Question

What distinguishes disruptive and directional selection pressures when both select for extreme genetic traits?

Answer 1

Disruptive selection pressures select for extreme genetic traits at both ends of the phenotype distribution, while directional selection pressures select for extreme genetic traits in one direction only. Disruptive selection, also known as diversifying selection, results in the creation of two or more distinct phenotypic classes, while directional selection results in the gradual shift of the population towards one extreme trait. In other words, disruptive selection increases genetic diversity, while directional selection reduces it. Additionally, disruptive selection may occur in stable environments with no selective pressures, while directional selection occurs in response to changing environmental conditions or due to differences in reproductive success.