BIOL 152 1st Edition Exam 1 Study Guide Lectures 1 12 Asexual Reproduction Single parent passes all of its genes to offspring Offspring is a clone Sexual Reproduction Each parent passes half of its genes Genetic Variation arrives by chance 1 Mutation Generates new variation New alleles are formed Somatic Mutation occurring in the body s tissues only affects one cell Germ line occurring in the reproductive cells passed onto the next generation affects all the cells and descendants and is more important Harmful Mutations Random changes to an organism Neutral Mutations No effect on the organism occur in the genome that is not important Advantageous Mutations Mutation that is beneficial in terms of survival or reproduction 2 Recombination Shuffles mutations to create new combinations of mutations New alleles are formed Darwin Wallace Thomas 1 Darwin Circumnavigation of the world in HMS Beagle Established theory of natural selection evolution Survival of the fittest he concluded only those organisms that are well suited for the environment will survive long enough to produce offspring Origin of Species 1858 2 Alfred Wallace Additional information to natural selection and evolution 3 Thomas Malthus Malthus stated there was an increase in human population and not enough resources to accommodate for everyone Darwin used this theory in his evolution theory Fitness relative contribution an individual makes to gene pool of the next generation Natural Selection Allele frequencies changing from generation to generation according to the allele s impact on the survival and reproduction of individuals Acts on individuals because individuals have mutations occur but with time the population evolves based on whether the mutation is harmful or beneficial If the mutation is harmful it will have no long term evolutionary impact Individuals that are best adapted to the environment are selected for Nature selects which variation will be inherited and which will be diminished Evolution change in allele or genotype frequencies of a population Genome total genetic complement of an individual organism Gene Pool all alleles at all gene loci in all individuals of a population species Genetic Structure any pattern in the genetic makeup of an individual Calculate allele and Genotype Frequencies Hardy Weinberg Equilibrium Theorem Theorem states that frequencies of alleles and genotypes in a population s gene pool remain constant from generation to generation Non evolving population Hardy Weinberg Equation p 2 2pq q 2 1 Conditions for Hardy Weinberg Equilibrium Theorem 1 2 3 4 5 No natural selection No gene flow no addition or subtraction of individuals No mutations Large population size Random mating When these conditions are violated the population s gene pool will no longer remain constant Prediction of alleles and frequencies When given an allele to predict the allele of the same generation it will be the same When population is in equilibrium frequency and allele will be the same no change in equilibrium Given two different alleles and asked to decide whether the population is equilibrium compare the two and if they are different then the population is not in equilibrium Forms of Natural Selection 1 Stabilizing Selection Acts against extreme phenotypes favoring the more common intermediate form Example The lizards at the extreme ends of the bell shape curve the super dark and super light are eaten because of the environment The intermediate in between dark and light lizards are favored making the distribution towards the middle 2 Disruptive Diversifying Selection Variation at both extremes favored Heterogeneous or disrupted environments Example The lizards in the middle of the bell shape curve in between dark and light are eaten and the super dark and super light lizards are favored by the environment 3 Directional Selection Frequency shifted to one direction or extreme Common during periods of environmental changes Example If the environment favors super dark lizards then the curve will be skewed benefiting the super dark lizards and the intermediate and light lizards will be eaten 4 Balancing Selection Evolutionary process that maintains two versions over time Maintenance of two or more alleles in a population 5 Positive Selection Increases frequency of certain alleles resulting in adaptation increased fitness May promote fixation of these alleles 6 Negative Selection Decrease frequency of harmful alleles that reduce fitness Gene Flow transfer of alleles between populations Isolated populations no gene flow How Migration Genetic Drift Chance changes in gene pool of small populations Lead to fixation of alleles Reduces genetic variability