of teeth in each half of the jaw. The number of teeth in half of the upper jaw is represented above a line and those on the lower jaw below the line. The first letter of each type of teeth is used in the formula i.e. i = incisors, c = canines, pm = premolars and m = molars. The total number is obtained by multiplying by two (for the two halves of each jaw). Adaptation of Teeth to Feeding
In general, incisors are for cutting, canines for tearing while premolars and molars are for grinding. However, specific modifications are observed in different mammals as an adaptation to the type of food they eat. Teeth of Herbivores
Incisors are long and flat with a sharp chisellike edge for cutting. The enamel coating is thicker in front than at the back so that as the tooth wears out, a sharp edge is maintained. Canines are reduced or absent. If absent, the space left is called the diastema. The diastema allows the tongue to hold food and push it to the grinding teeth at the back of the mouth. Premolars and molars:
These are transversely ridged. The ridges on the upper teeth fit into grooves on the lower ones. This gives a sideways grinding surface. The teeth of herbivores have open roots i.e., wide opening into the pulp cavity. This ensures a continued adequate supply of food and oxygen to the tooth. In some herbivores, such as rabbits and elephants, the incisors continue to grow throughout life. Teeth of Carnivores
Incisors are reduced in size and pointed. They are well suited for grasping food and holding prey. Canines are long, pointed and curved. They are used for piercing and tearing flesh as well as for attack and defence. Premolars and molars: In general, they are long and longitudinally ridged to increase surface area for crushing . Carnassial Teeth: These are the last premolars on the upper jaw and the first molars on the lower one. They are enlarged for cutting flesh. They act as a pair of shears. They also crush bones.
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They are enlarged for cutting flesh. They act as a pair of shears. They also crush bones. The teeth of carnivores have closed roots i.e., only a very small opening of the pulp cavity to allow food and oxygen to keep teeth alive. Once broken, no re-growth can take place. Teeth of Omnivores
Incisors have a wide surface for cutting. Canines are bluntly pointed for tearing. Premolars and molars have cusps for crushing and grinding. The premolars have two blunt cusps while the molars have three to four. Internal Structure of tooth
The tooth consists of two main parts:
Crown: The portion above the gum; it is covered by the enamel. Root: The portion below the gum; it is covered by the cement. The tooth has two roots. Neck: Is the region at the same level with the gum. It forms the junction between the crown and the root. It is covered by enamel. Incisors and canines have one root only. Premolars have one or two roots while molars have two to three roots each. Internally, the bulk of the tooth is made up of dentine which consists of living cells and extends to the root. It is composed of calcium salts, collagen and water. It is harder than bone but wears out with use. This is why it is covered by enamel which is the hardest substance in a mammal's body. Pulp Cavity: Contains blood vessels which provide nutrients to the dentine and remove waste products. It also contains nerve endings which detect heat, cold and pain. Cement: Fixes the tooth firmly to the jaw bone. Common Dental Diseases
Dental Carries
Dental carries are the holes or cavities that are formed as acid corrodes enamel and eventually the dentine. Causes
This is caused by bacteria acting on the food left between teeth and on the cusp. Acids are formed that eventually corrode the enamel. The pulp cavity is eventually reached. A lot of pain is experienced then. The bacteria then infect the pulp cavity and the whole tooth decays. Treatment
Treatment depends on the extent of the dental caries:
Extraction of Tooth. Filling - this involves replacing the dentine with amalgam, a mixture of hard elements e.g. silver and tin. Root Canal Treatment - This involves surgery and reconstruction. It saves severely damaged teeth. The nerves in the root canal are surgically severed. The tooth is cleaned and filled up with amalgam.
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It saves severely damaged teeth. The nerves in the root canal are surgically severed. The tooth is cleaned and filled up with amalgam. Periodontal Diseases
These are diseases of the gum. The gum becomes inflamed, and starts bleeding. Progression of the disease leads to infection of the fibres in the periodontal membranes and the tooth becomes loose. This condition is known as pyorrhoea. The diseases are caused by poor cleaning of the teeth. The accumulation of food particles leading to formation of plaque, lack of adequate vitamin A and C in the diet. Treatment
Nutrition - by taking adequate balanced diet rich in vitamins A and C. Antibiotics are used to kill bacteria. Anti-inflamatory drugs are given. Antiseptic is prescribed to use in cleaning the mouth daily to prevent further proliferation of bacteria. The plaque is removed-drilled away - a procedure known as scaling. Care of Teeth
In order to maintain healthy teeth the following points should be observed:
A proper diet that includes calcium and vitamins, particularly vitamin D is essential. The diet should also contain very small quantities of fluorine to strengthen the enamel. Large quantities of fluorine are harmful. The enamel becomes brown, a condition known as dental flourosis. Chewing of hard fibrous foods like carrots and sugar cane to strengthen and cleanse the teeth. Proper use of teeth e.g. not using teeth to open bottles and cut thread. Regular and thorough brushing of teeth after meals. Dental floss can be used to clean between the teeth. Not eating sweets and sugary foods between meals. Regular visits to the dentist for checkup. Washing the mouth with strong salt solution or with any other mouth wash with antiseptic properties. Digestive System and Digestion in Humans
Organs that are involved with feeding in humans constitute the digestive system. Digestive System and Associated Glands
Human digestive system starts at the mouth and ends at the anus. This is the alimentary canal. Digestion takes place inside the lumen of the alimentary canal. The epithelial wall that faces the lumen has mucus glands (goblet cells). These secrete mucus that lubricate food and prevent the wall from being digested by digestive enzymes. Present at specific regions are glands that secrete digestive enzymes. The liver and pancreas are organs that are closely associated with the alimentary canal. Their secretions get into the lumen and assist in digestions. Digestive system consists of:
Mouth.
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The liver and pancreas are organs that are closely associated with the alimentary canal. Their secretions get into the lumen and assist in digestions. Digestive system consists of:
Mouth. Oesophagus. Stomach. Small intestines - consist of duodenum, the first part next to the stomach, ileum - the last part that ends up in a vestigial caecum and appendix which are nonfunctional. Large intestines consist of: colon and rectum that ends in the anus. Ingestion, Digestion and Absorption
Feeding in humans involves the following processes:
Ingestion: This is the introduction of the food into the mouth. Digestion: This is the mechanical and chemical breakdown of the food into simpler, soluble and absorbable units. Absorption: Taking into blood the digested products. Assimilation: Use of food in body cells. Mechanical breakdown of the food takes place with the help of the teeth. Chemical digestion involves enzymes. Digestion in the Mouth
In the mouth, both mechanical and chemical digestion takes place. Food is mixed with saliva and is broken into smaller particles by the action of teeth. Saliva contains the enzyme amylase. It also contains water and mucus which lubricate and soften food in order to make swallowing easy. Saliva is slightly alkaline and thus provides a suitable pH for amylase to act on cooked starch, changing it to maltose. The food is then swallowed in the form of semisolid balls known as boluses. Each bolus moves down the oesophagus by a process known as peristalsis. Circular and longitudinal muscles along the wall of the alimentary canal contract and relax pushing the food along. Digestion in the Stomach
In the stomach, the food is mixed with gastric juice secreted by gastric glands in the stomach wall. Gastric juice contains pepsin, rennin and hydrochloric acid. The acid provides a low pH of 1.5-2.0 suitable for the action of pepsin. Pepsin breaks down protein into peptides. Rennin coagulates the milk protein casein. The stomach wall has strong circular and longitudinal muscles whose contraction mixes the food with digestive juices in the stomach. Digestion in the Duodenum
In the duodenum the food is mixed with bile and pancreatic juice. Bile contains bile salts and bile pigments.
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The stomach wall has strong circular and longitudinal muscles whose contraction mixes the food with digestive juices in the stomach. Digestion in the Duodenum
In the duodenum the food is mixed with bile and pancreatic juice. Bile contains bile salts and bile pigments. The salts emulsify fats, thus providing a large surface area for action of lipase. Pancreatic juice contains three enzymes:
Trypsin which breaks down proteins into peptides and amino acids,
Amylase which breaks down starch into maltose, and
Lipase which breaks down lipids into fatty acids and glycerol. These enzymes act best in an alkaline medium which is provided for by the bile. Digestion in ileum
Epithelial cells in ileum secrete intestinal juice, also known as succus entericus. This contains enzymes which complete the digestion of protein into amino acids, carbohydrates into monosaccharides and lipids into fatty acids and glycerol. Absorption
This is the diffusion of the products of digestion into the blood of the animal. It takes place mainly in the small intestines though alcohol and some glucose are absorbed in the stomach. The ileum is adapted for absorption in the following ways:
It is highly coiled. The coiling ensures that food moves along slowly to allow time for its digestion and absorption. It is long to provide a large surface area for absorption. The epithelium has many finger-like projections called villi (singular villus). They greatly increase the surface area for absorption. Villi have microvilli that further increase the surface area for absorption. The wall of villi has thin epithelial lining to facilitate fast diffusion of products of digestion. Has numerous blood vessels for transport of the end products of digestion. Has lacteal vessels; for absorption of fatty acids and glycerol and transport of lipids. Absorption of Glucose and Amino Acids
Glucose and other monosaccharides as well as amino acids are absorbed through the villi epithelium and directly into the blood capillaries. First they are carried to the liver through the hepatic portal vein, then taken to all organs via circulatory system. Absorption of Fatty Acids and Glycerol
Fatty acids and glycerol diffuse through the epithelial cells of villi and into the lacteal.
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Absorption of Glucose and Amino Acids
Glucose and other monosaccharides as well as amino acids are absorbed through the villi epithelium and directly into the blood capillaries. First they are carried to the liver through the hepatic portal vein, then taken to all organs via circulatory system. Absorption of Fatty Acids and Glycerol
Fatty acids and glycerol diffuse through the epithelial cells of villi and into the lacteal. When inside the villi epithelial cells, the fatty acids combine with glycerol to make tiny fat droplets which give the lacteal a milky appearance. The lacteals join the main lymph vessel that empties its contents into the bloodstream in the thoracic region. Once inside the blood, the lipid droplets are hydrolysed to fatty acids and glycerol. Absorption of Vitamins and Mineral Salts
Vitamins and mineral salts are absorbed into the blood capillaries in' the villi. Water is mainly absorbed in the colon. As a result the undigested food is in a semi-solid form (faeces) when it reaches the rectum. Egestion: This is removal of undigested or indigestible material from the body. Faeces are temporarily stored in the rectum then voided through the anus. Opening of the anus is controlled by sphincter muscles
Assimilation: This is the incorporation of the food into the cells where it is used for various chemical processes. Carbohydrates
used to provide energy for the body. Excess glucose is converted to glycogen and stored in the liver and muscles. Some of the excess carbohydrates are also converted into fat in the liver and stored in the adipose tissue' (fat storage tissue), in the mesenteries and in the connective tissue under the skin, around the heart and other internal organs. Proteins
Amino acids are used to build new cells and repair worn out ones. They are also used for the synthesis of protein compounds. Excess amino acids are de-aminated in the liver. Urea is formed from the nitrogen part. The remaining carbohydrate portion is used for energy or it is converted to glycogen or fat and stored. Lipids
Fats are primarily stored in the fat storage tissues. When carbohydrates intake is low in the body, fats are oxidised to provide energy. They are also used as structural materials e.g.
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Lipids
Fats are primarily stored in the fat storage tissues. When carbohydrates intake is low in the body, fats are oxidised to provide energy. They are also used as structural materials e.g. phospholipids in cell membrane. They act as cushion, protecting delicate organs like the heart. Stored fats under the skin act as heat insulators. Summary of digestion in humans
Importance of Vitamins, Mineral Salts, Roughage and Water in Human Nutrition
Vitamins
These are organic compounds that are essential for proper growth, development and functioning of the body. Vitamins are required in very small quantities. They are not stored and must be included in the diet. Vitamins Band C are soluble in water, the rest are soluble in fat. Various vitamins are used in different ways. Mineral Salts
Mineral ions are needed in the human body. Some are needed in small amounts while others are needed in very small amounts (trace). All are vital to human health. Nevertheless, their absence results in noticeable mulfunction of the body processes. Water
Water is a constituent of blood and intercellular fluid. It is also a constituent of cytoplasm. Water makes up to 60-70% of total fresh weight in humans. No life can exist without water. Functions of Water
Acts as a medium in which chemical reactions in the body takes place. Acts as a solvent and it is used to transport materials within the body. Acts as a coolant due to its high latent heat of vaporisation. Hence, evaporation of sweat lowers body temperature. Takes part in chemical reactions i.e. hydrolysis. Vitamins, sources, uses and the deficiency disease resulting from their absence in diet
Roughage
Roughage is dietary fibre and it consists mainly of cellulose. It adds bulk to the food and provides grip for the gut muscles to enhance peristalsis. Roughage does not provide any nutritional value because humans and all animals not produce cellulase enzyme to digest cellulose. In herbivores symbiotic bacteria in the gut produce cellulase that digests cellulose. Factors Determining Energy Requirements in Humans
Age: Infants, for instance, need a greater proportion of protein than adults. Sex: males generally require more carbohydrates than females. The requirements of specific nutrients for females depends on the stage of development in the life cycle.
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Factors Determining Energy Requirements in Humans
Age: Infants, for instance, need a greater proportion of protein than adults.
Sex: males generally require more carbohydrates than females.
The requirements of specific nutrients for females depends on the stage of development in the life cycle.
Adolescent girls require more iron in their diet; expectant and nursing mothers require a lot of proteins and mineral salts.
State of Health: A sick individual requires more of certain nutrients e.g.
proteins, than a healthy one.
Occupation: An office worker needs less nutrients than a manual worker.
Balanced Diet
A diet is balanced when it contains all the body's nutrient requirements and in the right amounts or proportions.
A balanced diet should contain the following:
Carbohydrates
Proteins
Lipids
Vitamins
Mineral Salts
Water
Dietary fibre or roughage
Malnutrition
This is faulty or bad feeding where the intake of either less or more than the required amount of food or total lack of some food components.
Deficiency Diseases
Deficiency diseases result from prolonged absence of certain components in the diet.
Examples are:
Marasmus:
Lack of enough food reuslts in thin arms and legs,
severe loss of fluid,
general body wasting
sunken eyes.
Kwashiorkor –
Lack of protein in the diet of children.
The symptoms of kwashiorkor include wasting of the body, red thin hair, swollen abdomen and scaly skin.
Other deficiency diseases are due to lack of accessory food factors (vitamins and mineral salts.).
Such diseases include rickets, goitre and anaemia.
Treatment of these deficiency diseases is by supplying the patient with the component missing in the diet.
THE END
Practical Activities
Experiments to show that Carbon (IV) Oxide is necessary for Photosynthesis
Experiment to Show Effect of Light on Photosynthesis
Experiment to Show the Effect of Chlorophyll on Photosynthesis
Experiment To Observe Stomata Distribution in Different Leaves
Test for Reducing Sugar
Test for non-reducing sugar
Test for Lipids;
(a) Grease Spot Test
(b) Emulsion Test
Test for Proteins -Biuret Test
Experiment To Investigate Presence of Enzyme in Living Tissue
Dissection of a Rabbit to show the Digestive System
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FORM FOUR BIOLOGY
Define the term genetics
Differentiate between heredity and variation
Distinguish between continuous and discontinuous variations
Describe continuous and discontinuous variations
Observe variations in plants and animals
Describe the structure, nature and properties of chromosomes
Describe the structure, nature and properties of DNA molecule
Differentiate between DNA and RNA
Distinguish between F1 and F2 generation
Determine Mendel’s first law of inheritance
Define other terms used in inheritance such as phenotype, genotype, dominant gene, recessive gene, haploid and diploid
Demonstrate monohybrid inheritance in plants and animals
Predict outcomes of various genetic crosses
Construct and make use of pannet squares
Work out genotypic and phenotypic ratios
Predict outcomes of various crosses
Determine the unknown genotypes in a cross using a test cross
Describe albinism as an example of monohybrid inheritance in human beings
Explain the inheritance of ABO blood groups in human beings
Explain the inheritance of rhesus factor as an example of monohybrid inheritance in human beings
Predict the inheritance of blood groups human beings
Describe incomplete dominance
Describe inheritance of colour in flowers of mirabilis jalapa
Describe Inheritance of sickle cell anemia in human beings
Explain how sex is determined in human beings
Describe sex linkages in human beings
Define linkage and sex-linkage
Describe linkage in human beings e.g.colour blindness and hemophilia
Describe colour blindness as an example of sex-linked trait in human beings
Interpret pedigree of inheritance
Describe the Inheritance of hemophilia as an example of sex-linked traits in human beings
Define mutation
Differentiate between mutations and mutagens
List down causes of mutations
State the types of mutations
List down the various chromosal mutations
Describe chromosal mutations
Explain the Effects of chromosal mutations
Describe gene mutations and their effects on organisms
Describe areas in which the knowledge of genetics has been applied
Explain the practical applications of genetics
Define evolution
Explain the current concepts of the origin of life
Explain the current concepts on origin of life
Describe the study of fossils as evidence of organic evolution theory
Describe comparative anatomy as evidence of organic evolution
Describe occurrence of vestigial structures and geographical distribution of organisms as evidence of organic evolution
Describe comparative embryology, cell biology and biochemistry as evidence of organic evolution
Describe evolution of hominids
Describe Lamarck’s theory
Describe and discuss the struggle for existence and survival for the fittest
Describe and discuss new concepts of Darwin’s theory
Describe natural selection in action
Describe natural selection in nature
Describe the isolation mechanism in speciation
Describe Artificial selection in plants and animals and how it leads to speciation
Explain the importance of sexual reproduction in evolution
Define stimulus
Define irritability
Define response
Define tactic and tropic responses
List down tactic responses in plants
List down tropic responses in plants
Differentiate between tactic and tropic responses
Define geotropism
Describe geotropism in roots and shoots of plants
Differentiate between Phototropism and geotropism
Carry out experiments demonstrating both Phototropism and geotropism in a plant seedling
Carry out experiments to demonstrate tactic responses to light and water
Carry out experiments to show chemotactic response using fruit juice
Define Hydrotropism and thigmotropism
State the importance of Tactic and tropic responses
Explain the production of Plant hormones and their effects on plants
Carry out experiment to investigate hydrotropism
Carry out experiment to investigate etiolation
Demonstrate the knee jerk in a reflex action
Defined Conditioned reflex actions
Describe Conditioned reflex action using parlous dog
Compare simple and conditioned reflex actions
Explain the role of endocrine system in a human being
Explain the effect over secretion and under secretion of thyroxin and adrenaline
Isolate and list the similarities and differences between the endocrine and the nervous system
State the effects of drug abuse on human health
Draw and label the mammalian eye
State the functions of the mammalian eye
Describe how the structure of the mammalian eye is adapted to its functions
Dissect and display parts of the mammalian eye
Describe how an image is formed and interpreted in the mammalian eye
Describe Accommodation in the mammalian eye
Name and explain the Common eye defects
Describe Common eye defects and their corrections
Investigate the blind spot In the eye
Investigate which eye is used more during vision
Name and describe Common eye diseases
Draw and label the mammalian ear
Describe the mammalian ear and how it is adapted to its functions
Describe the mechanism of hearing
Discuss thick ear drum, damaged cochlea, raptured eardrum, fussed ossicles, otitis media, ostosceleross and tinnitus
Define support and movement
Describe the necessity of movement in plants and animals
Review the tissue distribution in monocotyledonous an dicotyledonous plants
Describe support in woody and non-woody stems
Describe the role of tendrils and tender stems in support
Observe prepared sections of woody and herbaceous stems
Observe a wilting plant
List the types of skeletons
Describe the role of exoskeleton in insects
Describe the role and components of endoskeleton
Describe the role of skeleton in vertebrates
Draw the structure of a finned fish (tilapia)
Calculate the tail power
Explain how locomotion occurs in fish
Name and draw the different fins and state their functions
Draw the human skeleton and identify the component parts
Identify and draw the skull
Identify bones of Axial skeleton in the vertebral column
Identify the cervical vertebrae
Identify the structures of the thoracic vertebrae
Relate the structure of the thoracic vertebrae to their functions
Identify the structures of lumbar, sacral and candal vertebrae
Show how ribs articulate with thoracic vertebrae
Draw and label Ribs and sternum
Relate the structure to their functions
Identify components of Appendicular skeleton
Draw the scapula bone and relate it to its functions
Identify the bones of the fore limbs
Draw the structure of the humerus, radius and ulna
Draw and label bones of the hand
Draw the pelvic girdle
Name the bones of The pelvic girdle
Relate the structure to their functions
Identify, draw and label the femur, tibia and tibula bones
Relate their structure to their functions
Draw and label the bones of the foot
Relate the structure of bones of the foot to their functions
Define a joint
List the three types of joints
Describe the types of joints
List examples of movable joints, hinge joints and bell and socket joints
Define Immovable joints
Name Immovable joints
Define muscles
Explain the differences between the three types of muscles
Identifying biceps and triceps in the arm movement
Genetics
Introduction
Genetics is the study of inheritance.
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FORM FOUR BIOLOGY
Define the term genetics
Differentiate between heredity and variation
Distinguish between continuous and discontinuous variations
Describe continuous and discontinuous variations
Observe variations in plants and animals
Describe the structure, nature and properties of chromosomes
Describe the structure, nature and properties of DNA molecule
Differentiate between DNA and RNA
Distinguish between F1 and F2 generation
Determine Mendel’s first law of inheritance
Define other terms used in inheritance such as phenotype, genotype, dominant gene, recessive gene, haploid and diploid
Demonstrate monohybrid inheritance in plants and animals
Predict outcomes of various genetic crosses
Construct and make use of pannet squares
Work out genotypic and phenotypic ratios
Predict outcomes of various crosses
Determine the unknown genotypes in a cross using a test cross
Describe albinism as an example of monohybrid inheritance in human beings
Explain the inheritance of ABO blood groups in human beings
Explain the inheritance of rhesus factor as an example of monohybrid inheritance in human beings
Predict the inheritance of blood groups human beings
Describe incomplete dominance
Describe inheritance of colour in flowers of mirabilis jalapa
Describe Inheritance of sickle cell anemia in human beings
Explain how sex is determined in human beings
Describe sex linkages in human beings
Define linkage and sex-linkage
Describe linkage in human beings e.g.colour blindness and hemophilia
Describe colour blindness as an example of sex-linked trait in human beings
Interpret pedigree of inheritance
Describe the Inheritance of hemophilia as an example of sex-linked traits in human beings
Define mutation
Differentiate between mutations and mutagens
List down causes of mutations
State the types of mutations
List down the various chromosal mutations
Describe chromosal mutations
Explain the Effects of chromosal mutations
Describe gene mutations and their effects on organisms
Describe areas in which the knowledge of genetics has been applied
Explain the practical applications of genetics
Define evolution
Explain the current concepts of the origin of life
Explain the current concepts on origin of life
Describe the study of fossils as evidence of organic evolution theory
Describe comparative anatomy as evidence of organic evolution
Describe occurrence of vestigial structures and geographical distribution of organisms as evidence of organic evolution
Describe comparative embryology, cell biology and biochemistry as evidence of organic evolution
Describe evolution of hominids
Describe Lamarck’s theory
Describe and discuss the struggle for existence and survival for the fittest
Describe and discuss new concepts of Darwin’s theory
Describe natural selection in action
Describe natural selection in nature
Describe the isolation mechanism in speciation
Describe Artificial selection in plants and animals and how it leads to speciation
Explain the importance of sexual reproduction in evolution
Define stimulus
Define irritability
Define response
Define tactic and tropic responses
List down tactic responses in plants
List down tropic responses in plants
Differentiate between tactic and tropic responses
Define geotropism
Describe geotropism in roots and shoots of plants
Differentiate between Phototropism and geotropism
Carry out experiments demonstrating both Phototropism and geotropism in a plant seedling
Carry out experiments to demonstrate tactic responses to light and water
Carry out experiments to show chemotactic response using fruit juice
Define Hydrotropism and thigmotropism
State the importance of Tactic and tropic responses
Explain the production of Plant hormones and their effects on plants
Carry out experiment to investigate hydrotropism
Carry out experiment to investigate etiolation
Demonstrate the knee jerk in a reflex action
Defined Conditioned reflex actions
Describe Conditioned reflex action using parlous dog
Compare simple and conditioned reflex actions
Explain the role of endocrine system in a human being
Explain the effect over secretion and under secretion of thyroxin and adrenaline
Isolate and list the similarities and differences between the endocrine and the nervous system
State the effects of drug abuse on human health
Draw and label the mammalian eye
State the functions of the mammalian eye
Describe how the structure of the mammalian eye is adapted to its functions
Dissect and display parts of the mammalian eye
Describe how an image is formed and interpreted in the mammalian eye
Describe Accommodation in the mammalian eye
Name and explain the Common eye defects
Describe Common eye defects and their corrections
Investigate the blind spot In the eye
Investigate which eye is used more during vision
Name and describe Common eye diseases
Draw and label the mammalian ear
Describe the mammalian ear and how it is adapted to its functions
Describe the mechanism of hearing
Discuss thick ear drum, damaged cochlea, raptured eardrum, fussed ossicles, otitis media, ostosceleross and tinnitus
Define support and movement
Describe the necessity of movement in plants and animals
Review the tissue distribution in monocotyledonous an dicotyledonous plants
Describe support in woody and non-woody stems
Describe the role of tendrils and tender stems in support
Observe prepared sections of woody and herbaceous stems
Observe a wilting plant
List the types of skeletons
Describe the role of exoskeleton in insects
Describe the role and components of endoskeleton
Describe the role of skeleton in vertebrates
Draw the structure of a finned fish (tilapia)
Calculate the tail power
Explain how locomotion occurs in fish
Name and draw the different fins and state their functions
Draw the human skeleton and identify the component parts
Identify and draw the skull
Identify bones of Axial skeleton in the vertebral column
Identify the cervical vertebrae
Identify the structures of the thoracic vertebrae
Relate the structure of the thoracic vertebrae to their functions
Identify the structures of lumbar, sacral and candal vertebrae
Show how ribs articulate with thoracic vertebrae
Draw and label Ribs and sternum
Relate the structure to their functions
Identify components of Appendicular skeleton
Draw the scapula bone and relate it to its functions
Identify the bones of the fore limbs
Draw the structure of the humerus, radius and ulna
Draw and label bones of the hand
Draw the pelvic girdle
Name the bones of The pelvic girdle
Relate the structure to their functions
Identify, draw and label the femur, tibia and tibula bones
Relate their structure to their functions
Draw and label the bones of the foot
Relate the structure of bones of the foot to their functions
Define a joint
List the three types of joints
Describe the types of joints
List examples of movable joints, hinge joints and bell and socket joints
Define Immovable joints
Name Immovable joints
Define muscles
Explain the differences between the three types of muscles
Identifying biceps and triceps in the arm movement
Genetics
Introduction
Genetics is the study of inheritance. The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring.
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FORM FOUR BIOLOGY
Define the term genetics
Differentiate between heredity and variation
Distinguish between continuous and discontinuous variations
Describe continuous and discontinuous variations
Observe variations in plants and animals
Describe the structure, nature and properties of chromosomes
Describe the structure, nature and properties of DNA molecule
Differentiate between DNA and RNA
Distinguish between F1 and F2 generation
Determine Mendel’s first law of inheritance
Define other terms used in inheritance such as phenotype, genotype, dominant gene, recessive gene, haploid and diploid
Demonstrate monohybrid inheritance in plants and animals
Predict outcomes of various genetic crosses
Construct and make use of pannet squares
Work out genotypic and phenotypic ratios
Predict outcomes of various crosses
Determine the unknown genotypes in a cross using a test cross
Describe albinism as an example of monohybrid inheritance in human beings
Explain the inheritance of ABO blood groups in human beings
Explain the inheritance of rhesus factor as an example of monohybrid inheritance in human beings
Predict the inheritance of blood groups human beings
Describe incomplete dominance
Describe inheritance of colour in flowers of mirabilis jalapa
Describe Inheritance of sickle cell anemia in human beings
Explain how sex is determined in human beings
Describe sex linkages in human beings
Define linkage and sex-linkage
Describe linkage in human beings e.g.colour blindness and hemophilia
Describe colour blindness as an example of sex-linked trait in human beings
Interpret pedigree of inheritance
Describe the Inheritance of hemophilia as an example of sex-linked traits in human beings
Define mutation
Differentiate between mutations and mutagens
List down causes of mutations
State the types of mutations
List down the various chromosal mutations
Describe chromosal mutations
Explain the Effects of chromosal mutations
Describe gene mutations and their effects on organisms
Describe areas in which the knowledge of genetics has been applied
Explain the practical applications of genetics
Define evolution
Explain the current concepts of the origin of life
Explain the current concepts on origin of life
Describe the study of fossils as evidence of organic evolution theory
Describe comparative anatomy as evidence of organic evolution
Describe occurrence of vestigial structures and geographical distribution of organisms as evidence of organic evolution
Describe comparative embryology, cell biology and biochemistry as evidence of organic evolution
Describe evolution of hominids
Describe Lamarck’s theory
Describe and discuss the struggle for existence and survival for the fittest
Describe and discuss new concepts of Darwin’s theory
Describe natural selection in action
Describe natural selection in nature
Describe the isolation mechanism in speciation
Describe Artificial selection in plants and animals and how it leads to speciation
Explain the importance of sexual reproduction in evolution
Define stimulus
Define irritability
Define response
Define tactic and tropic responses
List down tactic responses in plants
List down tropic responses in plants
Differentiate between tactic and tropic responses
Define geotropism
Describe geotropism in roots and shoots of plants
Differentiate between Phototropism and geotropism
Carry out experiments demonstrating both Phototropism and geotropism in a plant seedling
Carry out experiments to demonstrate tactic responses to light and water
Carry out experiments to show chemotactic response using fruit juice
Define Hydrotropism and thigmotropism
State the importance of Tactic and tropic responses
Explain the production of Plant hormones and their effects on plants
Carry out experiment to investigate hydrotropism
Carry out experiment to investigate etiolation
Demonstrate the knee jerk in a reflex action
Defined Conditioned reflex actions
Describe Conditioned reflex action using parlous dog
Compare simple and conditioned reflex actions
Explain the role of endocrine system in a human being
Explain the effect over secretion and under secretion of thyroxin and adrenaline
Isolate and list the similarities and differences between the endocrine and the nervous system
State the effects of drug abuse on human health
Draw and label the mammalian eye
State the functions of the mammalian eye
Describe how the structure of the mammalian eye is adapted to its functions
Dissect and display parts of the mammalian eye
Describe how an image is formed and interpreted in the mammalian eye
Describe Accommodation in the mammalian eye
Name and explain the Common eye defects
Describe Common eye defects and their corrections
Investigate the blind spot In the eye
Investigate which eye is used more during vision
Name and describe Common eye diseases
Draw and label the mammalian ear
Describe the mammalian ear and how it is adapted to its functions
Describe the mechanism of hearing
Discuss thick ear drum, damaged cochlea, raptured eardrum, fussed ossicles, otitis media, ostosceleross and tinnitus
Define support and movement
Describe the necessity of movement in plants and animals
Review the tissue distribution in monocotyledonous an dicotyledonous plants
Describe support in woody and non-woody stems
Describe the role of tendrils and tender stems in support
Observe prepared sections of woody and herbaceous stems
Observe a wilting plant
List the types of skeletons
Describe the role of exoskeleton in insects
Describe the role and components of endoskeleton
Describe the role of skeleton in vertebrates
Draw the structure of a finned fish (tilapia)
Calculate the tail power
Explain how locomotion occurs in fish
Name and draw the different fins and state their functions
Draw the human skeleton and identify the component parts
Identify and draw the skull
Identify bones of Axial skeleton in the vertebral column
Identify the cervical vertebrae
Identify the structures of the thoracic vertebrae
Relate the structure of the thoracic vertebrae to their functions
Identify the structures of lumbar, sacral and candal vertebrae
Show how ribs articulate with thoracic vertebrae
Draw and label Ribs and sternum
Relate the structure to their functions
Identify components of Appendicular skeleton
Draw the scapula bone and relate it to its functions
Identify the bones of the fore limbs
Draw the structure of the humerus, radius and ulna
Draw and label bones of the hand
Draw the pelvic girdle
Name the bones of The pelvic girdle
Relate the structure to their functions
Identify, draw and label the femur, tibia and tibula bones
Relate their structure to their functions
Draw and label the bones of the foot
Relate the structure of bones of the foot to their functions
Define a joint
List the three types of joints
Describe the types of joints
List examples of movable joints, hinge joints and bell and socket joints
Define Immovable joints
Name Immovable joints
Define muscles
Explain the differences between the three types of muscles
Identifying biceps and triceps in the arm movement
Genetics
Introduction
Genetics is the study of inheritance. The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring. Factors that determine characters (genes) are passed on from parent to offspring through gametes or sex cells.
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FORM FOUR BIOLOGY
Define the term genetics
Differentiate between heredity and variation
Distinguish between continuous and discontinuous variations
Describe continuous and discontinuous variations
Observe variations in plants and animals
Describe the structure, nature and properties of chromosomes
Describe the structure, nature and properties of DNA molecule
Differentiate between DNA and RNA
Distinguish between F1 and F2 generation
Determine Mendel’s first law of inheritance
Define other terms used in inheritance such as phenotype, genotype, dominant gene, recessive gene, haploid and diploid
Demonstrate monohybrid inheritance in plants and animals
Predict outcomes of various genetic crosses
Construct and make use of pannet squares
Work out genotypic and phenotypic ratios
Predict outcomes of various crosses
Determine the unknown genotypes in a cross using a test cross
Describe albinism as an example of monohybrid inheritance in human beings
Explain the inheritance of ABO blood groups in human beings
Explain the inheritance of rhesus factor as an example of monohybrid inheritance in human beings
Predict the inheritance of blood groups human beings
Describe incomplete dominance
Describe inheritance of colour in flowers of mirabilis jalapa
Describe Inheritance of sickle cell anemia in human beings
Explain how sex is determined in human beings
Describe sex linkages in human beings
Define linkage and sex-linkage
Describe linkage in human beings e.g.colour blindness and hemophilia
Describe colour blindness as an example of sex-linked trait in human beings
Interpret pedigree of inheritance
Describe the Inheritance of hemophilia as an example of sex-linked traits in human beings
Define mutation
Differentiate between mutations and mutagens
List down causes of mutations
State the types of mutations
List down the various chromosal mutations
Describe chromosal mutations
Explain the Effects of chromosal mutations
Describe gene mutations and their effects on organisms
Describe areas in which the knowledge of genetics has been applied
Explain the practical applications of genetics
Define evolution
Explain the current concepts of the origin of life
Explain the current concepts on origin of life
Describe the study of fossils as evidence of organic evolution theory
Describe comparative anatomy as evidence of organic evolution
Describe occurrence of vestigial structures and geographical distribution of organisms as evidence of organic evolution
Describe comparative embryology, cell biology and biochemistry as evidence of organic evolution
Describe evolution of hominids
Describe Lamarck’s theory
Describe and discuss the struggle for existence and survival for the fittest
Describe and discuss new concepts of Darwin’s theory
Describe natural selection in action
Describe natural selection in nature
Describe the isolation mechanism in speciation
Describe Artificial selection in plants and animals and how it leads to speciation
Explain the importance of sexual reproduction in evolution
Define stimulus
Define irritability
Define response
Define tactic and tropic responses
List down tactic responses in plants
List down tropic responses in plants
Differentiate between tactic and tropic responses
Define geotropism
Describe geotropism in roots and shoots of plants
Differentiate between Phototropism and geotropism
Carry out experiments demonstrating both Phototropism and geotropism in a plant seedling
Carry out experiments to demonstrate tactic responses to light and water
Carry out experiments to show chemotactic response using fruit juice
Define Hydrotropism and thigmotropism
State the importance of Tactic and tropic responses
Explain the production of Plant hormones and their effects on plants
Carry out experiment to investigate hydrotropism
Carry out experiment to investigate etiolation
Demonstrate the knee jerk in a reflex action
Defined Conditioned reflex actions
Describe Conditioned reflex action using parlous dog
Compare simple and conditioned reflex actions
Explain the role of endocrine system in a human being
Explain the effect over secretion and under secretion of thyroxin and adrenaline
Isolate and list the similarities and differences between the endocrine and the nervous system
State the effects of drug abuse on human health
Draw and label the mammalian eye
State the functions of the mammalian eye
Describe how the structure of the mammalian eye is adapted to its functions
Dissect and display parts of the mammalian eye
Describe how an image is formed and interpreted in the mammalian eye
Describe Accommodation in the mammalian eye
Name and explain the Common eye defects
Describe Common eye defects and their corrections
Investigate the blind spot In the eye
Investigate which eye is used more during vision
Name and describe Common eye diseases
Draw and label the mammalian ear
Describe the mammalian ear and how it is adapted to its functions
Describe the mechanism of hearing
Discuss thick ear drum, damaged cochlea, raptured eardrum, fussed ossicles, otitis media, ostosceleross and tinnitus
Define support and movement
Describe the necessity of movement in plants and animals
Review the tissue distribution in monocotyledonous an dicotyledonous plants
Describe support in woody and non-woody stems
Describe the role of tendrils and tender stems in support
Observe prepared sections of woody and herbaceous stems
Observe a wilting plant
List the types of skeletons
Describe the role of exoskeleton in insects
Describe the role and components of endoskeleton
Describe the role of skeleton in vertebrates
Draw the structure of a finned fish (tilapia)
Calculate the tail power
Explain how locomotion occurs in fish
Name and draw the different fins and state their functions
Draw the human skeleton and identify the component parts
Identify and draw the skull
Identify bones of Axial skeleton in the vertebral column
Identify the cervical vertebrae
Identify the structures of the thoracic vertebrae
Relate the structure of the thoracic vertebrae to their functions
Identify the structures of lumbar, sacral and candal vertebrae
Show how ribs articulate with thoracic vertebrae
Draw and label Ribs and sternum
Relate the structure to their functions
Identify components of Appendicular skeleton
Draw the scapula bone and relate it to its functions
Identify the bones of the fore limbs
Draw the structure of the humerus, radius and ulna
Draw and label bones of the hand
Draw the pelvic girdle
Name the bones of The pelvic girdle
Relate the structure to their functions
Identify, draw and label the femur, tibia and tibula bones
Relate their structure to their functions
Draw and label the bones of the foot
Relate the structure of bones of the foot to their functions
Define a joint
List the three types of joints
Describe the types of joints
List examples of movable joints, hinge joints and bell and socket joints
Define Immovable joints
Name Immovable joints
Define muscles
Explain the differences between the three types of muscles
Identifying biceps and triceps in the arm movement
Genetics
Introduction
Genetics is the study of inheritance. The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring. Factors that determine characters (genes) are passed on from parent to offspring through gametes or sex cells. In fertilisation the nucleus of the male gamete fuses with the nucleus of the female gamete.
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The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring. Factors that determine characters (genes) are passed on from parent to offspring through gametes or sex cells. In fertilisation the nucleus of the male gamete fuses with the nucleus of the female gamete. The offspring show the characteristics of both the male and the female. Genetics is the study of how this heritable material operates in individuals and their offspring. Variations within Plant and Animal Species
Variation
The term variation means to differ from a standard. Genetics also deals with the study of differences between organisms belonging to one species. Organisms belonging to higher taxonomic groups e.g. phyla or classes are clearly different. Although organisms belonging to the same species are similar, they show a number of differences or variations such that no two organisms are exactly the same in every respect. Even identical twins, though similar in many aspects, are seen to differ if they grow in different environments. Their differences are as a result of the environment which modifies the expression of their genetic make-up or genotype. The two causes of variations are the genes and the environment. Genes determine the character while the environment modifies the expression of that character. Continuous and Discontinuous Variation
Continuous Variations
The differences between the individual are not clear-cut. There are intermediates or gradations between any two extremes. Continuous variations are due to action of many genes e.g. skin complexion in humans. In continuous variation, the environment has a modifying effect in that it may enhance or suppress the expressions of the genes. Continuous variation can be represented in form of a histogram. Example of continuous variation in humans is weight, height and skin complexion. Linear measurements:
In humans, height shows gradation from tall, to tallest. So does the length of mature leaves of a plant. In most cases, continuous variation is as a result of the environment. Discontinuous Variations
These are distinct and clear cut differences within a species. Examples include:
Ability to roll the tongue. An individual can either roll the tongue or not. Ability to taste phenylthiourea (PTC); some individuals can taste this chemical others cannot. Blood groups - and individual has one of the four blood groups A, B AB or O. There are no intermediates. Albinism - one is either an albino or not. Discontinuous variations is determined by the action of a single gene present in an individual.
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There are no intermediates. Albinism - one is either an albino or not. Discontinuous variations is determined by the action of a single gene present in an individual. Structure and Properties of Chromosomes
These are threadlike structures found in the nucleus. They are normally very thin and coiled and are not easily visible unless the cell is dividing. When a cell is about to divide, the chromosomes uncoil and thicken. Their structure, number and behaviour is clearly observed during the process of cell division. The number of chromosomes is the same in all the body cells of an organism. In the body cells, the chromosomes are found in pairs. Each pair is made up of two identical chromosomes that make up a homologous pair. However sex chromosomes in human male are an exception in that the Y-chromosome is smaller. Number of Chromosomes
Diploid Number (2n)
This is the number of chromosomes found in somatic cells. For example, in human 2n = 46 or 22 pairs (44 chromosomes) are known as autosomes (body chromosomes")
while 1 pair is known as the sex chromosomes. In Drosophila melanogaster, 2n = 8. Chromosome Structure
All chromosomes are not of the same size or shape. In human beings; each of the twenty three pairs have unique size and structure . On this basis they have been numbered 1 to 23. The sex chromosomes formthe 23rd pair. Properties of Chromosomes
Chromosomes are very long and thin. They are greatly and loosely coiled and fit within the nucleus. During cell division they shorten, become thicker and are easily observable. Each consists of two chromatids. The two chromatids are held at same position along the length, at the centromere. Chromatids separate during cell division in mitosis and in the second stage of meiosis. Chromosomes take most dyes and stain darker than any other part of the cell. This property has earned them the name "chromatin material"
Each chromosome is made up of the following components:
Deoxyribonucleic acid (DNA) - this carries the genes. It is the major component of the genetic material. Protein e.g. histones. Ribonucleic acid (RNA) is present in very small amounts. Enzymes concerned with DNA and RNA replication - these are DNA and RNA polymerases and ligases.
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histones. Ribonucleic acid (RNA) is present in very small amounts. Enzymes concerned with DNA and RNA replication - these are DNA and RNA polymerases and ligases. Structure of DNA
The structure of DNA was first explained in 1953 by Watson and Crick. DNA was shown to be a double helix that coils around itself. The two strands are parallel and the distance between the two is constant. Components of DNA
DNA is made up of repeating units called nucleotides. Each nucleotide is composed of:
A five-carbon sugar (deoxyribose). Phosphate molecule. Nitrogenous base, four types are available i.e,
Adenine - (A)
Guanine - (G)
Cytosine - (C)
Thymine - (T)
The bases are represented by their initials as A, G, C and T respectively. The sugar alternates with the phosphate, and the two form the backbone of the strands. The bases combine in a specific manner, such that Adenine pairs with Thymine and Guanine pairs with Cytosine. The bases are held together by hydrogen bonds. A gene is the basic unit of inheritance consisting of a number of bases in linear sequence on the DNA. Genes exert their effect through protein synthesis. The sequence of bases that make up a gene determine the arrangement of amino acids to make a particular protein. The proteins manufactured are used to make cellular structures as well as hormones and enzymes. The types of proteins an organism manufactures determines its characteristics. For example, albinism is due to failure of the cells of an organism to synthesise the enzyme tyrosine required for the formation of the pigment melanin. First Law of Heredity
It is also known as Law of Segregation (Mendel's First Law). The characters of an organism are controlled by genes occurring in pairs known as Alleles. By definition, an allele is an alternative form of a gene controlling a particular characteristic. Of a pair of such alleles, only one is carried in each gamete. This is explained by first meiotic anaphase stage, when the homologous chromosomes are separated so that each carries one of the allelic genes. Monohybrid Inheritance
This is the study of the inheritance of one character trait that is represented by a pair of genes on homologous chromosomes. Gregor Mendel (an Austrian monk) was the first person to show the nature of inheritance.
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This is explained by first meiotic anaphase stage, when the homologous chromosomes are separated so that each carries one of the allelic genes. Monohybrid Inheritance
This is the study of the inheritance of one character trait that is represented by a pair of genes on homologous chromosomes. Gregor Mendel (an Austrian monk) was the first person to show the nature of inheritance. He did this through a series of experiments using the garden pea, Pisum sativum. As opposed to others before him, the success in his work lay in the fact that:
He chose to study first a single character at a time (monohybrid inheritance). He then proceeded to study two characters at time (dihybrid inheritance) . He quantified his results by counting the number of offspring bearing each trait. Each character he chose was expressed in two clearly contrasting forms. Examples
Stem length: some plants were tall while others were short. Colour of unripe pods: some were green, others yellow. There were no intermediates. Mendel's Procedure
For each character, Mendel chose a plant that bred true. A true or pure breed continues to show a particular trait in all the offspring in several successive generations of self-fertilisation. He made one plant to act as the female by removing the stamens before the ovary was mature and protecting (e.g. by wrapping with paper). The female plant from contact with any stray pollen. When the ovary was mature, he carefully dusted pollen from the anthers of the selected male plant and transferred it to the stigma of the female plant. Observations were then made on the resulting seeds or on the plants obtained when those seeds were planted. Results
For each pair of contrasting characters he studied, Mendel obtained the same results. For example, when he crossed pure breeding tall plants with pure breeding short plants, the first offspring, known as the first filial generation (FI) were all tall. When these were selfed i.e. self-fertilisation allowed to take place, the second generation offspring also know as the second filial generation or F2 occurred in the ratio of 3 tall: 1 short. The same ratio was obtained for each of the other characters studied. From this it is clear that one character i.e. tall is dominant over the short character. A dominant character is that which is expressed alone in the offspring even when the opposite character is represented in the genotype.
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From this it is clear that one character i.e. tall is dominant over the short character. A dominant character is that which is expressed alone in the offspring even when the opposite character is represented in the genotype. The unexpressed character is said to be recessive. From these results and others obtained when he studied two characters at the same time, Mendel concluded that gametes carry factors that are expressed in the offspring. These factors are what we know today as genes. Mendel put forward the following laws of inheritance:
Of a pair of contrasting characters, only one can be represented in a gamete. For two or more pairs of such contrasting characters, each factor (gene) in the gamete acts independently of the others and may combine randomly with either of the factors of another pair during fertilisation. Genetic experiments carried out to date confirm Mendel's Laws of inheritance e.g. T.H. Morgan's work on inheritance in the fruit fly Drosophila melanogaster. Terms used in Genetics
Genotype:
The genes present in an individual. The genetic constitution of an individual. It is expressed in alphabetical notation.e.g TT,Tt
Phenotype:
The observed character or appearance i.e. the expression of the genes in the structure and physiology of the organism. In some cases the phenotype is the product of the genotype and the environment. Phenotype is expressed in words.eg TALL,SHORT,RED WHITE .etc. Alleles:
These are alternative forms of the same gene that control a pair of contrasting characters e.g. tall and short. They are found at the same position or gene-locus on each chromosome in a homologous pair. Homozygous:
This is a state where the alleles in an individual are similar e.g. TT (for tall)
Heterozygous:
This is a state where the alleles are dissimilar i.e. each of the two genes responsible for a pair of contrasting characters are present
e.g. Tt. (T for tall; t for short)
Hybrid:
This is the offspring resulting from crossing of two individuals with contrasting characters. Hybrid vigour or Heterosis:
The hybrid develops the best characteristics from both parents
i.e. it is stronger or healthier, or yields more than either parent. Use of Symbols
To represent genes in the chromosomes, letters are used. It is customary to use a capital letter for the dominant characteristic and small letter for the recessive one.
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it is stronger or healthier, or yields more than either parent. Use of Symbols
To represent genes in the chromosomes, letters are used. It is customary to use a capital letter for the dominant characteristic and small letter for the recessive one. The gametes are encircled. For example,a cross between a tall and a short pea plant is illustrated as follows;
Let –T- represent gene for tallness. Let -t- represent gene for shortness. Fertilization-using checker board or Punnet square
F1 genotype Tt
F1 Phenotypic ratio =All tall. F2 Genotype TT,2Tt,tt
F2 Phenotypic ratio;3 Tall;1 short
Test Cross or Back Cross
This is a eras made between the F 1 bearing the dominant trait with the homozygous recessive parent. It is called a back cross because of using the first parent. It is also a test cross because it tests the genotype of the individual. Complete Dominance
Mendel happened to choose characters that showed complete dominance,
i.e. the dominant trait completely masked the recessive one in the F1 generation. In man, certain characters are inherited in the same way
e.g. colour of the skin; normal colour is dominant to albinism (lack of skin pigment). The children are all normal but have the gene for albinism. Such individuals are referred to as carriers. Other characters that show complete dominance in humans are:
Ability to roll the tongue. Polydactyly (having more than 5 digits in one limb). Brachydactyly - having short fingers. Achondroplasia - dwarf with bow legs. Incomplete Dominance
In this kind of inheritance there is no dominant or recessive gene but the two are expressed equally in the offspring,
Resulting in blending of the characters. The gene for red colour (R) in cattle and the gene for white colour(W) show incomplete dominance or co-dominance. The offspring are neither red nor write but are intermediate between the two. They are said to be roan. In humans, the sickle cell gene and the normal gene are co-dominant. Inheritance of ABO blood groups in humans
Blood groups in human are determined by three alleles, A, B, and O. An individual can have only two of these genes. Genes A and Bare codominant, while gene 0 is recessive to A and B.
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Inheritance of ABO blood groups in humans
Blood groups in human are determined by three alleles, A, B, and O. An individual can have only two of these genes. Genes A and Bare codominant, while gene 0 is recessive to A and B. These are referred to as multiple alleles. The ABO Blood Group System
Rhesus Factor
The Rhesus factor is responsible for the presence of a protein (Antigen D) in the red blood cells. If blood from a Rhesus positive (Rh+) person is transferred into a person without the Rhesus factor (Rh-);
The recipients' body produces antibodies against the Rhesus factor. This causes agglutination of red blood cells which can be fatal if subsequent transfusion with Rh+ blood is done. Sex Determination in Humans
XY type e.g. human male
In males, two types of sperms are produced. Half of then containing X chromosomes and half Y chromosomes. During fertilisation only one sperm fuses with the egg. If it is an X-carrying sperm then a female zygote is formed;
If it is a Y-carrying sperm then a male zygote is formed. It follows then that the chances of getting a boy or girl are half or fifty-fifty. Note also that it is essentially the type of sperm that fertilises the egg that determines the sex. Linkage
The term linkage describe the situation where genes or certain characters are located on the same chromosome. Offspring produced by sexual reproduction show only the parental characteristics and only sometimes few new recombinants. i.e. offspring with combinations of characteristics not found in either of the parents due to crossing over in first prophase of meiosis. Genes are said to be linked when they are located close together on the same chromosome such that they are always inherited together. Sex linked genes
These are genes that are located on the sex chromosomes. Sex-linkage - refers to carrying of the genes on the sex-chromosome. Gene for a trait may be present, yet offspring does not show the trait. This happens in human females (XX) where a gene for the trait is recessive. The female acts as a carrier. In human, sex linked characters found on the X chromosome include:
Haemophilia:
This is a disease that affects the rate of clotting of blood, leading to excessive bleeding even from a minor cut. Haemophilia is more common in males than in females.
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The female acts as a carrier. In human, sex linked characters found on the X chromosome include:
Haemophilia:
This is a disease that affects the rate of clotting of blood, leading to excessive bleeding even from a minor cut. Haemophilia is more common in males than in females. A female my have the gene for haemophilia and not show the trait because the normal gene is dominant over the gene for haemophilia. Such females are referred to as carriers. If the carrier female offspring will be carriers while the other half will be normal. Half the males will be normal and the other heamophilic. Red-green colour-blindness
Red-green colour-blindness is caused by a recessive gene found on the X chromosome. It is inherited in the same way as haemophilia. More males 1:10,000, less female 1: 100 million afflicted. It is the inability to distinguish between red and green colours in humans. Genes found on y-chromosome include:
Hairy pinna and hairy nose are carried on the Y - chromosome. Premature balding. Mutations
Mutations are sudden changes in the genotype that are inherited. Mutations are rare in nature and mutated genes are usually recessive to the normal (wild type) genes. Most mutations are generally harmful and some are lethal. A somatic mutation is a genetic change in somatic cells. Somatic mutations are only inherited if asexual reproduction takes place e.g. as in plants and unicellular animals. A gene mutation is a change in genes of reproductive cells and is always inherited. The resultant individual is called a mutant. The mutant has different characteristics from the rest of the population. Types of Mutations
Chromosomal mutations - are changes in number or structure of chromosomes. Gene mutations - also called point mutations - are changes in the chemical nature of the gene. Mutagens:
These are agents that cause mutations. The include ultra-violet light, Gamma rays., x-rays and cosmic rays. Certain chemicals e.g. mustard gas and colchicines also induce mutations. Causes and consequences of chromosomal mutations
There are three main types of chromosomal mutations. Changes in the diploid number of chromosomes (allopolyploidy). The diploid number changes to 3n (triploid) or 4n (tetraploid) and so on. This results from the doubling of the chromosome number in the gamete (2n).
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Changes in the diploid number of chromosomes (allopolyploidy). The diploid number changes to 3n (triploid) or 4n (tetraploid) and so on. This results from the doubling of the chromosome number in the gamete (2n). This is due to failure of the chromosome sets to separate during meiosis. The phenomenon is known as polyploidy. It is common in plant's and has been employed artificially to produce varieties of crops with hybrid vigour e.g. bread wheat is hexaploid (6n). This is allopolyploidy). Change in the total number of chromosomes involving the addition or loss of individual chromosomes (autopolyploidy). This is due to failure of individual chromosomes to separate during meiosis. One gamete gains an extra chromosome while the other loses a chromosome. The term non-disjunction is used to describe the failure of chromosomes to separate. Non-disjunction results in several disorders in humans:
Down's syndrome
The individual has 47 chromosomes due to non-disjunction of chromosome 21. It is also known as trisomy 21. The individual has slanted eyes with flat and rounded face, mental retardation and large tongue and weak muscles. Turner's Syndrome
This brings about to a sterile and abnormally short female. It is due to loss of one of the sex chromosomes
i.e. the individual has one X chromosome (44 + X) instead of two (44 + XX). Klinefelter's Syndrome
This results in a sterile male who may be mentally retarded. It is due to an additional X chromosome
i.e. the individual i.e. 47 chromosomes (44 + XXY) instead of 46 (44 + XY). Changes in the structure of a chromosome during meiosis. A portion of a chromosome may break off and fail to unite again or it may be joined in the wrong way or to the wrong chromosome. These mutations are described as follows:
Deletion:
This is the loss of a portion of a chromosome,
Deletion results in individuals born with missing body parts . e.g. limbs in the extreme of cases. Inversion:
A portion may break from a chromosome and then rejoin to it after turning though an angle-of 1800 . Translocation:
This is when a portion is joined to a non-homologous chromosome. Duplication:
A certain section of an intact chromosome replicates such that the genes are repeated.
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Inversion:
A portion may break from a chromosome and then rejoin to it after turning though an angle-of 1800 . Translocation:
This is when a portion is joined to a non-homologous chromosome. Duplication:
A certain section of an intact chromosome replicates such that the genes are repeated. Gene Mutations
A gene mutation is a change in the structure of a gene. It may involve only a change in one base, e.g. adenine in place of thyamine yet the effect on the individual is profound e.g. sickle cell anemia . There are two main type of gene mutations:
Due to insertion or deletion of one or more (base) pairs. Substitution of base pairs e.g. purine for pyrimidine. Genetically inherited disorders in humans
Albinism is a mutation that alters the gene responsible for synthesis of skin pigment (melanin). The gene for albinism is recessive. Sickle cell anemia is a common condition in Kenya. Individuals with the sickle-cell gene produce abnormal haemoglobin. It is due to gene mutation caused by substitution of the base adenine for thymine. The result is the inclusion of the amino acid valine (in place of glutamic acid) in the haemoglobin synthesised. As a result the red blood cells become sickle shaped when oxygen concentration becomes low i.e. inside tissues. This leads to blockage of capillaries. Tissues do not get sufficient oxygen. Homozygous individuals are seriously anaemic and die in early childhood. Heterozygous individuals have a mixed population of normal and sickled red blood cells. They are not seriously anaemic and can lead fairly normal lives. Haemophila (bleeder's diseases) is due to lack of gene for production of proteins responsible for blood clotting. Practical Applications of Genetics
Study of genetics has been put into a wide variety of uses en-compasing plants and animals and in particular humans. Blood transfusion
Blood groups are genetically determined. As discussed earlier a person of blood group A can only get blood from another one of A or O. In case of emergencies and unavailability of blood, a patient may be given blood group A + when he/she is A-. First transfusion is fine since, by the time enough antibodies are produced most of the red blood cells of donor have completed their lifespan but a subsequent transfusion of A+ blood is fatal.
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As discussed earlier a person of blood group A can only get blood from another one of A or O. In case of emergencies and unavailability of blood, a patient may be given blood group A + when he/she is A-. First transfusion is fine since, by the time enough antibodies are produced most of the red blood cells of donor have completed their lifespan but a subsequent transfusion of A+ blood is fatal. Plant and Animal breeding
Genetics is applied mostly in plant and animal breeding in order to produce varieties that are most suitable to man's needs. This is done through artificial selection. Varieties are developed that are resistant to pests, diseases or harsh climatic conditions. Genetic counselling
Genetic counselling involves advising about hereditary diseases and disorders so that they can make informed decisions. This is done through:
Taking family history. Screening for genotypes e.g. through amniocentesis. In amniocentesis, cells are obtained from amniotic fluid during pregnancy. Conditions such as Down's syndrome can be detected using microscopy. Genetic Engineering
This is a technology that involves the manipulation of the genotype of an organism to get the desired trait. It also involves the transfer of gene coding for the desired trait from one organism to another. Application of Genetic Engineering
Pharmaceutical industries:
Making of hormones e.g. Human insulin and human growth hormone. Enzymes e.g. Alph-Anti-Trypsin (AAT) used to treat emphysema. (c) Proteins. Drugs and vaccines. Agricultural industries:
Transgenic animals and plants are produced which are also called Genetically Modified Organisms (GMO's). A variety of tomato with improved paste and a longer shell life. Sheep for producing desired proteins in milk. Plants resistant to pests and diseases. Cloning
This is the making of identical copies of genes, DNA and whole organisms. Cloning is used in plants - that is tissue culture e.g. in development of various varieties of bananas and Eucalyptus trees. The first mammal to be cloned successfully was Dolly - the sheep. A nucleus from the cell obtained from the udder of the sheep was inserted in an unfertilised egg without a nucleus. This zygote was introduced into the uterus of a sheep and developed to full term. Gene therapy
Involves injecting genes into patients of certain diseases
e.g. Parkinson's diseases.
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This zygote was introduced into the uterus of a sheep and developed to full term. Gene therapy
Involves injecting genes into patients of certain diseases
e.g. Parkinson's diseases. The injected gene alters metabolism to bring about the cure of the disease. Practical Activities
To demonstrate Continuous variations
Height of students
Students should work in pairs, use chalk and metre rule to mark level of top of head onto the wall
Or door as one student stands straight without shoes, next to the wall or door. The height for each student is recorded on chalk board. The frequency distribution of height is recording as the height is grouped into various classes. A histogram to represent frequency against height is drawn. The normal bell shaped curve is observed. Discontinuous variations - ability to roll tongue
The number of students who can roll their tongue is recorded as well as the number of non-tongue rollers. The ratio of tongue-rollers to non tonguerollers is worked out. Gene for the ability to roll the tongue is dominant, therefore is expected more tongue rollers. Demonstration of Mitosis and Meisosis
Mitosis
Plasticene is used to represent number and shapes of various chromosomes e.g. 8 in Drosophila melanogaster. Each stage of mitosis illustrated e.g. interphase,
Each is rolled to appear long is and coiled, prophase is each made into a ball and then shaped to the appropriate length; and split into two to represent chromatids. Centromeres for different chromosomes can be illustrated in different positions. Each stage of mitosis is illustrated and telophase can be illustrated by surrounding the "chromosomes" with a long many drawn plasticene to represent cell membrane. It is manipulated to show how telophase takes place. Meiosis
The same procedure is followed. Plasticine with contrasting colours is used to show clearly gene mixing in crossing over. Each pair of homologous chromosomes is represented by plasticene with two different colours e.g. red (paternal) blue for maternal chromosome. All the steps in the two stages of meiosis are illustrated up to the production of four haploid gametes. Human Finger Prints
The finger prints for each student's thumb, forefinger and middle fingers of the left hand is imprinted on a white paper. A rubber stamp with ink is used to and each finger -tip phalange is rolled onto the inkpad. For best results students work in pairs.
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Human Finger Prints
The finger prints for each student's thumb, forefinger and middle fingers of the left hand is imprinted on a white paper. A rubber stamp with ink is used to and each finger -tip phalange is rolled onto the inkpad. For best results students work in pairs. Observations are made at all forefingers, thumb prints and differences noted. The main patterns are noted. It is also noted that no two, fingerprints are exactly similar. end
EVOLUTION
Meaning of Evolution and Current Concepts
Evolution is the development of organisms from pre-existing simple organisms over a long period of time. It is based on the similarities in structure and function that is observed in all organisms. All are made up of cells, and similar chemical compounds are present. This indicates that all organism may have had a common origin. Evolution seeks to explain the diversity of life and also to answer the question as to the origin of life, as well as its present state. The Origin of Life
Human beings have tried to explain how life began. Currently held views are listed below:
Special creation -life was created by a supernatural being within a particular time. Spontaneous generation life originated from non-living matter all at once. e.g. maggots arise from decaying meat. Steady state - life has no origin. Cosmozoan - life on earth originate from elsewhere, outer space. Bio-chemical evolution-life originated according to chemical and physical laws. Only special creation and chemical evolution will be discussed. Special Creation
The earliest idea is that of special creation which is recorded in the old testament (Genesis 1: 1-26). It states that God created the world and all living things in six days. Some hold the six days literally, while others say it may represent thousands of years. According to his theory, the earth and all organisms were created mature. Similarities in structure and function denote the stamp of a "common Designer"
Evidence for this view arises from observations of life itself. Faith explains it all. By faith we understand that the universe was created by the command of God. Several scientists hold this view and their research confirms accounts in the old testament of a universal flood explains the disappearance of dinosaurs as vegetation decreased.
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Faith explains it all. By faith we understand that the universe was created by the command of God. Several scientists hold this view and their research confirms accounts in the old testament of a universal flood explains the disappearance of dinosaurs as vegetation decreased. Chemical Evolution
The following is the line of thought held in this view to explain origin of life:
The composition of atmospheric gases was different from what it is today:
There was less oxygen, more carbon (IV) oxide, hence no ozone layers to filter the ultra-violet light. The high solar energy reached the earth and brought together hydrogen, carbon (IV) oxide and nitrogen to make organic compounds. These were: hydrocarbons, amino acids, nucleic acids, sugars, amino acids and proteins. The proteins coalesced and formed colloids. Proteins and lipids formed a "cell membrane" that enclosed the organic compounds, to form a primitive cell. The cell was surrounded by organic molecules that it fed on
heterotrophically. This took place in water. From this cell progressively autotrophs evolved. That were similar to blue-green algae. They produced oxygen and as more oxygen was evolved ozone layer formed an blocked ultra violet radiation. This allowed formation of present day photo-autotrophs. Evidence for Organic Evolution
Most of the evidence for evolution is indirect . i.e. it is based on studies carried out on present-day animals and plants. Direct evidence is obtained from studying the remains of animals and plants of the past. Fossil Records
The study of fossils is called paleontology. Fossils are remains of organisms that lived in ancient times. Most fossils are remains of hard parts of the body such as bones, teeth, shells and exoskeletons. Some fossils are just impressions of the body parts, e.g. footprints, leaf-vennation patterns, etc. Fossils are usually found in sedimentary rocks which have been formed by deposition of sediments over millions of years. The deeper the layer of sediments, the older the fossils found in that layer. Modem man, Homo sapiens, evolved from ape-like creatures 25 million years ago. These evolved to upright, tool using creature called Australopithecus afarensis which had a cranial capacity of 400-500 cc. This evolved through several intermediates; Homo habilis and Homo erectus to modem day human. Homo sapiens has a cranial capacity of 1350 - 1450 cc.
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These evolved to upright, tool using creature called Australopithecus afarensis which had a cranial capacity of 400-500 cc. This evolved through several intermediates; Homo habilis and Homo erectus to modem day human. Homo sapiens has a cranial capacity of 1350 - 1450 cc. Homo sapiens is more intelligent. Main features in human evolution include bipedal posture, is an omnivore and has an opposable thumb. Limitations of the Fossil Evidence
Only partial preservation was usually possible because softer parts decayed. The fossil records are therefore incomplete. Distortion - parts of organisms might have become flattened during sedimentation. Subsequent geological activities e.g. erosion, earthquakes, faulting and uplifting may have destroyed some fossils. Geographical Distribution
Until about 250 million years ago, all the land masses on earth formed a single land mass (Pangaea). This is thought to have undergone continental drift, splitting into different continents. Consequently, organisms in certain regions became geographically isolated and did not have a chance to interbreed with other organisms in other regions. Such organisms underwent evolution in isolation and have become characteristically different from organisms in other regions. For example, pouched mammals (e.g. kangaroo, wallaby, koala bear) are found almost exclusively in Australia. The opossum is the only surviving representative of the pouched mammals in North America. Comparative Embryology
During the early stages of development, the embryos of different vertebrates are almost indistinguishable. Fish, amphibian, bird and mammalian embryos have similar, features, indicating that they arose from a common ancestor. Similarities include:
Visceral clefts, segmental muscle blocks (myotomes) and a single circulation. Comparative Anatomy
Comparative anatomy is the study of organs in different species with the aim of establishing whether the organism are related. Organisms which have the same basic features are thought to have arisen from a common ancestor. The vertebrate pentadactyl limb evolved in different ways as an adaptation to different modes of life. e.g. as a flipper in whales, as a wing in bats and as a digging hand in moles. Such organs are said to be homologous, i.e. they have arisen from a common ancestor but they have assumed different functions. This is an example of divergent evolution . The wing of a butterfly and that of a bird are said to be analogous.
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they have arisen from a common ancestor but they have assumed different functions. This is an example of divergent evolution . The wing of a butterfly and that of a bird are said to be analogous. i.e. they have originated from different ancestors but they perform the same function. This is an example of convergent evolution. Cell Biology
All eucaryotic cells have organelles such as mitochondria, membrane-bound nuclei, ribosomes, golgi bodies. Thus indicating that different organisms have a common ancestor. The presence of chloroplasts and cellulose cell walls indicates that green plants have a common ancestor. Blood pigments are conjugated proteins with a metal group. Similar pigments are found in different animal groups . e.g. haemoglobin is found in all vertebrates and in annelida (earthworm). This shows that all animals have a common origin. Mechanism of Evolution
The mechanism of evolution can be described as a process of natural selection acting on the heritable variations that occur among the members of a population. A population consists of a group of individuals of the same species. Each individual has a set of hereditary factors(genes). All the genes in a population constitute a gene pool. When reproduction takes place, genes pair with one another randomly. Genes which occur in great numbers in the gene pool, will occur in greater numbers in the next generation. Several theories have been proposed over the years to explain how evolution took place. Lamark’s theory
Lamark had observed that if a part of the body of an organism was used extensively, it became enlarged and more efficient;
If a part of the body was not fully used, it would degenerate. By use and disuse of various body parts, the organism would change and acquire certain characteristics. He suggested that these characteristics would them be passed on to the offspring(next generation). In 1809, lamark published his book ‘’Theory Of Evolution’’. He proposed that new life forms arise from use and disuse of parts of existing organisms and through the inheritance of acquired characteristics. Lamark’s theory has been disapproped in that although use and disuse of parts does lead to acquired characteristics, such characteristics are not inheritable since they are effects produced by the environment and not by genes. Evolution by natural selection
In 1859, charles Darwin published his theory of evolution’ in a book called origin of species by means of natural selection’.
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He proposed that new life forms arise from use and disuse of parts of existing organisms and through the inheritance of acquired characteristics. Lamark’s theory has been disapproped in that although use and disuse of parts does lead to acquired characteristics, such characteristics are not inheritable since they are effects produced by the environment and not by genes. Evolution by natural selection
In 1859, charles Darwin published his theory of evolution’ in a book called origin of species by means of natural selection’. Darwin’s theory was based on the following evidence;the population of a given species remains constant over a long period of time. The number of young ones is more than the number of adults. More offsprings are produced than can possibly survive. Variation occurs withing a given population,i.e all members of the same species are not alike. On the basis of these observations. Darwin made the following conclusions;
There is a struggle for existence among individuals in a given population. Individuals who are not suitably adapted (e.i. who have unfavourable variations)are less able to pass their characteristics to the next generation. Natural selection operates on the population, selecting those individuals with favourable variations;
i.e. environment favours individuals that are more adapted. They win competition e.g. for food and survive.i.e. ‘’survival of the fittest’’. They attain sexual maturity and pass on the characteristics to their offsprings. Natural selection
Peppered moth (Industrial melanism)
The peppered moth, Biston betularia, exists in two distinct forms;
A speckled white form(the normal form) and the melanic, dark form. The moths normally rest on the tree trunks and branches wherre they are camouflaged against predators. The first melanic moths were observed in 1848 around Manchester in Britain. Since that time, their numbers has increased tremendously, out-numbering the speckled white form. The increase in the population of the melanic form is correlated with environmental changes brought about by industrialization and pollution. Smoke and soot from factories have darkened the tree trunks over the years. This has resulted in the preservation of the mutation in Biston betularia leading to the evolution of the melanic form. This form is almost invisible against the dark background of the tree trunks and is less subject to predation than the speckled form.
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Smoke and soot from factories have darkened the tree trunks over the years. This has resulted in the preservation of the mutation in Biston betularia leading to the evolution of the melanic form. This form is almost invisible against the dark background of the tree trunks and is less subject to predation than the speckled form. The peppered form is more abundant in areas away from the soot and smoke of factories. This is because it is well camouflaged by the lichen-covered tree trunks against which it rests and is therefore not easily detected by predators. The existence of two or more distinct forms within a species (as exemplified by Biston betularia) is called polymorphism. Resistance to Drugs
Certain strains of organisms have developed resistance to drugs and antibiotics. Following continued use of such drugs and antibiotics, some of the individuals in a population of bacteria or other microorganisms survive and are able to pass their characteristics to the next generation. When a patient fails to take full dosage of the antibiotics prescribed the pathogen develops resistance to the drugs hence become difficult to control. Some mosquitoes have developed resistance to certain pesticides. Practical Activities
Comparison of Vertebrate Limbs
Limbs of various vertebrates are provided:
e.g. fish- Tilapia, amphibian-frog reptiles, lizard; bird - domestic fowl (chicken), mammal- rabbit. Their anatomy can be studied. The following can be noted:
That all limbs have five sets of bones;
A single upper bone- the femur in hind limb and the humerus in fore limb
Two lower limb bones -i.e. the tibia & fibula in the hind limb & ulna & radius in the forelimb. Small bones - i.e. ankle (tarsals) and wrist bones (carpals)
The bones making the foot and hand are metatarsals and metacarpals respectively. The bones of toes and of fingers i.e. phalanges
Observe the various modifications of these bones in the various animals. Limbs of different mammals e.g. rabbit, cow, donkey reveal that the anatomy is adapted to mode or type of movement . e.g. the horse has a single digit. An outdoor activity to observe various sty les of movement in different mammals can be studied. It is noted that some move on tips of toes (donkey) others on the whole leg (rabbit).
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the horse has a single digit. An outdoor activity to observe various sty les of movement in different mammals can be studied. It is noted that some move on tips of toes (donkey) others on the whole leg (rabbit). Comparision of Wings of bird-and insect
Wings of birds and insects (grasshopper, butterfly or moth) are obtained. A hand lens or a dissecting microscope is used to observe the specimens. The differences in their anatomy is noted. Insect wings are membranous while those of birds are made up of feathers that interlock. Education tour to Archeological site/local Museum
Visits to the local museum yield important information that greatly supplement study of evolution. The National museum in Nairobi has many fossils. Visit to the various archeological sites that exist in Kenya is recommended. end
RECEPTION, RESPONSE AND CO-ORDINATION
IN PLANTS AND ANIMALS
Introduction
The structures involved in detecting the changes may be located far away from the ones that respond. There is need for a communication system within the body. The nervous system and the endocrine system perform this function,
i.e. linking the parts of the body that detect changes to those that respond to them. Irritability
Living organisms are capable of detecting changes in their internal and external environments and responding to these changes in appropriate ways. This characteristic is called irritability, and is of great survival value to the organism. Stimuli
A stimulus is a change in the internal or external environment to which an organism responds. Examples of stimuli include light, heat, sound, chemicals, pH, water, food, oxygen and other organisms. Response
A response is any change shown by an organism in reaction to a stimulus. The response involves movements of the whole or part of the body either towards the stimulus or away from it. It also results in secretion of substances e.g. hormones or enzymes by glands. Co-ordination
Co-ordination is the working together of all the parts of the body to bring about appropriate responses to change in the environment. Reception
Reception is the detection of changes in the environment through receptors. Irritability in Plants
Response in plants is not as pronounced as in animals. This does not in anyway diminish the importance of irritability in plants. It is as important to their survival as it is in animals. Plants respond to a variety of stimuli in their environment. These stimuli include light, moisture, gravity and chemicals.
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It is as important to their survival as it is in animals. Plants respond to a variety of stimuli in their environment. These stimuli include light, moisture, gravity and chemicals. Some plants also show response to touch. Tropisms
Plants often respond by growing in a particular direction. Such growth movements are called tropisms. They are the result of unequal growth in the part of the plant that responds. The stimulus cause unequal distribution of growth hormones (auxins) produced in the plant. One side grows more than the other resulting in a bend either towards the stimulus (positive tropism) or away from the stimulus (negative tropism). Phototropism
If seedlings are exposed to light from one direction, their shoots grow towards the light. This response is called phototropism. Shoots are said to be positively phototropic because they grow towards the light. The tip of the shoot receives the light stimulus from one direction (unilateral stimulus) but the response occurs below the tip. The response of the shoot is due to a hormone called auxin produced at the tip. It diffuses down the shoot to this zone of cell elongation where it causes the cells to elongate. Light causes auxin to migrate to the darker side. The auxin is more concentrated in the dark side than on the light side. The cells on the dark side grow faster than the ones on the light side. A growth curvature is therefore produced. Survival value:
Positive phototropism by shoots ensure that sufficient light is absorbed by leaves for photosynthesis. Geotropism
Geotropism is a growth response to gravity. Roots are positively geotropic because they grow down towards the direction of the force of gravity;
shoots are negatively geotropic because they grow away from direction of force of gravity. If a seedling is kept in the dark with its plumule and radicle in a horizontal position, the plumule will eventually grow vertically upwards while the radicle will grow vertically downwards. The effect of gravity on roots and shoots can be explained as follows:
When the seedling is placed in a horizontal position, more auxin settles on the lower side of the root and shoot due to the effect of gravity. Shoots respond to a higher concentration of auxin than roots. The lower side of the shoot grows faster than the upper side. Resulting in a growth curvature that makes the shoot grow vertically upwards. Root growth is inhibited by high concentrations of auxin.
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The lower side of the shoot grows faster than the upper side. Resulting in a growth curvature that makes the shoot grow vertically upwards. Root growth is inhibited by high concentrations of auxin. Therefore, the lower side of the root grows at a slower rate than the upper side where there is less auxin concentration. This results in a growth curvature that makes the root grow vertically downwards. Survival Value:
Roots in response to gravity grow downwards where they absorb water and get anchored in the soil. This results in absorption of nutrients needed for growth. Hydrotropism
Hydrotropism is the growth of roots towards water (moisture) . Survival Value
It ensures that plant roots grow towards moisture to obtain water needed for photosynthesis and transport of mineral salts. Chemotropism
Chemotropism is the response of parts of a plant towards chemical substances,
e.g. the growth of the pollen tube towards the ovule in flowering plants is a chemotropic response. Survival Value
This ensures that fertilisation take place and the perpetuation of the species continues. Thigmotropism
Thigmotropism is a growth response to touch. e.g. tendrils of climbing plant bend around objects that they come in contact with. Survival Value
This provides support and the leaves stay in a position suitable for absorption of light and gaseous exchange for photosynthesis. Tactic Movements in Plants and other Organisms
A tactic movement is one made by a whole organism or a motile part of an organisms (e.g. a gamete) in response to a stimulus. Tactic movements are named according to the nature of the stimulus that brings about the response. Phototaxis is movement in response to direction and intensity of light. Free-swimming algae such as Chlamydomonas usually tend to concentrate where light intensity is optimum and will respond to light by swimming towards it. This is an example of phototactic response. Osmotaxis is movement in response to changes in osmotic conditions e.g. freshwater amoeba. Survival Value
Ensures favourable conditions for existence. Chemotaxis is movement in response to concentration of chemical substances. Survival Value
In bryophytes, antherozoids move towards archegonia to effect fertilisation
Survival Value of taxis:
These ensure conditions favourable for life bring maximum benefit to the organism.
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Survival Value
Ensures favourable conditions for existence. Chemotaxis is movement in response to concentration of chemical substances. Survival Value
In bryophytes, antherozoids move towards archegonia to effect fertilisation
Survival Value of taxis:
These ensure conditions favourable for life bring maximum benefit to the organism. Nastic Movements
A nastic movement is one made by part of a plant in response to stimulus which is not coming from any particular direction. Nastic movements are also named according to the nature of the stimulus. Seismonasty/haptonasty - response to shock. The 'sensitive plant' Mimosa pudica responds to touch by folding up its leaves. This is an example of a seismonastic response. Production of auxins and their effects on plant growth
Auxins are produced by plant apices, i.e. root apex and shoot apex. They bring about cell elongation resulting in growth. They are diffusible substances which effect growth when in very small amounts. Roots require lower concentrations than shoots. The effect of auxins on the growth of roots and shoots has already been discussed. Auxins also exert other effects on plant growth and development. There are various other chemical substances which have been shown to influence plant growth and development. Effects of Auxin on Plant Growth
Apical Dominance
Auxins inhibit the growth of side branches. This is referred to as apical dominance. If the terminal bud is removed, side branches develop from the lateral buds. This knowledge is applied in pruning. As long as the main stem is allowed to remain intact, the development of side branches is suppressed. Pruning the terminal bud removes the main sources of auxin, thus allowing side branches to sprout. Growth of adventitious roots
Adventitious roots develop from the stem. Auxins stimulate the growth of such roots. Parthenocarpy
This refers to the formation of fruits without fertilisation. This can be induced by treating unpollinated flowers with auxin. This phenomenon is applied in the development of seedless fruit varieties. Auxins, together with other plant hormones, are involved in secondary growth, falling of leaves and ripening of fruits. Reception, Responses and Coordination in Animals
The nervous and endocrine systems (together known as the neuro-endocrine system) act as a co-ordinating system. They linking the receptors to the effectors and regulating their activities. Receptors
Receptors are cells that detect or receive stimuli.
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Reception, Responses and Coordination in Animals
The nervous and endocrine systems (together known as the neuro-endocrine system) act as a co-ordinating system. They linking the receptors to the effectors and regulating their activities. Receptors
Receptors are cells that detect or receive stimuli. They may be scattered more uniformly all over the body surface
e.g. receptors for pain, touch, temperature; or they may be located in a special sense organ e.g. receptors for light, sound, taste and smell. Motor nerves link the Central Nervous System (CNS) to the effectors. Its cell body is located at one end of the axon. It transmits nerve impulses from the CNS to the effectors. Effectors
These are the cells, organs, or organelles which enable the organism to respond. They include muscles, glands, cilia and flagella. The Nervous System
Components of the nervous system in humans
Every organ is the human body is connected to nerves. The nervous system is made up of nerve cells (neurons) which transmit impulses from one part of the body to another. It consists of the following:
The Central Nervous System (CNS) is a concentrated mass of interconnected nerve cells which make up the brain and the spinal cord. The peripheral nervous system is made up of nerves which link the CNS to the receptors and the effectors. Sensory nerves link the sensory cells (receptors) to the central nervous system and transmit nerve impulses from a sense organ to the CNS. Structure and Functions of Neurons
A nerve cell consists of a cell body (centron) where the nucleus is located, and projections called dendrites arise. One of the projections is drawn out into an axon i.e. the longest process. Each axon contains axoplasm which is continuous with the cytoplasm in the cell body. The axon is enclosed in a fatty myelin sheath which is secreted by Schwarm cell. The myelin sheath is interrupted at approximately 1 mm intervals by constrictions known as nodes of Ranvier. The myelin sheath is enclosed by a thin membrane called the neurilemma, which is part of the Schwann cell in contact with axon. The myelin sheath and nodes of Ranvier enhance transmission of the impulse. There are three types of neurons:
Sensory neurone
Also known as afferent neurone.
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The myelin sheath is enclosed by a thin membrane called the neurilemma, which is part of the Schwann cell in contact with axon. The myelin sheath and nodes of Ranvier enhance transmission of the impulse. There are three types of neurons:
Sensory neurone
Also known as afferent neurone. Transmits impulses from sensory cells to the CNS. The cell body of a sensory nerve cell is located at some distance along the length of the axon outside the CNS. Motor neurone
Known as efferent or effector neurone
Transmit impulses from the CNS to the effectors(muscles and glands)
Its cell body is located inside the CNS. Intermediate or connector neurone
Also called relay neurone
Found inside the CNS. The connect sensory and motor neurons with each other and with other nerve cells in the CNS. Functions of the neurone
The nerve impulse is electrical in nature. Its transmission depends on differences in electrical potential between the inside and the outside of the axion. The outside is positive while the inside is negative. The stimulus triggers a change that affects the permeability of neurone membrane. The result is a change in the composition of ions on either side of the membrane. The outside becomes negative as the inside becomes positive due to sodium ions rushing in. The above constitutes a nervous impulse which is transmitted along the sensory neurone to the CNS. The speed of transmission is very high. Certain mammalian axions transmit impulses at the rate of 100m/s. The dendrites of neurons do not connect directly to each other, but they leave a small gap called synapse. The transmission of an impulse from one cell to the next takes place through synapse. Synaptic knobs are structures found at the ends of dendrites. Thus the dendrites of one nerve cell make contact with the dendrites of the adjacent nerve cell through the synapses. Impulses are transmitted in the form of a chemical transmitter substance which crosses the gap between one dendrite and the next. The transmitter substance is found within synaptic vesicles. The chemical substance is either acetylcholine or noradrnaline. The synaptic vesicles burst and release the transmitter substance when an impulse arrives at the synaptic knob. Impulses in motor neurone s are trans mitted to effectors. The space between motor end dendrite and muscle is known as neuro-muscular Junction. Synaptic vesicles in the ends of the dendrites release the transmitter substance across the neural muscular junction.
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Impulses in motor neurone s are trans mitted to effectors. The space between motor end dendrite and muscle is known as neuro-muscular Junction. Synaptic vesicles in the ends of the dendrites release the transmitter substance across the neural muscular junction. Functions of Major Parts of the Human Brain
The Central Nervous System (CNS) consists of the brain and the spinal cord. The CNS co-ordinates body activities by receiving impulses from sensory cells from different parts of the body. It then sends the impulses to the appropriate effectors. The brain is enclosed within the cranium or braincase. It is covered and protected by membranes known as meninges. When meninges are infected by bacterial or fungi they cause meningitis. The brain consist of the following parts:
Cerebrum. This is the largest part of the brain. It consists of two cerebral hemispheres. It is highly folded in order to increase the surface area. The cerebrum controls learning, intelligence, thought, imagination and reasoning. The medulla oblongata (brain stem). The medulla oblongata has centres which control breathing (ventilation) rate,
heart beat rate (cardiac frequency),
swallowing, salivation, blood pressure
temperature regulation, hearing, taste and touch. The cerebellum
Is located in front of the medulla and is a folded dorsal expansion of the hindbrain. It controls posture movement and balance. The hypothalamus
Controls functions such as body temperature and osmoregulation. The pituitary gland
Is an endocrine organ that secretes a number of hormones which control osmoregulation, growth, metabolism and sexual development. Optic lobes -control the sense of sight. Olfactory lobes -control the sense of smell. Spinal Cord
The spinal cord is located within the vertebral column and consist of the following:
The grey matter forms the central part of the spinal cord. It consists of nervecell bodies and intermediate nerve fibres. The white matter of the spinal cord carries sensory nerve fibers while the ventral root carries motor nerve fibers. Simple And Conditioned Reflex Actions
Simple Reflex Action
A simple reflex action is an automatic response to a stimulus. The route that is followed by impulses during a reflex action is called a reflex arc. A reflex action follows the following sequence:
A receptor is stimulated and an impulse is transmitted along a sensory nerve fibre to the spinal cord.
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Simple And Conditioned Reflex Actions
Simple Reflex Action
A simple reflex action is an automatic response to a stimulus. The route that is followed by impulses during a reflex action is called a reflex arc. A reflex action follows the following sequence:
A receptor is stimulated and an impulse is transmitted along a sensory nerve fibre to the spinal cord. The impulse is picked up by an intermediate neurone within the CNS. The intermediate nerve fibre transmit the impulse to a motor nerve fibre which is connected to an effector. The effector responds. Examples of reflex action include:
Pulling the hand away from a hot object. The knee jerk. Sneezing. Conditioned Reflexes
These are learned responses. When two or more stimuli are presented to an animal at the same time and repeatedly, the animal eventually responds to either stimulus. For example, if a hungry animal is presented with food, it will respond by salivating. If a bell is rung at the same time as the food is presented to the animal, the animal will learn to associate the sound of the bell with food. Eventually, the animal can be made to salivate at the sound of the bell alone. This response is called conditioned reflex and is one of the ways by which animals learn. The Role of Endocrine System in Human Beings
Endocrine system consists of glands that secrete hormones. The glands have no ducts and are known as endocrine glands. Other glands are known as exocrine glands because they have ducts. The pancreas has an outer exocrine portion and an inner endocrine portion. Hormones are chemical substances, protein in nature which are secreted at one part of the body and have effects on other parts not necessarily near the point of secretion. They are secreted directly into blood and transported by blood. Each hormone either has a generalised co-ordinating effect on the body or brings about a specific response in a particular target organ. Hormones produced in humans and the in effects on the body. Adrenaline
Enhance activity of sympathetic nervous system. Over secretion
Increased heartbeat
High blood pressure
Thin toneless muscles. Under secretion
Low blood pressure
Inability to withstand stress
Muscular weakness
Thyroxine
Over secretion is termed hyperthyroidism this causes:
Increased Basal Metabolic Rate (BMR) hence increased temperature. Person becomes very angry, nervous and hands may shake. Increased heartbeat which lead to cardiac failure.
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Under secretion
Low blood pressure
Inability to withstand stress
Muscular weakness
Thyroxine
Over secretion is termed hyperthyroidism this causes:
Increased Basal Metabolic Rate (BMR) hence increased temperature. Person becomes very angry, nervous and hands may shake. Increased heartbeat which lead to cardiac failure. Under secretion is termed hypothyroidism:
Poor growth and mental retardation (cretinism). Reduced metabolic rate hence decreased temperature. Person becomes inactive and slothful. Eyes and face become puffy as fluid gets stored under skin. In extreme cases the tongue is swollen and skin becomes rough. Enlarged thyroid gland. Comparison between endocrine and nervous system
Similarities
Both endocrine and nervous system are involved in the coordination of body functions. Both have target organs. Both are controlled via a negative feedback mechanism, i.e too high production results in a reduced production. Effects of drugs abuse on the human health. Drug abuse can be defined as misuse of drugs. Drugs are chemical compounds that affect the working of body or kill disease causing microorganisms. Prescription drugs
Are drugs prescribed by a doctor. Prescribed drugs can be abused through taking overdose which may cause death. Over the counter drugs(OCD)
Are self prescribed drugs. These have harmful effects and may lead to tolerance such that higher doses are needed. Below is a list of effects of hard drugs on human health
Lung cancer caused by nicotine. Emphysema. Liver cirrhosis -caused by alcohol. Interferes with vision - alcohol. Sterility - khat (rniraa). Sleeplessness - insomnia - khat (miraa). Hallucinations - Canabis sativa (Bang i). Digestive system is upset, nausea. Diarrhoea and vomiting. Headache and double vision. Skin tone changes - e.g. too dark. Appetite is extreme - very poor or very great. Weight loss. Personality changes e.g. irritable and confused. Convulsions, lethargy and depressions due to inhalation of solvents e.g. glue. Structure and Function of Parts of the Human Eye
Structure
The human eye is spherical in shape and situated within a socket or orbit in the skull. It is attached to the skull by three pairs of muscle, which also control its movement. It is made up of three main layers; sclerotic layer, choroid and the light sensitive retina.
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Structure and Function of Parts of the Human Eye
Structure
The human eye is spherical in shape and situated within a socket or orbit in the skull. It is attached to the skull by three pairs of muscle, which also control its movement. It is made up of three main layers; sclerotic layer, choroid and the light sensitive retina. Sclerotic layer
Outermost white part situated at the sides and back of the eye. Made up of collagen fibres. It protects the eye and gives its shape. Cornea
This is the transparent front part of the sclera that allows light to pass through. It is curved, bulging at the front. It thus reflects light rays hence helps to focus light rays onto the retina. Choroid
The second or middle layer. It has many blood vessels that supply nutrients to the eye and remove metabolic wastes from the eye. It has dark pigments to absorb stray light and prevent its reflection inside the eye. Ciliary body
Is glandular and secretes aqueous humour. It has blood vessels for supplying of nutrients excretion and gaseous exchange. It has ciliary muscles - which contract and relax to change the shape of lens during accommodation. Suspensory ligaments
Are inelastic and attach the lens onto the cilliary body holding it in position. Lens
Biconvex in shape, to refract light. Crystalline and transparent to allow light to pass through and focus it on to the retina. Aqueous humour
Found between lens and the cornea. Transparent to allow light to pass through it. It is watery thus helping in focusing. Helps maintain shape of eye ball. To convey nutrients and oxygen to cornea, and remove waste products. Iris
The coloured part of the eye has an opening - the pupil at the centre. Iris has circular and radial muscles which controls size of the pupil, hence the amount of light entering the eye through the pupil. Vitreous humour
It is a fluid. Found between lens and retina. Is viscous and gives eye the shape. It is transparent and refracts light. Retina
Retina contains light sensitive cells and is situated at the back of the eye. There are two types of light sensitive cells in the retina:
Rods - are sensitive to low-intensity light and detect black and white. Nocturnal mammals have more rods. Cones - are sensitive to high intensity of light;
They detect bright colour.
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There are two types of light sensitive cells in the retina:
Rods - are sensitive to low-intensity light and detect black and white. Nocturnal mammals have more rods. Cones - are sensitive to high intensity of light;
They detect bright colour. Diurnal mammals have more cones. Fovea centralis
Fovea centralis (yellow spot) is the most sensitive part of the retina. Consists mainly of cones for accurate vision (visual acuity). Optic nerve
Optic nerve, has neurons for transmission of impulse to the brain for interpretation. Blind spot
Blind spot is located at the point where the optic nerve leaves the eye on its way to the brain. It is not sensitive to light it has no rods or cones. Eye lid
Eye lid is a loose skin that covers the eye. It closes by reflex action. Protects it from mechanical damage and from too much light. Eyelashes
Prevent dust and other particles from entering eye. Conjuctiva
It is transparent and thin and allows light to pass through. It is a tough layer that is continuous with the epithelium of the eye lids. It protects the cornea. Accommodation
Accommodation refers to the change in the shape of the lens in order to focus images. Rays from a distant object would be focused at a point behind the retina if the lens were not adjusted appropriately. When the eye is focusing at a distant object, the cilliary muscles are relaxed and the suspensory ligament are stretched tight. The lens is pulled thin, thus allowing light rays from a distant object to be properly focused on to the retina. When the eye is looking at near object, the ciliary muscles contract and the suspensory ligament become slack. The lens becomes more convex. This allows light rays from near object to be focused onto the retina. Control of light intensity entering the eye
In bright light (high intensity) the circular muscles of the iris contract. The diameter of the pupil decreases and less light enters. This protects retina from damage by too much light. In dim light circular muscles of iris relax (radial ones contract). Pupil's size (diameter) increases, more light enters the eye. Image formation and Interpretation
Light rays from an object enter the cornea and are directed onto the lens through the pupil. They are refracted by the cornea and the lens. The latter brings the rays into fine focus.
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Image formation and Interpretation
Light rays from an object enter the cornea and are directed onto the lens through the pupil. They are refracted by the cornea and the lens. The latter brings the rays into fine focus. It makes the light rays converge so that an image is focused at a point on the retina. The image on the retina is inverted. This stimulate, the rods and cones on the retina and impulses generated are transmitted through the optic nerve to the brain. The brain interprets the image as upright. Common Eye Defects and their Correction
Short-sightedness (Myopia)
A shortsighted person cannot focus distant objects properly. Light rays from a distant object fall at a point in front of the retina. This may be due to the eyeball being too long. This defect can be corrected using spectacles with concave lenses. The lenses make the light rays diverge before they reach the eye. Long-sightedness (Hypermetropia)
A long-sighted person cannot focus near objects properly. Light rays from the object are not focused on the retina. This may be due to the eyeball being too short. This defect may be corrected by using spectacles with convex lenses which make light rays converge before they reach the eye. Astigmatism
Astigmatism refers to a condition in which the cornea or the lens is uneven, so that images are not focused properly on the retina. This defect can be corrected by wearing spectacles with special cylindrical lenses. Presbyopia is a condition in which light rays from a near object are not focused on the retina. This is caused by hardening or loss of elasticity of lense due to old age. This defect is corrected by wearing convex (converging) lenses. Structure and Functions of Parts of Human Ear
The Mammalian Ear
The mammalian ear performs two major functions:
hearing and detecting changes in the positions of the body to bring about balance and posture. The ear is divided into three sections. The Outer Ear
This consists of:
An outer flap, the pinna which is made up of cartilage. The function of the pinna is to catch and direct sounds. The external auditory canal is a tube through which sound travel. The lining of the tube secretes wax, which traps dust particles and microorganisms. The tympanum is a membrane stretching across the inner end of the external auditory canal. The tympanum vibrates when it is hit by sound waves.
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The lining of the tube secretes wax, which traps dust particles and microorganisms. The tympanum is a membrane stretching across the inner end of the external auditory canal. The tympanum vibrates when it is hit by sound waves. The Middle Ear
This is a chamber containing three small bones called the ear ossic1es, the malleus, incus and stapes. The three ossic1es articulate with one another to amplify vibrations. The vibrations are transmitted from the tympanum to the oval window. At the end of the chamber is a membrane called the oval window. When the tympanum vibrates, it causes the ear ossic1es to move forwards and backwards. This causes the oval window to vibrate. The Eustachian tube connects the middle ear to the pharynx. It allows air to get in and out of the middle ear, thus equalising the pressure between the inside and the outside of the tympanum. The Inner Ear
This consists of a series of chambers filled with fluid. It comprises the cochlea and semicircular canals. Cochlea is a coiled tube that occupies a small space and accommodates a large number of sensory cells. The cells are connected to the brain through the auditory nerve. They detect vibrations which lead to hearing. Hearing
The sound waves set the tympanum vibrating and are transformed into vibrations. The vibrations are transmitted to the oval window by the three ossicles. Vibrations of the oval window cause the fluids inside the cochlea tube to vibrate. The membranes inside the cochlea have sensory cells which change the sound vibrations to nerve impulses. These are transmitted to the brain through the auditory nerve. Hearing is perceived in the brain. Balance and posture
The semi-circular canals
There are three semi-circular canals in each ear. They are situated at right angles to each other and each one is sensitive to movement in a different plane. They are filled with fluid and each has a swelling called the ampulla at one end. Inside the ampulla are sensory cells. Balance and posture are detected by these cells. Movement of the head in a given direction causes the fluid to move the hairs on sensory cells. This transmit impulses to the brain through the auditory nerve so that the movement is registered. Defects of the ear
Acute labyrinthitis
This is an inflammation of the middle ear and cochlea. It may lead to deafness.
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This transmit impulses to the brain through the auditory nerve so that the movement is registered. Defects of the ear
Acute labyrinthitis
This is an inflammation of the middle ear and cochlea. It may lead to deafness. It can be treated by using certain drugs but sometimes an operation may be necessary. Tinnitis:
This is a sensation of noises in the ear. It is caused among others by accumulation of wax in the ear or use of certain drugs e.g. quinine. Treatment is by removal of wax, stopping use of the causative drug. Vertigo - Giddiness
This is disorientation of body in space - one of the causes is dilation of endolymph. Corrections: Use of appropriate drugs. Deafness. This is inability to hear. It is presented in various degrees in various individuals, some have partial hearing, others are completely deaf. This may be as a result of:
Chronic infection of cochlea. Lack of sensory cells. Excess wax in external auditory canal. Fusion of ear ossicles. Otitis Media
This is the inflammation of middle ear due to build-up of fluid. It is marked by the swelling of tissues surrounding the Eustachian tube due to infection or severe congestion. A strong negative pressure creates a vacuum in the middle ear. Treatment - use of antibiotics or surgery. Practical Activities
To investigate tactic response
Tactic response in fly maggots are investigated using choice chambers(s). Responses to various stimuli are observed e.g. to chemical substances - chemotaxis. On one side of choice chambers is placed beef/fish that has been dried in the sun. On the opposite chambers is placed rotting meat/fish. Ten maggots are placed at the center and choice chamber is covered. After 10 minutes the number of maggots at each end is counted. Most of the maggots have moved to the chamber with rotting meat. Tropisms
Maize or been seeds are soaked and germinated, to the stage when radical and coleoptile/plumule just appear . (about 5 days for beans and seven days for maize). Seedlings with straight radic1es and plumules are used .. Geotropism
The seedlings are placed horizontally on the medium (Soil or vermiculite or saw dust or sand). Observations are done after three days and results recorded.
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Seedlings with straight radic1es and plumules are used .. Geotropism
The seedlings are placed horizontally on the medium (Soil or vermiculite or saw dust or sand). Observations are done after three days and results recorded. Phototropism
A potted plant or a young seedling planted in a beaker is kept next to a window which is the only source of light in the laboratory. Alternatively, a dark box may be used. Observations are made after 3-5 days and results recorded. The shoots grow bending towards the same light. Etiolation
Young seedlings are placed in a dark box. It is kept moist but not exposed to light. After two weeks the seedlings are removed and observations made to note the following:
Colour of leaves is yellow. Size of leaves is small
Length of internodes is long
Length of stem elongated long and thin. Other seedlings that were grown in light are observed (as control) and similar measurements taken. They are green in colour with larger leaves, shorter internodes and the stem is shorter and thicker. Those in the dark have smaller yellow leaves, long thing stems with long internodes. (etiolated). Experiment to Determine Distance of the Blind Spot
Students should work in pairs so that one takes measurements while the other observes. A cross and a dot are marked on a white paper . The two points are 6-9 cm apart. The paper is held 50 cm away from the face. Closing the left eye, the paper is slowly moved towards the face as the right eye is fixed on the cross. At 50 cm distance the cross and the dot are seen clearly. As-the paper is moved closer to the face, the dot disappears. The distance at which the dot disappears is measured. This is the distance of the blind spot. When the light rays from the dot are focused on the blind spot it disappears hence the dot is not seen. The Knee Jerk Experiment
Students work in pairs, one student sits on the table, high stool or bench with one leg crossed over the other. The other student chops the crossed knee just below the knee cap with the edge of palm or wooden ruler. It is observed that the crossed knee jerks. This is a spinal reflex. END
Support and Movement in Plants and Animals
Necessity for support and movement
Movement is a characteristic of all living organisms. It enables animals and plants to adjust to their environment.
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This is a spinal reflex. END
Support and Movement in Plants and Animals
Necessity for support and movement
Movement is a characteristic of all living organisms. It enables animals and plants to adjust to their environment. Most animals move from place to place but some are sessile (i.e. fixed to the substratum). Majority of plants move only certain parts. However, though not easily observed all living protoplasm shows movement of one type or another. Necessity for support and movement in plants
They enable plants to be held upright to trap maximum light for photosynthesis and gaseous exchange. To hold flowers and fruits in appropriate position for pollination and dispersal respectively. To enable plants to grow to great heights and withstand forces of environment e.g. strong winds. Movement of male gametes to effect fertilisation and ensure perpetuation of a species. Plant parts move in response to certain stimuli in the environment of tropisms. Tissue distribution in Monocotyledonous and Dicotyledonous plants
Vascular bundles are the main support tissues in plants. In monocotyledonous stem they are scattered all over the stem. while in dicotyledonous stem they are found in a ring or rings. In monocots the xylem and phloem alternate around with pith in the centre. In dicots of the xylem forms a star in the centre - there is no pith. Phloem is found in between the arms of xylem. Dicotyledonous plants have cambium which brings about secondary growth resulting in thickening of the stem and root hence providing support. Secondary xylem becomes wood, providing more support to the plant. Role of support tissues in young and old plant
Plants are held upright by strengthening tissues ;
parenchyma,
collenchyma,
sclerenchyma
xylem tissue. Parenchyma and collenchyma are the main support tissues in young plants. Parenchyma –
They are found below the epidermis. They form the bulk of packing tissue within the plant between other tissues . They are tightly packed and turgid they provide support. Collenchyma –
Their cell walls have additional cellulose deposited in the corners. This provides them with extra mechanical strength. Sclerenchyma –
Their cells are dead due to large deposits of lignin on the primary cell wall.
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Collenchyma –
Their cell walls have additional cellulose deposited in the corners. This provides them with extra mechanical strength. Sclerenchyma –
Their cells are dead due to large deposits of lignin on the primary cell wall. The lignified wall is thick and inner lumen is small, hence provide support. Sclerenchyma fibres are arranged in elongated and in longitudinal sheets giving extra support. They are found in mature plants. Xylem –
Has two types of specialised cells. Vessels and tracheids. Vessels are thick-walled tubes with lignin deposited in them. They give support and strength to the plant. Tracheids are spindle-shaped cells arranged with ends overlapping. Their walls are lignified. They help to support and strengthen the plant. Plants with weak stems obtain their support in the following ways. Some use thorn or spines to adhere to other plants or objects. Some have twinning stems which grow around objects which they come into contact with. Others use tendrils for support. Tendrils are parts of a stem or leaf that have become modified for twinning around objects when they gain support. In passion fruit and pumpkin, parts of lateral branches are modified to form tendrils. In the morning glory, the leaf is modified into a tendril. Support and Movement in Animals
Necessity for support and movement in animals. Animals move from place to place:
In search of food. To escape from predators. To escape from hostile environment. To look for mates and breeding grounds. The skeleton, which is a support structure helps to maintain the shape of the body. Movement is effected by action of muscles that are attached to the skeleton. Types and Functions of Skeletons
Two main types will be considered. These are exoskeleton and endoskeleton. Exoskeleton
Exoskeleton is hard outer covering of arthropods made up of mainly chitin. Which is secreted by epidermal cells and hardens on secretion. It is strengthened by addition of other substances e.g. tannins and proteins to become hard and rigid. On the joints such as those in the legs the exoskeleton is thin and flexible to allow for movement. Functions of Exoskeleton
Provide support. Attachment of muscles for movement. Protection of delicate organs and tissues. Prevention of water loss. Endoskeleton:
It forms an internal body framework. This is a type of skeleton characteristic of all vertebrates.
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Prevention of water loss. Endoskeleton:
It forms an internal body framework. This is a type of skeleton characteristic of all vertebrates. The endoskeleton is made of cartilage, bone or both. It is made up of living tissues and grows steadily as animal grows. Muscles are attached on the skeleton. The muscles are connected to bones by ligaments. Functions
The functions of endoskeleton include support, protection and movement. Locomotion in a finned fish e.g. tilapia. Most of the fishes are streamlined and have backward directed fins to reduce resistance due to water. External features-of Tilapia
Scales tapers towards the back and overlap forwards to provide a smooth surface for a streamlined body. The head is not flexible. This helps the fish to maintain forward thrust. Slimy mucous enables the fish to escape predators and protects the scales from getting wet. The pectoral and pelvic fins are used mainly for steering, ensuring that the fish is balanced. They assist the fish to change direction. The dorsal and anal fins keep the fish upright preventing it from rolling sideways. The caudal or tail fin has a large surface area, and displaces a lot of water when moved sideways creating forward movement of the fish. In order to change position in water the fish uses the swim bladder. When filled with air the relative density of the body is lowered and the fish moves up in the water. When air is expelled, the relative density rises and the fish sinks to a lower level. Swimming action in fish is brought about by contraction of muscle blocks (myotomes). These muscles are antagonistic when those on the left contract, those on the right relax. The muscles are attached to the transverse processes on the vertebra. The vertebra are flexible to allow sideways movement. Mammalian skeleton
The mammalian skeleton is divided into two:
Axial and appendicular. Axial skeleton is made up of the skull and the vertebral column. Appendicular skeleton is made up of the pelvic and pectoral girdles and limbs (hind limb and forelimbs). The Axial Skeleton
This consists of the ;
skull,
the sternum,
ribs,
the vertebral column. The Skull
The skull is made up of cranium and facial bones. The cranium; encloses and protects the brain. It is made up of many bones joined together by immovable joints. The facial bones consists of the upper and lower jaws.
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The cranium; encloses and protects the brain. It is made up of many bones joined together by immovable joints. The facial bones consists of the upper and lower jaws. At the posterior end of the cranium are two smooth rounded protuberances, the occipital condyles. These condyles articulate with the atlas vertebra to form a hinge joint, which permits the nodding of the head. Sternum and ribs –
They form the rib-cage. The rib-cage encloses the thoracic cavity protecting delicate organs such as the heart and lungs. The ribs articulate with the vertebral column at the back and the sternum at the front. The Vertebral Column
The vertebral column is made up of bones called vertebrae placed end to end. The vertebrae articulate with one another at the articulating facets. In between one vertebra and another is the cartilaginous material called intervertebal disc. The discs act as shock absorbers and allow for slight movement. Each vertebra consists of a centrum and a neural arch which projects into a neural spine. The neural canal is the cavity enclosed by the centrum and the neural arch. The spinal cord is located inside the canal. The neural spine and other projections e.g. transverse processes serve as points of attachment of muscles. Type and number of vertebrae in human and rabbit
Cervical Vertebrae
These are found in the neck region of a mammal. The distinguishing feature is a pair of verte-braterial canals in the neural arch, through which the blood vessels of the neck pass. Another feature is the structure of the transverse processes. They are flattened out and are known as cervical ribs. The fIrst cervical vertebra is known as the Atlas. It has a large neural canal and no centrum. The second cervical vertebra, is called axis. The other five cervical vertebrae have no specific names. They have the same structure. The cervical vertebrae possess numerous processes for muscle attachment. Thoracic Vertebrae
Each thoracic vertebra has a large centrum ,a large neural canal, neural arch and a long neural spine that projects upwards and backward. There is a pair of prezygapophyses and postzygapophyses for articulation with other vertebra . They have a pair of short transverse process. The thoracic vertebra also articulates with pair of ribs at tubercular and capitular facets.
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There is a pair of prezygapophyses and postzygapophyses for articulation with other vertebra . They have a pair of short transverse process. The thoracic vertebra also articulates with pair of ribs at tubercular and capitular facets. Lumbar Vertebrae
Each lumbar vertebra has a large, thick centrum for support of the body. It has a neural spine that projects upwards and forwards. There is a pair of large transverse process that are directed forwards. Above the prezygapophyses lies a pair of processes called metapophyses,
Below postzygapophyses lies the anapophyses. Metapophyses and anapophysis serve for attachment pf muscles of the abdomen. In some mammals, there may be another process on lower side of centrum called hypapophysis also for muscle attachment. Sacral Vertebrae
The sacral vertebrae are fused together to form a rigid bony structure, the sacrum. The centrum of each vertebra is large, but the neural canal is narrow. The neural spine is reduced to a small notch. The transverse processes of the first sacral vertebra are large and wing-like
They are firmly attached to the upper part of the pelvic girdle. Caudal Vertebrae
Human beings have only four of these vertebrae which are fused together to form coccyx. Animals with long tails have many caudal vertebrae. A typical caudal vertebra appears as a solid rectangular mass of bone. The entire bone consists of the centrum only. Appendicular Skeleton
The appendicular skeleton consist of the limbs and their girdles. Bones of Fore-limbs
Pectoral girdle
Pectoral girdle is made of scapula, coracoid and clavicle. A cavity known as glenoid cavity occurs at the apex of the scapula. The humerus of the fore limb fits into this cavity. The clavice is a curved bone connecting the scapular to the sternum. Humerus
Humerus is found in the upper arm. It articulates with the scapula at the glenoid cavity of the pectoral girdle and forms a ball and socket joint. Ulna and radius
These are two bones found in the forearm.
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Humerus
Humerus is found in the upper arm. It articulates with the scapula at the glenoid cavity of the pectoral girdle and forms a ball and socket joint. Ulna and radius
These are two bones found in the forearm. The ulna has a projection called olecranon process and a sigmoid notch which articulates with the humerus. Bones of hind limb
Pelvic Girdle
The pelvic girdle consists of two halves fused at the pubic symphysis. Each half is made up of three fused bones:
the ilium,
ischium
pubis. Each half has cup-shaped cavity for the acetabulum for articulation with the head of the femur. Between the ischium and pubis is an opening obturator foramen where spinal nerves, blood vessels and a tough inflexible connective tissues pass. The ilium, ischium and pubis are fused to form the innominate bone. The Femur
The femur is the long bone joining the pelvic girdle and the knee. The head of the femur articulates with acetabulum forming the ball and socket joint at the hip. The femur has a long shaft. At the distal end it has condyles that articulate with the tibia to form a hinge joint at the knee. The patella covers the knee joint and prevents the upward movement of the lower leg. Tibia and Fibula
The tibia is a large bone, and the fibula a smaller bone is fused to it on the distal part. In humans the tibia and fibula are clearly distinguishable. Joints and Movement
Ajoint is a connection between two or more bones. Joints provide articulation between bones making movement possible. However some joints do not allow any movement e.g. the joints, between bones of the skull. Movable joints are of three main types:
Gliding joint
e.g., joints which occur between the vertebrae wrists and ankles. The ends of the bones that make the joint are covered with cartilage. The bones are held together by tough ligaments. Synovial joint
The joint is enclosed by fibrous capsule lined by synovial membrane which secretes synovial fluid into the synovial cavity. The synovial fluid lubricates the joint. They are called synovial joints. They include hinge joint and ball and socket joint. Hinge joint
e.g.
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They are called synovial joints. They include hinge joint and ball and socket joint. Hinge joint
e.g. knee joint. The joint allows movement in one plane. Ball and socket joint. e.g., hip joint. The joint allows rotation in all directions. Types, Locations and Function of Muscles
There are three types of muscles, located at various parts of the body. In order to function all use energy in form of ATP. These include smooth, skeletal and cardiac muscles. Smooth Muscle (Involuntary Muscles)
These are spindle-shaped and contain filaments with myofibrils. Each muscle is bound by plasma membrane. They are found lining internal organs such as alimentary canal, bladder, and blood vessels. They are controlled by involuntary part of the nervous system. They are concerned with movement of materials along the organs and tubes. They contract slowly and fatigue slowly . Skeletal Muscle (striated or voluntary muscle)
Skeletal muscles are striated and have several nuclei. They are long fibres each containing myofibrils and many mitochondria. They have cross-striations or stripes. They are also called voluntary muscles because the contraction is controlled by voluntary nervous system. They are surrounded by connective tissue and are attached to bones by tendons. Their contraction brings about movement of bone, resulting in locomotion. They contract quickly and fatigue quickly. Cardiac Muscle
Consist of a network of striated muscle fibres connected by bridges. Are short cells with numerous mitochondria and uninucleate. They are found exclusively in the heart. Contractions of cardiac muscles are generated from within the muscles and are rhythmic and continuous hence they are myogenic. They do not tire or fatigue. The rate can be modified by involuntary nervous system. Their contractions result in the heart pumping blood. Role of muscles in movement of the human arm
Muscles that bring about movement are antagonistic, i.e. when one set contracts the other relaxes. Antagonistic muscles of human forelimb
The biceps muscles of the forelimb act as flexors while the triceps muscles act as extensors. The biceps has its point of origin on the scapula and the point of insertion on the radius. The triceps has its points of origin on the scapula and humerus and is inserted on the ulna. When the muscles contract, the limb acts as a lever with the pivot at the joint.
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The biceps has its point of origin on the scapula and the point of insertion on the radius. The triceps has its points of origin on the scapula and humerus and is inserted on the ulna. When the muscles contract, the limb acts as a lever with the pivot at the joint. Contraction of biceps muscles bends (flexes) the arm while contractions of triceps extends the arm. Practical Activities
To observe prepared slides of transverse section of stems of herbaceous and woody plants. Permanent slides of transverse sections of:
Herbaceous plant and Woody plant are obtained. The permanent slide of a herbaceous plant is placed onto the stage of the microscope. Observations under the low power and medium power objective is made. A plan diagram is drawn and labelled. The permanent slide of a woody plant is placed on the stage of the microscope. Observations under the low power and medium power objectives are made. A plan diagram is drawn and labelled. In both cases, support tissues such as parenchyma, collenchyma, sc1erenchyma and xylem are observed. To observe wilting in young herbaceous plants. A herbaceous potted plant e.g. bean plant is obtained. The plant is placed on the bench near a window and left for 3 days without watering on the third and subsequent day. The shoot droops due to fall in turgor pressure; caused by water loss. To examine the exoskeleton in an arthropod. Obtain a beetle and observe the external structure. The exoskeleton is on the outer surface with muscles attached on inner side. The exoskeleton is hardened by chitin. Movement is due to joints on the limbs. Also examine various shed cocoons of insects e.g., butterfly. To observe the external features of a finned fish. Fresh Tilapia is obtained and placed on a tray. Observations are made on the external features of the fish. A labelled drawing is made. Features like scales, fins a streamlined body and an operculum are seen. Opened operculum reveals the gills. To examine bones of the axial skeleton of a rabbit. Bones of the vertebra column are obtained. These are cervical, thoracic, lumbar and sacral. For each of the bones the distinguishing features are listed down. Labelled drawings of the anterior and lateral views is made. To observe bones of appendicular skeleton.
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For each of the bones the distinguishing features are listed down.
Labelled drawings of the anterior and lateral views is made.
To observe bones of appendicular skeleton.
Bones of pectoral girdle and fore limb are obtained i.e., scapula, humerus, ulna and radius.
Labelled drawing of each bone is made.
Observations on how the bones articulate with one another is made.
Bones of pelvic girdle and hind limbs are obtained i.e., pelvic girdle, femur, tibia and fibula.
Labelled drawings of each, bone is made.
The distinguishing features of each bone is noted.
Observations on how the bones articulate with one another is made.
END
BEST WISHES
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FORM THREE BIOLOGY
By the end of form three work, the learner should be able to:
Classify common organisms into their main taxonomic units
Write scientific names of organisms correctly
List the kingdoms of organisms
Describe the general characteristics of Kingdom monera
Describe the general characteristics of Kingdom protoctista
Observe, draw and name parts of spirogyra, amoeba, paramecium and euglena
Describe the general characteristics of Kingdom fungi
List down all the members of kingdom fungi
Draw and name parts of bread mold (mucor), yeast and mushrooms
Describe the main characteristics of kingdom plantae
Describe the main characteristics of bryophyta
Identify examples of hyophyta
Observe draw and name parts of liverworts and moss plants
Identify examples of pleridophyta
Observe draw and name parts of fern plant
Identify examples of division spermatophyta
Identify major sub-division of spermatophyta
List main characteristics of angiospermae
Differentiate between angiospermae and gymnospermae
State the characteristics of angiospermapyta
Identify and state major characteristics of classes of angiospermapytaegdicotyledonae&monocotyledonoe
describe the general characteristics of kingdom animalia
describe the general characteristics of Phylum arthropoda
list down the classes of the Phylum arthropoda
describe the general characteristics of Class crustacean
describe the general characteristics of Class insect
describe the general characteristics of Class arachnida
list down the members of class arachnida and insect
Describe the general characteristics of Classeschilopoda and diplopoda
List down the members of class chilopoda and diplopoda
Describe the general characteristics of Phylum chordate
describe the general characteristics of Pisces and amphibian
describe the general characteristics of reptilian
describe the general characteristics of Class aves
Describe the general characteristics of Class Mammalia
Identify different types of members of Class Mammalia
Construct a simple dichotomous to identify given organisms
Use an already constructed dichotomous key to identify given organisms
Use an already constructed dichotomous key to identify given organisms
draw and label organisms correctly
Define the term ecology and identify terms used in ecology
Define the term ecology and identify terms used in ecology
Identify the types of ecosystems
State and explain how light determines distribution of organisms in an ecosystem
Identify and describe how temperature determines distribution of organisms in an ecosystem
Identify and describe how Rainfall and humidity determines distribution of organisms in an ecosystem
describe how Wind and atmospheric pressure determines distribution of organisms in an ecosystem
Write down correct answers to questions asked in the test
describe how salinity affects the distribution of organisms in aquatic ecosystems
describe how waves, currents and tides affects the distribution of organisms in aquatic ecosystem
Describe how Edaphic factors affects the distribution of organisms in an ecosystem
Measure certain factors in samples of different soils
Describe how Geological factors affect the distribution of organisms in an ecosystem
Describe how Abiotic factors affect the distribution of organisms in an ecosystem
Describe how competition affects the distribution of organisms in an ecosystem
Describe how Predation and Symbiosis affects the distribution of organisms in an ecosystem
Differentiate between Parasitism and saprophytism
Describe how Parasitism and saprophytism influence the distribution of organisms in an ecosystem e.g.
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FORM THREE BIOLOGY
By the end of form three work, the learner should be able to:
Classify common organisms into their main taxonomic units
Write scientific names of organisms correctly
List the kingdoms of organisms
Describe the general characteristics of Kingdom monera
Describe the general characteristics of Kingdom protoctista
Observe, draw and name parts of spirogyra, amoeba, paramecium and euglena
Describe the general characteristics of Kingdom fungi
List down all the members of kingdom fungi
Draw and name parts of bread mold (mucor), yeast and mushrooms
Describe the main characteristics of kingdom plantae
Describe the main characteristics of bryophyta
Identify examples of hyophyta
Observe draw and name parts of liverworts and moss plants
Identify examples of pleridophyta
Observe draw and name parts of fern plant
Identify examples of division spermatophyta
Identify major sub-division of spermatophyta
List main characteristics of angiospermae
Differentiate between angiospermae and gymnospermae
State the characteristics of angiospermapyta
Identify and state major characteristics of classes of angiospermapytaegdicotyledonae&monocotyledonoe
describe the general characteristics of kingdom animalia
describe the general characteristics of Phylum arthropoda
list down the classes of the Phylum arthropoda
describe the general characteristics of Class crustacean
describe the general characteristics of Class insect
describe the general characteristics of Class arachnida
list down the members of class arachnida and insect
Describe the general characteristics of Classeschilopoda and diplopoda
List down the members of class chilopoda and diplopoda
Describe the general characteristics of Phylum chordate
describe the general characteristics of Pisces and amphibian
describe the general characteristics of reptilian
describe the general characteristics of Class aves
Describe the general characteristics of Class Mammalia
Identify different types of members of Class Mammalia
Construct a simple dichotomous to identify given organisms
Use an already constructed dichotomous key to identify given organisms
Use an already constructed dichotomous key to identify given organisms
draw and label organisms correctly
Define the term ecology and identify terms used in ecology
Define the term ecology and identify terms used in ecology
Identify the types of ecosystems
State and explain how light determines distribution of organisms in an ecosystem
Identify and describe how temperature determines distribution of organisms in an ecosystem
Identify and describe how Rainfall and humidity determines distribution of organisms in an ecosystem
describe how Wind and atmospheric pressure determines distribution of organisms in an ecosystem
Write down correct answers to questions asked in the test
describe how salinity affects the distribution of organisms in aquatic ecosystems
describe how waves, currents and tides affects the distribution of organisms in aquatic ecosystem
Describe how Edaphic factors affects the distribution of organisms in an ecosystem
Measure certain factors in samples of different soils
Describe how Geological factors affect the distribution of organisms in an ecosystem
Describe how Abiotic factors affect the distribution of organisms in an ecosystem
Describe how competition affects the distribution of organisms in an ecosystem
Describe how Predation and Symbiosis affects the distribution of organisms in an ecosystem
Differentiate between Parasitism and saprophytism
Describe how Parasitism and saprophytism influence the distribution of organisms in an ecosystem e.g. Tick and cattle
Describe the interaction between organisms in an ecosystem
Describe the role of decomposers in Nitrogen cycle & carbon cycle
Define the terms food chain and food web
Construct food chains and food webs
Describe energy flow in a local ecosystem and Construct food chains and food webs
Define population
List down the characteristics of population
Explain the use of quadrants and transects as methods of Population estimation
Explain the capture –recapture method of population estimation
Use quadrant method to estimate population of named organisms within the compound
Describe total count, aerial count and aerial photography and other methods of population estimation
Relate to the adaptations of xerophytes to their habitats
Relate to the adaptations of mesophytes to their habitats
Relate to the adaptations of hydrophytes to their habitats
Observe, draw and label parts of named hydrophytes, mesophytes and xerophyte plants
Relate to the adaptations of halophytes to their habitats
Explain pollution and give examples of pollutants
Describe the various air pollutants
Discuss the effects of air pollution on the environment
Suggest methods of controlling air pollution
Describe various causes of Land/ soil pollution
Discuss the effects of Land/ soil pollution and human health in rural and urban centers
Suggest methods of controlling Land/ soil pollution
Describe the causes of Water pollution
Identify other causes of environmental pollution in rural and urban centers
Discuss the effects of water pollution on human health in rural and urban centers and other organisms
Suggest methods of controlling water pollution
Identify symptoms of cholera and typhoid fever
State methods of transmission
Suggest control measures
Identify the causes, symptoms and methods of transmission and control of malaria
Identify the causes, symptoms and methods of transmission of amoebic dysentery
Suggest control methods of amoebic dysentery
Identify the causes, symptoms and methods of transmission of ascariosis
Identify the causes, symptoms and methods of transmission and control of schistomiasis
Define reproduction and state its importance
Differentiate between asexual and sexual reproduction
Describe the appearance and location of chromosomes
Define mitosis
Describe chromosomicmovement during mitosis
Describe e the movement of chromosomes in mitosis
Identify stages of mitosis
Identify and describe stages of mitosis
State the significance of mitosis in reproduction
Define meiosis
State the stages of meiosis
Describe the chromosome movement during meiosis
Observe the stages of meiosis
Describe the movement of chromosomes during meiosis
State the significance of meiosis in reproduction
Differentiate between mitosis and meiosis
State and describe the importance of Binary fission
Observe spore formation in bread mould (mucor) and binary fission in paramecium
State and describing the importance of budding in reproduction
Observing drawing and budding cells of yeast
Describe the external structure of a typical flower
Describe the internal structure of a typical flower
Observe, describe and draw different types of pollen grains
Describe the structure of ovules
Describe other characteristics of flowers
Describe and compare adaptations of wind and insect pollinated flowers
Describe the features and mechanisms that hinder self-pollination and self-fertilization
Describe the process of fertilization in flowering plants
Describe and explain how embryo and seeds are formed in flowering plants
Describe how fruits are formed in flowering plants
Differentiate between a fruit and a seed
Describe and explain how different seeds and fruits are dispersed
Classifying various types of fruits and describe their placentation
Differentiate between internal and external fertilization
Describe external fertilization in amphibians
Relate the structure of mammalian male reproductive system to its functions
Relate the structure of mammalian male reproductive organ and spermatozoa to its function
Relate the structure of mammalian female reproductive system to its function
Relate the structure of mammalian ovum to its function
Describe internal fertilization in mammals
Describe the fertilization process
Describe implantation and the role of the placenta in mammals
Define gestation in mammals
Identify different gestation periods in different mammals
Describe birth and explain parental care
Describe the role of hormones in reproduction of humans
Describe the role of hormones in the menstrual cycle
Identify symptoms and explain the methods of transmission and prevention of gonorrhea and herpes simplex
Identify symptoms and explain the methods of transmission and prevention of syphilis and trichomoniasis
Identify symptoms and explain the methods of transmission and prevention of candidiasis and hepatitis
Identify the causes and modes of transmission of HIV/AIDS and prevention of HIV and AIDS
Identify effects of HIV/AIDS in human economy
Identify the symptoms of HIV/AIDS and stages of HIV and AIDS
Explain ways of preventing and controlling the spread of HIV/AIDS
Discuss the social effects of HIV/AIDS
Explain the advantages and disadvantages of sexual and asexual reproduction
Define the terms growth and development
Describe the sigmoid growth curve
Describe the phases of sigmoid curve
Describe the intermittent growth curve
Analyze data on growth rate
Draw growth curves
Define seed dormancy
Identify factors affecting viability and dormancy of seeds
Identify factors affecting seed dormancy
Define seed germination
Differentiate between types of seed germination
Identifying Conditions necessary for germination - oxygen
Investigate the necessity of water and warmth
Describe the region of growth in seedlings
Identify the regions of growth
Determine the regions of growth in seedlings
Measure the aspect of growth in a given seedling
Describe growth in plants I.e.
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FORM THREE BIOLOGY
By the end of form three work, the learner should be able to:
Classify common organisms into their main taxonomic units
Write scientific names of organisms correctly
List the kingdoms of organisms
Describe the general characteristics of Kingdom monera
Describe the general characteristics of Kingdom protoctista
Observe, draw and name parts of spirogyra, amoeba, paramecium and euglena
Describe the general characteristics of Kingdom fungi
List down all the members of kingdom fungi
Draw and name parts of bread mold (mucor), yeast and mushrooms
Describe the main characteristics of kingdom plantae
Describe the main characteristics of bryophyta
Identify examples of hyophyta
Observe draw and name parts of liverworts and moss plants
Identify examples of pleridophyta
Observe draw and name parts of fern plant
Identify examples of division spermatophyta
Identify major sub-division of spermatophyta
List main characteristics of angiospermae
Differentiate between angiospermae and gymnospermae
State the characteristics of angiospermapyta
Identify and state major characteristics of classes of angiospermapytaegdicotyledonae&monocotyledonoe
describe the general characteristics of kingdom animalia
describe the general characteristics of Phylum arthropoda
list down the classes of the Phylum arthropoda
describe the general characteristics of Class crustacean
describe the general characteristics of Class insect
describe the general characteristics of Class arachnida
list down the members of class arachnida and insect
Describe the general characteristics of Classeschilopoda and diplopoda
List down the members of class chilopoda and diplopoda
Describe the general characteristics of Phylum chordate
describe the general characteristics of Pisces and amphibian
describe the general characteristics of reptilian
describe the general characteristics of Class aves
Describe the general characteristics of Class Mammalia
Identify different types of members of Class Mammalia
Construct a simple dichotomous to identify given organisms
Use an already constructed dichotomous key to identify given organisms
Use an already constructed dichotomous key to identify given organisms
draw and label organisms correctly
Define the term ecology and identify terms used in ecology
Define the term ecology and identify terms used in ecology
Identify the types of ecosystems
State and explain how light determines distribution of organisms in an ecosystem
Identify and describe how temperature determines distribution of organisms in an ecosystem
Identify and describe how Rainfall and humidity determines distribution of organisms in an ecosystem
describe how Wind and atmospheric pressure determines distribution of organisms in an ecosystem
Write down correct answers to questions asked in the test
describe how salinity affects the distribution of organisms in aquatic ecosystems
describe how waves, currents and tides affects the distribution of organisms in aquatic ecosystem
Describe how Edaphic factors affects the distribution of organisms in an ecosystem
Measure certain factors in samples of different soils
Describe how Geological factors affect the distribution of organisms in an ecosystem
Describe how Abiotic factors affect the distribution of organisms in an ecosystem
Describe how competition affects the distribution of organisms in an ecosystem
Describe how Predation and Symbiosis affects the distribution of organisms in an ecosystem
Differentiate between Parasitism and saprophytism
Describe how Parasitism and saprophytism influence the distribution of organisms in an ecosystem e.g. Tick and cattle
Describe the interaction between organisms in an ecosystem
Describe the role of decomposers in Nitrogen cycle & carbon cycle
Define the terms food chain and food web
Construct food chains and food webs
Describe energy flow in a local ecosystem and Construct food chains and food webs
Define population
List down the characteristics of population
Explain the use of quadrants and transects as methods of Population estimation
Explain the capture –recapture method of population estimation
Use quadrant method to estimate population of named organisms within the compound
Describe total count, aerial count and aerial photography and other methods of population estimation
Relate to the adaptations of xerophytes to their habitats
Relate to the adaptations of mesophytes to their habitats
Relate to the adaptations of hydrophytes to their habitats
Observe, draw and label parts of named hydrophytes, mesophytes and xerophyte plants
Relate to the adaptations of halophytes to their habitats
Explain pollution and give examples of pollutants
Describe the various air pollutants
Discuss the effects of air pollution on the environment
Suggest methods of controlling air pollution
Describe various causes of Land/ soil pollution
Discuss the effects of Land/ soil pollution and human health in rural and urban centers
Suggest methods of controlling Land/ soil pollution
Describe the causes of Water pollution
Identify other causes of environmental pollution in rural and urban centers
Discuss the effects of water pollution on human health in rural and urban centers and other organisms
Suggest methods of controlling water pollution
Identify symptoms of cholera and typhoid fever
State methods of transmission
Suggest control measures
Identify the causes, symptoms and methods of transmission and control of malaria
Identify the causes, symptoms and methods of transmission of amoebic dysentery
Suggest control methods of amoebic dysentery
Identify the causes, symptoms and methods of transmission of ascariosis
Identify the causes, symptoms and methods of transmission and control of schistomiasis
Define reproduction and state its importance
Differentiate between asexual and sexual reproduction
Describe the appearance and location of chromosomes
Define mitosis
Describe chromosomicmovement during mitosis
Describe e the movement of chromosomes in mitosis
Identify stages of mitosis
Identify and describe stages of mitosis
State the significance of mitosis in reproduction
Define meiosis
State the stages of meiosis
Describe the chromosome movement during meiosis
Observe the stages of meiosis
Describe the movement of chromosomes during meiosis
State the significance of meiosis in reproduction
Differentiate between mitosis and meiosis
State and describe the importance of Binary fission
Observe spore formation in bread mould (mucor) and binary fission in paramecium
State and describing the importance of budding in reproduction
Observing drawing and budding cells of yeast
Describe the external structure of a typical flower
Describe the internal structure of a typical flower
Observe, describe and draw different types of pollen grains
Describe the structure of ovules
Describe other characteristics of flowers
Describe and compare adaptations of wind and insect pollinated flowers
Describe the features and mechanisms that hinder self-pollination and self-fertilization
Describe the process of fertilization in flowering plants
Describe and explain how embryo and seeds are formed in flowering plants
Describe how fruits are formed in flowering plants
Differentiate between a fruit and a seed
Describe and explain how different seeds and fruits are dispersed
Classifying various types of fruits and describe their placentation
Differentiate between internal and external fertilization
Describe external fertilization in amphibians
Relate the structure of mammalian male reproductive system to its functions
Relate the structure of mammalian male reproductive organ and spermatozoa to its function
Relate the structure of mammalian female reproductive system to its function
Relate the structure of mammalian ovum to its function
Describe internal fertilization in mammals
Describe the fertilization process
Describe implantation and the role of the placenta in mammals
Define gestation in mammals
Identify different gestation periods in different mammals
Describe birth and explain parental care
Describe the role of hormones in reproduction of humans
Describe the role of hormones in the menstrual cycle
Identify symptoms and explain the methods of transmission and prevention of gonorrhea and herpes simplex
Identify symptoms and explain the methods of transmission and prevention of syphilis and trichomoniasis
Identify symptoms and explain the methods of transmission and prevention of candidiasis and hepatitis
Identify the causes and modes of transmission of HIV/AIDS and prevention of HIV and AIDS
Identify effects of HIV/AIDS in human economy
Identify the symptoms of HIV/AIDS and stages of HIV and AIDS
Explain ways of preventing and controlling the spread of HIV/AIDS
Discuss the social effects of HIV/AIDS
Explain the advantages and disadvantages of sexual and asexual reproduction
Define the terms growth and development
Describe the sigmoid growth curve
Describe the phases of sigmoid curve
Describe the intermittent growth curve
Analyze data on growth rate
Draw growth curves
Define seed dormancy
Identify factors affecting viability and dormancy of seeds
Identify factors affecting seed dormancy
Define seed germination
Differentiate between types of seed germination
Identifying Conditions necessary for germination - oxygen
Investigate the necessity of water and warmth
Describe the region of growth in seedlings
Identify the regions of growth
Determine the regions of growth in seedlings
Measure the aspect of growth in a given seedling
Describe growth in plants I.e. Primary and secondary growths
investigate primary and secondary growth in a seedling
Explain the role of hormones in regulation of growth and development in plants
Explain Apical dominance in plants
Define metamorphosis
Distinguish between complete and incomplete metamorphosis
Describe complete metamorphosis in housefly and anopheles mosquito
Describe incomplete metamorphosis in a cockroach
Describe and explain the Role of growth hormones in metamorphosis in insects
Observe metamorphosis in some insects
Classification II
General Principles of Classification
Classification is the science that puts organisms into distinct groups to make their study easy and systematic.
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FORM THREE BIOLOGY
By the end of form three work, the learner should be able to:
Classify common organisms into their main taxonomic units
Write scientific names of organisms correctly
List the kingdoms of organisms
Describe the general characteristics of Kingdom monera
Describe the general characteristics of Kingdom protoctista
Observe, draw and name parts of spirogyra, amoeba, paramecium and euglena
Describe the general characteristics of Kingdom fungi
List down all the members of kingdom fungi
Draw and name parts of bread mold (mucor), yeast and mushrooms
Describe the main characteristics of kingdom plantae
Describe the main characteristics of bryophyta
Identify examples of hyophyta
Observe draw and name parts of liverworts and moss plants
Identify examples of pleridophyta
Observe draw and name parts of fern plant
Identify examples of division spermatophyta
Identify major sub-division of spermatophyta
List main characteristics of angiospermae
Differentiate between angiospermae and gymnospermae
State the characteristics of angiospermapyta
Identify and state major characteristics of classes of angiospermapytaegdicotyledonae&monocotyledonoe
describe the general characteristics of kingdom animalia
describe the general characteristics of Phylum arthropoda
list down the classes of the Phylum arthropoda
describe the general characteristics of Class crustacean
describe the general characteristics of Class insect
describe the general characteristics of Class arachnida
list down the members of class arachnida and insect
Describe the general characteristics of Classeschilopoda and diplopoda
List down the members of class chilopoda and diplopoda
Describe the general characteristics of Phylum chordate
describe the general characteristics of Pisces and amphibian
describe the general characteristics of reptilian
describe the general characteristics of Class aves
Describe the general characteristics of Class Mammalia
Identify different types of members of Class Mammalia
Construct a simple dichotomous to identify given organisms
Use an already constructed dichotomous key to identify given organisms
Use an already constructed dichotomous key to identify given organisms
draw and label organisms correctly
Define the term ecology and identify terms used in ecology
Define the term ecology and identify terms used in ecology
Identify the types of ecosystems
State and explain how light determines distribution of organisms in an ecosystem
Identify and describe how temperature determines distribution of organisms in an ecosystem
Identify and describe how Rainfall and humidity determines distribution of organisms in an ecosystem
describe how Wind and atmospheric pressure determines distribution of organisms in an ecosystem
Write down correct answers to questions asked in the test
describe how salinity affects the distribution of organisms in aquatic ecosystems
describe how waves, currents and tides affects the distribution of organisms in aquatic ecosystem
Describe how Edaphic factors affects the distribution of organisms in an ecosystem
Measure certain factors in samples of different soils
Describe how Geological factors affect the distribution of organisms in an ecosystem
Describe how Abiotic factors affect the distribution of organisms in an ecosystem
Describe how competition affects the distribution of organisms in an ecosystem
Describe how Predation and Symbiosis affects the distribution of organisms in an ecosystem
Differentiate between Parasitism and saprophytism
Describe how Parasitism and saprophytism influence the distribution of organisms in an ecosystem e.g. Tick and cattle
Describe the interaction between organisms in an ecosystem
Describe the role of decomposers in Nitrogen cycle & carbon cycle
Define the terms food chain and food web
Construct food chains and food webs
Describe energy flow in a local ecosystem and Construct food chains and food webs
Define population
List down the characteristics of population
Explain the use of quadrants and transects as methods of Population estimation
Explain the capture –recapture method of population estimation
Use quadrant method to estimate population of named organisms within the compound
Describe total count, aerial count and aerial photography and other methods of population estimation
Relate to the adaptations of xerophytes to their habitats
Relate to the adaptations of mesophytes to their habitats
Relate to the adaptations of hydrophytes to their habitats
Observe, draw and label parts of named hydrophytes, mesophytes and xerophyte plants
Relate to the adaptations of halophytes to their habitats
Explain pollution and give examples of pollutants
Describe the various air pollutants
Discuss the effects of air pollution on the environment
Suggest methods of controlling air pollution
Describe various causes of Land/ soil pollution
Discuss the effects of Land/ soil pollution and human health in rural and urban centers
Suggest methods of controlling Land/ soil pollution
Describe the causes of Water pollution
Identify other causes of environmental pollution in rural and urban centers
Discuss the effects of water pollution on human health in rural and urban centers and other organisms
Suggest methods of controlling water pollution
Identify symptoms of cholera and typhoid fever
State methods of transmission
Suggest control measures
Identify the causes, symptoms and methods of transmission and control of malaria
Identify the causes, symptoms and methods of transmission of amoebic dysentery
Suggest control methods of amoebic dysentery
Identify the causes, symptoms and methods of transmission of ascariosis
Identify the causes, symptoms and methods of transmission and control of schistomiasis
Define reproduction and state its importance
Differentiate between asexual and sexual reproduction
Describe the appearance and location of chromosomes
Define mitosis
Describe chromosomicmovement during mitosis
Describe e the movement of chromosomes in mitosis
Identify stages of mitosis
Identify and describe stages of mitosis
State the significance of mitosis in reproduction
Define meiosis
State the stages of meiosis
Describe the chromosome movement during meiosis
Observe the stages of meiosis
Describe the movement of chromosomes during meiosis
State the significance of meiosis in reproduction
Differentiate between mitosis and meiosis
State and describe the importance of Binary fission
Observe spore formation in bread mould (mucor) and binary fission in paramecium
State and describing the importance of budding in reproduction
Observing drawing and budding cells of yeast
Describe the external structure of a typical flower
Describe the internal structure of a typical flower
Observe, describe and draw different types of pollen grains
Describe the structure of ovules
Describe other characteristics of flowers
Describe and compare adaptations of wind and insect pollinated flowers
Describe the features and mechanisms that hinder self-pollination and self-fertilization
Describe the process of fertilization in flowering plants
Describe and explain how embryo and seeds are formed in flowering plants
Describe how fruits are formed in flowering plants
Differentiate between a fruit and a seed
Describe and explain how different seeds and fruits are dispersed
Classifying various types of fruits and describe their placentation
Differentiate between internal and external fertilization
Describe external fertilization in amphibians
Relate the structure of mammalian male reproductive system to its functions
Relate the structure of mammalian male reproductive organ and spermatozoa to its function
Relate the structure of mammalian female reproductive system to its function
Relate the structure of mammalian ovum to its function
Describe internal fertilization in mammals
Describe the fertilization process
Describe implantation and the role of the placenta in mammals
Define gestation in mammals
Identify different gestation periods in different mammals
Describe birth and explain parental care
Describe the role of hormones in reproduction of humans
Describe the role of hormones in the menstrual cycle
Identify symptoms and explain the methods of transmission and prevention of gonorrhea and herpes simplex
Identify symptoms and explain the methods of transmission and prevention of syphilis and trichomoniasis
Identify symptoms and explain the methods of transmission and prevention of candidiasis and hepatitis
Identify the causes and modes of transmission of HIV/AIDS and prevention of HIV and AIDS
Identify effects of HIV/AIDS in human economy
Identify the symptoms of HIV/AIDS and stages of HIV and AIDS
Explain ways of preventing and controlling the spread of HIV/AIDS
Discuss the social effects of HIV/AIDS
Explain the advantages and disadvantages of sexual and asexual reproduction
Define the terms growth and development
Describe the sigmoid growth curve
Describe the phases of sigmoid curve
Describe the intermittent growth curve
Analyze data on growth rate
Draw growth curves
Define seed dormancy
Identify factors affecting viability and dormancy of seeds
Identify factors affecting seed dormancy
Define seed germination
Differentiate between types of seed germination
Identifying Conditions necessary for germination - oxygen
Investigate the necessity of water and warmth
Describe the region of growth in seedlings
Identify the regions of growth
Determine the regions of growth in seedlings
Measure the aspect of growth in a given seedling
Describe growth in plants I.e. Primary and secondary growths
investigate primary and secondary growth in a seedling
Explain the role of hormones in regulation of growth and development in plants
Explain Apical dominance in plants
Define metamorphosis
Distinguish between complete and incomplete metamorphosis
Describe complete metamorphosis in housefly and anopheles mosquito
Describe incomplete metamorphosis in a cockroach
Describe and explain the Role of growth hormones in metamorphosis in insects
Observe metamorphosis in some insects
Classification II
General Principles of Classification
Classification is the science that puts organisms into distinct groups to make their study easy and systematic. Modern scientific classification is based on structure and functions.
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Tick and cattle
Describe the interaction between organisms in an ecosystem
Describe the role of decomposers in Nitrogen cycle & carbon cycle
Define the terms food chain and food web
Construct food chains and food webs
Describe energy flow in a local ecosystem and Construct food chains and food webs
Define population
List down the characteristics of population
Explain the use of quadrants and transects as methods of Population estimation
Explain the capture –recapture method of population estimation
Use quadrant method to estimate population of named organisms within the compound
Describe total count, aerial count and aerial photography and other methods of population estimation
Relate to the adaptations of xerophytes to their habitats
Relate to the adaptations of mesophytes to their habitats
Relate to the adaptations of hydrophytes to their habitats
Observe, draw and label parts of named hydrophytes, mesophytes and xerophyte plants
Relate to the adaptations of halophytes to their habitats
Explain pollution and give examples of pollutants
Describe the various air pollutants
Discuss the effects of air pollution on the environment
Suggest methods of controlling air pollution
Describe various causes of Land/ soil pollution
Discuss the effects of Land/ soil pollution and human health in rural and urban centers
Suggest methods of controlling Land/ soil pollution
Describe the causes of Water pollution
Identify other causes of environmental pollution in rural and urban centers
Discuss the effects of water pollution on human health in rural and urban centers and other organisms
Suggest methods of controlling water pollution
Identify symptoms of cholera and typhoid fever
State methods of transmission
Suggest control measures
Identify the causes, symptoms and methods of transmission and control of malaria
Identify the causes, symptoms and methods of transmission of amoebic dysentery
Suggest control methods of amoebic dysentery
Identify the causes, symptoms and methods of transmission of ascariosis
Identify the causes, symptoms and methods of transmission and control of schistomiasis
Define reproduction and state its importance
Differentiate between asexual and sexual reproduction
Describe the appearance and location of chromosomes
Define mitosis
Describe chromosomicmovement during mitosis
Describe e the movement of chromosomes in mitosis
Identify stages of mitosis
Identify and describe stages of mitosis
State the significance of mitosis in reproduction
Define meiosis
State the stages of meiosis
Describe the chromosome movement during meiosis
Observe the stages of meiosis
Describe the movement of chromosomes during meiosis
State the significance of meiosis in reproduction
Differentiate between mitosis and meiosis
State and describe the importance of Binary fission
Observe spore formation in bread mould (mucor) and binary fission in paramecium
State and describing the importance of budding in reproduction
Observing drawing and budding cells of yeast
Describe the external structure of a typical flower
Describe the internal structure of a typical flower
Observe, describe and draw different types of pollen grains
Describe the structure of ovules
Describe other characteristics of flowers
Describe and compare adaptations of wind and insect pollinated flowers
Describe the features and mechanisms that hinder self-pollination and self-fertilization
Describe the process of fertilization in flowering plants
Describe and explain how embryo and seeds are formed in flowering plants
Describe how fruits are formed in flowering plants
Differentiate between a fruit and a seed
Describe and explain how different seeds and fruits are dispersed
Classifying various types of fruits and describe their placentation
Differentiate between internal and external fertilization
Describe external fertilization in amphibians
Relate the structure of mammalian male reproductive system to its functions
Relate the structure of mammalian male reproductive organ and spermatozoa to its function
Relate the structure of mammalian female reproductive system to its function
Relate the structure of mammalian ovum to its function
Describe internal fertilization in mammals
Describe the fertilization process
Describe implantation and the role of the placenta in mammals
Define gestation in mammals
Identify different gestation periods in different mammals
Describe birth and explain parental care
Describe the role of hormones in reproduction of humans
Describe the role of hormones in the menstrual cycle
Identify symptoms and explain the methods of transmission and prevention of gonorrhea and herpes simplex
Identify symptoms and explain the methods of transmission and prevention of syphilis and trichomoniasis
Identify symptoms and explain the methods of transmission and prevention of candidiasis and hepatitis
Identify the causes and modes of transmission of HIV/AIDS and prevention of HIV and AIDS
Identify effects of HIV/AIDS in human economy
Identify the symptoms of HIV/AIDS and stages of HIV and AIDS
Explain ways of preventing and controlling the spread of HIV/AIDS
Discuss the social effects of HIV/AIDS
Explain the advantages and disadvantages of sexual and asexual reproduction
Define the terms growth and development
Describe the sigmoid growth curve
Describe the phases of sigmoid curve
Describe the intermittent growth curve
Analyze data on growth rate
Draw growth curves
Define seed dormancy
Identify factors affecting viability and dormancy of seeds
Identify factors affecting seed dormancy
Define seed germination
Differentiate between types of seed germination
Identifying Conditions necessary for germination - oxygen
Investigate the necessity of water and warmth
Describe the region of growth in seedlings
Identify the regions of growth
Determine the regions of growth in seedlings
Measure the aspect of growth in a given seedling
Describe growth in plants I.e. Primary and secondary growths
investigate primary and secondary growth in a seedling
Explain the role of hormones in regulation of growth and development in plants
Explain Apical dominance in plants
Define metamorphosis
Distinguish between complete and incomplete metamorphosis
Describe complete metamorphosis in housefly and anopheles mosquito
Describe incomplete metamorphosis in a cockroach
Describe and explain the Role of growth hormones in metamorphosis in insects
Observe metamorphosis in some insects
Classification II
General Principles of Classification
Classification is the science that puts organisms into distinct groups to make their study easy and systematic. Modern scientific classification is based on structure and functions. Organisms with similar anatomical and morphological characteristics are placed in one group while those with different structures are grouped separately.
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Primary and secondary growths
investigate primary and secondary growth in a seedling
Explain the role of hormones in regulation of growth and development in plants
Explain Apical dominance in plants
Define metamorphosis
Distinguish between complete and incomplete metamorphosis
Describe complete metamorphosis in housefly and anopheles mosquito
Describe incomplete metamorphosis in a cockroach
Describe and explain the Role of growth hormones in metamorphosis in insects
Observe metamorphosis in some insects
Classification II
General Principles of Classification
Classification is the science that puts organisms into distinct groups to make their study easy and systematic. Modern scientific classification is based on structure and functions. Organisms with similar anatomical and morphological characteristics are placed in one group while those with different structures are grouped separately. Modern studies in genetics and cell biochemistry are used to give additional help in classifying organisms. There are seven major taxonomic groups. The kingdom is the largest group. Others are phylum (division for plants) class, order, family, genus and species, the smallest. Binomial Nomenclature
Living organisms are named using Latin or Latinised names. Every organism has two names. This double naming is called binomial nomenclature. This system of naming was devised by Carolus Linnaeus in the 18th Century. The first name is the generic name - the name of the genus. The second name is the name of the species. The generic name starts with a capital letter while that of the species starts with a small letter. The names are written in italics or are underlined in manuscripts. Examples:
Bean =Phaseolus vulgaris. Phaseolus is the generic name,
vulgaris is specific name. Dog =Canis familiaris. Canis is the generic name
,familiaris the specific name. General Characteristics of Kingdoms
Organisms are classified into five kingdoms. Monera,
Protoctista,
Fungi,
Plantae
Animalia. Viruses do not fit neatly into any of the above kingdoms. They are simple and not cellular. They are metabolically inactive outside the host cell. Most of them can be crystallised like chemical molecules. Therefore they do not exhibit the characteristics of living organisms.
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They are metabolically inactive outside the host cell. Most of them can be crystallised like chemical molecules. Therefore they do not exhibit the characteristics of living organisms. Examples of Organisms in Each Kingdom and Their Economic Importance
Kingdom Monera
General Characteristics
Unicellular and microscopic
Some single cells ,others colonial
Nuclear material not enclosed within nuclear membrane-prokaryotic
Have cell wall but not of cellulose. Have few organelles which are not membrane bound
Mitochondria absent
Mostly heterotrophic, feeding saprotrophically or parasitically,some are autotrophic. Reproduction mostly asexual through binary fission
Most of them are anaerobes but others are aerobes
Most move by flagella
Examples include Escherichia coli, Vibrio cholerae and Clostridium tetani. Spherical known as Cocci. Rod shaped - e.g. Clostridium tetani
Spiral shaped e.g. sprilla
Coma shaped- Vibrios -e.g., Vibrio cholerae. Economic importance of bacteria Benefits to man include:
They are used in food processing e.g., Lactobacillus used in processing of cheese, yoghurt. Involved in synthesis of vitamin Band K, in humans and breakdown of cellulose in herbivores. Genetic Engineering
Bacteria are easily cultured and are being used for making antibiotics, aminoacids and enzymes e.g. amylase, and invertase e.g., Escherichia coli. Nutrient cycling:
Saprophytes
They are involved in decomposition of dead organic matter. They are useful in the nitrogen cycle. Nitrogen fixing and nitrifying bacteria. They increase soil fertility. Modem sewage works use bacteria in treatment of sewage. Cleaning oil spills in oceans and lakes. Harmful Effects
Bacteria cause disease:
To humans (e.g. Cholera). To animals (e.g. Anthrax). Bacteria cause food spoilage. Others cause food poisoning e.g. Salmonella. Denitrifying bacteria reduce soil fertility e.g., Pseudomonas denitrificans. Kingdom Protoctista
Examples include ;
Algae such as spirogyra, Chlamydomonas, euglena, Sargassum
And protozoa such as amoeba, paramecium and Trypanosoma.
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Salmonella. Denitrifying bacteria reduce soil fertility e.g., Pseudomonas denitrificans. Kingdom Protoctista
Examples include ;
Algae such as spirogyra, Chlamydomonas, euglena, Sargassum
And protozoa such as amoeba, paramecium and Trypanosoma. General Characteristics
They are said to be eukaryotic since their nucleus is bound by a membrane
Most are mobile, and use flagella, cilia and pseudopodia. Some are sessile. They reproduce mainly asexually, by binary fission, fragmentation and sporulation. Some reproduce sexually by conjugation. Some are heterotrophic e.g. paramecium. Others are autotrophic e.g. spirogyra. Economic importance of protoctista
Algae are the primary producers in aquatic food chains. They release a lot of oxygen to the atmosphere. Some cause human diseases like malaria and amoebic dysentry ,sleeping sickness
Some are source of food for humans e.g. sargassum is a source of iodine
Skeletons of diatoms used in paint making. Spirogyra: They have spiral chloroplast. They are green, thread-like filaments
Chlamydomonas:
This is a unicellular green algae and has a cup shaped chloroplast. They move towards light using the flagella
Cilia assist the organism to move. The shape is due to the presence of a thin flexible pellicle. Kingdom Fungi
Multicellular fungi are made of thread-like structures called hyphae (singular hyphae) that form a mycelium. .e.g.Saccharomyces cereviseae(bread yeast). Others include Penicillium, Rhizopus, and edible mushroom
Economic Importance of Fungi
Beneficial Effects
Some fungi are used as food e.g. mushrooms. Some are decomposers which enhance decay to improve soil fertility - recycling of nutrients e.g., toadstools. Some are useful in brewing and bread making e.g., yeast. Yeast is used as food - a rich source of Vitamin B. Some are useful in production of antibiotics e.g., Penicillium griseofulvin. Used in sewage treatment e.g., Fusarium spp. Harmful Effects
Some cause food poisoning by producing toxic compounds e.g.
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Some are useful in production of antibiotics e.g., Penicillium griseofulvin. Used in sewage treatment e.g., Fusarium spp. Harmful Effects
Some cause food poisoning by producing toxic compounds e.g. Aspergillus flavus which produces aflatoxins. Some cause food spoilage, fabric and wood spoilage through decomposition. Some cause diseases to humans e.g., athlete's foot and ringworms. Others cause diseases to plants e.g., potato blight (Irish potatoes) rust in tomatoes and smuts in cereals. Kingdom Plantae
General Characteristics
They are multicellular and eukaryotic. They are photosynthetic and have a pigment chlorophyll. Their cells have cellulose cell walls. They reproduce sexually, others asexually. Kingdom Plantae has three major divisions:
Bryophyta,
Pteridophyta
Spermatophyta. Division Bryophyta
These include mosses and liverworts. Plant body is not differentiated into root, stem and leaves. They have simple structures which resemble leaves and stems. They have rhizoids for absorbing water and anchoring the plant to substratum. Life cycle consists of two morphologically different plants, the gametophyte and sporophyte. The two alternate. They show alternation of generations. The gamete producing gametophyte is the persistent plant. The sporophyte is attached to the gametophyte and is nutritionally dependent on it. They lack vascular system. Sexual reproduction is dependent on water. Division Pteridophyta:
These include ferns and horsetails. General Characteristics
They have root and shoot system. Leaves are compound known as fronds, they have a vascular system. They show alternation of generations whereby the spore bearing sporophyte is the main plant. Spores are borne in clusters on the underside of leaves making sari. The gametophyte is an independent minute structure called prothallus which is short lived. Sexual reproduction is dependent on water. Division Spermatophyta
These are the seed bearing plants. General Characteristics
Plant body is differentiated into root, stem and leaves. Vascular tissue consists of xylem and phloem. Sexual reproduction is independent of water. Male gametophyte (pollen grain) germinates and grows to reach female gametophyte.
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