Evolution and population genetics
Adaptation
The process where a species or population becomes suited to its environment.
Allele frequency
The relative frequency of an allele at a particular locus in a population, expressed as a fraction or percentage.E.g
Allopatric speciation
Speciation that occurs after geographic separation e.g via a natural barrier such as a mountain range/river.
Adaptive radiation
A rapid increase in the number of lineages.
Coevolution
Adaptive changes in an organism triggered by an adaptive change in another organism.
Convergent evolution
The acquisition of the same biological trait in unrelated or distantly related organisms.
Frequency dependant selection
When fitness is dependent upon the frequency of a phenotype or genotype in a population.
Fitness
The relative reproductive capacity of an individual (also accounting for viability to maturity), scaled to fall between values of 0 and 1.
Gene pool
The set of all genes in a population.
Genetic drift
The change in the frequency of an allele in a population due to random chance.
Genotype
The genes that code for a trait e.g genes coding for eye colour. See also phenotype.
Inbreeding
The breeding of closely related individuals.
Interbreeding
Breeding between different species.
Macroevolution
Processes of evolution that happen over large timescales E.g adaptive radiation, extinction and stasis.
MEPs
Populations that have detectable amounts of de novo nucleotide changes among DNA sequences sampled at different time points.
Microevolution
Mechanisms that alter the frequencies of alleles E.g mutation, migration, genetic drift, natural selection. Over time these mechanisms can cause changes in the population that leads to a speciation event.
Natural selection
The process that results in the adaptation of an organism to its environment by selection of advantageous traits. Natural selection increases the frequency of advantageous alleles and leads to a decrease in the frequency of deleterious alleles, it acts at the level of the individual selecting for those that have a higher overall fitness compared to the rest of the population.
Parapatric speciation
When speciation occurs even though the population is continuous (i.e there are no physical barriers and individuals from the different populations can mix). In parapatric speciation populations evolve reproductive isolation from one another while continuing to exchange genes in the same ecological niche.
Peripatric speciation
Speciation that occurs after small populations of individuals break off as sub-populations that become isolated from the main population. These populations become separated by ecological factors wher sub-populations occupy distinct niches in their environment. (Similar to allopatric speciation but involves a smaller initial population size break off)
Phenotype
Traits that we can observe, e.g morphologies such as height, colour, shape.
Population
A group of individuals of a species that live and breed together in the same geographical location.
Population bottleneck
An event that dramatically reduces the population size e.g hunting, natural disasters.
Radiation
Rapid cladogenesis which represents adaptation as lineages move into a new niche or new habitat, see also adaptive radiation.
Recombination
Exchange of genetic sequence between chromosomes, in sexual reproduction this takes place during meiosis (cell division in sex cells) that occurs between homologous chromosomes.
Reproductively distinct
When a subpopulation has an altered reproductive system that makes it unable to breed with the rest of the population.
Species
Generally described as populations of individuals that interbreed and share morphological and genetic characteristics. Some organisms that are considered genetically and morphologically distinct can interbreed and produce viable offspring (hybridisation) so the definition becomes unclear here.
Speciation
The creation of a new species that is reproductively distinct from existing species, also called a speciation event. See types of speciation (allopatric, sympatric, parapatric).
Stasis
When there is a lack of evolutionary change over long time periods.
Sympatric speciation
Speciation that occurs even though there is no physical barrier separating populations.
Trait
A characteristic that is determined by genetics e.g height, hair colour, also called phenotype.