Chapter 12: The Forces of Evolutionary Change — Other Mechanisms of Evolution (Vocabulary)

Vocabulary flashcards covering key terms from Chapter 12 on Hardy-Weinberg, genetic drift, gene flow, nonrandom mating, natural selection, and related concepts.

Evolution

Change in heritable traits from generation to generation; occurs in populations, not individuals, and can lead to new species.

Allele frequency

Proportion of a particular allele in a population's gene pool.

Hardy-Weinberg equilibrium

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

Null hypothesis (population genetics)

Assumption that allele frequencies do not change from one generation to the next.

p

Frequency of the dominant allele in a population (in Hardy–Weinberg terms).

q

Frequency of the recessive allele in a population (in Hardy–Weinberg terms).

p^2

Frequency of the homozygous dominant genotype (AA) in the next generation under Hardy–Weinberg equilibrium.

2pq

Frequency of the heterozygous genotype (Aa) in the next generation under Hardy–Weinberg equilibrium.

q^2

Frequency of the homozygous recessive genotype (aa) in the next generation under Hardy–Weinberg equilibrium.

Assumptions of Hardy-Weinberg equilibrium

No natural selection, no mutations, large population, random mating, and no migration.

Genetic drift

Random changes in allele frequencies due to chance events, often reducing genetic variation and driving evolution, especially in small populations.

Founder effect

A form of genetic drift that occurs when a small group starts a new population, changing allele frequencies.

Population bottleneck

A sharp reduction in population size causing genetic drift and loss of variation.

Nonrandom mating

Mating that is not random; can alter genotype frequencies and drive evolutionary change.

Sexual selection

A form of nonrandom mating where traits that increase mating success influence evolution.

Artificial selection

Human-directed selection that changes mating and trait frequencies.

Gene flow

Movement of alleles between populations, which tends to reduce differences between populations.

Migration

The act of individuals moving between populations, contributing to gene flow.

Natural selection

Differential survival or reproduction based on traits, leading to adaptive evolution.

Adaptive evolution

Evolution driven by natural selection, resulting in advantageous traits becoming more common.

Neutral evolution

Evolution driven by genetic drift or mutations with no selective advantage (non-adaptive).

Variation

Differences in heritable traits among individuals in a population.

Isolation

Separation of populations that reduces gene flow and can lead to speciation.

Hardy-Weinberg equation

p^2 + 2pq + q^2 = 1, with p + q = 1, linking allele frequencies to genotype frequencies.

Allele frequency change

A shift in the proportion of alleles in a population from one generation to the next (evidence of evolution).

Alleles

Different forms of a gene.

Genetic variation

The presence of different alleles or genotypes within a population.

Population size

The number of individuals in a population; crucial for the strength of genetic drift.