ANATOMY

Detailed explanation-1: -Whales, lizards, humans, and birds all have the same basic limb layout. But how did such different animals wind up with the same sort of limb? The answer is that they inherited it from a common ancestor, just as cousins might inherit the same trait from their grandfather.

Detailed explanation-2: -The whale flipper shares a similar morphology to bird and mammal appendages (Figure 2) indicating that these species share a common ancestor.

Detailed explanation-3: -Humans, whales, lizards, and birds all have differently shaped forelimbs, reflecting their different lifestyles. But those different forelimbs all share the same set of homologous bones-the humerus, the radius, and the ulna. These same bones can even be seen in fossils of the extinct lobe-finned fish, Eusthenopteron.

Detailed explanation-4: -The last common ancestor of birds and mammals (the clade Amniotes ) lived about 310 – 330 million years ago, so 600 million years of evolutionary time in all separates humans from Aves, 300 million years from this common ancestor to humans, plus 300 million years from this ancestor to birds.

Detailed explanation-5: -Physical features shared due to evolutionary history (a common ancestor) are said to be homologous. To give one classic example, the forelimbs of whales, humans, birds, and dogs look pretty different on the outside. That’s because they’re adapted to function in different environments.