An introductory lab that examines the assumptions behind natural selection using an engaging interactive simulation of green crabs preying on periwinkle snails. Students are able to "violate" each assumption in turn to explore whether evolution by natural selection still occurs. Exercises are targeted to address common misconceptions among biology students. Suitable for non-majors and introductory biology courses.
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This laboratory recreates the famous experiments of Paine and colleagues in the Pacific Northwest with the sea star Pisaster (and 8 other marine intertidal species). Students do transplant experiments to figure out competitive relationships and sample gut contents to construct a food web. Next they use their data to predict what will happen when each predator is removed from the system. Finally, they do the removal experiments and compare their results with their predictions. This is a great introductory lab in that it explores basic ecological concepts and although it is not difficult, it asks students to think critically, synthesizing experimental data to make predictions. It also provides a nice foundation for discussions of the important roles that different species can play in a community.
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An interactive simulation of the classic malaria and sickle-cell anemia system is used to explore natural selection and genetic drift. Students examine African villages with different malaria death rates. First they use the Hardy-Weinberg equation to calculate the expected proportion of sickle-cell carriers from HbS and HbA allele frequencies. Then they examine how the allele frequencies change with changes in malaria risk and with different "founder" scenarios. Finally they explore genetic drift without selection by looking at different-sized villages where both diseases have been cured. An optional advanced section allows independent exploration of evolutionary forces using a basic population genetics model with adjustable parameters for selection strength, immigration rate, and population size. This is one of our most popular labs for introductory biology courses.
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This lab confronts common misconceptions about diffusion using engaging simulated molecular-level experiments. The lab first focuses on how individual molecules move under different conditions. It then sets up a fun experiment that allows students to explore whether nerve cells could use diffusion to move materials from the cell body to the synapses at the tips of their axons. Students run races in axons of different lengths and record how long it takes for "peptide" molecules to diffuse down their length. A new concluding exercise explores diffusion in plant leaves, asking whether CO₂ molecules that start among high concentrations of other CO₂ molecules move faster than CO₂ molecules that start among high concentrations of water molecules. By the end of the lab, students not only discover the need for cellular and organ level transport mechanisms, but also overcome some commonly held misconceptions (see our Publications page for details).

Introduces students to evolutionary trees using an interactive simulation of Columbine flower diversification. Students observe Columbine populations split and diverge while an expanding evolutionary tree illustrates each population's history. Students further learn to interpret evolutionary trees by creating their own and reconstructing the history of mystery populations. Suitable for both introductory and advanced biology and evolution courses.
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