AP Biology - Microevolution

Directional Selection

One end of phenotypic range is selected against, population mean is the same and variation decreases/same

Disruptive Selection

Middle of phenotypic range is selected against, population mean same and variation increases

Stabilizing Selection

Both extremes of phenotypic range and selected against, population mean same and variation decreases

Balancing Selection

Both alleles are favored

Heterozygote Advantage

Heterozygous phenotype is most advantageous

Frequency-dependent Selection

Rare phenotypes are favored

Male Competition

Males fight for female access (intrasexual selection)

Female Choice

Females choose competing males (intersexual selection)

Sexual Dimorphism

Phenotype difference between males and females of a species

Population

Group of species in the same place

Gene pool

All alleles in a population

Allele frequency

Proportion of each allele in a gene pool

Geographic Variation

Allele frequentcy varies in different populations of a species

Allele Frequency Equation

freq(A) = 2(#AA)+(Aa)/2(population)

Microevolution

Change in allele frequencies of a population over generations

p

frequency of dominant allele

q

frequency of recessive alleles

HWE

Equilibrium implying no evolution in a population

What are the 5 assumptions of HWE

Random mating

No selection

No migration

No mutation

Large population size

What can be assumed with HWE

AA =p²

Aa = 2pq

aa = q²

Mechanisms of Evolution

Natural Selection

Genetic Drift

Gene Flow

Genetic Drift

Random allele frequencies changes due to non-mating (random events)

Founder Effect

Type of genetic drift, few individuals leave to form a new population

Bottleneck Effect

Type of genetic drift, massive die off shrinks population

Gene Flow

Migration

Chi²

(O-E)²/E

Alternative Hypothesis

The tested hypothesis

Null hypothesis

The opposite of the alternative hypothesis