In this activity, beans of two different colors demonstrate evolutionary forces, plus the effects of population size on these forces. Use red and white beans of similar size. In these experiments, the beans represent two different alleles for a gene controlling a single trait. In small containers, such as shallow bowls or jars, create populations of 100 beans. The containers should be carefully labeled with both the number of beans and the gene frequency, so that it is easy to determine their contents.
Students work in pairs.
When populations are so small that not many individuals are reproducing, the effect of random genetic drift is greater. The differences in sample size will demonstrate how change can occur more quickly when populations are small. The 5 beans are placed in the student s empty container. Again, count the number of red beans, determine the gene frequency, record your findings, and return the beans to their container. The first student collects data in a similar fashion to the original experiment, but draws populations of 10 beans in each trial instead of 5.