Biology: Evolution

Speciation

the process by which one species splits into two or more species.

Biological species concept

A group of populations whose members have the potential to interbreed in nature and produce fertile offspring.

Reproductive isolation

prevents genetic exchange and maintains the gap between species through the fact that members of different species do not breed with one another.

Hybrids

The result of breeding distinct species. A mix of the two.

Morphological species concept

A definition of species in terms of measurable anatomical criteria.

Ecological species concept

Identifies species in terms of ecological niches, focusing on unique adaptations to particular roles in the biological community.

Phylogenetic species concept

Defines a species as the smallest group of individuals that share a common ancestor and thus form one branch on the tree of life.

Prezygotic barriers

prevent mating or fertilization in a species.

Postzygotic barriers

operate after hybrid zygotes are formed.

Habitat isolation

Species live in different habitats within the same area and rarely meet.

Temporal isolation

Breeding occurs at different times of the day or different seasons.

Behavioral isolation

different courtship rituals or other behaviors prevent mate recognition between species.

Mechanical Isolation

Differences in physical structures prevent successful mating.

Gametic isolation

Male and female gametes of different species fail to unite.

Reduced hybrid viability

The development or survival of hybrids is impaired.

Reduced hybrid fertility

Hybrids fail to produce functional gametes.

Hybrid breakdown

Offspring of hybrids are feeble or infertile.

Allopatric Speciation

The formation of species in populations that are geographically isolated from one another.

Sympatric speciation

a new species arises within the same geographical area as its parent species.

Polyploid

their cells have more than two complete sets of chromosomes.

Adaptive radiation

The evolution of many diverse species from a common ancestor.

Hybrid zones

members of different species meet and mate, producing at least some hybrid offspring.

Punctuated equilibria

long periods of little change, or equilibrium, punctuated by abrupt episodes of speciation.