1. The Theory of Natural Selection

2. Review - Theory
A well-supported explanation for why something happens in nature
Supported by observations, inferences, hypothesis, laws & principles

3. Evolution
How a species changes over time

4. What scientific explanation can explain the diversity (many types) of life on Earth?

5. Biodiversity – the wide range (types) of living things

6. Charles Darwin English naturalist (1800’s)
Proposed the theory of natural selection to explain how evolution occurs

7. Selection
A process of determining which traits are going to be advantageous/good and which is deleterious/bad
Artificial- people choose traits (dogs, corn, etc)
Natural- the environment chooses

8. Key Processes of Natural Selection
Genetic variation
Overproduction of offspring
Struggle for survival
Differential survival & reproduction

9. Genetic Variation
Inherited variation of traits is present among individuals of a population

10. Genetic Variation

11. Mutation A random change in DNA creating new traits/alleles
Produces variation
Allele- different forms of a gene (represented by letters
upper case= dominant
Lower case = recessive

12. Overproduction of Offspring
Populations have the potential to produce more offspring than an areas resources can possibly support

13. Overproduction of Offspring

14. Struggle for Survival
A individual’s survival depends on its ability to compete successfully for food, water and other resources and to avoid predators & disease.

15. Differential Survival & Reproduction
Individuals with the most successful traits (highest fitness) in their environment are more likely to survive
Over many generations the population changes as the frequency of the trait increases or decreases

16. Fitness
A measure of how successful an organism survives and reproduces, making healthy babies.
High Fitness = many babies
Low Fitness = few babies

17. Adaptation
An anatomical, physiological or behavioral change that improves a population’s ability to survive