Some PRACCIS lessons have students develop their own models based on evidence they have encountered. Students revise their models after they evaluate the fitness of them to evidence or after they revisit the criteria of modeling. For example, in our lesson on chloroplasts, students’ goal is to develop a model to explain the function of chloroplasts. Students conduct an experiments, read adapted scientific reports, and conduct simulated investigations on computers to develop a model that explains the evidence. After class discussions, students go back to revise their models.
For example, in our unit on natural selection, students working in pairs use five pieces of evidence to develop their own models of why mountain sheep’s horns in the American West have become smaller over about 50 years. At that point, teachers may have students present models, and the class can discuss which models are best.
