Final answer:
In stabilizing selection, heterozygotes do not always have the highest fitness, as individuals with average phenotypes are favored. Stabilizing selection reduces genetic variance in a population.
Step-by-step explanation:
In stabilizing selection, the individuals with average phenotypes have the highest fitness. This means that heterozygotes do not always have to have the highest fitness. Stabilizing selection favors individuals with phenotypes that are closer to the average and reduces the genetic variance in a population.