Which term describes structures in different species that are similar because of a common ancestry?

Which term describes structures in different species that are similar because of a common ancestry?

• A. Vestigial structures
• B. Analogous structures
• C. Convergent evolution
• D. Homologous structure

Answer: (D)

Structures in different species that share a common origin come from a homologous relationship. This means the similarity comes from a shared developmental blueprint inherited from a common ancestor, even if the parts have diverged to serve different functions. For example, the forelimbs of humans, cats, whales, and bats all follow the same bone pattern—humerus, radius, ulna, carpals, metacarpals, and phalanges—showing they originated from the same limb design and later adapted for grasping, running, swimming, or flying. This idea embodies divergent evolution, where related organisms evolve different traits. Vestigial structures are remnants that have lost much of their original function, illustrating ancestry but not the broad, cross-species similarity described by a shared limb plan. Analogous structures arise from similar functions but not shared ancestry, often due to convergent evolution, which can produce superficially similar features in unrelated lineages.

Structures in different species that share a common origin come from a homologous relationship. This means the similarity comes from a shared developmental blueprint inherited from a common ancestor, even if the parts have diverged to serve different functions. For example, the forelimbs of humans, cats, whales, and bats all follow the same bone pattern—humerus, radius, ulna, carpals, metacarpals, and phalanges—showing they originated from the same limb design and later adapted for grasping, running, swimming, or flying. This idea embodies divergent evolution, where related organisms evolve different traits.

Vestigial structures are remnants that have lost much of their original function, illustrating ancestry but not the broad, cross-species similarity described by a shared limb plan. Analogous structures arise from similar functions but not shared ancestry, often due to convergent evolution, which can produce superficially similar features in unrelated lineages.