1. Evolution

2. What is evolution? Biological evolution is NOT just a change over time. The definition of evolution is Descent with Modification Some sort of change within a lineage.

3. What is a species? Biological species concept: This concept states that "a species is a group of actually or potentially interbreeding individuals who are reproductively isolated from other such groups."

4. Mechanisms of Evolution How does evolution work? What are the selective forces that cause evolution to occur? How can we get genetically DIFFERENT organisms that come from the SAME common ancestor?

5. Descent with Modification Recall, there needs to be some long term change of the gene frequency over time. Drought causes a decrease in food. More beetles have genes for green color and years later more brown beetles than green ones. A B

6. Modes of evolution 1.Genetic Variability 2.Mutation 3.Genetic Drift 4.Natural Selection

7. Genetic Variation Gene Flow Movement of genes from one population to another. Sex Sexual reproduction causes new combinations of genes. Mutation Changes in DNA

8. Mutations Mutations are RANDOM 2 Types: Somatic-not in gametes so they are not heritable. Germ-found in gametes so they are heritable. Causes: 1.DNA copying error 2. Environment

9. Effects of Mutation Negative effects –Persist in very low frequencies –Could be a lethal mutation or cause sterility Positive effects –Beneficial mutations spread rapidly –Individuals with a beneficial mutation have a selective advantage

10. Genetic Drift Frequencies of particular alleles may change by random chance Prevalent in small populations

11. Bottleneck Effect Drastic reduction in population High risk of mutation Little Variability

12. Founder Effect Founder effect – few individuals in a new population High risk of mutation Little Variability

13. Natural Selection Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce. organismstraits reproduce

14. From Theory to Reality There is no magic threshold when a new species is “made” Evidence Supports Theory of Evolution –Vestigial Elements Elements that have appeared to have lost any usability Eyes in cave organisms No light = no eyes, but organisms still have eye sockets

15. Making new species New species are made when... –Isolation of two populations –Reduced gene flow between them –Selection/Genetic drift –Altered genetic composition

16. Once Isolation Occurs Selection – different pressures driving different phenotypes/genotypes Genetic Drift – change in genetic makeup of a population to do random changes ***Isolation of “populations” allows these random changes to accumulate***