1. Population Genetics
Population Genetics

2. Populations A group of the same species living in an area
No two individuals are exactly alike (variations)
More Fit individuals survive & pass on their traits

3. Modern Synthesis Theory
Combines Darwinian selection and Mendelian inheritance
Population genetics - study of genetic variation within a population
Emphasis on quantitative characters

4. Modern Synthesis Theory
Today’s theory on evolution
Recognizes that GENES are responsible for the inheritance of characteristics
Recognizes that POPULATIONS, not individuals, evolve due to natural selection & genetic drift
Recognizes that SPECIATION usually is due to the gradual accumulation of small genetic changes

5. Microevolution
Changes occur in gene pools due to mutation, natural selection, genetic drift, etc.
Gene pool changes cause more VARIATION in individuals in the population
This process is called MICROEVOLUTION
Example: Bacteria becoming unaffected by antibiotics (resistant)

6. The Gene Pool
Members of a species can interbreed & produce fertile offspring
Species have a shared gene pool
Gene pool – all of the alleles of all individuals in a population

7. Allele Frequencies Define Gene Pools
500 flowering plants
480 red flowers
20 white flowers
320 RR
160 Rr
20 rr
As there are 1000 copies of the genes for color,
the allele frequencies are (in both males and females):
320 x 2 (RR) x 1 (Rr) = 800 R; 800/1000 = 0.8 (80%) R
160 x 1 (Rr) + 20 x 2 (rr) = 200 r; 200/1000 = 0.2 (20%) r

8. Gene Pools
A population’s gene pool is the total of all genes in the population at any one time. 
Each allele occurs with a certain frequency (.01 – 1).

9. The Hardy-Weinberg Theorem
Used to describe a non-evolving population.
Shuffling of alleles by meiosis and random fertilization have no effect on the overall gene pool. 
 Natural populations are NOT expected to actually be in Hardy-Weinberg equilibrium.

10. The Hardy-Weinberg Theorem
Deviation from Hardy-Weinberg equilibrium usually results in evolution
Understanding a non-evolving population, helps us to understand how evolution occurs
                        .

11. Sources of genetic variation (Disruption of H-W law)
Mutations - if alleles change from one to another, this will change the frequency of those alleles
2. Genetic recombination - crossing over; independent assortment
3. Migration - immigrants can change the frequency of an allele by bringing in new alleles to a population.
- emigrants can change allele frequencies by taking alleles out of the population

12. Sources of genetic variation (Disruption of H-W law)
4. Genetic Drift - small populations can have chance fluctuations in allele frequencies (e.g., fire, storm).
- bottleneck; founder effect
5. Natural selection - if some individuals survive and reproduce at a higher rate than others, then their offspring will carry those genes and the frequency will change for the next generation.

13. Hardy-Weinberg Equilibrium
                                   
The gene pool of a non-evolving population remains constant over multiple generations; i.e., the allele frequency does not change over generations of time.
The Hardy-Weinberg Equation:
                                    1.0 = p2 + 2pq + q2
                                               
where p2 = frequency of AA genotype; 2pq = frequency of Aa plus aA genotype; q2 = frequency of aa genotype