01:119:115 Lecture Notes - Lecture 21: Gradualism, Chromosome, Ecological Niche
3 Apr 2016
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Hybrids - offspring of crosses between different species. Reproductive isolation can be classified by whether factors act before or after fertilization: prezygotic barriers - block fertilization from occurring i. ii. iii. Habitat isolation - two species encounter each other rarely, or not at all, because they occupy different habitats, even though they may not be isolated by physical barriers. Temporal isolation - species that breed at different times of the day, different seasons, or different years cannot mix their gametes. Behavioral isolation - courtship rituals and other behaviors unique to a species are effective barriers: mechanical isolation - morphological differences can prevent successful v. mating. Gametic isolation - sperm of one species may not be able to fertilize eggs of another species: postzygotic barriers - prevent the hybrid zygote from developing into a viable, fertile adult i. ii. iii. Reduced, hybrid viability - genes of different parent species may interact and impair the hybrid"s development.
