Final answer:
Stabilizing selection is a form of natural selection that favors the average phenotype over extreme variations, reducing genetic variance and leading to a more uniform appearance within a population.
Step-by-step explanation:
The primary characteristic of stabilizing selection in the context of continuous traits in a population is that it favors the average phenotype and selects against extreme variations. This type of natural selection results in decreased genetic variance within the population, as exemplified by a population of mice that blends in with the forest floor to avoid predation. Individuals with extreme phenotypes (too light or too dark fur) are more likely to be preyed upon, so those with fur color that closely matches the environment are more likely to survive and reproduce. Consequently, stabilizing selection leads to a more uniform appearance within the population with less phenotypic variation.