Chapter 12: The Forces of Evolutionary Change continuation 5

Flashcards covering key vocabulary related to evolutionary change, genetic drift, Hardy-Weinberg principle, nonrandom mating, and gene flow, based on Chapter 12 lecture notes.

Biological Evolution

Changes in heritable traits from generation to generation, which may lead to the development of different species.

Evolution (Population Level)

Occurs in populations or species when allele frequencies change from one generation to the next, over time; it does not occur in individuals.

Hardy-Weinberg Equilibrium

The unlikely situation in which allele frequencies do not change between generations, serving as a null hypothesis for testing evolution.

Assumptions of Hardy-Weinberg Equilibrium

A population must meet all of the following: no natural selection, no mutations, a population large enough to eliminate genetic drift, random mating, and no migration.

Genetic Drift

Allele frequencies shift dramatically due to chance events that remove individuals or alleles, often decreasing variation within a population.

Natural Selection vs. Genetic Drift

Natural selection removes individuals based on traits (adaptive evolution), while genetic drift removes individuals randomly without regard to traits (non-adaptive or neutral evolution). Both decrease variation.

Founder Effect

A type of genetic drift occurring when only a few individuals establish a new population, potentially changing the allele frequency compared to the source population.

Population Bottleneck

A type of genetic drift that occurs when a disaster drastically reduces the size of a population, leading to a loss of genetic variation.

Nonrandom Mating

Mating patterns in a population are altered, often by sexual or artificial selection, which prevents random mating and causes evolution.

Gene Flow

The movement of alleles between populations, typically caused by migration, which affects allele frequencies in both populations and reduces overall genetic differences between them.

p (Hardy-Weinberg Principle)

Represents the frequency of the dominant allele in the population.

q (Hardy-Weinberg Principle)

Represents the frequency of the recessive allele in the population.

p^2 (Hardy-Weinberg Principle)

Represents the frequency of homozygous dominant individuals in the next generation.

q^2 (Hardy-Weinberg Principle)

Represents the frequency of homozygous recessive individuals in the next generation.

2pq (Hardy-Weinberg Principle)

Represents the frequency of heterozygous individuals in the next generation.

Real Populations and Hardy-Weinberg

In real populations, the assumptions of Hardy-Weinberg equilibrium are always violated, meaning allele frequencies continually change due to natural selection, mutations, genetic drift, non-random mating, and migration.