AP Bio Unit 7 || Population Genetics and Hardy Weinberg

Gene Pool

Genetic Makeup of a population

Microevolution

Small scale genetic changes of a population, driven by random occurences

Random Occurences in mircoevolution

Mutations, genetic drift, gene flow/migration, and natural selection

Mutations

Mutations result in genetic variation in organisms

• forms new allels/phenotypes

• faster reproduction rate = more mutations in the gene pool

Genetic Drift

Chance events that cause changes in allele frequencies from one generation to the next

2 types of genetic drift

bottleneck and founder effect

Bottleneck effect

Occurs when a population encounters a non-selective disaster (floods, famine, fires, ect.), drastically reducing genetic diversity. The surviving gene pool may no longer represent the original population.

Founder Effect

Occurs when a few individuals of a population become isolated from the main population. A new gene pool is established and it is not representative of the main population.

Gene Flow

The movement of allels between populations due to migration of individuals or gametes.

Relative Fitness

Number of offspring an individual produces compared to the average number of offspring

Reproductive success is measured by ______ ______.

Relative fitness

Three modes of natural selection

1. Directional selection

2. Stabilizing Selection

3. Disruptive selection

Directional selection

Selection towards one extreme phenotype

Stabilizing selection

Selection towards the mean and against extreme phenotypes

Disruptive selection

Selection against the mean toward extreme phenotypes

Sexual selection

A form of natural selection where traits are favored because they increase an individual’s chances of mating rather than survival. (Peacock’s tail).

Hardy Weinberg Equillibrium

Asses if natural selection or other factors are acting on a population’s evolution at a locus; determines what the allele frequencies would be if the population was NOT evolving. If the calculated values match the actual values, then the population is not evolving.

Five conditions must be met to establish Hardy Weinberg Equillibrium

1. No mutations: No new alleles added to the gene pool

2. Random Mating: Individuals pair randomly without any preference for specific traits

3. No natural selection: All individuals have an equal chance of surviving and reproducing, regardless of their traits

4. Large population size: The population is large enough to prevent genetic drift (random changes in allele frequencies)

5. No gene flow

Hardy-Weinber Equation

p² + 2pq + q² = 1

• p² = percentage of homozygous dominant individuals (AA)

• 2pq = percentage of the heterozygous genotype (Aa)

• q² = percentage of the homozygous recessive genotype (aa)

p + q = 1

• p is the frequency of the dominant allele

• q is the prequency of the recessive allele

Dogs ___ to assert their ____.

PEE … DOMINANCE