Evolution of Populations (Microevolution) Lecture Flashcards

This set of vocabulary flashcards covers the core concepts of population evolution, including mechanisms of microevolution, Hardy-Weinberg equations, and types of natural selection.

Microevolution

Changes that have occurred in a population’s allele frequencies over generations.

Population

A group of individuals of the same species occupying a given area that can interbreed.

Polymorphism

The presence of two or more distinct forms of a trait within a population, such as light and dark mice.

Gene pool

The collection of all alleles present in a population.

Allele frequency

A measure of how common an allele is in the population, calculated as the count of one allele relative to the whole population.

Mutations

The only source of new genes or new alleles by changing the DNA sequence; only those occurring in gametes ($ext{sperm/egg}$) can be passed to offspring.

Genetic equilibrium

A theoretical state in which a population is not evolving, which only occurs if the five Hardy-Weinberg Assumptions are met.

Hardy-Weinberg formula for allele frequencies

$$p + q = 1$$

Hardy-Weinberg formula for individual frequencies

$$p^2 + 2pq + q^2 = 1$$

$$p$$

In the Hardy-Weinberg formula, the frequency of the dominant allele.

$$q$$

In the Hardy-Weinberg formula, the frequency of the recessive allele.

$$p^2$$

In the Hardy-Weinberg formula, the frequency of homozygous dominant individuals.

$$2pq$$

In the Hardy-Weinberg formula, the frequency of heterozygous individuals.

$$q^2$$

In the Hardy-Weinberg formula, the frequency of homozygous recessive individuals.

Natural selection

The mechanism of microevolution involving differential success in reproduction; it is the only mechanism that consistently causes adaptive evolution.

Genetic Drift

Chance events that cause allelic frequency to change unpredictably, primarily in small populations, tending to reduce genetic variation.

Gene Flow

The movement of alleles among populations via the transfer of fertile individuals or gametes ($ext{pollen}$), which tends to reduce differences between populations.

Adaptation

Characteristics of an organism that enhance survival in a particular environment.

Fitness

The state of individuals possessing favorable variations that allow for survival and reproduction.

Founder Effect

A type of genetic drift occurring when a few individuals become isolated from a larger population and start a new population with a different allele frequency.

Bottleneck Effect

A sudden reduction in population size due to an environmental change, resulting in a surviving gene pool that may not reflect the original population.

Inbreeding

A condition in populations that eliminates variations in alleles and increases recessive, rare conditions, such as polydactyl in the Amish population.

Directional Selection

Natural selection that favors individuals at one end of the phenotypic range, causing a shift in allele frequency in a consistent direction.

Stabilizing Selection

Natural selection that favors intermediate phenotypes and eliminates extreme forms of a trait, such as human birth weights.

Disruptive Selection

Natural selection that favors individuals at both extremes of the phenotypic range, eliminating intermediate forms.

Sexual dimorphism

The occurrence of two distinct forms based on gender, resulting from sexual selection for competitive mating advantages.

Artificial selection

Process where humans select and mate organisms with desirable traits to produce specific phenotypes.

Heterozygote Advantage

A form of balancing selection where the heterozygous genotype ($Aa$) maintains two alleles because it provides a benefit, such as resistance to malaria in sickle-cell carriers.