What is Organism?
[[File:six organisms.jpg|thumb|A [[brown bear]], an [[cattle]], a [[chicken]], a [[bottlenose dolphin]], a [[guineafowl]], a wild pig.]] [[File:E. coli Bacteria (7316101966).jpg|thumb|''[[Escherichia coli]]'' is a microscopic single-celled organism, and a [[prokaryote]] as well.]] [[File:Amoeba (Amöbe) 01.jpg|thumb|[[Amoebae]] are single-celled [[eukaryotes]]]] [[File:Fungi in Borneo.jpg|thumb|[[Polypore]] fungi and [[angiosperm]] trees are large many-celled eukaryotes.]] [[File:PhylogeneticTree, Woese 1990.PNG|thumb|400px|[[Phylogenetic]] [[Tree of life (biology)|tree of life]] ([[Carl Woese]]). Viruses do not appear here because there is no evidence of how they relate to the other three kingdoms of life]] An '''organism''' is any individual [[Life|living]] thing. It is easy to recognize a living thing but, not so easy to define it. Obviously, [[animal]]s and [[plant]]s are organisms. Organisms are [[biotic]], or living, parts of the [[environment]]. Rocks and sunshine are parts of the non-living [[environment]]. Organisms usually have six basic needs to continue their [[metabolism]]. They need [[air]], [[water]], [[nutrient]] ([[food]]), [[energy]], a [[Habitat|place to live]], and [[homeostasis]] (being able to maintain itself). However, not all living things need all these at the same time. Some organisms do not need access to air at all. Living things have cells, take and use energy, grow and develop, share similar chemicals, sense and respond to change (stimulus), and reproduce. A little thought is needed about [[viruses]]. There is no agreement as to whether they should be regarded as living. They are made of [[protein]] and [[nucleic acid]], and they [[evolution|evolve]], which is a really important fact. However, they exist in two quite different phases. One phase is [[dormancy|dormant]], not active. The other is inside a living [[cell]] of some other organism. Then the virus is very active reproducing itself. Consider the parallel with a [[computer program]]. When in use it is active; when it is not,