BIOA02H3 Lecture : Speciation
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BIOA02H3 Full Course Notes
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Mechanisms of reproductive incompatibility fall into 2 categories: prezygotic reproductive barriers, operate before fertilization occurs (a) habitat isolation. Therefore never come into contact (b) temporal isolation. Mating periods do not overlap. (c) mechanical isolation. Differences in size and shape of reproductive organs. Duck genitalia: male penis & female reproductive tract (d) gametic isolation. Eggs don"t have appropriate chemical signals for sperm of another species. Or sperm is not able to attach to and penetrate the egg. (e) behavioural isolation. Individuals reject or fail to recognize potential mating partners. e. g. courtship r ituals: postzygotic reproductive barriers: Survival and reproduction of hybrid offspring are reduced. (a) low hybrid zygote viability. Fail to mature or have severe abnormalities. (b) low hybrid adult viability. Survival rate of hybrids is less than that of normal offspring (c) hybrid infertility. If populations are reunited before complete reproductive isolation has developed, 3 possible outcomes: hybrid offspring as fit as original populations: