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Mechanisms of Speciation key event of a potential origin of species occurs when the gene pool of other pop is somehow severed from other pop of the parent sp. When gene pool isolated the splinter population can follow its evolutionary course. Changes in allele unaffected by gene flow from other pop. Reproductive isolation can result from 2 general senserios ALLOPATRIC speciation and SYMPATRIC specition ALLLOPATRIC SPECIATION geological processed can fragment a pop into 2 or more isolated pop. Ex mountain split./ land bridge/ lake using pop to isolate. Mountain lions birds and other big population survive this geological change but small pop become isolated and have its gene pool changed survivors don't necessary evolve into new species. They can adapt and start to change looks from ancestors. Speciation occurs when evolution of reproductive barriers occurs. SYMPATRIC SPECIATION\ occurs in a single generation if genetic change produces a reproductive barrier between mutant and parent pop. Doesn't happen much in animals but more in plants new plant sp have happened because of cell division that resulted in extra set of chromosomes. If a new sp happens this way means they have polyploid cells. Cant produce fertile hybrid wit patent sp. So reproductive isolation and speciation have occurred. POLYLOID don't always happen come from single parent sp but some from hybridization also. Ex oats potatoes bananas, peanuts, barley plums, sugarcane, coffee, wheat.f
REPRODUCTIVE Barriers Between Species what prevents biological sp that are closely related from interbreeding???? we think of barriers as PREZYGOTIC or POSTZYGOTIC, depending on whether they block interbreeding before/after fertilization of eggs. (zygotes) PREZYGOTIC BARRIER- prevents mating. Maybe time based/habitat isolation.\ t he sex organs are incompatible of some species...or some species copulate but their gamete are incompatible or don't survive to meet and fertilization doesn't happen. POSTZYGOTIC BARRIER- are mechanism that operate should interspecies mating actually occur and form zygotes. (egg from one species while sperm from another. EXAMPLE- mule is a hybrid of female hoarse and Male donkey,
THE ORIGIN OF SPECIES what is a species(sp.)???? identify sp. By biological sp concepts. Species as a pop. or group whose members have the potential to interbreed with-one another in nature to produce fertile offspring. Species can breed. Humans can breed because there the same species. Biological species concepts to all situation ex. based the definition of species on reproductive compatibility excluded organism that reproduce asexually. Biologists developed several other ways to define species. Classification of most organism is based mainly on observable and measurable physical trait. Distinguish fossils species mainly on observable physical trait. Second approach identifies identifies sp. In terms of their appearance. Another classification defines a species as a set of organisms with unique genetic hist. Biological species concept is particularly useful when focusing on ho e discrete groups of organisms may arise n be maintained by reproductive isolation,
Mechanisms of Speciation
