Question

In peppered moth populations, light and dark moths are selected for in different environments. What type of selection is this, and what would a distribution curve for all peppered moths look like?

Answer 1

This type of selection is called disruptive selection. In disruptive selection, individuals with extreme phenotypes are favored over individuals with intermediate phenotypes.

In the case of peppered moths, light moths are favored in environments with lighter backgrounds, such as lichen-covered trees, while dark moths are favored in environments with darker backgrounds, such as trees affected by pollution. This results in the two extreme phenotypes (light and dark moths) being favored over the intermediate phenotype (medium-toned moths).

A distribution curve for all peppered moths would show two peaks, one for the light moths and one for the dark moths, with fewer individuals falling in the middle. The curve would have a bimodal shape, reflecting the disruptive selection at play in the population.