Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which type of anatomical structures indicate a common ancestor?

1. Analogous anatomical structures

2. Vestigial anatomical structures

3. Homologous anatomical structures

4. Functional anatomical structures

The correct answer is: Homologous anatomical structures

Homologous anatomical structures provide evidence of a common ancestor because they are similar in form and structure due to shared evolutionary origin, despite potentially serving different functions in modern organisms. For instance, the forelimbs of humans, whales, and bats exhibit similar bone structures; however, they have evolved to perform various functions such as grasping, swimming, and flying, respectively. This commonality in structure but diversity in function reflects how these species have diverged from a shared lineage over time. In contrast, analogous anatomical structures arise from convergent evolution, where different species independently evolve similar traits as adaptations to similar environments or functions, without sharing a recent common ancestor. Vestigial anatomical structures, though derived from ancestors and still present in current species, do not indicate common ancestry in the context of functional evolutionary adaptation—they are remnants that have lost their original function. Functional anatomical structures are often not indicative of common ancestry but rather describe how parts fit together to enable the organism's survival. Thus, homologous structures are the key indicators of common ancestry in the study of evolutionary biology.