Which type of selection occurs when an environment changes and favors a new trait?

• A. Stabilizing selection
• B. Natural selection
• C. Directional selection
• D. Disruptive selection

Answer: (C)

When the environment changes and a new trait becomes advantageous, directional selection shifts the population toward that trait. Individuals with the new trait have higher fitness and leave more offspring, so that trait becomes more common with each generation. Over time, the average phenotype moves in the direction of the favored trait. A classic example is a population of moths becoming predominantly a darker color when darker camouflage offers better protection from predators in a polluted environment. This illustrates how changing conditions lead to a gradual shift in traits that are advantageous. In contrast, stabilizing selection would favor the average trait and reduce variation, while disruptive selection would favor extreme traits in different individuals, not a single shift toward one new trait. Natural selection is the overall process, and directional selection is the pattern that occurs when a new trait becomes advantageous due to environmental change.