Genetic Drift

In the basic lab, student teams set up two islands composed of equal proportions of genotypic alleles. In this simulation the islands will be bowls, one large and one small.  Each bowl will be populated with beans of the same shape and size, but of different colors.  Students will blindly sample half of the beans on each island to reproduce and the non-reproducing beans are eliminated.  After students have recorded the number and proportion of alleles in each new population, they blindly resample each population again and again record the new proportion of alleles left on each island.  After five iterations, the students can stop and compare the initial vs. final proportions of alleles left on each island.  Genetic drift should have occurred much more dramatically on the small island than on the large island. Great teacher notes and directions, good student directions, and the inclusion of analysis of tables and graphs to develop conclusions makes this a great web site. This simulation builds student understanding of processes other than natural selection that can influence evolution.

Standards & Objectives

Academic standards
CLE 3005.2.6
Deliver effective oral presentations.
CLE 3210.4.5
Recognize how meiosis and sexual reproduction contribute to genetic variation in a population.
CLE 3210.5.3
Explain how genetic variation in a population and changing environmental conditions are associated with adaptation and the emergence of new species.
CLE 3210.5.5
Explain how evolution contributes to the amount of biodiversity.
Alignment of this item to academic standards is based on recommendations from content creators, resource curators, and visitors to this website. It is the responsibility of each educator to verify that the materials are appropriate for your content area, aligned to current academic standards, and will be beneficial to your specific students.

Lesson Variations

Blooms taxonomy level: 
Extension suggestions: 
  • For an extension of the fundamentals of genetic drift, have your students simulate a bottleneck or founder event by starting with a large population of known proportions of alleles (known number of beans and their colors) and then randomly sample a small number of those beans from the initial population to begin a new population that you can let grow.  After four or five generations of growth, you can compare the proportion of alleles in the new population vs. the initial population.

Helpful Hints


  • Big Island Bowl
  • Little Island Bowl
  • Bean Organisms: Brown, Red, White, Pink, and Black-Eyed
  • Data Table