Biology Vocab Evolution

Adaptation

A form of a heritable trait that enhances an individual's fitness.

Adaptive radiation

Macroevolutionary pattern in which a lineage undergoes a burst of genetic divergences that give rise to many species.

Allele frequency

Proportion of one allele relative to all alleles at a particular locus in a population's chromosomes.

Allopatric speciation

Speciation pattern in which a physical barrier arises and separates populations, ending gene flow between them.

Analogous structures

Similar body structures evolved separately in different lineages (by morphological convergence).

Balanced polymorphism

Maintenance of two or more alleles of a gene at high frequency in a population.

Biogeography

Study of patterns in the geographic distribution of species and communities.

Bottleneck

The reduction in population size is so severe that it reduces genetic diversity.

Coevolution

The joint evolution of two closely interacting species is a macroevolutionary pattern in which each species is a selective agent for traits of the other.

Comparative morphology

Scientific study of similarities and differences in body plans.

Directional selection

The mode of natural selection is when forms of a trait at one end of a range of variation are adaptive.

Disruptive selection

Mode of natural selection in which forms of a trait at both ends of a range of variation are adaptive, and intermediate forms are selected against.

Evolution

Change in a line of descent.

Fitness

Degree of adaptation to an environment, as measured by the individual's relative genetic contribution to future generations.

Fixed allele

Refers to an allele for which all members of a population are homozygous.

Fossil

Physical evidence of an organism that lived in the ancient past.

Founder effect

After a small group of individuals found a new population, allele frequencies in the new population differ from those in the original population.

Frequency-dependent selection

Natural selection in which a trait's adaptive value depends on its frequency among members of a population.

Gene flow

The movement of alleles between populations.

Gene pool

All the alleles of all the genes in a population; a pool of genetic resources.

Genetic drift

Change in allele frequency due to chance alone.

Genetic equilibrium

Theoretical state in which an allele's frequency never changes in a population's gene pool.

Half-life

Characteristic time it takes for half of a quantity of a radioisotope to decay.

Homologous structure

Body structures that are similar in different lineages evolved from a common ancestor.

Macroevolution

Evolutionary patterns and trends on a larger scale than microevolution.

Microevolution

Change in allele frequency.

Morphological convergence

The evolutionary pattern in which similar body parts (analogous structures) evolve separately in different lineages.

Morphological divergence

The evolutionary pattern in which a body part of an ancestor changes differently in its different descendants.

Natural selection

A major mechanism of evolution: the differential survival and reproduction of individuals of a population based on differences in shared, heritable traits. Outcome of environmental pressures.

Parapatric speciation

Speciation pattern in which populations speciate while in contact along a common border.

Plate tectonics theory

Theory that Earth's outermost layer of rock is cracked into plates, the slow movement of which conveys continents to new locations over geologic time.

Population

A group of organisms of the same species who live in a specific location and breed with one another more often than they breed with members of other populations.

Radiometric dating

Method of estimating the age of a rock or fossil by measuring the content and proportions of a radioisotope and its daughter elements.

Reproductive isolation

The end of gene flow between populations; part of speciation.

Sexual dimorphism

A trait that differs between males and females of a species.

Sexual selection

The Mode of natural selection in which some individuals outreproduce others of a population because they are better at securing mates.

Speciation

Emergence of a new species.

Stabilizing selection

The mode of natural selection in which an intermediate form of a trait is adaptive, and extreme forms are selected against.

Sympatric speciation

Speciation pattern in which speciation occurs within a population, in the absence of a physical barrier to gene flow.