Which process describes the action that increases the frequency of advantageous traits in a population over generations?

• A. Natural selection
• B. Genetic drift
• C. Mutation
• D. Gene flow

Answer: (A)

Natural selection increases the frequency of advantageous traits by differential survival and reproduction. When an environment favors a particular trait, individuals exhibiting that trait tend to survive longer and leave more offspring, passing the beneficial allele to the next generation. Over many generations, that trait becomes more common in the population. A classic example is the peppered moth, where darker coloration offered better camouflage in polluted environments, leading to more survivors and more copies of the dark allele. In contrast, genetic drift is random change in trait frequencies that can happen by chance, especially in small populations. Mutation adds new genetic variation but doesn’t by itself raise the frequency of advantageous traits unless those new variants are favored by selection. Gene flow moves alleles between populations and can spread or dilute traits, but the process that actively increases advantageous trait frequencies is natural selection.