1. Evolution: Speciation

2. I. Evolution as Genetic Change
Natural Selection on single-gene traits can lead to changes in allele frequencies and thus to evolution
Natural Selection on polygenic traits can affect the distributions of phenotypes in 3 ways:
Directional Selection: towards 1 extreme
Stabilizing Selection: towards the middle
Disruptive Selection: towards both extremes
Genetic Drift: unlike natural selection, is a change in gene frequency due to random chance

3. I. Evolution as a Genetic Change

4. I. Evolution as Genetic Change
Evolution vs. Genetic Equilibrium: 5 conditions are required to maintain genetic equilibrium:
Random Mating
Large Population
No Migration
No Mutations
No Natural Selection
Hardy-Weinberg principle says allele frequency will remain constant unless 1 or more factors causes change

5. Reproductive Isolation
results from
which include
produced by
which result in
Reproductive Isolation
Isolating mechanisms
Behavioral isolation
Temporal isolation
Geographic isolation
Behavioral differences
Different mating times
Physical separation
Independently evolving populations
Formation of new species

6. II. The Process of Speciation
Isolating Mechanisms
Behavioral Isolation: mating behaviors of two populations differ. (Courtship displays, nest-building, male-male competition)

7. II. The Process of Speciation
Geographic Isolation: physical distance separates two populations

8. II. The Process of Speciation
Temporal Isolation-two populations reproduce at different times (different mating seasons)
Reproductive Isolation-two populations are genetically isolated because they cannot produce fertile offspring.
Examples: dog x cat= gametes are incompatible

9. II. The Process of Speciation
Species vs. Population
Evolution acts on the phenotype of a population.
Once a population has evolved enough that it can no longer interbreed with surrounding populations, it can be labeled as a new species.
A species is a group of organisms that normally interbreed in nature to produce fertile offspring.
Horse X Donkey = Mule (non-fertile)
Bottlenose and Atlantic spotted dolphins (produces a fertile hybrid)
Lion X Tiger = Liger (does not occur due to geographical isolation.)

10. Mule 
 Liger

11. III. DNA and Bootstrapping
DNA Bootstrapping is a process of using computer analyses of DNA sequences from different species to compare DNA similarities and develop cladograms to indicate relatedness and descent.