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species

species

a population or group of populations whose members have potential to breed with one another in nature to produce viable, fertile offspring

taxonomy

the classification of species

speciation

the origin of new taxonomic groups

anagenesis

• phyletic evolution

• transformation from one species to another (original species no longer exists)

cladogenesis

• branching evolution

• new species arise from a population that buds from a parent species

allopatric speciation

geographical barrier isolates populations and prevents gene flow

adaptive radiation

spreading out of new species from a common ancestor

sympatric speciation

• new species arise within the area of parent populations

• anything that’s not a geographic barrier that stops organisms from being able to mate

polyploidy

occurs in plants causing chromosome numbers to multiply in some individuals

prezygotic barriers

• impede mating between species

• habitat, temporal, behavioral, mechanical, gametic

postzygotic barriers

• prevent hybrid zygotes from developing into fertile, viable adults

• hybrid infertility, reduced viability, hybrid breakdown

hybrid

cross between two species

hybrid zones

a region in which members of different species meet and mate

reinforcement

• strengthening reproductive barriers

• hybrid zone gets smaller

fusion

• weakening of reproductive barriers

• hybrid zone gets bigger

stability

continued formation of hybrids

extinction

• the disappearance of species from Earth

• generally occurs gradually