Question

what are the 5 agents of evolutionary change

Answer 1

The five primary agents (mechanisms) that cause evolutionary change are:

- Mutation — random changes in DNA that create new alleles. Example: a point mutation that gives antibiotic resistance in bacteria.
- Natural selection — differential survival/reproduction of individuals with certain heritable traits. Example: darker moths becoming common on polluted tree bark.
- Genetic drift — random changes in allele frequencies, strongest in small populations (includes bottleneck and founder effects). Example: allele loss after a population crash.
- Gene flow (migration) — movement of alleles between populations via individuals or gametes. Example: pollen transfer introducing new alleles to a plant population.
- Non-random mating (including sexual selection) — preferential mating that changes genotype frequencies (and can change allele frequencies when mate choice favors certain alleles). Example: females preferentially choosing brightly colored males.

(If none of these act on a population, allele frequencies remain constant — the Hardy–Weinberg equilibrium.)