Evolution

Divergent evolution of anatomical structures, such as forelimbs, indicate homology.

Homology indicates common ancestry and acts as the evidence of evolution.

When same structure develops along different directions due to adaptation to different needs, they are called homologous structures.

Convergent evolution does not act as the evidence for evolution, because species can develop similar features without a common ancestor.

Fossils are remains of hard parts of life-forms found in rocks.

A study of fossils in different sedimentary layers indicates the geological period in which they existed. Embryological support for evolution was proposed by Ernst Heckel based upon the observation of certain features during embryonic stage common to all vertebrates that are absent in adult. But later, this proposal was disapproved on careful study performed by Karl Ernst von Baer.

The organs which have similar functions but are different in their structural details and origin are called analogous organs. The wings of bat are analogous to wings of pigeon. It is due to the fact that the basic structure of the wings of the mammal is different from the wings of bird. However, their function is similar. Similarly, gills of prawn and lungs of man, both are respiratory organs yet they have very different basic structure.