Chapter 23: The Evolution of Populations

Vocabulary flashcards covering key concepts, mechanisms, and definitions from Chapter 23: The Evolution of Populations.

Microevolution

The change in allele frequencies in a population over generations, representing evolution at its smallest scale.

Genetic Variation

Differences in genes or other DNA sequences among individuals, which serve as a prerequisite for evolution by natural selection.

Phenotypic Plasticity

The ability of a single genotype to produce different phenotypes under different environmental conditions.

Point Mutation

A change in a single nucleotide within a DNA sequence.

Heterozygote Protection

The maintenance of a pool of alleles that could be beneficial if the environment changes, accomplished by hiding recessive harmful mutations from natural selection in heterozygous individuals.

Neutral Variation

Genetic variation that confers no selective advantage or disadvantage, often occurring in noncoding regions or due to genetic code redundancy.

Population

A group of individuals of the same species that live in the same area and interbreed.

Gene Pool

All copies of every allele at every locus in all members of a population.

Fixed Locus

A state where all individuals in a population are homozygous for the exact same allele at a specific locus.

Hardy–Weinberg Model

A mathematical model describing the expected genetic makeup for a population that is not evolving at a particular locus.

Hardy–Weinberg Equilibrium

A stable state where allele and genotype frequencies in a population remain constant from generation to generation, serving as a null hypothesis of no evolution.

Adaptive Evolution

A continuous process in which traits that enhance survival or reproduction increase in frequency in a population over time.

Genetic Drift

A process in which chance events cause allele frequencies to fluctuate unpredictably from one generation to the next, tending to reduce genetic variation.

Founder Effect

A form of genetic drift that occurs when a few individuals become isolated from a larger population, establishing a new population with allele frequencies different from the parent population.

Bottleneck Effect

A severe reduction in population size due to a sudden environmental change, resulting in a gene pool that may no longer reflect the original population's gene pool.

Gene Flow

The movement of alleles among populations through the transfer of fertile individuals or gametes.

Relative Fitness

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.

Directional Selection

A mode of natural selection that favors individuals at one extreme end of the phenotypic range.

Disruptive Selection

A mode of natural selection that favors individuals at both extremes of the phenotypic range over intermediate phenotypes.

Stabilizing Selection

A mode of natural selection that favors intermediate variants and acts against extreme phenotypes.

Sexual Selection

A process in which individuals with certain heritable traits are more likely to obtain mates than other individuals of the same sex.

Sexual Dimorphism

A difference in secondary sexual characteristics between males and females of the same species.

Intrasexual Selection

Direct competition among individuals of one sex (often males) for mates of the opposite sex.

Intersexual Selection

A form of sexual selection (mate choice) occurring when individuals of one sex (usually females) are choosy in selecting their mates.

Balancing Selection

Natural selection that preserves variation at some loci by maintaining two or more phenotypic forms in a population.

Frequency-Dependent Selection

A type of balancing selection in which the fitness of a phenotype depends on how common it is in the population.

Heterozygote Advantage

A situation in which heterozygotes at a particular locus have higher fitness than both types of homozygotes.