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)
3. 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 B
total # of B and b

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
# red flowers/ Total # of individuals
video

8. Hardy – Weinberg Genetic Equilibrium
Ideal hypothetical population that is not evolving (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???

9. 16-2 Disruption of Genetic Equilbrium

10. Mutation
Gene flow – the ability of genes (alleles) to be shared among members of a species (immigration and emigration)
3. Genetic Drift – change in allele frequencies due to chance, usually because the population is small
When gene flow stops, the 2 populations might now become separate species (Ex. Dogs and wolves) Speciation in progress.

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

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

13. 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

14. 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)

15. 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

17. The Birth and Death of Genes

18. 16-3 Formation of Species

19. 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

20. 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!!!

21. 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. Allopatric speciation- when a new species arises as a result of geographic isolation
Gene flow stops
Gene pools separate
Most likely to occur in small pop.
Becomes reproductively isolated

24. Reproductive Isolation – species become genetically isolated
Barriers to successful breeding between groups in the same area
May arise from disruptive isolation
Ex. Different mating times

25. Sympatric speciation- occurs when 2 groups become reproductively isolated in the same geographic area
Reduce gene flow by exploring new niche

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

30. Ring Species
video