1 Transformation: bacteria simply absorb, across their cell membrane and cell wall, DNA that is floating around in the environment. 2  Conjugation: bacteria directly transfer DNA from one bacterium to another through structures called pilli. Transformation: bacteria simply absorb, across their cell membrane and cell wall, DNA that is floating around in the environment. 2  Conjugation: bacteria directly transfer DNA from one bacterium to another through structures called pilli.
Food begins its journey through the digestive system in the mouth, before being pushed by a series of involuntary muscle contractions through the esophagus, then the stomach, and then the small and large intestines.
Structure: The esophagus is a muscular tube which leads from the pharynx, at the back of the mouth, to the stomach, the first main organ of digestion. Function: To carry chewed food from the pharynx to the stomach. Food moves along it by a muscular contraction known as peristalsis.t completes the chemical digestion of food and the subsequent absorption of nutrients takes place in the small intestine. Nutrients are absorbed through the villi into the blood and lymph vessels. Hardly any food is absorbed elsewhere in the digestive system.