Kaplan Nursing Entrance Practice Exam

Which of the following terms refers to structures not inherited from a common ancestor but that perform similar functions?

1. Homologous structures

2. Analogous structures

3. Vestigial structures

4. Cellular structures

The correct answer is: Analogous structures

The term that refers to structures not inherited from a common ancestor but that perform similar functions is "analogous structures." These structures arise through convergent evolution, where different species evolve similar traits or functions independently in response to similar environmental pressures or challenges. For example, the wings of bats and the wings of insects serve the same function of flight, but they do not share a common evolutionary ancestor that had wings. In contrast, homologous structures are similar because they were inherited from a common ancestor, such as the forelimbs of mammals, birds, and reptiles, which may serve different functions but share a similar underlying structure. Vestigial structures are remnants of organs or structures that had a function in an early ancestor but no longer perform that function in the current organism, like the human appendix. Cellular structures refer to components within cells and do not relate to evolutionary relationships or functions across different species. Thus, "analogous structures" accurately describes the phenomenon of similar function arising independently of shared ancestry.