Speciation Definitions

Evolution

Change in allele frequencies within a population over time.

Species

A group of organisms that can naturally interbreed to produce fertile offspring.

Speciation

The formation of new species from a common ancestor.

Population

A group of members of the same species, in the same location, at the same time.

Deme

A population with little or no gene flow with other populations of the same species.

Cline

A gradual change in a phenotypic characteristic across a geographic range of a species.

Ring species

A species that displays a gradual change in a phenotypic characteristic, with adjacent populations able to interbreed, but ends of the ring unable to do so.

Punctuated equilibrium

A model of evolution characterized by long periods of stasis punctuated by short bursts of rapid change.

Gradualism

A slow, constant rate of evolutionary change over time.

Divergent evolution

Speciation where two or more new species arise from one common ancestor.

Adaptive radiation

Speciation where one common ancestor splits into multiple new species.

Convergent evolution

Unrelated species evolve similar traits due to similar selection pressures.

Parallel evolution

Related species evolve similar characteristics despite no gene flow.

Coevolution

Joint evolution of two species that exert selection pressure on each other.

Homologous structures

Similar structures in different species that indicate a common ancestor.

Analogous structures

Structures with similar function but different evolutionary origins.

Vestigial organs

Reduced or functionally lost structures that provide evidence of a common ancestor.

Genome

The complete set of DNA of an organism, including all its genes.

mtDNA

Mitochondrial DNA, passed down through the maternal line.

nDNA

DNA found within the nucleus of a cell.

Gene flow

The transfer of genes and alleles between populations through reproduction.

Ploidy

The number of sets of chromosomes in a cell.

Euploidy

Complete sets of chromosomes (e.g., n, 2n, 3n).

Eupolyploidy

Having at least one extra complete set of chromosomes.

Aneuploidy

An abnormal number of chromosomes due to non-disjunction.

Amphiploidy

Formation of a fertile hybrid due to somatic doubling after allopolyploidy.

Inbreeding

Interbreeding between closely related individuals.

Outbreeding

Interbreeding between individuals that are not closely related.

Hybrid vigour

Increased robustness in hybrids from interbreeding different species.

Non-disjunction

Failure of chromosomes to separate properly during cell division.

Autopolyploidy

Abnormal chromosome number from parents of the same species.

Allopolyploidy

Abnormal chromosome number from parents of different species.

Colchicine

A drug that inhibits spindle formation during meiosis.

Instant speciation

Sudden chromosomal change creating a new species in one generation.

Selection pressure

Environmental factor that influences the survival and reproduction of organisms.

Mimicry

One species adopting characteristics of another to avoid predation.

Specialists

Species with a narrow ecological niche.

Generalists

Species with a wide ecological niche.

Prezygotic RIM

Reproductive isolation mechanism that prevents offspring formation before fertilization.

Postzygotic RIM

Reproductive isolation mechanism that prevents the viability of offspring after fertilization.

Allopatric speciation

Speciation due to physical barriers.

Sympatric speciation

Speciation occurring without physical barriers.

Vicariance

A geographical event causing large-scale allopatric speciation.

Niche differentiation

Different resource use by organisms to reduce competition.

Phylogeny

The evolutionary history of a group of organisms.

Clade

A group of organisms including a common ancestor and all its descendants.