BIOL 112 1st Edition Lecture 6 Outline of Last Lecture I Voyage of the H M S Beagle A Observations II Post Voyage III Alfred Russel Wallace 1823 1913 IV Factors that Influenced Darwin V Darwin s Thinking Process A Three Observations B Two Conclusions VI What we Know Now VII Darwinian Evolution VIII Tests of Darwin s Theory IX Moth Selection X Selection in Action Penicillin XI Natural Selection in Action XII Sphecomyrma XIII Tiktaalik XIV Archeopteryx XV Other Phenomena A Moth Bee Mimicry B M llerian Mimicry XVI Status of Darwin s Theory 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 Outline of Current Lecture XVII Darwinian Theory XVIII Darwin vs Mendel XIX Important Terms XX Hardy Weinberg Equilibrium XXI Mathematical Modeling XXII Condition 1 Large Population Current Lecture I Darwinian Theory Toward the end of the 19th century Darwin s theory was in trouble Couldn t explain inheritable If favorable gene combinations are selected for how can you keep them together through several generations Standard genetic model at the time was blending inheritance No one was familiar with Mendel s work yet and if they were they didn t understand it By the turn of the 20th Century Mendel s work was rediscovered by Hugo de Vries Dutch geneticist discovered mutations new alleles found and publicized Mendel s papers II Darwin vs Mendel Evolution scientists realized the need to revise Darwin s Theory to include major parts of Mendelian Genetics Darwin Mendel Genetics became synthesized together in the 1920s and 1930s by Fisher Wright and Haldane Product is called Neo Darwinian Theory of Evolution Two paradigms were combined into one Darwin Natural Selection acting on variations in phenotypes Mendel Genetic Variability mutations and recombinations and Principles of Heredity Evolution became a change in the genetic content of a population over time III Important Terms Gene Pool Sum of all genetic information in a reproducing population Allele Gene Frequencies Relative proportion of alleles in a population Genotype Frequencies Relative proportion of genotypes in a population What happens if allele frequencies change Evolution has occurred by definition Population Genetics Application of Mendelian principles to populations of organisms The image to the right can help solve for allele frequencies based on phenotypes from a parent population IV Hardy Weinberg Equilibrium Differences from Classical Mendelian Genetics We are considering all eggs and all sperm pollen in the reproductive population not just those from two organisms in one breeding pair Conditions to be met to work mathematics Breeding population is very large No mutations in population No immigration or emigration no one comes in from the outside or leaves to change the population genotypes Reproduction is random the ability for all genotypes to contribute to the gene pool is equal genotypes is not related to the success of the future population If all conditions are met the population is in a stable state in which allele frequencies and genotype frequencies will not change from generation to generation Population is in Hardy Weinberg Equilibrium Population will not evolve unless outside forces intervene Thus outside forces will tend to cause evolution allele frequency change Mathematical formula derived from the Hardy Weinberg Model Binomial Equation Starting with allele frequencies f A p f a q p q 2 1 p2 2pq q2 1 Thus you can identify genotype frequencies f AA p2 f Aa 2pq f aa q2 How to solve for p and q p 2 p2 2pq 2 population OR 2 times the frequency of homozygous dominant plus the heterozygous all divided by 2 times the total population p 2f AA f Aa 2 AA Aa aa q 2 q2 2pq 2 population OR 2 times the frequency of homozygous recessive plus the heterozygous all divided by 2 times the total population q 2f aa f Aa 2 AA Aa aa There are practice Hardy Weinberg problems posted on Dr Aufderheide s eCampus page There will be a couple of these problems on the exam so make sure you practice them I will do one example on the study guide V Mathematical Modeling H W allows mathematical modeling of gene frequencies and evolution Permits quantitative predictions of evolutionary trends in population Population is stable no evolution when in Hardy Weinberg equilibrium So violations of H W equilibrium conditions means the populations is undergoing evolution This can characterize the consequences of these violations VI Condition 1 Large Population Non always true in natural populations Some populations small or fluctuate widely over time If population small random changes in gene frequency can occur be cause of statistical fluctuations in gene frequency Genetic Drift Changes in allele frequency from statistical fluctuations not related to selective advantage disadvantages If f A 1 0 or 0 then no further drift can occur Population is fixed Bottleneck Effect Extreme form of genetic drift Large population crashes Can be caused by an extreme event like a volcanic eruption During crash death is so widespread that allele frequencies among survivors might not represent the frequencies before the crash The few survivors can bring back that particular allele New population from survivors has different allele frequencies