<p> A process, change, method, characteristic or The different functions of the same structure feature that an organism or species possesses, shows adaptation of a common structure, e.g. the develops or evolves that suits/adjusts the forelimb. organism to its environment to increase its chances of survival and reduce competition. It is one of the main points of Darwin's theory of evolution by natural selection.</p><p> adaptation adaptive radiation</p><p>Body parts that perform the same function in Comparing the structures of plants and animals, different organisms, but differ in their structure, e.g. used as evidence that organisms share a common the wings of insects and birds. ancestor, e.g. homologous structures, the forelimbs of many animals share the same basic structure but differ in their functions.</p><p> analogous structures comparative anatomy</p><p>Comparing the developing embryos of vertebrates The study of how the embryo develops before shows a similarity between certain structures, e.g. birth or emergence from the egg. the position of the brain, eyes, gill slits and tail of the fish, tortoise, rabbit, bird, chick and human. This suggests that organisms descended from common ancestors.</p><p> embryology comparative embryology</p><p>This is about how modern plants and animals have The remains of organisms that lived long ago. gradually developed from pre-existing forms over long periods of time, i.e. changes in species by natural selection in response to environmental changes. Survival of the fittest by adaptation, variation and over-reproduction.</p><p> fossil(s) evolution Same structure found on different organisms, The way nature selects organisms with advantageous originating from a common ancestor, but with different genes which allow them to adapt to the environment, functions, e.g. pentadactyl limb (forelimb). and pass them on to successive generations.</p><p> homologous structure natural selection</p><p>Five-fingered limb found in nearly all terrestrial States that all living organisms have descended from vertebrates. common ancestors, and over millions of years simple organisms have developed into more complex ones.</p><p> pentadactyl limb theory of evolution</p><p>Formulated by Charles Darwin. All species have, by Formulated by Jean Baptiste Lamarck. If part of an a series of gradual changes (i.e. better adaptations), organism was used it would grow and enlarge, whereas evolved from pre-existing different species. a part not used would waste away.</p><p> theory of natural selection theory of use and disuse</p><p>A tissue or organ whose size, due to loss of function, has been reduced over evolutionary time, e.g. human appendix.</p><p> vestigial form (structure)</p>