Biology 2150 Chapter 21 Notes I Genetics of Populations and Evolution A Species breads that can t intermix and produce fertile offspring B Population groups of organisms within a species that can interbreed C Gene pool all alleles present in all individuals of a species II Genetic variation traits A Some genetic variation is phenotypically detectable in easy to observe B Some can only easily be detected at the level of molecules C Genetic variation can be caused by mutations 1 Only germ line reproductive cells can be passed on to the next generation 2 Mutations can be rare common a Advantageous results in a better adapted phenotype b Deleterious results in a less well adapted phenotype c Neutral no adaptive effect common D Genetic variation can also be caused by recombination 1 Recombination the shuffling of alleles into new combinations III Measuring Variation A Can be seen in observable traits 1 This works for traits that are a Controlled by one gene b Not influenced by the environment B Can be seen through gel electrophoresis look for variation in proteins C Can be seen through DNA sequencing 1 Gel electrophoresis is when blood or tissue samples are used to 1 This allows us to look differently at any DNA sequence variation IV Evolution over time A Evolution a change in a species or population in time 1 Specifically a change in allele or genotype frequency in a population B Populations that are not evolving are in Hardy Weinberg equilibrium V Hardy Weinberg Equilibrium Conditions A All genotypes are equally well adapted 1 There is no difference in the survival and reproductive alleles B No gene flow C No mutations 1 Populations must not be added to or subtracted from 1 No new alleles arise in the population D No genetic drift 1 Populations must be sufficiently large enough to prevent loss of alleles by chance events E Random mating A It describes the expected frequency of genotypes from allele frequency 1 No mate preference VI Hardy Weinberg Relations B Dominant allele p Recessive allele q C Genotype frequencies p q 1 AA p 2 aa q 2 Aa 2pq D Therefore the Hardy Weinberg equation is p 2 2pq q 2 1 E If the Hardy Weinberg conditions are met we can compute the frequencies of three possible phenotypes VII Theory of Evolution by Natural Selection A Survival is not random luck B Some individuals have a better chance of surviving and reproducing VIII Theory of Evolution by Natural Selection A More offspring are produced than survive to adulthood B Inherited variation among individuals of a species create adaptation 1 The best adapted individuals survive and reproduce C Adaptation any characteristic that improves survival success 1 Adaptation is an organism s ability to match the challenges of their environment 2 Adaptation is often the result of natural selection D Fitness Any contribution that an individual makes to the gene pool of the next generation relative to the contribution of others IX Natural Selection Drives Evolution A Variation new alleles enters a population through mutations B Recombination sexual reproduction mixes alleles in different combinations among individuals in the population C These genetic variations result in slightly different individual phenotypes X Natural Selection patterns A Changes in frequency of traits in a population follow one of three basic 1 Stabilizing selection selects against extremes 2 Directional selection selects against once of the two extremes 3 Disruptive selection Selects against the status quo
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