1. Theory of Natural Selection

2. Darwin Proposed the Theory of Natural Selection to Explain Evolution
Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms.
A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

3. Ideas that Shaped Darwin’s Thinking
James Hutton:
Proposed a theory of geological change
States that natural forces change earth’s surface shape
States that these changes are slow and the Earth was much older than thousands of years

4. Ideas that Shaped Darwin’s Thinking
Charles Lyell
Wrote the book “Principles of Geography”
States that geographical features can be built up or torn down
Darwin thought if earth changed over time, what about life?

5. Ideas that Shaped Darwin’s Thinking
Jean Baptist Lamark
Proposed that species change with a tendency toward perfection (Giraffe necks)
Traits that are used are passed down to offspring
Traits that are not used are not passed down

7. Ideas that Shaped Darwin’s Thinking
Thomas Malthus
19th century English economist who wrote “On the Principle of Population”
Stated that if a population grew too large, then there would be insufficient living space and a lack of food so population would decline

8. Populations tend to rise and fall overtime
As the population decreases, food supply returns
As food supply returns, population grows again

9. Ideas that Shaped Darwin’s Thinking
Selective Breeding-
The process of humans selecting traits they want to appear in offspring to produce desired traits
Used in farming to create sheep with fine wool
Used to create different breeds of dogs and cats

11. Ideas that Shaped Darwin’s Thinking
Russell Wallace
wrote an essay summarizing evolutionary change from his field work in Malaysia
Gave Darwin the drive to publish his findings

12. Also called “Survival of the Fittest”
Darwin’s Conclusion: Evolution happens through the process of natural selection!
Also called “Survival of the Fittest”
Some individuals are better suited for their environment
These individuals will survive and reproduce better than the others
These favorable traits will be passed down in offspring and appear more in future generations

13. Natural Selection
Over time, natural selection results in changes in inherited characteristics of a population.
These changes increase a species fitness in its environment

14. Requirements for Natural Selection
Overproduction:
There must an overproduction of offspring so that some can live while others will die.

15. Requirements for Natural Selection
Genetic Variation:
There must be differences among the individuals so that some do better than others.
Ex. Color, aggression, intelligence, behaviors, speed

16. Requirements for Natural Selection
Competition:
There must be a struggle to survive due to limited resources.
Ex. Limited resources could include food, water, shelter, mates, territory

17. Requirements for Natural Selection
Successful Reproduction:
There must be successful individuals who pass down their favorable traits to offspring.
If none are able to, then the population will go extinct!