How can natural selection alter allele frequencies in a population?

• A. By favoring advantageous alleles, increasing their frequency over generations.
• B. By randomly converting alleles without fitness consequences.
• C. By ensuring all individuals have identical genotypes.
• D. By removing all mutations from the gene pool.

Answer: (A)

Natural selection changes allele frequencies by favoring variants that increase fitness, so those alleles become more common in the population over generations. When individuals with advantageous traits survive and reproduce more, their alleles are passed on more often, gradually increasing in frequency. This relies on variation that is heritable and on differences in fitness shaped by the environment.

The idea that allele frequencies change randomly without fitness consequences isn’t how evolution is guided; natural selection isn’t a random process. Also, natural selection doesn’t produce identical genotypes across all individuals, and it cannot remove all mutations from the gene pool—new mutations keep arising, and selection acts on them over time.