AP Biology Natural Selection Vocabulary

evolution

Descent with modification; the process by which species accumulate differences from their ancestors as they adapt to different environments over time; also defined as a change in the genetic composition of a population from generation to generation.

natural selection

A process in which individuals that have certain favorable inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

taxonomy

A scientific discipline concerned with naming and classifying the diverse forms of life.

fossils

A preserved remnant or impression of an organism that lived in the past, usually found in sedimentary rock.

catastrophism

The theory that Earth's geological features and major changes in life forms were primarily caused by sudden, violent, and short-lived catastrophic events like asteroid impacts or massive floods, rather than gradual processes, leading to mass extinctions and rapid shifts in the fossil record.

gradualism

The theory that evolution occurs through a slow and steady accumulation of small changes over long periods of time, meaning new species evolve from existing ones through gradual, often imperceptible changes rather than sudden, major leaps.

uniformitarianism

The principle that the same natural processes operating today have always operated throughout Earth's history, meaning that studying current geological processes can help us understand past events, often summarized as "the present is the key to the past.”

descent with modification

The concept that living species today are descendants of ancestral species, with gradual changes accumulating over generations through natural selection, resulting in the diversity of life we see today; essentially, it's another way of saying "evolution" as defined by Charles Darwin.

artificial selection

The selective breeding of domesticated plants and animals by humans to encourage the occurrence of desirable traits.

biogeography

The scientific study of the past and present geographic distribution of species. Also provides evidence of evolution.

homologous structures

Structures in different species that are similar because of common ancestry.

vestigial organs

A feature of an organism that is a historical remnant of a structure that served important functions in the organism’s ancestors, but serve no current purpose

gene pool

Consists of all the alleles for all loci in a population

Hardy-Weinberg equilibrium

A population in which mating is random and none of the mechanisms of evolution are acting is in this. Allele and genotype frequencies remain constant from generation to generation for a population in this.

genetic drift

A process where allele frequencies fluctuate unpredictably from one generation to the next. It reduces genetic variation through loss of alleles, especially in small populations

bottleneck effect

Can result from a drastic reduction in population size due to a sudden environmental change. By chance, the resulting gene pool may no longer be reflective of the original population’s gene pool

founder effect

Occurs when a few individuals become isolated from a larger population. Allele frequencies in the small population can be different from those in the larger parent population due to chance

polymorphism

The occurrence of two or more distinct forms or phenotypes within a population of the same species, meaning that individuals of the same species can exhibit different physical characteristics due to variations in their genes at a specific locus.

microevolution

A change in allele frequencies in a population over generations

macroevolution

Broad patterns of evolutionary change above the species level. Examples of this type of change include the origin of a new group of organisms through a series of speciation events and the impact of mass extinctions on the diversity of life and its subsequent recovery.

speciation

An evolutionary process in which one species splits into two or more species.

anagenesis

A mode of evolution where a single species gradually changes over time within a single lineage, evolving into a new species without branching off into multiple lineages, essentially replacing the ancestral species completely.

cladogenesis

A pattern of evolutionary change that produces biological diversity by budding one or more new species from a parent species that continues to exist.

allopatric speciation

The formation of new species in populations that are geographically isolated from one another, which interrupts gene flow.

sympatric speciation

The formation of new species in populations that live in the same geographic area.

adaptive radiation

A period of evolutionary change in which a common ancestor evolves into many diversely adapted species, whose adaptations allow them to fill different ecological roles in their communities.

hybrid zone

A geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry.