Biological Evolution and Mechanisms of Change

Vocabulary terms and definitions covering the mechanisms of biological evolution, natural selection, genetics, reproduction types, speciation, and extinction.

Biological evolution

A scientific framework that analyzes how heritable traits (morphology, molecular sequences, and behavioral traits) change in frequency within a population over time.

Microevolution

Biological evolution occurring on a small time and spatial scale that affects the gene pool of a single population.

Macroevolution

Biological evolution where small genetic changes accumulate over vast lengths of time, producing noticeable changes in species.

Natural selection

A mechanism of evolution that causes changes in inherited trait frequencies over time because different individual traits allow organisms to deal more or less effectively with their environment.

Artificial selection

The process by which humans select preferred traits and intentionally breed organisms for a particular set of characteristics.

Fitness

A measure of how a particular trait contributes to reproductive success in a given environment; the ability of organisms to survive and reproduce.

Overproduction of Offspring

A prerequisite for natural selection wherein species produce more offspring than the environment can support, increasing competition for resources but raising the chance that some survive.

Genetic variation

The inherited variability among individuals in a population seen in different phenotypes, providing the raw material upon which selective forces can act.

Adaptation

A process leading to the increase in frequency of a structure, physiological process, or behavior that improves an organism's ability to survive and reproduce in a given environment.

Descent with modification

The concept that successive living species descend from previous generations with adaptations or changes, potentially yielding populations adapted to new niches or habitats.

Sexual reproduction

A reproductive process involving meiosis to produce gametes and fertilization, where two parents contribute genetic information to generate unique offspring with new allele combinations.

Asexual reproduction

A rapid mode of reproduction (including budding, fragmentation, binary fission, and vegetative propagation) yielding offspring that are genetically identical to a single parent.

Species

A population or group of populations whose individual members possess the potential to interbreed and produce fertile offspring in nature.

Gene pool

All the genes, including all the different alleles, possessed by all the individuals within a given population.

Genetic drift

The random fluctuation in allele frequencies of a population over time due to chance events, producing phenotypic changes that are more apparent in small populations.

Gene flow

The movement of genes into or out of a population resulting from the migration of individuals, which increases the genetic variability of the receiving population.

Genetic isolation

A state where organisms are limited in their genetic exchange and variety, typically due to geographical location or resource constraints.

Genetic equilibrium

A condition described by the Hardy-Weinberg principle where allele frequencies within a species do not change because five conditions (large population, no migration, random mating, no mutations, no natural selection) are met.

Speciation

The evolutionary formation of a new species from a preexisting species occurring when populations become isolated and their gene pools cease to blend.

Adaptive radiation

A divergent evolutionary process in which multiple distinct species branch off from a common ancestor by evolving diverse characteristics suited for different niches.

Coevolution

The process whereby two or more species residing in close proximity evolve reciprocal adaptations in response to one another.

Gradual extinction

The slow-paced elimination of a species over time caused by competition with other organisms, climatic shifts, or natural disasters, occurring at roughly the same rate as speciation.

Mass extinction

The rapid elimination of numerous species caused by sudden, catastrophic environmental events (such as meteor impacts or massive volcanic eruptions) that prevent species from adapting.