Final answer:
Stabilizing selection is the process where intermediate phenotypes are favored and extremes are selected against, leading to decreased genetic variance. Examples include mice fur color in a forest environment, aligning their camouflage with the forest floor, preventing predation.
Step-by-step explanation:
Stabilizing selection is a type of natural selection where the intermediate phenotype is favored over the extreme variations. An example of this is the fur color of mice living in the forest. Natural selection is likely to favor mice that have fur color most closely matching the floor of the forest, which allows for better camouflage from predators. Mice with fur colors that are much lighter or darker than the forest floor will stand out, increasing their chance of predation, and are thus selected against. This process results in a narrower range of phenotypic variation and a decrease in genetic variance within a population.
Contrastingly, directional selection favors one extreme phenotype, leading to a shift in phenotypic distribution towards that extreme, which increases the genetic variance in a population. On the other hand, disruptive selection, or diversifying selection, favors more than one extreme phenotype while selecting against the intermediate, which can also increase genetic variance.