1. THE EVOLUTION OF POPULATIONS
CHAPTER 23

2. POPULATIONS
Localized group of individuals belonging to the same species
Species – group of individuals who have the potential to interbreed and produce fertile offspring
Similarities in individuals are
Morphological – structural
Physiological – metabolic activities
Behavioral – similar responses to same stimuli

3. Gene Pool Total aggregate of genes in a population at any one time
Nearly all genes in available pool have two or more slightly different molecular forms – alleles
In closed population, only mutation brings about changes to the gene pool

4. Genetic Variation
Difference in genes or other DNA segments among individuals of the same population
Genotype is inherited
Phenotype is the environmental influence on genotype
Average heterozygosity – average percent of loci that are heterozygous; measure of the relative age of a specific population
Variation between populations often due to geographic variations

5. Genetic Variation Sources of variation
Formation of new alleles through mutation
Altering of gene number and position due to errors in meiosis
Rapid reproduction rate increases potential for variation
Sexual reproduction shuffles genes more effectively than asexual

6. Hardy Weinberg Equilibrium
Idea that allele frequency is constant from generation to generation
Used to assess whether a population is evolving at a specific locus by determining what the population would be like if it were NOT evolving at that locus
Scenario created is compared to actual population; no change – no evolution; change – evolution is occurring

7. Hardy Weinberg Equilibrium
All 5 conditions must be met for there to be no evolution occurring:
No mutations
Random mating
No natural selection
Extremely large population size
No gene flow

8. Altering Allele Frequencies in a Population
Natural Selection – only mechanism that consistently causes adaptive evolution
Genetic Drift – chance events that change allele frequencies
Gene Flow – transfer of alleles into or out of a population