1. Aim: How does evolution occur by natural selection?

2. Ice Age “Survival of the Fittest”

3. How Does Evolution Occur? EVOLUTION is a slow change in a species over time. Evolution occurs by a process called NATURAL SELECTION. Read this cartoon, what do you think NATURAL SELECTION is?

4. Lamarck’s theory of Evolution Lamarck believed that by the selective USE or DISUSE of characteristics, organisms lost or acquired certain traits that would be passed on to the offspring.

5. Darwin Considered the “father” of evolution. Charles Darwin traveled to the Galapagos island, an uninhabited environment, where he studied evolution (Darwin’s Finches)

6. Natural Selection NATURAL SELECTION is the KEY to Darwin’s theory. According to this theory, evolution is controlled by NATURE. Only the organisms that are able to SURVIVE and REPRODUCE will pass on their genes.

7. Natural Selection vs. Artificial Selection People select the desirable traits that will appear in the Offspring. Environment selects the desirable traits that will appear in the offspring.

8. Conditions that are vital to Evolution: Overproduction Variation Struggle For Survival Best Adapted To Survive Darwin did NOT have knowledge of the genetic basis of inheritance

9. Overproduction More offspring are produced than can survive (most die young). Organisms such as bacteria, fish, insects, and rabbits have high reproductive rates because the chance that their young will survive is minimal. Overproduction leads to COMPETITION!!

10. Variation Variation: Individuals have differences in their appearance, structure, or genes. Source of variation: –Sexual Reproduction (sperm + egg) –Meiosis (Indp. Ass. & Crossing Over) –Mutation (Change in DNA) + =

11. Mutations Mutations change the base sequence of DNA. Most mutations are HARMFUL, but some can help the organism SURVIVE.

12. Adaptive Value Adaptive Value: a change that produces a trait that helps an organism survive. –Ex: Camouflage If all the members of a species were the same then an environmental change would wipe out the entire species. VARIATION increases the chance that some members of a species will survive.

13. Best Adapted To Survive The ENVIRONMENT chooses which traits have adaptive value. An individual that has traits favorable in a certain environment will live to reproduce and pass on those traits, others will die out.

14. Struggle For Survival “Survival of the fittest” Only those BEST suited will survive because of competition for finite (limited) resources (oxygen, water, food, and shelter)

15. Conditions that lead to Evolution:

16. Patterns Of Change Species with SHORT reproductive cycles that produce MANY offspring tend to evolve more quickly than species with LONG life spans and FEW offspring. Types: 1)Gradualism – evolution occurs steadily through time (Slow & Continuous). 2)Punctuated Equilibrium- species stay the same for long periods of time and then change rapidly. ------------- ------------------------ No Change

17. Examples of Natural Selection Industrial Melanism Antibiotic / Pesticide Resistance

18. Antibiotic Resistance When bacteria are exposed to an antibiotic there is a chance that a few will have a gene that makes them resistant. The bacteria WITHOUT the resistance will be killed, while those that are RESISTANT will survive and pass on their genes for antibiotic resistance. Antibiotic X Resistant Bacteria The antibiotic is the selecting agent Ex: Punctuated Equlibrium

19. Why should we be concerned about antibiotic overuse? http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html Why does evolution matter now?

20. Pesticide Resistance Insect A- Has resistance to A Insect B- Has resistance to B Insect C- Has resistance to C What would happen to the population if insecticide A were sprayed on the field ?

21. The pesticide selected only those flies that were resistant to pesticide A to survive. In other words, some insects had a MUTATION that allowed them to survive the presence of the insecticide. These insects were then able to reproduce and pass their mutation into the next generation.

22. Extinction The disappearance of an entire species (ex. Dinosaurs) It can be caused by temperature changes, pollution, or landscape changes.