BIOL 152 9thEdition Lecture 2 Outline of Last Lecture I Natural Selection II Adaptive Adaptations III Speciation Outline of Current Lecture I The Smallest Unit of Evolution II Genetic Variation III Hardy Weinberg Equation Current Lecture I II 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 change o Natural selection o Genetic drift o Gene flow o Mutation only natural selection causes adaptive evolution Genetic Variation Makes Evolution Possible Evolution requires variation in heritable traits A Genetic Variation o Variation from differences in genes o Phenotype genotype and environmental influences o Natural selection ONLY acts on genetic component B Variation within a population o Discrete vs Quantitative Characters Discrete either or basis Quantitative vary along a continuum height skin color o Genetic Variation variation in genes or nucleotides 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 III Genes average heterozygosity average percent of loci that are heterozygous in a population o Nucleotides measured by comparing the DNA sequences of pairs of individuals C Sources of Genetic Variation o 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 mutation D Sexual Reproduction o Can shuffle existing alleles into new combinations o For production of genetic differences that make adaptation possible recombination of alleles mutation Hardy Weinberg Equation What is a population o Localized group of individuals capable of interbreeding producing fertile offspring o Gene pool all the allele for all loci in a population o a fixed locus occurs when a population is homozygous for the same allele A The Hardy Weinberg Principle o Describes a population that s not evolving o Criteria not met population evolving B Hardy Weinberg Equilibrium o Frequencies of alleles and genotypes remain constant in a population o Random Contribution of gametes to next generation leads to unchanging allele frequencies o Mendelian inheritance preserves genetic variation in a population o 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 frequencies o The frequency of alleles in a population will add up what p q 1 o Describing Individuals CR CR p x p p 2 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 Equilibrium o Theorem describes a hypothetical population that s not evolving o In a real population allele and genotype frequencies do change over time o 5 conditions rarely met in nature NO mutations Random mating NO natural selection Extremely large population size NO gene flow