1. Mechanisms of Evolution

2. Evolution – a change in the population’s
gene pool over time
These changes can be caused by:
Genetic drift
Natural selection

3. The gene pool has changed, evolution has occurred.
Genetic Drift – a change in the gene pool caused by chance
Ex: A natural disaster removes all but a few members of the population.
Result: The remaining individuals have a smaller gene pool, some variations may have been lost. The next generation will lack those variations.
The gene pool has changed,
evolution has occurred.

4. Migration will also change the gene pool.
Immigration will add genes to the gene pool
Emigration will decrease the gene pool

5. Natural Selection- Overproduction occurs in all species
Variations occur in all species
Struggle for survival- resources are limited, not all born will survive
Survival of the fittest- those best adapted to their environment will survive and reproduce.

6. How do variations occur?
Viruses alter a cell’s DNA
Chemicals and radiation can cause mutations
If this occurs in the egg or sperm
it will be passed to the offspring
Sexual reproduction causes a mixing of genes

7. Fitness: ability of an individual to survive and reproduce
- central to the process of Evolution
- individuals with low fitness either
die or produce few offspring

8. Adaptation: Inherited characteristic that increases an organisms chance for survival
Ex: Speed, Camouflage, Claws, etc.

9. Evolution is driven by environmental change.
As the environment changes, different adaptations will increase fitness.
Adaptations that decrease fitness will eventually die out of the gene pool.

10. Evolution of pesticide resistance in response to selection