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The Finch Module

Learn about the initial variation in beak size among finches and how changes in the environment, specifically drought, lead to selective pressure resulting in a shift in available food. Discover the impact of longer beaks on seed consumption and how natural selection plays a role in the evolution of these fascinating birds.

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The Finch Module

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  1. The Finch Module Caroline and Conrad’s Theory

  2. Overview of Explanation • Initial variation evident in beak size • Change in environment causes selective pressure • Resulting shift in food available • Natural selection for longer beak

  3. Initial Variation in Beak Size

  4. Change in Environment: Drought

  5. Food Supply Plants used as food: • Chamae • Portulaca • Cactus • Tribulus

  6. Effects of Drought • Tribulus becomes most prevelant

  7. Longer beak allows for more of the seed to fit into the finch’s mouth, making it easier for the finch to crack open the shell and eat the seed. How is a longer beak significant to the tribulus plant?

  8. Dry 76 Wet 77 Changes in Beak Length

  9. Small Beak Length • Example: 11.1 mm

  10. Large Beak Length • Example: 12.74 mm

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