Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
On the Galápagos Islands, populations of medium ground finches (Geospiza fortis) show differences in beak depth - the distance from the top to the bottom of the beak. This small variation has big effects on what types of seeds the birds can eat.
During drought years, small, soft seeds become scarce, leaving mostly large, hard seeds. Finches with deeper, stronger beaks can crack these tougher seeds more easily, while those with smaller beaks struggle to find food.
Researchers from Princeton University recorded how beak depth affected survival rates during a drought year on Daphne Major Island.
Beak Depth (mm) | % of Individuals Able to Eat Hard Seeds | Survival Rate (%) |
|---|---|---|
7.0–8.0 | 20 | 40 |
8.1–9.0 | 55 | 65 |
9.1–10.0 | 90 | 88 |
This variation in beak depth gives some finches a clear advantage when resources are limited. Birds with deeper beaks can access more food and are more likely to survive and reproduce, passing on their traits. Over time, environmental pressures (like drought) can shift the population’s average beak size, an observable example of natural selection.
This is a classic example of how variation within a species affects survival and reproduction. The finches inherit genes for beak size, but environmental conditions determine which variations are advantageous in a given year.
Make a claim, provide the evidence, and explain your reasoning for the statement:
“Finches with deeper beaks survive better during droughts when only hard seeds are available.”
Respond with three parts: a clear claim, specific evidence from the table or graphs, and reasoning that links the evidence to your claim.
Refer to Table 1 in the Finch Beak Depth and Seed Type resource.
Describe how beak depth affects the ability to eat hard seeds and the survival rate during droughts.
What advantage do finches with deeper beaks have during droughts?
How does beak depth variation show both inheritance and difference among finches?
Explain how the drought environment affected which finches survived and reproduced.