An important evidence in favour of organic evolution, is the occurence of homologous and vestigial organs. Homologous organs are those which have the common origin and are built on the same fundamental pattern but they perform different functions and have different appearances e.g.. Whales front flipper, bats wings, cats paw, horse front leg, birds wing, oxs front leg and human hand. Vestigial organs in animals are those having no function now, in them, but had important functions in their ancestors. Analogous organs are quite different in fundamental structure and embryonic origin but perform the same function. The study of analogous organs illustrates the occurrence of convergent evolution.