Evolution of Populations

Flashcards covering the vocabulary for Chapter 18: Evolution of Populations, including genetic variation, natural selection types, genetic drift, and isolating mechanisms.

Evolution (genetic terms)

Any change in the frequency of alleles in a population over time.

Genotype

The combination of alleles an individual carries.

Phenotype

All physical, physiological, and behavioral characteristics of an organism, such as eye color or height; the trait upon which natural selection acts directly.

Evolutionary Fitness

An individual's success in passing genes to the next generation.

Evolutionary Adaptation

Any genetically controlled trait that increases an individual's fitness.

Mutation

A heritable change in genetic information.

Neutral Mutation

A mutation that does not affect phenotype and therefore does not affect fitness.

Lateral Gene Transfer

The passing of genes from one individual to another individual that is not its offspring, often occurring in bacteria via plasmids.

Genetic Recombination

The shuffling of genes during meiosis and crossing-over that produces heritable differences within families.

Single-Gene Trait

A trait controlled by only one gene, which may have only two or three distinct phenotypes.

Polygenic Trait

A trait controlled by two or more genes, leading to many possible genotypes and a range of phenotypes typically forming a bell curve.

Directional Selection

Form of natural selection in which individuals at one end of the curve have higher fitness than individuals elsewhere in the curve.

Stabilizing Selection

Form of natural selection in which individuals near the center of the curve have higher fitness than individuals at either end.

Disruptive Selection

Form of natural selection in which phenotypes at both the upper and lower ends of the curve have higher fitness than individuals near the middle.

Genetic Drift

A random change in allele frequency in a population, often occurring in small populations when individuals leave more descendants by chance.

Bottleneck Effect

A change in allele frequency following a dramatic reduction in the size of a population, often due to a natural disaster.

Founder Effect

A situation in which allele frequencies change as a result of the migration of a small subgroup of a population to a new habitat.

Genetic Equilibrium

A condition in which allele frequencies in a population's gene pool do not change.

Hardy-Weinberg Principle

Principle stating that allele frequencies in a population should remains constant unless one or more of five specific factors causes change: nonrandom mating, small population size, gene flow, mutations, or natural selection.

Hardy-Weinberg Equation

The mathematical representation of genotype frequencies where $p^2 + 2pq + q^2 = 1$ and allele frequencies where $p + q = 1$.

Sexual Selection

A practice in which individuals select mates based on size, strength, or coloration, resulting in nonrandom mating.

Reproductive Isolation

Condition in which two populations can no longer interbreed, leading to the splitting of the gene pool into separate species.

Behavioral Isolation

Form of reproductive isolation in which two populations that were once able to interbreed evolve differences in courtship rituals or other behaviors.

Geographic Isolation

Form of reproductive isolation in which two populations are separated by geographic barriers such as rivers, mountains, or bodies of water.

Temporal Isolation

Form of reproductive isolation in which two or more species reproduce at different times.

Hox Genes

A group of regulatory genes that determines which parts of an embryo develop into specific structures like arms, legs, or wings, and control their sizes and shapes.

Molecular Clock

A method that uses mutation rates in DNA to estimate the time that two species have been evolving independently.