Think about a population of owls. For simplification purposes let's say that an owl's flight can be loud or silent and is a function of classic Mendelian genetics. Some of the owls in the population are loud, and some of the owls in the population are silent. Flying loudly is the dominant trait, so individuals that fly loudly can have 2 genotypes FF and Ff. Individuals that fly silently are homozygous recessive and will have the genotype ff.
This population of owls specializes on eating gerbils, and gerbils are good at hearing owls. What will happen to the gene frequency for the flight alleles over many generations? In general, what will happen to the number of loud and silent flyers over time?