analogous structure definition biology
Analogy, in biology, similarity of function and superficial resemblance of structures that have different origins. For example, the wings of a fly, a moth, and a bird are analogous because they developed independently as adaptations to a common function—flying. The presence of the analogous structure, in this case the wing, does not reflect evolutionary closeness among the organisms that possess it. Bat and pterosaur wings constitute an example of analogous structures, while the bat wing is homologous to human and other mammal forearms, sharing an ancestral state despite serving different functions. The opposite of convergent evolution is divergent evolution in which related species evolve different traits. Analogy is one aspect of evolutionary biology and is distinct from homology, the similarity of structures as a result of similar embryonic origin and development, considered strong evidence of common descent. Please contribute to this project, if you have more information about this term feel free to edit this page. This page was last modified on 4 March 2011, at 10:44.This page has been accessed 75,912 times. A structure can be homologous at one level, but only analogous at another. For example, the bird and bat wings are analogous as wings, but homologous as forelimbs because the organ served as a forearm (not a wing) in the last common ancestor of tetrapods. Analogous structures are similar or resembling in certain respects, e.g. in function or in appearance but not in evolutionary origin or developmental origin. An example is wings of a butterfly and wings of a hummingbird are analogous. Word origin: Greek análogos proportionate. Functionally similar features arising through convergent evolution are termed analogous, in contrast to homologous structures or traits, which have a common origin but not necessarily a similar function. In many cases analogous structures, or analogues, tend to become similar in appearance by a process termed convergence. An example is the convergence of the streamlined form in the bodies of squid, shark, seal, porpoise, penguin, and ichthyosaur, animals of diverse ancestry. Physiological processes and behaviour patterns may also exhibit analogous convergence. Convergent evolution is the independent evolution of similar features in species of different lineages. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is homoplasy, from Greek for same form. The recurrent evolution of flight is a classic example of convergent evolution. The principle of homology: The biological relationships (shown by colors) of the bones in the forelimbs of vertebrates were used by Charles Darwin as an argument in favor of evolution. In the context of biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different taxa. A common example of homologous structures in evolutionary biology are the wings of bats and the arms of primates. Evolutionary theory explains the existence of homologous structures adapted to different purposes as the result of descent with modification from a common ancestor.
Functionally similar features arising through convergent evolution are termed analogous.