BIOLOGY 1M03 Lecture Notes - Lecture 5: Species, Genetic Drift, Phylogenetic Tree
12 Oct 2016
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Document Summary
Populations can be recognized as distinct species if they are reproductively isolated from each other, if they have distinct morphological characteristics, if they exploit different sets of resources, or if they form independent branches on a phylogenetic tree. Populations can become genetically isolated from each other if they occupy different geographic areas, if they use different habitats or resources within the same area, or if one population is polyploid and cannot breed with the other. When populations that have diverged come back into contact, several outcomes are possible (fusion, reinforcement through pre and post zygotic isolation - remaining differentiated or continuing to diverge, hybrid zone formation, speciation by hybridization, extinction) When gene flow ceases between populations, they then may diverge genetically as a result from action involving any among the other 4 factors (most remarkably natural selection, genetic drift, or mutation) This genetic divergence eventually may lead to speciation, the origin of new species.
