Unit 1 Evolution: Population Genetics (Video Notes)

Vocabulary flashcards covering key terms in population genetics, Hardy-Weinberg, and natural selection from the lecture notes.

Evolution

The change in allele frequencies in a population over time.

Allele

A variant form of a gene at a given locus.

Gene

A DNA sequence that encodes a trait.

Population genetics

Study of genetic variation in populations and how evolution changes genetic composition.

Hardy-Weinberg Equilibrium

A null model where allele frequencies remain constant across generations in the absence of evolutionary forces.

p (allele frequency)

Frequency of the dominant allele in a population.

q (allele frequency)

Frequency of the recessive allele in a population.

p^2

Genotype frequency of homozygous dominant individuals (BB) under HW equilibrium.

2pq

Genotype frequency of heterozygous individuals (Bb) under HW equilibrium.

q^2

Genotype frequency of homozygous recessive individuals (bb) under HW equilibrium.

HW Assumptions

No mutation, no gene flow, random mating, very large population size, no selection.

Mutation

The ultimate source of new genetic variation; changes in DNA sequence; rates are typically low.

Gene Flow

Movement of alleles between populations (migration; pollen and seeds).

Nonrandom Mating

Mating that is not random with respect to genotype; includes assortative, disassortative, or inbreeding; increases homozygosity.

Genetic Drift

Random fluctuations in allele frequencies, more pronounced in small populations; can lead to loss of alleles; includes founder and bottleneck effects.

Founder Effect

A few individuals establish a new population, leading to different allele frequencies.

Bottleneck Effect

A drastic reduction in population size causing loss of genetic variation due to random sampling of survivors.

Natural Selection

Differential reproduction based on genotype/phenotype; can be natural or artificial; only agent that produces adaptive changes.

Selection

Process by which certain genotypes have higher fitness and leave more offspring.

Assortative mating

Mating between phenotypically similar individuals; increases homozygosity.

Disassortative mating

Mating between phenotypically different individuals; increases heterozygosity.

Inbreeding

Mating with relatives; increases homozygosity; does not inherently change allele frequencies.

Fitness

Reproductive success of a genotype or phenotype.

Variation

Genetic differences among individuals; required for evolution.

Adaptation

A trait that increases fitness in the environment; often a result of natural selection.

Sexual selection

A form of natural selection where traits influence mating success; can cause sexual dimorphism.

Sexual dimorphism

Differences in traits between males and females due to differential selection.

Direction-Selected trait shift

A pattern where the mean trait value changes in one direction over time.

Disruptive selection

Selection that favors two extreme phenotypes, producing a bimodal distribution.

Stabilizing selection

Selection that favors intermediate phenotypes, narrowing the distribution.