Mammals have a particularly good sense of earing thanks to their inner ear which includes three tiny bones. Reptiles, in contrast, have a single inner ear bone. The lower jaw of reptiles is composed of multiple bones while the lower jaw of mammals is a single bone. Fossil and developmental evidence indicate that the inner ear bones of mammals evolved from lower jawbones. This suggests that the inner ear bones of mammals are   1. an analogy 2. an exaptation 3. a living fossil 4. a transitional trait 5. a vestigial structure

Mammals have a particularly good sense of earing thanks to their inner ear which includes three tiny bones. Reptiles, in contrast, have a single inner ear bone. The lower jaw of reptiles is composed of multiple bones while the lower jaw of mammals is a single bone. Fossil and developmental evidence indicate that the inner ear bones of mammals evolved from lower jawbones. This suggests that the inner ear bones of mammals are

1. an analogy

2. an exaptation

3. a living fossil

4. a transitional trait

5. a vestigial structure