1. Class Notes 4 Mechanisms of evolution

2. I. Natural Selection happens because of genetic variation. * If a population looks the same, there can be no evolution. So where does this variation come from? Mutations, migration and sex Mutations, migration and sex

3. A. Mutations 1. Mutations in a population can cause new traits to appear in an individual. 2. If the mutation is successful, it can be passed on. Ex: curled cat ears caused by a single mutation!

4. B. Gene flow 1. Also called migration 2. When individuals move from one population to another, bringing their genes with them.

5. C. SEX!!!!!!! 1. Sex produces new gene combinations and even more variation in a population. 2. Could create better or worse combos

6. II. Random events A. Can affect natural selection. When the population is changed by a chance event it is called genetic drift. B. Survival of individuals is based on luck, not their individual adaptations.

7. III. Closing thoughts… A. Individuals do not evolve… 1. Evolution DOES NOT mean that this bear will grow a coat! 2. If it isn’t born with it, it’s not adapted, and it will die .

8. B. Populations accumulate gradual changes over time leading to speciation.  Ex 1: land mammalevolving to a whale

9. …leading to speciation Ex 2: a partially functioning eye in a flatworm…can only see light or dark

10. Ex:  Ex 3 Feathers on non-flyingdinosaur

11. Summary Why is genetic variation necessary for natural selection? What produces this variation? Can an individual evolve? Explain.