BIOL 150 Lecture Notes - Lecture 7: Mansio, Meiosis, Natural Selection
Document Summary
Process of speciation begins when gene flow is reduced or eliminated. Physical separation often results in genetic isolation. Vicariance - isolation of groups by physical barrier (mountain, new waterway, continental drift) Allopatric = different + homeland: dispersal. Clolonizing populatin likelt to be different from source population due to chance, that is, genetic drift: speciation in symparty. Species that live in the same geographic area are said to be sympatric. External events - result in disruptive selection favoring extreme phenotypes based on ecological niches. Sympatric populations are not physically isolated, but they may become isolated by preferences for different habitats. Apple maggot flies - eat, sleep, breath on apples. Apple trees in n america <300 years ago. Hawthorn flies, native to n america, live on hawthorn fruits. Fly"s ability to discriminate scents is genetically based. Hybrids cannot discriminate between apple and hawthorn fruits. Postzygotic: most general to most specific, most general to most specific.
