Microevolution & Natural Selection

Vocabulary flashcards covering key terms and examples related to microevolutionary processes, mechanisms driving allele frequency changes, and forms of natural selection.

Microevolution

Change in allele frequencies within a population over time.

Macroevolution

Evolutionary change that results in the formation of new species or broader taxonomic groups.

Population (evolutionary definition)

All members of the same species occupying a specific area and interbreeding.

Allele

An alternate form of a gene at a particular locus.

Allelic Frequency

Proportion of a specific allele among all alleles for a given gene in a population.

Genotype

The genetic makeup of an individual organism.

Genotype Frequency

Proportion of a specific genotype within a population.

Genetic Variation

Amount of different genotypes present in a population.

Allelic Equilibrium

State in which allele frequencies remain constant from generation to generation (no evolution).

Mutation

Permanent change in DNA sequence; ultimate source of new alleles.

Gene Flow

Movement of alleles between populations via migration of breeding individuals.

Immigration

Individuals entering a population, introducing new alleles.

Emigration

Individuals leaving a population, removing alleles.

Nonrandom Mating

Mate selection based on genotype or phenotype rather than chance.

Assortative Mating

Individuals preferentially mate with others that share similar phenotypes, increasing homozygosity.

Sexual Selection

Type of natural selection favoring traits that increase mating success.

Genetic Drift

Random changes in allele frequencies due to chance, strongest in small populations.

Bottleneck Effect

Severe reduction in population size yields a gene pool based on a few survivors.

Founder Effect

When a small group colonizes a new area, rare alleles may become common by chance.

Natural Selection

Process in which individuals with higher fitness reproduce more, altering allele frequencies.

Adaptation

Heritable trait that increases an organism’s fitness in a specific environment.

Fitness (evolutionary)

Relative reproductive success of an individual compared with others.

Polygenic Trait

Trait controlled by multiple genes, producing a continuous range of phenotypes.

Directional Selection

Selection that favors one extreme phenotype, shifting the population mean.

Industrial Melanism

Example of directional selection where darker phenotypes rise due to polluted environments.

Drug Resistance

Directional selection in bacteria leading to survival of antibiotic-resistant strains.

Stabilizing Selection

Selection that favors intermediate phenotypes and acts against extremes.

Human Birth Weight

Classic example of stabilizing selection; infants ~8 lb have highest survival.

Disruptive Selection

Selection that favors two or more extreme phenotypes over intermediates.

British Land Snails

Example of disruptive selection; different shell patterns favored in fields vs. forests.

Paradise Whydah

Bird species illustrating sexual selection through elongated tail feathers in males.

Allele Loss

Potential disappearance of rare alleles from a small population through genetic drift.