Answer:
The bones of forelimbs of whale, bate, cheetah, and man are similar in structure because they are homologous organs. The organs which have the same fundamental structure but are different in functions are called homologous organs. These organs follow the same basic plane of organization during their development. But in the adult condition, these organs are modified to perform different functions as an adaptation to different environments. The homologous structures are a result of divergent evolution. Homology indicates common ancestry, so they share a common ancestor.