August 12, 2005

The class began the day by reviewing the scientific process. Then Kent told them the story of dark Peppered Moths in Manchester, UK. Starting in 1848, about the time that coal-burning factories appeared in Manchester, the city began to be coated in soot. Approximately 50 years later, 98% of all the peppered moths in Manchester were dark. The original theory was that darker moths blend in better, while lighter moths stuck out like a "sore thumb."

In the 1920's, however, a scientist named Heslop Harrison thought that the pollution itself might be causing the mutation in color. The students used a Stella model to find the rate of genetic mutation that caused in the peppered moths. They discovered that for Harrison's theory to be correct, they would need a 4% rate of mutation, while scientists have only ever found a rate of 0.005%. It would take 36,648 years to achieve a population of 98% dark peppered moths!

The overall theme of the day was to learn about the various factors that can affect an experiment, and how they should avoid making assumptions.