Question

Distinguish between homologous organs and analogous organs. In which category would you place wings of a bird and wings of a bat? Justify your answer giving a suitable reason.

Answer 1

Homologous organs	Analogous organs
Homologous organs are those organs which are similar in origin but different in function.	Analogous structures are those which are different in origin but similar in function.
They represent a case of divergent evolution.	The existence of analogous structures suggests the occurrence of convergent evolution.
The presence of a structure or physiological process in an ancestral organism, which has become greatly modified in more specialized, apparently related organisms, may be interpreted as indicating a process of descent by modification. In this case the function of organs diversified and became different from the common ancestor.	It may be explained in terms of the environment, acting through the agency of natural selection, favouring those variations which confer increased survival and reproductive potential on those organisms which possess them. In this case different organs with different origins start performing similar functions and differ from their ancestral trait.
Example: The forelimbs of birds and humans	Example: The forelimbs of birds and bats

The wings of a bird and a bat are similar in function but this similarity does not mean that these animals are more closely related. If we carefully look at these structures, then we will find that the wings of a bat are just the folds of skin that are stretched between its fingers whereas the wings of birds are present all along the arm. Therefore, these organs are analogous organs.