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Lecture 35

BIOL 1020 Lecture 35: Lecture 35

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Biological Sciences
BIOL 1020
Joy Stacey

Lecture 35 Overview: The smallest unit of evolution One misconception is that organisms evolve, in the Darwinian sense, during their lifetimes Natural selections acts on individuals, but only populations evolve Microevolution is a change in allele frequencies in a population over generations ** Mutation and sexual reproduction produce the genetic variation that makes evolution possible ** Two processes, mutation and sexual reproduction, produce the variation in gene pools that contributes to differences among individuals Variation Within a Population Both discrete and quantitiative characters contribute to a variation within a population Discrete characters can be classified on an eitheror basis o Mendels flowers Either have trait or do not Quantitative characters vary along a continuum within a population Eg. Human skin color Variation Between populations Most species exhibit geographic variation, difference between gene pools of separate populations or population subgroups o Eg. Squirrels in Winnipeg and squirrels in lake of the woods Mutation Mutations are changes in the nucleotide sequences of DNA Mutations cause new genes and alleles to arise Only mutations in cells that produce gametes can be passed on to offspring o Any other mutation would not be passed to next generation Sexual reproduction ** more important than mutations for humans and sexually reproducing organisms Sexual reproduction can shuffle existing alleles into new combinations In organisms that reproduce sexually, recombination of alleles is more important than mutation in producing the genetic difference that make adaptation possible. o Requires energy but is extremely important The HardyWeinberg equation can be used to test whether a population is evolving
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