[Campbell Biology P.534] The upper forelimbs of humans and bats have fairly similar skeletal... | Practice 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 bats than in humans or whales.
  • D: Whales are not properly classified as mammals.

Explanation

The shared ancestry and similar divergence time suggest homologous structures. The significant differences in whale forelimbs, despite this common ancestry, are best explained by strong natural selection pressures in the aquatic environment, leading to their specialized form a flipper that is highly adapted for swimming.