Lecture 7 BIO 311D 2nd EditionOutline of Last Lecture I. Hardy Weinberg population equationsII. Assumptions of H-W equilibriumIII. How can microevolution happen?Outline of Current Lecture I. Microevolution occurs when H-W equilibrium assumptions are not metII. The process of evolution by natural selectionCurrent LectureI. Microevolution occurs when H-W equilibrium assumptions are not metA. Micro change in allele frequencyMacro new species formB. Genetic Drif- Bottleneck: natural disaster; change in proportion of one color beetle over another- Founder: by “chance”; a small population that migrated became the founder C. Gene flow- Alleles introduced into population- Two different population side by side and one member of a population enters another populationD. Mutation- Mutated allele that changes the trait- Can be favorable, neutral or deleteriousE. Non- random mating- Inbreeding - By chance, sperm travels to all eggs “in the water” II. The process of evolution by natural selectionA. Natural selection operates on individuals (according to their phenotypes), not on allelesB. The pattern of evolution by natural selection depends upon the particular environment at the timeC. Fitness: Individual’s genetic contribution to the next generation (w= relative fitness) The individual must survive and reproduce D. Natural Selection: individuals with higher fitness in a particular environment survive and reproduce more than individuals with lower fitnessE. Steps in the process:(!) Genetically based variation in a population, due initially to random mutation(2) In a given environment, not all individuals succeed; some have greater reproductive success than others(3) Individuals with phenotypes that are better adapted to the environment pass more copies oftheir alleles into the next generation(4) As a result, there is a change in allele frequency in the population over time (=mircoevolution)F. Modes of selection- Directional- Disruptive: i.e. bill size of African seed-crackers- Stabilizing: i.e. human birth weight G. An adaptation is an aspect of the phenotype (morphological, biochemical, behavioral) that givesan individual a fitness advantage in a certain environment i.e. evolution of antibiotic resistance in
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