CBSE Class 10 Answered

The study of comparative anatomy particularly of animals, offers a valuable evidence in favour of organic evolution. The evidences come from :

i) Homologous organs - Homologous organs are organs of different organisms, which are dissimilar externally but similar in origin and in fundamental structural plan. e.g. hand of man and wing of bird. There are other organs called analogous organs which are similar in function and external appearance, but dissimilar in origin and structural plan.

The only explanation for homologous organs is that these animals are the diverging descendants of the common ancestor. Homologous characteristics help to identify an evolutionary relationship between apparently different species.

ii) Vestigial organs - These organs are the remnants of the past and no longer fulfil the function for which they were originally intended. For e.g - Presence of wing skeleton in kiwi despite the absence of well developed wings.

The only reason one can give of such vestigial organs is that they are inherited from the ancestors in which they were functional. They serve as a permanent reminder of the continuity of life.

Wing of insect, wing of bird and wing of bat are all analogous to each other.