BIOL10005 Lecture Notes - Lecture 24: Allopatric Speciation, Continental Drift, Genetic Drift

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Deviations from h-w (cid:272)a(cid:374) (cid:271)e used to esti(cid:373)ate ea(cid:272)h ge(cid:374)otype"s fit(cid:374)ess. Relative fitness is divided by the highest ratio. If heterozygote is fittest, we can get balanced polymorphism: genetic drift. Alleles become more or less common simply by chance. In small populations, drift is stronger, outcome of evolution is unpredictable. In large populations, drift is directionless, unlike selection, it doesn"t favour any particular allele. In infinite population, the allele frequency stays 50:50: population bottleneck. When there is a catastrophic reduction in population, some alleles are lost. A group of closely related organisms that are very similar to each other and usually capable of interbreeding and producing fertile offspring. Reproductive isolation between populations -> restricted gene flow -> genetic and phenotypic differentiation -> speciation. Geographic barrier that leads to speciation (cid:894)deserts, river, continental drift, (cid:895) New species evolve from a single ancestral species while inhabiting the same geographic region -> disruptive speciation.

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