1. Activity 2
Variation in Finches

2. Finches on the Galapagos Islands
Darwin observed a variety of finches based on shape and size of beaks
On each island, there existed a population of finches with a specific shape and size beak
Darwin also concluded that these finches derived from one common ancestor.

3. A common ancestor?

4. Variation amongst beak shape and size

5. Specialized beaks for…
Feeding on cactus flowers
Using twigs as tools to pry insects from bark
Eating eggs
Eating leaves
Blood
Eating ticks

7. What is causing this variation?
Directions: Based on the images and text in slides 3-5, respond to the following questions:
2. What seems to be the environmental pressure that is causing the variation seen in these finches on the Galapagos Islands?
3. How do you know this? What evidence can you provide from the images and text?

8. Food resources on each island
The variation seen in the finches on each island is due to the food sources available on each of the islands.
Each island has available certain types of food sources which require a different shape and size of beak in order to retrieve food.
Therefore, depending on the food source available on a given island, the finches will have a specific beak shape and size.

9. Challenge: Making connections
How does this variation seen in the beaks of these finches support Darwin’s theory of natural selection? In your response, provide evidence from the images/text in this PowerPoint AND prior knowledge of natural selection.