Chapter 15 Darwin proposed three concepts for evolutionary change - Species do not change over time- Divergent species share a common ancestor- Natural selection causes change Charles Darwin and Alfred Russel Wallace credited for idea of natural selection Evolution=changes in genetic makeup of populations over time- Evolution occurs in populations not in individuals Processes that affect genetic makeup of populations over time i. Gene flow(movement of gametes)ii. Genetic drift (random changes in allele frequencies from one gen. to next)iii. Nonrandom mating Mutation=any change in the nucleotide sequences of DNA Alleles=different forms of genesi. Sum of all copies of alleles of population is a gene pool Adaptation=favored trait that evolves through natural selection Population bottleneck: small # of individuals survive due to environmental event Founder effect:change in allele frequencies due to small # of individuals Sexual selection=nonrandom mating in which phenotype influences matei. Intrasexual selection: feature(s) that improve ability to find mate and competeii. Intersexul selection:feature(s) that improve attractiveness Hardy-Weinburg equilibrium-model in which allele frequencies do not change through gen. and genotype frequencies predicted from allele frequenciesi. No net mutationii. No differential selection among genotypes(= fitness(survival and reproduction))iii. No gene flow(population isolated and allele frequency remains same)iv. Population infinitev. Mating random(all mating is random) If all 5 H-W equil. Points proven the null hypothesis is proven (no difference between/among treatment groups) Qualitative traits:(black vs white) discrete qualities Quantitative traits: variation of traits Stabilizing selection:preserves avg. characteristics of pop. By favoring avg. individuals(“purifying selection”)◦ reduces variations in pop. but does not change mean(selection against deleterious mutations) Directional selection:favor individuals that vary in one direction ◦ may result in positive selection(favors particular genetic variant) Disruptive selection:favors both extremes◦ increase variation in pop. Nucleotide substitution=change in single nucleotide in DNA (point mutation)◦ synonymous substitution:sub. that does not change encoded amino acid◦ nonsnonymous substitution:sub. that does change encoded amino acid Neutral theory:most mutations neutral Genome size relies on amt of non-coding genes Muller's ratchet: accumulation of deleterious mutations that lack genetic recombination Lateral gene transfer: allows genes, organelles, fragments of genes to move horizontally p+q=1.0 is allele frequency (p+q)^2=1.0 is genotype frequency  genotypes are diploid, alleles are haploid Phenotypic plasticity: one phenotype can create more different phenotypes Genetic variation=sum of all allele frequencies in pop.◦ Genetic variation+allele frequency=phenotypic