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Mechanism of Evolution

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Western University
Biology 2483A
Hugh Henry

Mechanism of EvolutionPhenotypegenotype plus the environmentdriven by differences in allele frequenciesMutationsraw materials that fuel adaptations fundamentallyrequire mutations to come up with different allelesthis is something that doesnt occur very oftenNot going to see very many changesonce in a whilehappens so infrequently we wont see short term changesStabilizingfavoring ones in the middleFlies that inject larvaes in plant gullswasps select small gull sizes know theres a flywant to have their eggs grow on the larvae because they have trouble with the larger onesbirds open the larger onesYou can have some examples in the population where 1 allele that is favoured essentially becomes fixed Geese is an examplehappen to involve hemoglobin with high affinity for oxygenmassive advantage for survival and reproduction Very strong forceall or nothingGenetic drift is a random processmainly affects small populations10 flowershalf are pink half are whitebranch falls and wipes out one phenotyperandom chancedifferent when the population is largerComputer simulations looking at populationsrandom eliminations from a populationeach line is a simulationlooking at the pointssometime you lose it entirely or it becomes fixed at 100Nothing is being favoured Larger populations are more towards the centerThe initial frequency of the A allele is 50 in all populations By generation 20 genetic drift has led to the fixation of the A allele in 7 populations and to its loss in 5 other populations Concept of genetic driftless variation in population Less Solution was to increase genetic variation by bringing in other organisms and get rid of harmful alleles By 1993 the greater prairie chicken population in Illinois had dropped to fewer than 50 birds and was experiencing the negative effects of genetic drift on small populations Centuries agomassive habitat over run with chickens and now barely anythingIn 1820 the prairies in which greater prairie chickens live covered most of Illinois In 1993 less than 1 of the original prairie habitat remained and the greater prairie chicken could be found in only 2 locationsvariation if you are losing alleles Chickens population was less than 50 because of land use changeconverted to farmlandlow genetic variation but this was manifest in terms of reproductionhalf of the
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