1. Mechanisms of Natural Selection and Evolution

2. Natural Selection Review
Four parts of Natural Selection include: 1. Overproduction of Offspring
2. Genetic Variation***MUST BE PRESENT***
3. Struggle to Survive
4. Successful Reproduction

3. Natural Selection influences genetics
If an allele is responsible for a beneficial trait, the frequency of the allele will increase with time as a result of natural selection.
Multiple types of selection:
Directional Selection – when multiple variations of a trait exist, the environment selects for one of the “extremes” of the trait
Stabilizing Selection – when multiple variations of a trait exist, the environment selects for the “middle” trait
EXAMPLE: Giraffe necks
Directional: selecting for long necks over time
Stabilizing: selecting for medium length necks

4. How does Evolution work?
Evolution is governed by the principles of genetics
It is a change in successive generations of organisms, due to:
random mutation
Adaptation
Natural selection
Extinction

5. MUTATIONS
Genetic mutations and variety produced by sexual reproduction allow for diversity within a given population.

6. A mutation may result in change that is:
1. Favorable; improves a species’ ability to exist in its environments.

7. Mutations can also be neutral.
2. Unfavorable: does not improve a species’ ability to exist in its environment.
Mutations can also be neutral.

8. Adaptation
Adaptations are structures, functions, or behaviors that enable a species to survive.
Generally evolve over LONG periods of time – could be millions of years.

9. Natural Selection
the survival and reproduction of the individuals in a population that exhibit the traits that best enable them to survive in their environment.
The Survival of the Fittest

10. Extinction Extinction occurs when an ENTIRE species dies off.
Extinction often occurs as a result of the lack of variation in the genetics of a population.

11. Artificial Selection
When humans choose organisms with specific characteristics as breeding stock, they are performing the role of the environment
This is called “artificial selection”
Example of artificial selection in plants: five vegetables derived from wild mustard

12. Artificial Selection in Animals: Dog Breeding
German shepherd
Yorkshire terrier
English springer spaniel
Mini-dachshund
Golden retriever
Hundreds to thousands of years of breeding (artificial selection)
Ancestral dog