Evolution Terms
Evolution is the change in living things over generations, and the reason life is so diverse. These terms cover natural selection, genetic drift and gene flow, how new species form, the fossil record, and how relationships between species are traced.
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A
- AdaptationEvolutionAn adaptation is an inherited trait, shaped by natural selection, that helps an organism survive and reproduce in its current environment.
- Adaptive radiationEvolutionAdaptive radiation is the rapid evolution of many new species from one ancestral species, each adapted to a different way of life or ecological niche.
- AlleleGeneticsAn allele is any of the alternative forms of a gene or DNA sequence that can occupy the same position, or locus, on a chromosome.
- Analogous structuresEvolutionAnalogous structures are body parts in different species that look alike or do the same job but evolved separately rather than from a shared ancestor.
- AngiospermBotanyAn angiosperm is a flowering plant, a seed plant whose ovules develop inside an ovary that ripens into a fruit enclosing the seeds.
- ArchaeaMicrobiologyArchaea are single-celled prokaryotes that form their own domain of life, distinct from bacteria in their membranes, cell walls and genes.
- Artificial selectionEvolutionArtificial selection is the process in which people choose which plants or animals breed, so that the traits they want become more common over generations.
B
- BiodiversityEcologyBiodiversity is the variety of life in a place or on Earth as a whole, from genetic differences within species to the range of species and ecosystems.
- Bottleneck effectEvolutionThe bottleneck effect is the loss of genetic variation that follows a sudden, steep fall in population size, leaving only a few survivors to breed.
C
- Cambrian explosionPaleontologyThe Cambrian explosion is the relatively rapid appearance of most major animal groups in the fossil record, beginning about 540 million years ago.
- ChordateZoologyA chordate is an animal of the phylum Chordata, which at some stage has a notochord, pharyngeal slits, a hollow dorsal nerve cord and a tail.
- CoevolutionEvolutionCoevolution is the process in which two or more species that interact closely each drive evolutionary change in the other over many generations.
- Common ancestorEvolutionA common ancestor is an ancestral species or population from which two or more later species or groups of organisms have all descended.
- CompetitionEcologyIn ecology, competition is an interaction in which organisms needing the same scarce resource, such as food, light or space, reduce each other's success.
- Convergent evolutionEvolutionConvergent evolution is the independent evolution of similar traits in unrelated lineages that face similar environmental pressures.
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E
- Ecological nicheEcologyAn ecological niche is a species' role in its community: the conditions it tolerates, the resources it uses and how it interacts with other species.
- EukaryoteCell BiologyA eukaryote is an organism whose cells keep their DNA inside a membrane-bound nucleus and contain other membrane-bound organelles.
- EusocialityEntomologyEusociality is the most complex form of animal social life, in which colony members share brood care and only a few reproduce while the rest work.
- EvolutionEvolutionEvolution is change in the inherited traits of populations over generations, the process that has produced all life's diversity from common ancestors.
- ExtinctionPaleontologyExtinction is the permanent loss of a species, which happens when the last living individual of that species dies.
F
- FitnessEvolutionIn evolution, fitness is an organism's success at surviving and reproducing, measured by its genetic contribution to the next generation.
- FossilPaleontologyA fossil is any preserved evidence of past life in rock or sediment, from bones, shells and leaves to footprints and burrows.
- Founder effectEvolutionThe founder effect is the loss of genetic variation and shift in allele frequencies that occurs when a few individuals start a new population.
G
- Gene flowEvolutionGene flow is the movement of alleles from one population into another when individuals or their gametes migrate and then breed.
- Genetic driftEvolutionGenetic drift is a random change in allele frequencies from one generation to the next, caused by chance rather than by natural selection.
- Geologic time scalePaleontologyThe geologic time scale divides Earth's 4.6-billion-year history into eons, eras, periods and epochs, marked by events in the rock record.
- GymnospermBotanyA gymnosperm is a seed plant whose seeds develop exposed on cone scales or similar structures rather than enclosed in an ovary, as in pines and cycads.
H
- Hardy–Weinberg equilibriumGeneticsHardy–Weinberg equilibrium is the state in which allele and genotype frequencies in a population stay constant from one generation to the next.
- HomininPaleontologyA hominin is any member of the human lineage, the group of species, including modern humans, that are more closely related to us than to chimpanzees.
- Homologous structuresEvolutionHomologous structures are body parts in different species that share an underlying plan because they were inherited from a common ancestor.
- Hox genesDevelopmental BiologyHox genes are a family of genes coding for transcription factors that give each region along an animal's head-to-tail axis its identity during development.
M
- MammalZoologyA mammal is a vertebrate animal that has hair and feeds its young on milk made by the mother's mammary glands.
- Mass extinctionPaleontologyA mass extinction is an event in which a large share of Earth's species, often three-quarters or more, dies out in a geologically short time.
- Multiple sequence alignmentBioinformaticsA multiple sequence alignment lines up three or more DNA, RNA or protein sequences so that positions sharing an evolutionary origin fall in one column.
- MutationGeneticsA mutation is a lasting change in an organism's DNA sequence, ranging from a single altered base to large rearrangements of chromosomes.
- MutualismEcologyMutualism is a relationship between two species in which both partners benefit, such as flowering plants and the insects that pollinate them.
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P
- PhenotypeGeneticsA phenotype is the set of observable traits of an organism, such as its height or blood group, produced by its genotype acting with its environment.
- Phylogenetic treeEvolutionA phylogenetic tree is a branching diagram that shows the evolutionary relationships among organisms or genes as a hypothesis of shared descent.
- PhylumZoologyA phylum is a major rank in biological classification, below kingdom and above class, grouping organisms that share a basic body plan.
- PopulationEcologyIn ecology, a population is all the individuals of one species that live in the same area at the same time and can breed with one another.
S
- Sequence alignmentBioinformaticsSequence alignment is a way of lining up two or more DNA, RNA or protein sequences so that matching positions share a column, showing how similar they are.
- Sexual selectionEvolutionSexual selection is a form of natural selection in which traits spread because they help individuals win mates, even when they make survival harder.
- SpeciationEvolutionSpeciation is the evolutionary process in which one ancestral species splits into two or more species whose members can no longer interbreed.
- SpeciesEvolutionIn biology, a species is a set of populations whose members can interbreed in nature and produce fertile offspring, isolated from other such sets.
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V
- VertebrateZoologyA vertebrate is an animal with a backbone of vertebrae and a skull around the brain, such as a fish, amphibian, reptile, bird or mammal.
- Vestigial structureEvolutionA vestigial structure is a body part inherited from an ancestor that has become reduced and lost most or all of the function it had in that ancestor.
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