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. Evolution 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 EvolutionLab, the depth of the beak is the quantitative trait. You will investigate how this trait changes under different biological and environmental conditions.
You can manipulate various biological parameters (initial beak size, heritability of beak size, variation in beak size, clutch size, and population size) and two environmental parameters (precipitation, and island size) of the system, then observe changes in the distributions of beak size and population numbers over time.
Assignment 1:
Getting to Know EvolutionLab: The Influence of Precipitation on Beak Size and Population Number
1. The first screen that will appear in Evolution Lab presents an initial summary (Input Summary) of the default values for each of the parameters that you can manipulate.
Notice that default values on both islands are the same. Click on the Change Inputs button at the left of screen to begin an experiment. A view of initial beak size will now appear.
In the Change Input view you can change the biological and environmental parameters in EvolutionLab to design an experiment. This 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