1. Population Genetics Population
“Localized group of individuals…capable of interbreeding and producing fertile offspring”
Isolated from other populations of the same species to some extent

2. Fig. 23.6

3. Population Genetics Population
Gene pool – All genes in a population at a given time
Fixed allele – Only one allele at a particular locus in a population
In a population, each allele has a frequency
Ex: Population of wildflowers with two alleles (CR, CW) at locus for flower pigment
Homozygous CR – Red flowers
Homozygous CW – White flowers
Heterozygous – Pink flowers
Population – 320 plants with red flowers, 160 with pink flowers, 20 with white flowers
Question – Allele frequencies for CR and CW?

4. Population Genetics Hardy-Weinberg Theorem
Describes distribution of alleles and traits in populations that are not evolving
Population in genetic equilibrium
Frequencies of alleles and genotypes in a gene pool remain constant over generations
Mendelian inheritance preserves variation

6. Population Genetics Hardy-Weinberg Theorem
Permits calculation of allele frequencies from genotype frequencies and vice-versa
Frequency of any allele can be described as a number between 0 and 1
Ex: Population of wildflowers (alleles CR, CW)
Sum of allele frequencies = 1
Frequencies of alleles = p, q
p + q = 1
(p + q)2 = p2 + 2pq + q2 = 1
p2 – Freq. of CRCR individuals in population
2pq – Freq. of CRCW individuals in population
q2 – Freq. of CWCW individuals in population

7. Fig. 23.8

8. Population Genetics Hardy-Weinberg Theorem
Proportion of alleles in population doesn’t change over successive generations, provided five conditions are met
No net mutations
Random mating
Mates not selected based on genotype
No natural selection
Favors certain geno- and phenotypes, leading to changes in allele frequencies
Extremely large population size
Random fluctuation (genetic drift) more prevalent and influential in small populations
No gene flow

9. Microevolution
Evolution occurs when populations don’t meet all the H-W assumptions
Process by which a population’s genetic structure changes = microevolution
Changes in allele frequencies result from five evolutionary processes
Mutation
Nonrandom mating
Natural selection
Genetic drift
Gene flow