Evolutionary Biology BIOL 3350 Dr Lisa Rapaport Lecture 7 Part 1 Notes Natural Selection I Understanding Selection and Fitness A What is natural selection 1 Non random differential propagation of phenotypes within a generation HWE is the null hypothesis it is what we expect to happen More favorable characteristics become more common in the next generation see a change Evolution is acting between generation evolution is where we Natural selection works within generation but changes are seen between generation which is evolution Traits have to be heritable in order for evolution to occur II Agents of Evolution A Deviations from Hardy Weinberg Equilibrium 1 If a population is not in HWE then we can conclude that some kind of force is acting on the population 2 Sexual selection is a subset of natural selection B Measuring Natural Selection 1 Natural selection is not just about survival it is about 2 Absolute fitness contribution of phenotype to the next reproduction as well generation 3 Differences in survival change the strength of selection and change the rate at which allele frequencies change 4 Big difference in survival causes quick change 5 Very little differences rate of change is very slow and selection is weak 6 Very large differences fast rate and selection is acting to rapidly change the next generations 7 Natural selection is a measure of how an individual does relative to everyone else in the population natural selection is not an absolute measurement 8 Relative fitness compares everyone in the population to the one who does the best 9 Selection coefficient measures how poorly a phenotype does against the best phenotype The higher the number for selection coefficient the worse it is doing 1
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