Percipitation Levels and the Affects to Beak Size

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Precipitation Levels and the Affects to Beak Size

Dixie Woodard


November 22, 2010
Alison Barrett

Precipitation Levels and the Affects to Beak Size

The experiment demonstrates the affect of precipitation levels to the beak size of finches on Darwin Island and Wallace Island. The levels of rainfall not only affect the beak sizes of the finches but also the population over time. The experiments were conducted over a period of three hundred years. The parameters remained constant over the three hundred year span to determine the effect of more or less precipitation on the food sources for the finches. The level of rainfall controls the types of seeds the birds eat. More rainfall creates smaller, softer seeds. Less rainfall creates harder, larger seeds. The experiments proved that over time, the birds on the island with the least amount of precipitation had larger beaks. The birds’ beaks were larger because they adapted to the new type of food source of larger, harder seeds. The population of the finches on Darwin Island was considerably larger for the first two hundred years. At one point, the populations were almost identical even though the beak sizes were dramatically different. This experiment will provide data that proves precipitation levels affect the beak sizes and the population of finches. The materials used in this experiment were a computer, printer, and access to the Evolution Lab on the University of Phoenix website. Software programs used were Microsoft Word for the text information and IrfranView for the graphs. The independent variables chosen to manipulate in the first run were the precipitation levels. That was the only parameter changed and remained constant for three hundred years. The experiment increased the precipitation level on Darwin Island to 40.0 cm from 20.0 cm. The precipitation level on Wallace Island was reduced from 20.0 cm to 10.0 cm. The experiment was conducted over a three hundred...
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