BIOL 103 Lecture Notes - Lecture 10: Dusky Seaside Sparrow, Species Problem, Sympatric Speciation
25 Nov 2016
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Speciation: evolution of two or more distinct species from single ancestral species. When complete a new branch is added to tree of life. If gene flow ends allele frequencies in isolated populations are free to diverge populations evolve independently of each other. If mutation, selection and genetic drift cause isolated populations to diverge sufficiently, distinct types or species form. Species: defined as evolutionarily independent population or group of populations. Four criteria to identify species are commonly used: the biological species concept, morphospecies concept, ecological species concept, phylogenetic species concept. Biological species concept: critical criterion for identifying species is reproductive isolation. This is logical because no gene flow occurs between populations that are reproductively isolated from each other. If two populations do not interbreed or produce viable and fertile offspring they are separate populations. Reproductive isolation can result from variety of events and processes. Prezygotic isolation: prevents individuals or species from mating.
