1. Evolution and Natural Selection
Part 2

2. Darwin hypothesized that species change over many generations and become better adapted to new conditions.

3. Galapagos Organisms: Darwin compared the organisms from the Galapagos Islands to organisms that live elsewhere. He also compared organisms living on the different islands.

4. Many of the birds and plants on the islands resembled those on the mainland. However, he also noted important differences between the organisms.

5. Darwin became convinced that species do not always stay the same
Darwin became convinced that species do not always stay the same. He thought species could change and even produce new species over time.

6. Darwin also discovered many differences among the organisms on the different Galapagos islands. You could tell which island a tortoise was from by looking at the shape of its shell.

7. Birds were also different from one island to the next
Birds were also different from one island to the next. Darwin concluded that the finch species were all related to a common ancestor that came from the mainland.

8. Over time, different finches developed different beak shapes and sizes that were well suited to the food that they ate. Beak shape is an example of an adaptation.

9. Birds with long, pointed, sharp beaks pick at cacti
Birds with long, pointed, sharp beaks pick at cacti. Those with short, thick beaks crush seeds. Birds with narrow, pointed beaks grasp insects. Those with short, hooked beaks tear open fruit.

10. Look at the different beak structures
Look at the different beak structures. Draw a line from each finch to the type of food you think it eats.

11. Review:
The scientific theory of ______ explains how living things are descended from earlier organisms.
What evidence did Darwin use to support his theory of evolution?
What type of evidence is the best indicator of how closely two species are related? Explain your answer.