Microevolution refers to small-scale changes in allele frequencies within a population over time. These changes are driven by several evolutionary mechanisms, each playing a distinct role in shaping genetic diversity. However, not all genetic processes contribute to microevolutionary change.

Mechanisms That Drive Microevolution

The primary forces that alter allele frequencies and drive microevolution include:

• Mutation: Introduces new genetic variants (alleles) into a population, serving as the ultimate source of genetic diversity.

• Genetic Drift: Causes random fluctuations in allele frequencies, especially in small populations, leading to evolutionary change by chance.

• Natural Selection: Favors alleles that confer a survival or reproductive advantage, increasing their frequency in the population over generations.

• Gene Flow (Migration): Moves alleles between populations, introducing new genetic material and altering allele frequencies.

The Role of Random Mating

Random mating is the process by which individuals pair by chance, not by genotype or phenotype. While it ensures that alleles combine randomly to form genotypes, it does not itself change allele frequencies in the population. Instead, random mating maintains Hardy-Weinberg equilibrium, preserving the existing genetic structure unless acted upon by other forces such as mutation, selection, drift, or migration.

Random mating does not introduce new variation or change allele frequencies—it simply shuffles existing alleles into new combinations.

Summary Table

Correct Answer

The process that does NOT contribute to micro-evolutionary change is:

(2) Random mating

Random mating alone does not alter allele frequencies and therefore does not drive microevolutionary change in populations