Final answer:
Natural selection disrupts Hardy-Weinberg equilibrium because genotypes with higher fitness produce more offspring, thereby altering allele frequencies in a population.
Step-by-step explanation:
Natural selection violates the Hardy-Weinberg equilibrium because different genotypes can have different relative reproductive success, which is also called fitness. This variation in fitness among individuals in a population result in some genotypes being more likely to pass on their genes to the next generation, leading to changes in allele frequencies over time.
Thus, natural selection is one of several mechanisms that can disrupt the Hardy-Weinberg equilibrium, alongside mutation, genetic drift, gene flow, and non-random mating.