Ch 23 microevolution-160-11-st

Ch 23 microevolution-160-11-st - The evolution of...

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The evolution of Populations Chap 23
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Terms to remember while studying genetic variation Alleles :variant forms of a single gene Polymorphism : Occurrence of different alleles of a gene in a population Gene pool : All alleles of all genes in a population Genotype,Phenotype,heterozygous, Homozygous Population- Population is a group of interbreeding organisms present in a specific location at a specific time Allelic frequency- is the frequency of the particular allele Understanding population genetics
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Variation in a population Mutation and sexual reproduction produce the genetic variation that makes evolution possible -duplications can produce expanded genome w/new loci that may take on new functions -sexual reproduction more important on a generation to generation time scale -nearly all phenotypic variations result from recombinational shuffling
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Mutations Provide Raw Material For Evolution One type of mutation at the level of the gene. One type of mutation at the level of the chromosome. Mutations are usually neutral or harmful in their effects; only rarely are they beneficial. Mutations provide raw materials for evolution . Chromosomal rearrangement ,. gene duplication [expanded genome] Mutation rate is low in prokaryotes, but have many generations in a short period of time Mutation rates low in plants & animals- 1 in 100,000 genes per generation
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Diploidy Maintains genetic variation in the form of hidden recessive alleles Meiotic recombination and fertilization generate the genetic variation on which nat. selection acts genetically the same- no variation Figure 23.16 Asexual reproduction Female Sexual reproduction Female Male Generation 1 Generation 2 Generation 3 Generation 4 Recombination Sex is important!
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The Genetic Basis of Evolution For evolution to occur, genetic differences must at least partially account for phenotypic differences. Genetic basis for evolution -most are quantitative characteristics that vary along a continuum, not always discrete -part of the chromosome set may differ in diff populations
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Example of non genetic variation Difference is expression of a gene, not heritable Figure 23.9 A, B (a) Map butterflies that emerge in spring: orange and brown (b) Map butterflies that emerge in late summer: black and white
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(b) One more example…. Chemicals in their food
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This note was uploaded on 11/06/2011 for the course BIL 160 taught by Professor Krempels during the Spring '08 term at University of Miami.

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Ch 23 microevolution-160-11-st - The evolution of...

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