Which concept states that individuals best adapted to their environment survive and reproduce, increasing the frequency of their alleles?

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

Answer: (B)

Natural selection is the process by which individuals with traits that fit their environment survive and reproduce more successfully, so those advantageous alleles become more common in the population over generations. This directly captures how adaptation spreads: if a trait helps an organism survive or reproduce, its genetic variation is passed on more often, shifting allele frequencies toward that trait. Over time, the population becomes better suited to its environment because the alleles underlying the beneficial traits accumulate.

The other mechanisms describe different ways allele frequencies can change without linking the change to adaptation to the environment. Genetic drift involves random changes in allele frequencies due to chance events, not because the traits improve survival or reproduction. Gene flow is the movement of alleles between populations, which can alter frequencies but isn’t driven by differential survival in a local environment. Mutation introduces new alleles, but it’s the variation source rather than the process that increases advantageous alleles through differential reproduction.