1. Darwin’s Theory

2. Darwin’s Observations
Background Info: Charles Darwin
Set sail on the HMS Beagle
5 year trip around the world
Naturalist: a person who studies the natural world
He wanted to learn about the living things he saw on the voyage
He made many stops along the coast of South America then to the Galapagos islands
His important observations included
Diversity of living things
The remains of ancient organisms
The characteristics of organisms on the Galapagos Islands

3. Diversity
Darwin was amazed by the tremendous diversity of living things
Scientists have observed 1.7 million species of organisms on Earth
Species
A groups of similar organisms that can mate with each other and produce fertile offspring

4. Fossils
Fossil
Preserved remains or traces of an organism that lived in the past

5. Galapagos Organisms
Darwin observed the greatest diversity of organisms on the Galapagos Islands
Comparisons to South American Organisms
Many Galapagos organisms were similar to organisms on mainland South America
Darwin hypothesized that the ancestors of Galapagos animals and plants came from mainland South America
Blown out to sea during a storm?
Set adrift on a fallen log?

6. Comparisons Among the Galapagos Islands
Darwin traveled from island to island
He noticed many differences among the organisms
Dome-shaped tortoise shells
Saddle-shaped tortoise shells

7. Adaptations Adaptation
The finches Darwin saw on the islands were noticeably different
Most obvious difference was the size and shape of their beaks
Finches that ate insects: narrow, needle-like beaks
Finches that ate seeds: strong, wide beaks
Adaptation
A trait that helps an organism survive and reproduce

8. Evolution
Darwin reasoned that plants or animals that arrived on the Galapagos Islands faced conditions different from mainland South America
He hypothesized the species gradually changed over time
Organisms became better adapted to the new conditions
Evolution
The gradual change in a species over time
Scientific Theory
A well-tested concept that explains a wide range of observations
Darwin’s Theory of Evolution

9. Selective Breeding
Breeding animals by only allowing certain animals to mate
Example
Race horses are selectively bred to obtain the trait of speed
Darwin bred pigeons with ONLY large, fan-shaped tail feathers

10. Natural Selection Book by Charles Darwin, The Origin of Species
Explanation of how evolution COULD occur in nature
Natural Selection
The process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other member of the same species
Factors that affect the process of natural selection
Overproduction
Competition
Variations

11. Overproduction
Effect cause by species producing more offspring than can survive
Example
Insects

12. Variations Differences between individuals of the same species Example
Different foods eaten by the same species of insects

14. Competition Effect caused by limited food and other resources Example
Direct (physical fights)
Indirect (not finding enough food to eat)

16. Environmental Change
Environment can affect an organism’s ability to survive
This can then lead to selection
Monkey Flowers
Can’t grow in soil with high concentration of copper

17. Genes and Natural Selection
Darwin could not explain what caused variations or how they were passed on
Scientists later learned, variations can result from mutation and the shuffling of alleles during meiosis
Genes are passed from parents to offspring
Only traits inherited, or controlled by genes can be acted upon by natural selection