Sources of Inherited Variation

1. Sources of Inherited Variation Mutations & Sexual Reproduction

2. Something to Ponder… • Why do you think knowledge of chromosomes and genes are important in understanding Evolution?

3. MUTATIONS • DNA is found in the chromosomes of a cell. • DNA is composed of long sequences that form a code, which when translated by the cell, gives an organism specific inherited traits. • Genes are segments of DNA that code for specific traits. Each gene has a specific DNA sequence.

4. MUTATIONS…continued • Though DNA typically remains the same throughout life, sometimes changes will occur. • MUTATIONS are random changes in the DNA itself, and they provide a continuous supply of new genetic information.

5. How Do Mutations Happen? • Environmental factors such as chemicals or radiation. • Errors that arise when cells use or make copies of the DNA molecules. • Many types of mutations… • Some involve the loss or duplication of entire sections of DNA. • Some involve simple changes to the DNA sequence.

6. Mutations are relatively rare in individuals, roughly about one new mutation per sex cell. • In large populations reproducing over many generations, however, the number of mutations is substantial.

7. Types of Mutations • Neutral Mutation – a mutation that has no effect on the organism. • Harmful Mutation – a mutation that reduces and organism’s fitness. • Beneficial Mutation – a mutation that enhances an organism’s fitness. • Fitness – an organism’s reproductive success • **most mutations are neutral or harmful

8. Sexual Reproduction & Variability • READ PAGES 154 & 155 • 1. Why is there a greater amount of inherited variability in sexually reproducing organisms compared to asexually reproducing organisms? • 2. Why are sexually-reproducing species so variable? Describe, in detail, three reasons. • 3. Connect Darwin’s Theory of Evolution with Genetic Mechanisms