CRQ QUESTION: A species of birds lives on an island. The thickness of the birds’ beaks varies within the population. The birds feed mainly on seeds from plants. Birds with thinner breaks can eat only small seeds. Only birds with thicker beaks can crush and eat large seeds.

There are many small seeds during years with more rain. During dry years, there are very few small seeds and many large seeds. The large seeds are harder to crush than small seeds.

The graph below shows the average beak thickness in the bird population from 1979-1985. 1980 and 1982 were dry years; 1984 was a wet year; 1979, 1981, 1983, and 1985 received normal rainfall.

Explain why the average break thickness changed between wet and dry years
Explain how break thickness would have changed during the next ten years (1986-1996) if these were wet years.
Name the process that led to this change.

Answer: The average beak thickness changed between wet and dry years because during the wet years the seeds were small and easily broken so the birds didn't have a need for thick beaks but during the dry years the seeds were large and harder to break open so the birds had the need for thick beaks. If the the next ten years (1986-1996) were wet years then the birds beaks would either continue to get smaller in size or continue to get smaller to a certain point and then stay at that size for the rest of the time. The process that led to this change is evolution. Evolution is when organisms adapt to their changing environments and can result in novel traits, altered genes, and new species. In the case of these birds the thickness of there beaks changed due to the size of the seeds they had available to eat.