How does natural selection affect allele frequencies in a population?

Natural selection is a fundamental mechanism of evolution that influences allele frequencies within a population. It operates by favoring certain traits that enhance survival and reproductive success in a given environment. When individuals with advantageous alleles are more likely to survive and reproduce, those alleles are passed on to the next generation more frequently than others that confer less advantage.

As a result, over time, the frequencies of alleles that contribute to beneficial traits increase in the population. This selective pressure shapes the genetic makeup of the population, leading to adaptations that enhance fitness in response to environmental challenges. Consequently, the correct choice emphasizes that natural selection does not affect all alleles uniformly; rather, it actively shapes the genetic variation by preferentially increasing the prevalence of advantageous alleles.

The other options do not accurately reflect the role of natural selection. For instance, suggesting that all alleles become equally common would imply that there is no selective pressure, which contradicts the principle of natural selection. Proposing that natural selection leads to genetic drift misrepresents the processes, as genetic drift is a separate mechanism influenced by random sampling. Lastly, stating that it has no effect on genetic variation overlooks the significant impact natural selection has on shaping allele frequencies and the overall genetic structure of populations.