1. Theory of Evolution

2. Evolution
Definition: the change in allele frequencies in a population over time
Alleles are the different variations/forms of a particular genetic trait.
Allelic frequency deals with how often a particular allele appears in a population.

3. Jean Baptiste Lamarck French Naturalist
published ideas on evolution

4. Lamarck’s Hypothesis
During organism’s lifetime, physical features  size b/c use or  size b/c disuse
Organisms pass down acquired traits to offspring

5. Examples
Short-necked vs. long-necked giraffes
Body builders

6. Thomas Malthus
Human population increasing faster than supply of resources
Pop. growth limited by disease, famine, war

7. Charles Lyell – 1830s Leading geologist of Darwin’s time.
Surface of Earth changed slowly over long periods of time

8. Charles Darwin 22 yrs old HMS Beagle naturalist
Spent 5 yrs observing & collecting 1000s of plants & animals from jungles, grasslands, desert, etc.

9. Darwin noticed…
Unique animals & plants on islands looked similar to those on mainland but w/some differences

10. Darwin’s Finches
Collected 13 types finches – looked like different species

11. After the Voyage… Spent 20+ years studying collections
Results: variations w/in same species enable some to survive & reproduce, while those w/other variations do NOT survive or reproduce

12. Also studied…
Farmers’ breeding of plants & animals with more desirable traits
Artificial selection - selective breeding of plants/animals w/desirable traits

13. Artificial Selection
Lots of change can be achieved in a relatively short time
Darwin reasoned that natural selection could change species over 100s or 1000s of generations

14. Origin of Species
published his book, The Origin of Species by means of Natural Selection.

15. Natural Selection
Organisms w/favorable variations for a certain environment will survive, reproduce, & pass these variations to offspring
“Survival of fittest”
Fitness – ability of an organism to survive & reproduce in its specific environment

16. For example…
If a rabbit lived in an environment where it snowed all the time—what color of fur would be more advantageous?
Why?
Environment determines which traits are an advantage.

17. Main points of Darwin’s theory
Genetic variations in populations
Overproduction of offspring
Struggle for existence
Organisms w/favorable variations will survive, reproduce, & pass traits to next generation
Ex. Hummingbirds w/longer beaks