Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

What term describes structures that have little or no function but were probably used by ancestral organisms?

1. Vestigial structures

2. Evolutionary traits

3. Adaptive features

4. Functional organs

The correct answer is: Vestigial structures

The term that describes structures with little or no current function, which were likely functional in ancestral organisms, is vestigial structures. These structures provide evidence of evolution, indicating how certain traits have diminished in utility over time as species adapt to their environments. For example, the human appendix is often cited as a vestigial structure, as it no longer plays a significant role in digestion as it may have in the diets of our herbivorous ancestors. In contrast, evolutionary traits refer to characteristics that have evolved in response to environmental pressures, while adaptive features are those that provide an advantage in surviving and reproducing in a particular environment. Functional organs are parts of an organism that perform specific, essential functions for survival, contrasting with the concept of vestigial structures that have lost their primary utility over time.