An organ that serves no useful function in an organism is called a

• A. Vestigial structures
• B. Adaptive trait
• C. Analogous structures
• D. Homologous structures

Answer: (A)

Vestigial structures are remnants of features that were useful in ancestors but have lost their original function in the current organism. This explains why an organ can exist even when it no longer serves a purpose today. Examples in humans include the coccyx (tailbone) and sometimes the appendix or wisdom teeth, which reflect evolutionary history rather than current necessity.

An adaptive trait would be something that still provides a fitness advantage today, not something that’s nonfunctional. Analogous structures look alike and perform similar jobs but evolved independently in different lineages, not from a common ancestor. Homologous structures share a common origin but can be repurposed for different functions. These ideas describe different evolutionary relationships or pressures and don’t describe an organ that has become functionless.