Structure left over from an ancestor, that serves no useful function in an organism.

Structure left over from an ancestor, that serves no useful function in an organism.

• A. Vestigial organ
• B. Embryology evidence
• C. Fossil evidence
• D. Behavioral isolation

Answer: (A)

Vestigial structures are remnants of features that were functional in ancestors but no longer serve a useful purpose in the current organism. They illustrate evolution by showing how inherited traits can persist even after their original function is lost, often becoming reduced in size or adapted for a different role. Examples in humans include the appendix, the coccyx (tailbone), and pelvic bones found in whales and some snakes—features that were useful to ancestors but are no longer essential now. Embryology evidence, fossil evidence, and behavioral isolation describe other aspects of evolution. Embryology looks at developmental similarities across species, fossil evidence tracks historical forms through time, and behavioral isolation concerns barriers to mating between populations. None of these specifically define a structure as a nonfunctional remnant of an ancestor, which is what vestigial means.

Vestigial structures are remnants of features that were functional in ancestors but no longer serve a useful purpose in the current organism. They illustrate evolution by showing how inherited traits can persist even after their original function is lost, often becoming reduced in size or adapted for a different role. Examples in humans include the appendix, the coccyx (tailbone), and pelvic bones found in whales and some snakes—features that were useful to ancestors but are no longer essential now.

Embryology evidence, fossil evidence, and behavioral isolation describe other aspects of evolution. Embryology looks at developmental similarities across species, fossil evidence tracks historical forms through time, and behavioral isolation concerns barriers to mating between populations. None of these specifically define a structure as a nonfunctional remnant of an ancestor, which is what vestigial means.