We have learned how selection can change the frequencies of alleles and genotypes in populations.
Selection typically eliminates variation from within populations.
This would be true if it were not for the reality of Mutation which will restore genetic variation eliminated by selection. Thus, mutations are the fundamental raw material of evolution. We will be gin by considering what mutation will do as an evolutionary force acting by itself. Simply, mutation will change allele frequencies, and hence, genotype frequencies. However, it is instructive to examine the conditions where evolutionary forces oppose one another to give us a feel for the complexity of evolutionary processes.