A species of crayfish that lives in caves produces eyestalks like its above-ground relatives, but has no eyes. Eyestalks in cave-dwelling crayfish are thus                   . a. an evolutionary error; b. a dominant mutation; c. biogeographical evidence of evolution; d. a vestigial trait; e. evidence that evolutionary theory may be incorrect

Key Concepts

Vestigial Traits

Vestigial traits are anatomical structures or behaviors that have lost most or all of their original function through the course of evolution. In the case of the cave-dwelling crayfish, the eyestalks may serve little to no purpose in a dark environment, indicating that they are remnants of a functional trait found in their ancestors.

Evolutionary Adaptation

Evolutionary adaptation refers to the process by which a species becomes better suited to its environment through natural selection. The presence of eyestalks in cave-dwelling crayfish, despite the absence of eyes, suggests that these structures may have once played a role in survival, but have since become less relevant in their current habitat.

Natural Selection

Natural selection is a mechanism of evolution where organisms better adapted to their environment tend to survive and produce more offspring. In the context of the crayfish, the lack of eyes in a dark cave environment may indicate that natural selection has favored other traits over the development of functional eyes, leading to the retention of eyestalks as a non-functional feature.