Which of the following describes structures that have lost their original function in a species but are still present?

Vestigial structures are remnants of organs or features that once had a functional role in an organism's ancestors but have since lost their original purpose through the process of evolution. These structures serve as evidence of evolutionary history by reflecting adaptations to changing environments or lifestyles.

For example, the pelvic bones in whales are considered vestigial because they no longer serve a function in locomotion but indicate that their ancestors were land-dwelling mammals that had functional hind limbs. This illustrates how species can retain aspects of their evolutionary heritage even when those features are no longer useful.

In contrast, adaptive traits, which are beneficial variations that enhance an organism's fitness for its environment, are still in active use. Analogous structures arise from convergent evolution and serve similar functions in different species, despite having different evolutionary origins. Homologous structures share a common ancestry and may serve similar functions, but they do not necessarily indicate an absence of function like vestigial structures do. Thus, the description most accurately reflecting structures that have lost their original function while remaining present in a species is indeed vestigial structures.