BIL 160 Lecture Notes - Lecture 4: Hybrid Speciation, American Bullfrog, Hybrid Zone
28 Apr 2016
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Document Summary
Microevolution: genetic change with a species over generations. Macroevolution: reproductive isolation between members of previously isolated populations resulting in two new daughter/sibling species. (read the link posted on her website: prezygotic isolation (prevents formation of viable zygotes) Environmental/spatial isolation (ex: frogs and bull frogs) Behavioral isolation (courtship rituals, complex give and take, rituals, prevents wasted effort with animal that won"t produce offspring) ex: birds of paradise . Gametic isolation (sperm and ova chemically incompatible and won"t form zygote) Hybrid inviability: zygote forms but dies after a series of cell divisions. Hybrid sterility: viable hybrid is produced but can"t produce offspring. Hybrid breakdown: successive generations of hybrids suffer greatly lowered because of meiotic difficulties fertility --> sterility. Eventually, they are selected out of the population. Species reinforcement: hybrids aren"t well suited, isolation is maintained. Species fusion: not separated to long, eventually share common gene pool.
