Fig. 1

Screenshot of EvoBeaker Darwinian Snails Lab. In this culminating exercise, students are given two different stretches of coastline (top two panels), one “East” which crabs have reached (right) and one “West” which is still free of crabs (left). They also have four tanks where they can perform experiments. Students must design and carry out experiments to show that the difference in shell average shell thickness between the two areas (shown in the histograms on the right) is likely due to natural selection. To do this, they must show that there is variation, it is heritable, and there is selection, the three principles they learned in the more directed earlier parts of the lab