MUTATIONS
Lack of mutations in a population limits genetic change because no old alleles are turned into new alleles. The frequency of all alleles remains the same. Once a mutation occurs, the allele frequency is changed. Mutations add to the genetic variability of populations over time and are thus the ultimate source of variation for evolution. Mutations increase genetic variability that can be acted on by natural selection. In this way, mutations increase the opportunity for evolution of adaptations different from characteristics of the ancestral population.