How do we know if a population is evolving?

1. How do we know if a population is evolving?

2. When is a population not evolving? • How do we know if a gene pool has changed? • The Hardy-Weinberg Principle can help answer these questions.

3. The Hardy-Weinberg Principle states: • Genetic equilibrium will be reached if the frequency of alleles remains stable generation after generation. • Genetic equilibrium = no evolution occurring.

4. Hardy-Weinberg Principle • Conditions necessary for genetic equilibrium are: • No mutation occurs • Immigration and emigration do not occur (population is isolated from other populations) - no gene flow. • Population is very large • Mating is totally random • All individuals survive and reproduce equally (no natural selection)

5. Hardy-Weinberg Principle • It is virtually impossible to meet these conditions. • Allelic frequencies do change in populations, therefore evolution occurs. • The main application of this principle is calculating allele and genotype frequencies in a population.

6. In a population, the sum frequency of alleles will equal 1. • This can be expressed as: • p + q = 1 • Where: • p = frequency of the dominant allele • q = frequency of recessive allele

7. Hardy-Weinberg Equation • p2 + 2pq + q2 = 1 • Where: • p2 = frequency of individuals homozygous for the dominant allele • 2pq =frequency of heterozygous individuals • q2 = frequency of individuals homozygous for the recessive allele