CBSE Class 10 Science 2020 · Paper 31/1/1 · Question 20

Homologous structures are organs that have the same basic structure and origin but are modified to perform different functions. Example: the forelimbs of vertebrates, such as the leg of a lizard, the wing of a bird, the flipper of a whale and the arm of a human, have the same basic design of bones but are used for walking, flying, swimming and grasping. (Any other correct example earns credit.) Yes, it is necessary. The similarity in the basic design of homologous structures shows that their ancestors were common: the design was inherited from a common ancestor and then modified for different functions. Structures that are similar without such common ancestry are analogous, not homologous.