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BIOL 208 (January 8, 2014) - Evolution, Fitness, Variation

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University of Alberta
Biology (Biological Sciences)
James Cahill

*  indicates point that I think are important BIOL 208 (January 8, 2014) What is Evolution? • Evolution doesn’t necessarily cause any visible change • Is the changes in allelic frequencies over time within the gene pool o *Is always ongoing, there is no end goal • Gene pool = the sum total of all the alleles in a population Allele – forms of a gene • *Only populations can evolve…. Individuals cannot evolve What CAUSES phenotypic variation among individuals within a population? • Mutations can create alleles and this will contribute to evolution • General Equation: o Let:  V P phenotypic variation  V G genetic variation  V E environmental effects • Ex. fertilize plants so that they grow bigger… we are not causing evolution by doing this o *VP= V +GV E  “What is” = nature + nurture • Not all phenotypic variations result in evolution since they may not be heritable 2 o *h = heritability on a scale of 0 to 1  0 means that it is completely environmentally determined  1  means that the trait if completely genetically determined 2 o h = V /G =PV /(G +VG) E o Examples: *  indicates point that I think are important  Horn size in bighorn sheep  h-squared = 0.69  Beak size in Darwin’s finches  h-squared = 0.65-0.90  Human height  h-squared = 0.8  Human longevity  h-squared <0.25 • *Evolution requires variation What Causes Evolution? • Mutation o Mutation-induced evolution is rare  Mutation itself is not rare • Natural Selection o Basic Principle: Lots of offspring produced but not all survive o Extremely important in most populations o Traits vary among individuals within a population and may be heritable o Some heritable traits give individuals an advantage  *Fitness is the proportional representa
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