What reflects how closely related different species are in evolutionary terms?

The degree of similarities between different species is a key indicator of how closely related they are in evolutionary terms. This concept is grounded in evolutionary biology, where the similarities in DNA sequences, anatomical structures, and metabolic processes among various organisms suggest a shared ancestry. The more traits or genetic sequences two species have in common, the more likely they are to have evolved from a recent common ancestor. This is often examined through methods such as comparative anatomy, molecular biology, and phylogenetics, where scientists construct evolutionary trees to illustrate these relationships based on the degree of similarities observed.

The other concepts play different roles in ecology and evolutionary theory but do not directly address the question of evolutionary relatedness. For example, gene pools refer to the total genetic diversity within a population and can change due to evolutionary forces. Natural selection is a mechanism that drives evolution but does not directly measure how closely species are related. Species barriers, such as reproductive isolation, affect how species diverge and evolve but do not indicate closeness in evolutionary terms.