1. Chapter 16 Population Genetics and Speciation
16-1 Genetic Equilibrium

2. Terms to Know
Population genetics – study of evolution from a genetic point of view
Microevolution – evolution at the genetic level
Bell Curve – most members of the population have similar traits; only a few are at the extremes
Can SHIFT over time!!!

4. Variations of Traits Within a Population
Causes of Variation
Mutations
TAGATC -> TAAATC
Recombination (crossing-over and independent assortment)
(during meiosis – see pic!)
Random pairing of gametes
Which sex cells combine successfully

5. The Gene Pool
Gene pool = the total genetic information available in a population
Allele Frequency = number of a certain allele / total number of alleles in a population
Calculated by … # of allele A
total # of A and a

6. What is the allele frequency?
Half a population of four o clocks are red/ half are white.
What is the frequency of the r allele?
0.50 or 50%

7. The Gene Pool
Phenotype Frequency = # of individuals with a phenotype / total # of individuals within the population

8. The Gene Pool
Phenotype Frequency = # of individuals with a phenotype / total # of individuals within the population
# red flowers/ Total # of individuals

9. Hardy – Weinberg Genetic Equilibrium
Ideal hypothetical population that is not evolving (ie not changing over time)
5 criteria (must be met)
No net mutations occur
No one enters or leaves the population
The population is large
Individuals mate randomly
Selection does not occur
Why might a population never be in HW genetic equilibrium???

10. Assignment
Pg 320 Q’s (1-5)
Answer in complete sentences!
Turn in when completed!
Read pg’s and answer the Q’s given.

11. 16-2 Disruption of Genetic Equilbrium

12. Mutation
Gene flow – the process of genes moving from one population to the next
- Immigration
- Emigration
3. Genetic Drift – allele frequencies in a population change usually because the population is small

13. 4. Nonrandom mating – mate selection is influenced by geographic proximity, mates with similar traits, and sexual selection

14. - stabilizing selection - disruptive selection - directional selection
5. Natural Selection – some members are more likely to survive and reproduce
- stabilizing selection
- disruptive selection
- directional selection

15. Types of Selection
Stabilizing selection - individuals with average forms of a trait have the highest fitness
Ex. Large lizards will be spotted by predators; small lizards can’t run fast enough to get away from predators

16. Types of Selection
Disruptive Selection – individuals with either extreme of the trait has the greatest fitness
Ex. White moths on white trees cannot be seen; Dark moths on dark trees cannot be seen; medium colored moths will be seen on both trees (eaten by birds)

17. Types of Selection
Directional selection – more extreme form of a trait has the greatest fitness
Ex. Anteaters with the longest tongues will get the most food

19. 16-3 Formation of Species

20. The Concept of Species Speciation – the process of species formation
Morphology – internal and external appearance of an organism
Species – morphologically similar and can interbreed to produce fully fertile offspring

21. Morphological vs Biological Species Concept
2 competing concepts (ideas) on how to determine different species
Morph = based solely on appearance
Bio = based on who can reproduce with who successfully (not useful for extinct or asexual organisms)
What do we use today?
Mix of BOTH!!!

22. Isolation and Speciation
Geographic isolation – physical separation of members of a species
Ex. River dries up into several small pools; fish diverged enough to be considered separate species

23. Reproductive Isolation – species become genetically isolated
Ex. The offspring of interbreeding species may die early or may not be fertile
Ex. Different mating times

24. Rates of Speciation
Gradualism – speciation occurs at a regular, gradual rate
Punctuated Equilibrium – sudden, rapid change then long periods of no change