Question

(a) Explain the terms 'analogous organs' and 'homologous organs' with examples.
(b) In what way are analogous organs evidence for evolution?

Answer 1

(a) Analogous organs are those organs which have different basic structure, but perform the same function. For example, the wing of an insect and a bird have completely different basic structure, but they perform the same function—of flying.
Homologous organs are those organs which have same basic structure but perform different functions. For example, the forelimbs of humans, cheetahs, whales and bats have the same basic structural plan. But the forelimbs in humans are used for grasping, in cheetah for running, in whales for swimming and in bats for flying.

(b) The presence of analogous organs in different animals provide evidence for evolution by telling us that though they are not derived from common ancestors, they can still evolve to perform similar functions to survive, flourish and keep on evolving in the prevalent environment. Thus, the presence of analogous organs provide a mechanism for evolution.