Allele frequencies will remain constant unless one or more factors cause the frequencies to change.

If there is no change, there is no evolving.

Natural selection acts on the range of phenotypes in a population.

Evolution occurs as a population’s genes and their frequencies change over time.

All of the alleles of a population’s genes together make up a gene pool.

Allele frequency - % of any specific allele in the gene pool.

Genetic equilibrium – a population in which the frequency of alleles remains the same over generations.

Mutations are one cause of genetic change.

Lethal mutations disappear quickly, but mutations that cause a useful variation become part of the gene pool

Genetic drift – the alteration of allele frequencies by chance events.

Gene flow – transport of genes into or out of a population by migrating individuals.

Genetic drift, gene flow, and mutations can greatly affect small populations.

Natural selection is usually the most significant cause of changes in any gene pool.

Some variations increase or decrease an organism’s chance of survival in an environment.

Variations are controlled by alleles.

Allelic frequencies in a gene pool will change due to natural selection of variations.

If conditions are not met the genetic equilibrium is disrupted –

*population evolves and changes*

If conditions are met the genetic equilibrium stays the same–

*population does not evolve*

Genotype proportions remain constant – calculated from allele frequencies

P+Q = 1 or 100 percent = 1 or 100 percent(allele frequencies)(allele frequencies)

P22 + + 2PQ + Q2 = 1 or 100 percent1 or 100 percent(genotype frequencies)

P = frequency of the dominant allele in the population

Q = frequency of the recessive allele in the population

P2 = percentage of homozygous dominant individuals

Q2 = percentage of homozygous recessive individuals

2PQ = percentage of heterozygous individuals

If 98 out of 200 individuals in a population express the recessive phenotype, what percent of the population are

homozygous dominant?