Florida Biology EOC Practice Test

What term describes a structure in an organism that no longer serves its original function?

1. Analogous structures

2. Homologous structures

3. Vestigial structures

4. Primitive structures

The correct answer is: Analogous structures

The term that describes a structure in an organism that no longer serves its original function is "vestigial structures." These structures are remnants of evolutionary ancestors and have diminished in size or functionality over time. A classic example is the human appendix, which is thought to be a vestige of a larger cecum that was used for digesting cellulose in the diet of early herbivorous ancestors. Vestigial structures provide important evidence for the theory of evolution, highlighting how organisms adapt to their environment and how certain features can become redundant as species evolve. In contrast, analogous structures arise from convergent evolution, where different species develop similar traits independently, typically due to similar environmental pressures. Homologous structures are features that share a common ancestry, even if they serve different functions in the current organisms. Primitive structures refer to more basic or less specialized features present in earlier forms of life, but do not necessarily indicate a loss of function.