Chapter 23-1

Chapter 23-1 - Chapter 23 : The Evolution of Populations...

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Chapter 23 : The Evolution of Populations Population: a group of individuals of the same species o Example: homo sapieans in this room Populations evolve, not individuals Evolution o A change in allele frequency over time Western Historical Context Gregor Mendel o Austrian monk whose breeding experiments with peas shed light on the rules of inheritance o Contemporary of Darwin Modern synthesis o A conceptual synthesis of Darwinian evolution, Mendelian inheritance, and modern population genetics Logarithmic growth o Potential for rapid population growth when resources are not limiting Resource availability generally limits population size o Both of these things lead to a competition for resources “struggle for existence phenotypic variability o morphology, physiology, behavior Natural Selection o Survival and reproduction of the “fittest” individual
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o Selected from the variability of the population Some variability results from heritable genotypic differences Microevolution o Small changes that occur in a population over time that may lead to . .? Adaptive evolution o A change in the phenotypic constitution of a population owning to a selection of inheritable variation among phenotypes that changed in genotypic consultation of the population For evolution to occur, there has to be a change in genotype of population which changed phenotypes Phenotype vs. Genotype Know basic genotypes and phenotypes ! Phenotypes: all expressed traits of an organism Genotypes: the entire genetic make up of an individual or a subset of an individual genes o Its full complement of genes and the two alleles that comprise each locus These must change in order to evolve o Change in allele frequency over time o Adaptive evolution Can you have a change in alleles that has no change in fitness? o Yes, and it doesn’t matter because the phenotype doesn’t have an advantage Evolution
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A change in allele frequency in a population over time o Basically, a change in the gene pool. Population genetics Examines the frequency distribution and inheritance of alleles within a population Natural selection -> allele frequencies Evolution o Due to differential reproduction among organisms bearing different allele o Fitness of the selected allele determines viability of offspring o Evolutionary changes are not “good” or “progressive” in any absolute sense. Mutations and all can sometimes be bad.
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This note was uploaded on 11/15/2010 for the course BIOL 1202 taught by Professor Gregg during the Spring '08 term at LSU.

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Chapter 23-1 - Chapter 23 : The Evolution of Populations...

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