1. Sources of Variation
1. Introduction
1a. A population is typically well adapted to meet the needs of its environment

2. Sources of Variation
1. Introduction
1b. What happens if the environment changes, either suddenly or slowly?
1c. What happens if a population is moved to an environment for which most of its individuals are not well suited?
1d. This is where the importance of variation within a population comes into play.
Before After

3. Checkpoint 1
Suppose a population with very little variation is struck by disease. Explain why this population would have more difficulty surviving the disease than would a population with more variation.
vs.

4. Sources of Variation
2. Genetic Assortment
2a. Genetic assortment during meiosis is one source of variation within a population.
2b. Because of meiosis, every sex cell in an organism has a different combination of alleles than any other sex cell in that organism.

5. Sources of Variation
3. Mutation
3a. Another source of variation within a population comes from mutation.
- DNA does a good job when it copies itself,
but mistakes sometimes happen.
3b. Example:
- A species of roses that has made nothing but red-
blooming plants for dozens of generations may
suddenly produce a plant that makes white blossoms.

6. Checkpoint 2
In what type of cell (body or sex) will a mutation NOT be passed on to an organism’s offspring?

7. Sources of Variation
3. Mutation
(continued)
3c. Mutations usually hurt or kill the organism, but not always.
3d. Sometimes a mutation produces a trait that makes one individual slightly more fit for its environment.

8. Sources of Variation
3. Mutation
(continued)
3e. Because this individual is slightly more fit than its peers, it is more likely than its peers to live long enough to reproduce and pass the new trait on to its offspring.

9. Sources of Variation
4a. Variation within a population is the raw material on which natural selection works.
4b. Without variation, there would be no options within traits for nature to “select for”, and evolution simply could not happen.
4. Importance of Variation

10. Agenda Assignment: Homework: Sources of Genetic Variation
Variation, Adaptation, and Natural Selection Reading Questions.