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SPECIATIONthe process by which one species splits into 2 or more species | -focal point of evolutionary theory because the appearance of new species is the source of biological diversity | -it forms the bridge between microevolution and macroevolution |
PREZYGOTIC BARRIERSimpede mating or hinder fertilization if mating does occur | - habitat isolation | -temporal isolation | -behavior isolation | -mechanical isolation | -gametic isolation |
HOW FAST DOES SPECIATION OCCUR?-the time interval between speciation events varies considerable, from a few thousand years to tens of millions of years | - punctuated equillibrium: isolated episodes of rapid speciation between long periods of little to no change | gradualism: accumulation of gradual changes over time |
| | WHAT IS A SPECIESa group of populations whose members can interbreed in nature and produce viable, fertile offspring, but cannot produce viable, fertile offspring with other such groups |
POSTZYGOTIC BARRIERSbarriers that prevent the hybrid zygote from developing into a viable, fertile adult | -reduced hybrid viability | -reduced hybrid fertility | -hybrid breakdown |
TYPES OF SPECIATIONAllopatric Speciation | geographic barrier between the 2 populations | Sympatric Speciation | populations that live in the same geographic area | -polyploidy | -habitat differentiation | -sexual selection |
| | WHY DOES SPECIATION OCCURreproductive isolation | the existence of biological barriers that impede members of 2 species from interbreeding and producing viable offspring |
HOW DOES SPECIATION OCCUR?- speciation can occur in 2 main ways depending on how gene flow is interrupted between populations of the existing species | - allopatric speciation-geographic isolation | -sympatric speciation- no geographic isolation |
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