AP Chapter 23.2

Mechanisms for Microevolution

Mutation Variation Natural Selection Speciation

Quick Review: Natural Selection

Organisms better suited to the environment

SURVIVE & REPRODUCEat a greater rate than those

less suited to the environment and this is how…

SPECIES EVOLVE

Quick Review: EvolutionMutation Variation Natural Selection

Speciation

1. Macroevolution (Speciation):Changes which occur at or above the species

level

2. Microevolution (Population Genetics):Changes which occur within the species level

Studying Evolution

Microevolution is awesome!

Microevolution:A small scale shift in allele frequencies over

timeMechanisms for Microevolution:

1. Mutations/Recombination2. Genetic Drift3. Gene Flow4. Natural Selection

Microevolution

I still love math!

1. Mutations/RecombinationRarely impact plants and animals

1/100,000 genes98% of our DNA is junk (noncoding)Somatic cell mutations die with animal

Only Gamete mutations are inherited

1. Mutations/RecombinationOnce a mutation occurs, nearly all phenotypic

variations will result from shuffling of existing alleles

2. Genetic DriftChanges in the gene pool of a population

Typical Effect: decrease in genetic variationThe smaller the population, the greater the

effect

Small population survives a disaster

2. Genetic Drift: Bottleneck effect

Small population is responsible for colonization

2. Genetic Drift: Founder effect

Individuals from different populations interbreedResult of immigration/emigration

3. Gene Flow

Promotes favorable traitsDisposes unfavorable traits

4. Natural Selection

Changes in the biosphere, select better suited alleles

4. Natural Selection: Environment

Individuals choose mates based on particular traits

4. Natural Selection: Sexual selection

Changes that affect the gene pool of a population

Mutation Variation Natural Selection Speciation

Summary: Microevolution