1. What evidence do we have for evolution? (5)

2. Is this population evolving?
What do you think?
Is this population evolving?

3. This population IS evolving
Allele frequency changes from one generation to the next

4. Mechanisms of Evolution

5. Evolution is the change in allele frequency
Remember…evolution occurs
Over time
In populations…NOT individuals
On phenotypes

6. Two Main Sources of Genetic Variation
1) Mutations 2) Gene Shuffling

7. 1) Mutations Caused by mistakes during replication
Any change in a sequence of DNA.
Caused by mistakes during replication

8. 2) Gene Shuffling
Recombination of genes: Occurs during the production of gametes in meiosis

9. How Does Variety Arise? Video
2) Gene Shuffling
Recombination as homologous chromosomes move independently during meiosis
Crossing over: the exchange of genetic material during prophase I
How Does Variety Arise? Video

10. Gene Pool & Allelic Frequency
Gene Pool: Entire collection of all the alleles in a population
Allelic Frequency: The number of times an allele appears in the gene pool

11. Gene Pool & Allelic Frequency
Gene Pool: 12 green alleles and 8 brown alleles
Allelic Frequency of green: 12/20
Allelic Frequency of brown: 8/20

12. Evolution is the change in allele frequency
Occurs in one of three ways:
Gene Flow
Genetic Drift
Natural Selection

13. 1) Gene Flow ~ The movement of alleles into or out of a population
Can increase or decrease genetic variation

14. 2. Genetic Drift Random change in allelic frequencies due to chance.
Decreases genetic variation

15. Types of Genetic Drift
Founder Effect ~ A small group of individuals colonize a new habitat or new area

16. Types of Genetic Drift
Bottleneck ~ a sharp reduction in the size of a population due to environmental events (flooding, earthquake, etc.)

17. 3) Natural Selection Decreases genetic variation
~ Most common source of evolutionary change
Decreases genetic variation

18. Main Mechanisms of Evolution Video