Lecture 7 BIO 311D 2nd Edition Outline of Last Lecture I Hardy Weinberg population equations II Assumptions of H W equilibrium III How can microevolution happen Outline of Current Lecture I Microevolution occurs when H W equilibrium assumptions are not met II The process of evolution by natural selection Current Lecture I Microevolution occurs when H W equilibrium assumptions are not met A Micro change in allele frequency Macro new species form B 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 population D Mutation Mutated allele that changes the trait Can be favorable neutral or deleterious E Non random mating Inbreeding By chance sperm travels to all eggs in the water II The process of evolution by natural selection A Natural selection operates on individuals according to their phenotypes not on alleles B The pattern of evolution by natural selection depends upon the particular environment at the time C 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 fitness E 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 of their 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 gives an individual a fitness advantage in a certain environment i e evolution of antibiotic resistance in bacteria
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