UGA BIOL 1107 - Microevolution and Natural Selection (4 pages)

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Microevolution and Natural Selection

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Microevolution and Natural Selection


Dr. Constable went over the Hardy-Weinberg equation again and explained why it doesn't work for small populations. Additionally, she defined some basic terms associated with microevolution.

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University of Georgia
Biol 1107 - Principles of Bio I
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BIOL 1107 1nd Edition Lecture 34 Outline of Last Lecture I II III Gene Pool Allele Frequency Examples Outline of Current Lecture I Hardy Weinberg II Non random mating III Changes in allele frequency definitions Current Lecture I Hardy Weinberg Hardy Weinberg accurately predicts population if o No mutations o Random mating o No gene flow o Natural selection When expectations are NOT met o AA Aa aa 0 25 0 5 0 25 A 0 5 II a 0 5 Non random mating Does non random mating occur in humans No When expectations are NOT met o AA 5 000 2 400 o Aa 10 000 5 000 o Aa 5 000 2 600 20 000 10 000 AA 2 600 Aa 5 000 aa 2 400 10 000 larger population These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute A 0 5 0 49 A 0 5 0 51 When expectations are NOT met o AA 2 0 AA 2 o Aa 6 3 Aa 3 o Aa 2 2 aa 0 A 0 5 0 3 a 0 5 0 7 III 0 7 0 3 sizes This is why Hardy Weinberg doesn t work for small populations Changes in allele frequency Genetic drif change due to random event Founder effect the reduced genetic diversity that results when a population is descended from a small number of colonizing ancestors Bottleneck happens after natural disaster Migration causes change in allele frequency that also interferes with HardyWeinberg Fitness likelihood of passing on genes to the next generation Natural selection the process whereby organisms better adapted to their environment tend to survive and produce more offspring The theory of its action was first fully expounded by Charles Darwin and is now believed to be the main process that brings about evolution Directional selection a mode of natural selection in which an extreme phenotype is favored over other phenotypes causing the allele frequency to shift over time in the direction of that phenotype Under directional selection the advantageous allele increases as a consequence of differences in survival and reproduction among different phenotypes The increases are independent of the dominance of the allele and even if the allele is recessive it will eventually become fixed Stabilizing selection opposite of disruptive selection Instead of favoring individuals with extreme phenotypes it favors the intermediate variants It reduces phenotypic variation and maintains the status quo Disruptive selection describes changes in population genetics in which extreme values for a trait are favored over intermediate values In this case the variance of the trait increases and the population is divided into two distinct groups Q John is studying lizards with a maximum lifespan of eight years How long will it take for John to see these lizards evolve A He could see evolution if he compared lizards from one generation to lizards from another generation in a period of environment flux Q Mosquitoes have heritable variation for insecticide resistance amount and kind however all mosquitoes require standing water for the development of offspring To which of the following control methods would the mosquitoes be least likely to develop resistance A 1 3 see answers on elc New

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