Final answer:
Natural selection tends to decrease the amount of variation associated with a trait in a population.
Step-by-step explanation:
As natural selection acts on a trait in a population, the amount of variation associated with that trait in the population is likely to decrease. Natural selection can result in stabilizing selection, which favors individuals with average phenotypes and reduces genetic variance. For example, in a population of mice living in the woods, natural selection would favor mice with fur that closely matches the color of the forest floor, reducing variation in coat color.