Answer:
When a population is in Hardy-Weinberg equilibrium for a gene, it does not evolve and allelic frequencies will remain the same for generations.
There are five basic Hardy-Weinberg assumptions: there is no mutation, the mating is random, there is no gene flow, the population size is infinite and there is no selection.
If the assumptions are not met for a gene, the population can evolve for that gene (that is, the allelic frequencies of that gene may change).
The mechanisms of evolution are violations of the different Hardy-Weinberg assumptions: mutation, non-random mating, genetic flow, finite population size (gene drift) and natural selection.
