Natural selection that drives evolutionary change by selecting for greater or lesser frequency of a given trait in a population.

• A. Stabilizing selection
• B. Gene flow
• C. Directional selection
• D. Inbreeding

Answer: (C)

Directional selection shifts a population’s trait distribution by consistently favoring one extreme, so the average trait value moves in that direction over generations. When the extreme phenotype has higher fitness, it becomes more common while the other phenotypes decline, driving evolutionary change. This matches the idea of selecting for greater or lesser frequency of a trait value. For example, if larger beaks confer a fitness advantage during a drought with large seeds, over time more individuals will have larger beaks. Stabilizing selection, by contrast, favors intermediate phenotypes and reduces variation without shifting the mean toward an extreme. Gene flow changes allele frequencies between populations through migration rather than differential survival within a population, and inbreeding alters genotype frequencies by mating among relatives rather than acting as a selective process.