BZ 110 1st Edition Lecture 7Outline of Last Lecture I. Evolution (Ch 4)II. Natural Selection (4.4)III. Evolution cont. (4.5)IV. Evidence of macroevolution: biogeographyOutline of Current Lecture I. Population and Gene Pools (5.1)II. Population genetics (5.2)III. Evolutionary mechanisms (5.3)Current LectureI. Population and Gene Pools (5.1)- Individuals do not evolve, but changes in populations occur over time- Evolution: requires that genetic changes are passed from one generation to another within populations- Population: groups of individuals of the same species that occupy the same area at the same time and have the same kinds of genes- Gene pool: sum of all alleles for all traits in a population- Allele: alternate form of a gene- Variety within individuals of a population result from having various combinations of alleles at each locuso Sources of variation: independent assortment, crossing over, random fertilizationII. Population genetics (5.2)- Population genetics: The study of genetic events in a population- Hardy- Weinberg theorem (equilibrium): derived a mathematical model that describes what happened to alleles in a populationo Theorem states: missing of alleles at meiosis and their subsequent recombinationdo not alter the relative frequencies of alleles in future generation if certain assumption are meto Genotype frequency can be calculated by expanding binomial (p+q)^2 where p and q are allele frequencieso P^2+2pq+q^2=1These 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.- Assumptions of the Hardy- Weinberg theorem: o Population must be largeo No immigration of emigrationo No mutationso Reproduction must be randomo Natural selection doesn’t occur- If these are met evolution foes not occur- If allele frequencies are changing, than a population is evolvingIII. Evolutionary mechanisms (5.3)- Small populations are more likely to be affected by random events that increase or decrease the frequencies of alleles in poplations- Genetic Drift: occurs when chance events influence allelic frequencieso- Types of genetic drift: o Founders effect: when a few individuals from a parental population colonize to a new area Ex: german Baptist (dunkers) of eastern Pennsylvania, 60% if individuals have blood type A With new colony there may be distinct genetic make upo Population Bottleneck: when the number of individuals in a population is drastically reduced EX: north elephant seal was hunted to near extinction in the late 1800s, legislation to protect the animals was enacted in 1922- Immigration or emigration upsets Hardy- Weinberg equilibrium resulting in changes in allelic frequency- Gene flow: changes in allelic frequencies from the migration of individuals- If gene flow occurs between two populations (in both directions), the populations will become more similar- A lack of gene flow between groups may lead to distinct differences between those groupso EX: elephants of Africa’s tropical forests vs. savannah’s forest- Mutations: the origins of new alleles and the ultimate source of genetic variationo the likelihood of a mutation is not affected by the mutations usefulnesso mutations that occur in germ-line cells can be passed to future generations these mutations can influence the evolution of a group of organisms - Selection pressure: the tendency for natural selection to occur and upset hardy-Weinberg equilibrium - Natural selection may affect the range of phenotypes in 3 ways:o Directional selection  Peppered moth exampleo Disruptive selection Plainfin Midshipman fisho Stabilizing selection Horse shoe crabs, human birth rateo- Polymorphism: occurs in populations when 2 or more distinct forms (phenotypes) exist in a population without a range of phenotype between them- Balanced polymorphism: occurs when different phenotypes are maintained at stablefrequencieso EX: sickle cell anemiaKey terms: evolution, population, gene pool, allele, population genetics, Hardy- Weinberg theorem, genetic drift, gene flow, mutations, selection pressure, polymorphism, balanced