Final answer:
Individuals that do not adapt to critical biological parameters are subjected to directional selection, which favors one extreme phenotype over another. The peppered moth evolution in England due to industrial pollution is a classic example of this type of selection.
Step-by-step explanation:
Individuals in a population that die because they do not meet a critical biological parameter, such as the example of the peppered moth, are subjected to directional selection. This form of natural selection selects for phenotypes at one extreme end of the spectrum of variation in a population.
The peppered moth case study exemplifies directional selection resulting from environmental change due to the Industrial Revolution. Initially, light-colored moths blended in with the lighter trees and lichens but the darkening of tree bark due to pollution favored the survival of darker-colored moths, which in turn became more prevalent in the population. In essence, directional selection shifted the population's allele frequencies towards the dark-colored phenotype, illustrating a clear evolutionary response to changes in the environment that affected the moths' survival and reproductive success.