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 genes i 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 mate i ii Intrasexual selection feature s that improve ability to find mate and compete 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 frequencies i No net mutation ii No differential selection among genotypes fitness survival and reproduction iii No gene flow population isolated and allele frequency remains same iv Population infinite v 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 variation