In this activity, a visual model of the reactions of photosynthesis (and to a lesser extent, respiration) is provided to students. Students evaluate the model in groups, and subsequently use it to answer questions about the model as presented, as well as the results of perturbations to the pathways indicated in the model. These “perturbation” questions require students to step back and analyze the entire process, as opposed to individual components. This activity is intended for non-majors, but could easily be modified to effectively challenge majors-level students, and is amenable to use in both small and large classes.