Chapter 24: Origin of Species

BIOL 102

Speciation

formation of a new species

reproductive isolation

when biological barriers impede members of two species from interbreeding and producing viable, fertile offspring

prezygotic factor

barrier of reproduction that occurs before fertilization

postzygotic factor

barrier of reproduction that occurs after fertilization

temporal isolation

a type of prezygotic factor that impedes reproduction because two species are on separate breeding schedules

habitat isolation

a type of prezygotic factor that impedes reproduction because members of two species move or are otherwise separate physically

behavioral isolation

a type of prezygotic factor that impedes reproduction because of certain actions or behaviors

Gametic isolation

a type of prezygotic factor that impedes reproduction because the sperm of one species may not be able to fertilize the eggs of another

mechanical isolation

a type of prezygotic factor that impedes reproduction because of differing survival techniques which never allow them to interact

hybrid inviability

a type of postzygotic factor that impedes reproduction because an embryo is able to be produced, but cannot survive further development

Hybrid sterility

a type of postzygotic factor that impedes reproduction because the offspring that two species produces is not able to reproduce itself.

Allopatric speciation

A new species is created when one species is separated by geographical features, creating a new subpopulation

Sympatric speciation

when speciation occurs in populations that live in the same area due certain factors such as polyploidy, sexual selection, and habitat differentiation

Hybrid Zone

a region in which members of different species mate and produce hybrid offspring

Three ways hybrid zones can develop

reinforcement, fusion, and stability

hybrid zone reinforcement

species continues to diverge and stop producing hybrid

hybrid zone fusion

species becomes one and does not produce hybrid offspring

hybrid zone stability

fit hybrids continue to be produced

gradual speciation

species diverge gradually through small steps over time

punctuated speciation

species continue to exhibit a large change in a relatively short period of time followed by long period of stasis

What do hybrid zones reveal?

factors that cause reproductive isolation

At what pace does speciation occur?

speciation can occur either rapidly or slowly and can result in changes from many or few genes