1. What has caused SUPERBUGS (antibiotic resistant bacteria) like MRSA?
8-5 Notes: Natural Selection
What has caused SUPERBUGS (antibiotic resistant bacteria) like MRSA?

2. how did organisms become so well adapted to their environment?
What has caused the great diversity of life?

3. DARWIN’S EXPLANATION
Darwin proposed that animals evolved to fit their environments.

4. Darwin realized that animals have many offspring and some don’t survive.
The survivors are better suited to their environment.

5. HE CALLED THIS PROCESS….
Natural Selection

6. Darwin said that in nature, the environment creates selective pressure
Natural Selection
Mechanism by which EVOLUTION occurs
The environment is the selective agent
Darwin said that in nature, the environment creates selective pressure

7. Steps of Natural Selection
Overproduction
-organisms have many offspring, but not all will survive.

8. 2. Genetic Variation
Individuals vary within a population
New traits appear due to genetic mutations

9. 3. Struggle to Survive
Organisms compete for resources (food, water, shelter, and mates) or get away from predators
Some adaptations allow organisms to survive at a higher rate

10. 4. Differential Reproduction (Descent with Modification)
Organisms with the best adaptations will survive and reproduce passing these beneficial traits down to their offspring

11. Natural Selection
Natural Selection acts on inherited traits or behaviors
As environment changes, different traits will become beneficial.

12. Artificial Selection
Humans breed for specific traits causing differences in species (i.e. dog breeding)

13. Insects become resistant to insecticides.
Examples of Natural Selection
Insects become resistant to insecticides.
1. Insecticide kills off most insects.

14. 2. Those insects that survive have a gene that makes them resistant.

15. 3. Resistant insects reproduce with other resistant insects.

16. 4. Their offspring have the resistant gene
4. Their offspring have the resistant gene. Insecticides don’t work very well over time!

17. Other examples of evolution:
Bacteria become resistant to antibiotics
Don’t take antibiotics unless you have a bacteria infection!

18. MRSA

19. Peppered Moths in England
There were more light moths (on light trees) before 1850.
There were more dark moths (on dark trees) after 1850.

20. Pocket mice
selection-and-adaptation