The finches on Darwin and Wallace Islands feed on seeds produced by plants growing on these islands. There are three categories of seeds: soft seeds, produced by plants that do well under wet conditions; seeds that are intermediate in hardness, produced by plants that do best under moderate precipitation; and hard seeds, produced by plants that dominate in drought conditions. The lab is based on a model for the evolution of quantitative traits-characteristics of an individual that are controlled by large numbers of genes. These traits are studied by looking at the statistical distribution of the trait in populations and investigating how the distribution changes from one generation to the next. For the finches in Evolution Lab, the depth of the beak is the quantitative trait. I investigated how this trait changes under different biological and environmental conditions. I manipulated various biological parameters (initial mean beak size, heritability of beak size, variation in beak size, fitness, and clutch size) and one environmental parameter (precipitation) of the system, and observed changes in the distributions of beak size and population numbers over time. Assignment 2: The Influence of Precipitation on Beak Size and Population Number The first experiment is designed to study the influence of beak size on finch population numbers. For finches, deep beaks are strong beaks, ideally suited for cracking hard seeds, and shallow beaks are better suited for cracking soft seeds. I experimented first with the finches’ adaptation and evolution of their population over 300 years, and changed the Wallace birds beak size to 28mm, and Darwin’s birds stayed at the default of 12mm. I hypothesize a since there are more hard seeds (64%) on the islands than soft seeds (4%). The birds with the smaller beak (Darwin) will not be able to get enough food which may cause some of the birds to die, resulting in a decrease in the smaller beak bird’s population and an...
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