Forces of Evolutionary Change

This flashcard set covers the mechanisms of evolution, historical figures in evolutionary thought, Hardy-Weinberg equilibrium, and modes of natural and sexual selection as discussed in Lecture 14.

Evolution

The process by which populations of organisms change over generations.

Natural Selection

A process whereby organisms better adapted to their environment tend to survive and produce more offspring.

Descent with Modification

The principle that life descends through generations from a common ancestor with changes occurring through genetic inheritance.

Struggle for Existence

A concept from Thomas Robert Malthus stating that plants and animals produce more offspring than can survive, leading to competition for resources.

Uniformitarianism

Charles Lyell's principle that the same natural laws and forces that molded the planet in the past operate continuously in the present.

Wallace Line

An invisible boundary discovered by Alfred Russel Wallace that separates the distinct zoological regions of Asia and Australia.

Modern Evolutionary Synthesis

Julian Sorell Huxley's comprehensive explanation of nature supported by evidence from multiple branches of biology including genetics, botany, and paleontology.

Allelic Frequency

The percentage of a particular allele out of all alleles within a population.

Species

Groups of organisms that can successfully breed together to produce viable, reproductive offspring.

Population

A group of individuals from the same species that are geographically isolated.

Microevolution

Changes in allele frequencies within a population over a short time frame.

Hardy-Weinberg Equilibrium

An assumption that allele and genotype frequencies do not change between generations if natural selection, mutations, migration, and non-random mating are absent and the population is infinitely large.

Hardy-Weinberg Allele Formula

$p + q = 1$, where $p$ is the frequency of the dominant allele and $q$ is the frequency of the recessive allele.

Hardy-Weinberg Genotype Formula

$p^2 + 2pq + q^2 = 1$, where $p^2$ is the frequency of the homozygous dominant genotype, $2pq$ is the frequency of the heterozygous genotype, and $q^2$ is the frequency of the homozygous recessive genotype.

Stabilizing Selection

A mode of natural selection where average values of a characteristic are favored over extreme phenotypes.

Directional Selection

A mode of natural selection where one extreme of a characteristic confers a survival advantage, shifting the population phenotype in one direction.

Disruptive Selection

A rare mode of natural selection where a phenotypic trait moves toward both of its extremes.

Intersexual Selection

A type of sexual selection where individuals of one sex (often females) choose mates based on attractiveness, such as the feathers of a peacock.

Intrasexual Selection

A type of sexual selection where members of the same sex compete or use intimidation to defeat competitors for mating access.

Gene Flow

The movement of alleles from one population to another, occurring when individuals migrate or populations join.

Genetic Drift

A chance alteration of gene frequencies in a population that most strongly affects small populations.

Bottleneck Effect

A form of genetic drift occurring when a population is drastically reduced in size, resulting in a loss of genetic diversity.

Founder Effect

A form of genetic drift occurring when a few individuals migrate to a new, isolated location to start a new population with limited genetic variation.

Fitness

The relative success of an individual at passing on its genes to the next generation compared to other individuals in the population.

Selective Pressure

A measure of how strongly an environment selects for or against a particular trait.

Artificial Selection

The process by which humans choose and breed organisms for specific phenotypic traits, such as the development of different vegetables from wild mustard.