In natural selection, natural selection acts on ___ but the change over time happens at the __?

In natural selection, natural selection acts on ___ but the change over time happens at the __?

• A. genes; organisms
• B. individuals; population
• C. populations; individuals
• D. alleles; genomes

Answer: (B)

Natural selection acts on individuals because fitness differences are realized in an organism’s survival and reproduction. An individual with a favorable trait leaves more offspring, increasing that trait’s representation in the next generation. But evolution—the gradual change in a population’s inherited makeup over time—occurs at the population level, as allele frequencies shift across many generations. In short, selection targets individuals; the cumulative change shows up in populations.

Natural selection acts on individuals because fitness differences are realized in an organism’s survival and reproduction. An individual with a favorable trait leaves more offspring, increasing that trait’s representation in the next generation. But evolution—the gradual change in a population’s inherited makeup over time—occurs at the population level, as allele frequencies shift across many generations. In short, selection targets individuals; the cumulative change shows up in populations.