1. The Evolution of Populations

2. Overview the smallest unit of evolution
True or False:
– Organisms evolve, in the Darwinian sense, during their lifetimes
– Individuals evolve
– Populations evolve
– Genetic variations in populations contribute to evolution

3. Gene Pools and Allele Frequencies
Population- a localized group of individuals that are capable of interbreeding and producing fertile offspring.
Gene pool- the aggregate of genes in a population at any one time
Thus a species may have two populations… ex. Caribou populations in the Yukon
Fixed allele- all individuals are homozygous, only one allele exists in the population for that gene

4. Concept 23.1: Population genetics provides a foundation for studying evolution
Microevolution- change in the genetic makeup of a population from generation to generation
Different from Darwin’s definition of evolution
Darwin explanation of evolution considered unsatisfactory because did not consider how the heritable variations required for natural selection appear in populations or how organisms transmit these variations to their offspring

5. The Modern Synthesis
Population genetics- the study of how populations change genetically over time
Modern synthesis- a comprehensive theory of evolution that integrated ideas from many other fields.
Mendelian genetics
Darwinian theory of evolution through natural selection

6. Hardy- Weinberg Theorem
This theorem states that the frequencies of alleles and genotypes in a population’s gene pool remain constant from generation to generation , provided that only Mendelian segregation and recombination of alleles are at work.
Involves gene pools that are not evolving
Mendelian inheritance preserves genetic variation from one generation to the next
Hardy-Weinberg equilibrium describes a population in which random mating occurs
It describes a population where allele frequencies do not change

7. (p+q) X (p+q) = (p2+2pq+q2) Allele frequencies allele genotype
Of male gametes frequencies frequencies
of female in next generation
gametes

8. Proportionally at a locus with with two alleles, the three genotypes will equal one:
p2+2pq+q2=1
Meaning a population which continued to mate randomly generation after generation, would have allele and genotype frequencies which remained constant

9. For a Population to be in Hardy- Weinberg Equilibrium it must follow the five following standards

10. The population is large There is no gene flow
Meaning there’s no migration of individuals or gametes into or out of the population
Mutations do not alter the gene pool
Mating is random
All individuals are equal in reproductive success
Meaning natural selection is not occurring within the population

11. When population deviate from Hardy- Weinberg equilibrium, the gene pool changes, and evolution occurs
4 main causes of evolutionary change are:
1) Genetic drift
2) Gene flow
3)Natural selection (only contributes to adaptive evolution)
4) Mutation (only over time)