Which term describes the gradual changes in a population over generations?

• A. Evolution
• B. Adaptation
• C. Mutation
• D. Natural selection

Answer: (A)

Over many generations, a population's genetic makeup can shift as allele frequencies change due to different survival and reproduction rates. This is evolution. It’s a slow, cumulative process that can lead to new traits becoming common and even new species over long timescales. An individual trait that helps an organism survive in a given environment is an adaptation, but it’s a feature that results from evolution rather than the overall process itself. Mutation provides new genetic variation, the raw material for evolution, but by itself doesn’t describe the population-wide change across generations. Natural selection is one mechanism that drives evolution by favoring organisms with advantageous traits, allowing those alleles to spread through the population. Since the question describes gradual changes in a population over generations, evolution is the best fit.