A population not in Hardy-Weinberg equilibrium indicates that one or more of the five evolutionary agents are operating in a population 1.1 Causes of micro-evolution Five agents of evolutionary change 1. Mutation:A change in a cell’s DNA
– Mutation rates are generally so low they have little effect on Hardy-Weinberg proportions of common alleles.
– Ultimate source of genetic variation
2. Gene flow:A movement of alleles from one population to another
– Powerful agent of change
– Tends to homogenize allele frequencies
3. Nonrandom Mating:mating with specific genotypes
– Shifts genotype frequencies
– Assortative Mating: does not change frequency of individual alleles; increases the proportion of homozygous individuals
– Disassortative Mating: phenotypically different individuals mate; produce excess of heterozygotes
4. Genetic drift:Random fluctuation in allele frequencies over time by chance
- important in small populations
founder effect-few individuals found new population (small allelic pool)
bottleneck effect-drastic reduction in population, and gene pool size