01:119:115 Chapter Notes - Chapter 21: Species Problem, Species, Allopatric Speciation
28 Mar 2016
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Group of populaions whose members can interbreed in nature and produce viable, ferile ofspring. Do not exchange gene with diferent species > reproducively isolated. Reproducive isolaion > mechanisms to prevent two diferent species from interbreeding and producing viable, ferile ofspring. Hybrids = ofspring of crosses b/w species. Diferent type of reproducive barriers ferilizaion: prezygoic isolaion mechanisms. Prezygoic barriers: occur before zygote formed > prevent ferilizaion from taking place. Postzygoic barriers prevent the hybrid zygote from developing into a viable, ferile adult: reduced hybrid variability. Geneic incompaibility > embryo dies early in development or has impaired survival in its environment ex: ***********: reduced hybrid ferility. Hybrids produced, but are sterile or not very ferile > probably bc meiosis does not occur normally ex: male donkey + female horse = a mule (sterile) (female horse 2n=64 and male donkey 2n=62: hybrid breakdown.
