BIOL 152 9thEdition Lecture 2Outline of Last Lecture I. Natural SelectionII. Adaptive/AdaptationsIII. SpeciationOutline of Current Lecture I. The Smallest Unit of EvolutionII. Genetic VariationIII. Hardy-Weinberg EquationCurrent LectureI. The Smallest Unit of Evolution- Organisms do NOT evolve- Natural selection acts on individuals o Populations evolve- Microevolution: change in allele frequencies in a population over generations (time)- 4 mechanisms cause allele frequency changeo Natural selectiono Genetic drift o Gene flowo Mutation- only natural selection causes adaptive evolutionII. Genetic Variation Makes Evolution Possible- Evolution requires variation in heritable traits A. Genetic Variationo Variation from differences in geneso Phenotype = genotype and environmental influenceso Natural selection ONLY acts on genetic component B. Variation within a populationo Discrete vs. Quantitative Characters Discrete: either-or basis Quantitative: vary along a continuum (height, skin color…)o Genetic Variation = variation in genes or nucleotidesThese 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. Genes: average heterozygosity – average percent of loci that are heterozygous in a populationo Nucleotides: measured by comparing the DNA sequences of pairs of individualsC. Sources of Genetic Variationo New genes and alleles can arise by mutation or gene duplication  Mutations in gametes can be passed to offspring; rarely beneficial;more likely neutral or harmful Duplicated genes can take on new functions by further mutationD. Sexual Reproductiono Can shuffle existing alleles into new combinationso For production of genetic differences that make adaptation possible; recombination of alleles > mutationIII. Hardy – Weinberg Equation- What is a population?o Localized group of individuals capable of interbreeding & producing fertileoffspring o Gene pool: all the allele for all loci in a populationo a fixed locus occurs when a population is homozygous for the same alleleA. The Hardy-Weinberg Principleo Describes a population that’s not evolvingo Criteria not met? = population evolving B. Hardy-Weinberg Equilibriumo Frequencies of alleles and genotypes remain constant in a populationo Random Contribution of gametes to next generation leads to unchanging allele frequencieso Mendelian inheritance preserves genetic variation in a populationo Allele frequencies are calculated by:  Diploid organisms – how does one calculate the total number of alleles at a simple locus in a population? (Denominator) How does one calculate the number of dominant alleles? (numerator for dominant alleles) How does one calculate the number of recessive alleles? (numerator for recessive alleles)o By convention, we use p and q to represent their frequencieso The frequency of alleles in a population will add up what? p + q = 1o Describing Individuals CRCR = p x p = p2 CWCW = q x q = q2 CRCW can be achieved by CRCW or CWCR. So CRCW= pq and CWCR = qp- Combined = 2pq- If these frequencies represent all individuals in a population, THEN o P2 + 2pq + q2 = ?o All frequencies of these events should add to 1 or 100%C. Conditions for Hardy-Weinberg Equilibriumo Theorem describes a hypothetical population that’s not evolvingo In a real population, allele and genotype frequencies do change over timeo 5 conditions rarely met in nature NO mutations Random mating NO natural selection Extremely large population size NO gene