evo. lec. 7-11

• Genetic drift is a change in allele frequencies caused by "random sampling" in populations
• Genetic drift is always acting at some level in real populations
• It represents the constant "background noise" of evolution
• Genetic drift is the random change of allele frequencies from one generation to the next due to "random sampling"
• Genetic drift causes more variable and extreme changes in allele frequency in smaller populations
• Alleles are fixed more rapidly in small populations resulting in a loss of variation
• All populations started at p=0.5, but have evolved genetic differences via drift. Smaller populations evolve differences faster
• Drift is the sum of all sources of randomness that randomly add to or subtract from the fitness of individuals
• Random environmental events are a large source of random sampling
• Drift causes alleles to change randomly in frequency, much like coin flips or sampling marbles
• The census size is often not the same as the size of the actual gene pool
• Effective population size (Ne) dictates the strength of drift, not the census size (Nc)
• Reductions in population size can cause drift to become stronger
• Founder effects occur when some individuals become isolated from a larger population
• The bottleneck effect magnifies the effect of genetic drift
• Mutations with large fitness effects can easily overcome drift
• Mutations with small fitness effects can't overcome drift
• In small populations, drift can cause deleterious alleles to fix
• The ability of selection to overcome drift depends on their relative "strengths"
• In small populations, natural selection needs to be very strong to overcome drift
• Genetic diversity is one of three levels of biological diversity requiring conservation
• Genetic theory predicts that levels of genetic variation should increase with effective population size
• Genetic variation within species should be related to population size
• Genetic variation within species should be related to island size
• Genetic variation should be related to population size within taxonomic groups
• Genetic variation in animals should be negatively correlated with body size
• Genetic variation should be negatively correlated with rate of chromosome evolution
• Genetic variation across species should be related to population size
• Vertebrates should have less genetic variation than invertebrates or plants
• Island populations should have less genetic variation than mainland populations
• Genetic variation is related to population size
• Small population size reduces the evolutionary potential of wildlife species
• Genetic variation increases with the effective population size
• Soul# (1976) provided evidence that genetic variation in wildlife fauna is related to population size
• Variation in genetic diversity is predicted to increase with population size
• Variation in genetic diversity is related to population size within taxonomic groups
• Widely distributed species have greater genetic variation than species with restricted distribution
• Genetic variation in animals correlates negatively with body size
• Genetic variation correlates negatively with the rate of chromosomal evolution
• Vertebrates have less genetic variation than invertebrates or plants