How does natural selection drive adaptation in a population?

How does natural selection drive adaptation in a population?

• A. Variation within a population plus differential survival leads to allele frequency shifts favoring advantageous traits.
• B. All individuals are identical; no adaptation occurs.
• C. Adaptation arises only through genetic drift in small populations.
• D. Natural selection increases genetic variation.

Answer: (A)

Variation in a population provides the material natural selection acts on. When the environment favors certain traits, individuals with the corresponding alleles are more likely to survive and reproduce. Their offspring inherit those alleles, so those advantageous alleles become more common over generations. As this process repeats, the population becomes better suited to its environment—that’s adaptation driven by natural selection. If everyone were identical, there’d be no variation for selection to act on, so no differential survival to drive adaptation. While genetic drift can change allele frequencies by chance, especially in small populations, natural selection specifically hinges on fitness differences among individuals. And natural selection doesn’t generally increase genetic variation; it tends to reduce variation at the traits it strongly favors (though other forces can maintain or reintroduce variation).

Variation in a population provides the material natural selection acts on. When the environment favors certain traits, individuals with the corresponding alleles are more likely to survive and reproduce. Their offspring inherit those alleles, so those advantageous alleles become more common over generations. As this process repeats, the population becomes better suited to its environment—that’s adaptation driven by natural selection.

If everyone were identical, there’d be no variation for selection to act on, so no differential survival to drive adaptation. While genetic drift can change allele frequencies by chance, especially in small populations, natural selection specifically hinges on fitness differences among individuals. And natural selection doesn’t generally increase genetic variation; it tends to reduce variation at the traits it strongly favors (though other forces can maintain or reintroduce variation).