Question

Below is a diagram indicating the limb bones of a crocodile, a bat, a whale, and a bird. Similar bones are highlighted in the same colors.



Crocodiles, bats, whales, and birds have similar limb bones. What do these similarities suggest?
A.
Crocodiles, bats, whales, and birds evolved from a common ancestor.
B.
The common ancestor of birds and crocodiles was a whale.
C.
A similar limb structure evolved in each species independently and by chance.
D.
Bats and crocodiles share an ancestor with whales but not with birds.

Answer 1

A.

The same set of limb bones (humerus, radius, ulna, carpals, metacarpals, phalanges) in different forms shows homology — modification of a common tetrapod ancestor’s limb for different functions (flight, swimming, walking). C is wrong (that would be convergent evolution). B and D contradict the pattern of shared ancestry across tetrapods.