Question

The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data?

(A) Forelimb evolution was adaptive in people and bats, but not in whales.

(B) Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.

(C) Genes mutate faster in whales than in humans or bats.

(D) Whales are not properly classified as mammals.

Short answer

1. The statement “Forelimb evolution was adaptive in people and bats, but not in whales” is false.
2. The statement “Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy” is true.
3. The statement “Genes mutate faster in whales than in humans or bats” is false.
4. The statement “Whales are not properly classified as mammals” is false.

Step-by-step solution

Mammals 

The group of animals that possess mammary glands in addition to the other chordate characteristics are called mammals. Mammals can successfully dwell in terrestrial and aquatic environments. Whales, humans, and bats are common examples of mammals.

Explanation for option (A)

The forelimb evolution in the given mammalian species can be called adaptive. The adaptive evolution worked for all the given mammalian species, including whales.

Thus, the changes were adaptive for bats, humans, and whales.

Therefore, the given statement is false.

Explanation for option (B)

The molecular studies show a common ancestral origin of bats, humans, and whales, but their forelimbs differ in functions. The forelimbs of bats evolved to flight adaptation; whales adapted their forelimbs to swim while humans adapted them for their own respective needs.

Thus, adaptive changes occurred in all three mammals according to their environmental needs, which led to significant changes in the forelimb anatomy.

Therefore, the given statement is true.

Explanation for option (C)

There is no such evidence that the mutation of genes occurs faster in males than in humans or bats. One cannot make such an interpretation by the observations provided.

Thus, whales do not mutate more rapidly than humans or bats.

Therefore, the given statement is false.

Explanation for option (D)

Whales are aquatic animals that are grouped explicitly under the class mammals. There is no improper classification regarding whales being mammals.

Thus, whales are mammals.

Therefore, the given statement is false.