Origin of Species and Biological Species Concept

Biological species concept (what is a species?)

Group of populations that can interbreed and produce viable offspring

Reproductive isolation

Barriers that prevent interbreeding and production of viable offspring; limits formation of hybrids

Prezygotic barriers

Barriers that prevent fertilization and formation of hybrids

Habitat isolation

Barriers due to different habitats preventing mating

Temporal isolation

Barriers due to breeding at different times of day

Behavioral isolation

Barriers due to differences in courtship rituals

Mechanical isolation

Barriers due to morphological differences preventing mating

Gametic isolation

Barriers due to sperm of one species unable to fertilize eggs of another species

reduced hybrid viability

genes of parents impair hybrid's development/survival

reduced hybrid fertility

hybrids fail to produce functional gametes

hybrid breakdown

offspring of hybrids are weak or infertile

Postzygotic barriers

Barriers that reduce hybrid viability and fertility

Morphological species concept

Distinguishes species based on body shape and structural features

Ecological species concept

Defines species based on ecological niche

Allopatric speciation

Speciation that occurs due to geographic separation

sympatric speciation

The formation of new species in populations that live in the same geographic area

polyploidy

condition in which an organism has extra sets of chromosomes

autopolyploid

an individual that has more than two chromosome sets that are all derived from a single species

allopolyploid

fertile with each other, but not parent species.

habitat differentiation

subpopulation exploits a habitat, food source, or other resource not used by the parents.

hybrid zone

a geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

reinforcement

natural selection strengthens prezygotic barriers to reproduction

fusion

gene flow occurs when reproductive barriers weaken

stability

The state or quality of being stable in hybrid zones

punctuated equilibria

periods of stasis punctuated by sudden change in evolution