Final answer:
Stabilizing selection is a type of natural selection that narrows the range of phenotypic variation by selecting against phenotypes at both extremes. An example of this is human birth weight, where normal birth weight has a higher chance of survival than low or high birth weight.
Step-by-step explanation:
Stabilizing selection is a type of natural selection that occurs when phenotypes at both extremes of the phenotypic distribution are selected against, resulting in a narrowing of the range of phenotypic variation. An example of stabilizing selection is human birth weight, where babies that are very large or very small at birth have lower chances of survival compared to those with normal birth weight. This helps keep birth weight within a relatively narrow range.
Stabilizing selection is a mode of natural selection that favors an average phenotype and reduces genetic variance by selecting against extreme variations, as seen in the brown fur of mice in a forest environment.
Understanding Stabilizing Selection
Stabilizing selection is a form of natural selection where the population's mean stabilizes on a particular trait value that is not at the extremes. This type of selection reduces the range of phenotypic variation and genetic variance in a population by selecting against extreme phenotypes. For instance, in a forest of consistently brown terrain, mice that blend into the environment have greater chances of survival, leading to a population that favors these average brown tones while selecting against lighter or darker extremes. On the other hand, directional selection shifts the phenotype distribution towards one extreme, and disruptive selection favors extreme phenotypes at both ends of the spectrum, thus increasing genetic variance.