This resource was not designed to build towards this science and engineering practice, but can be used to build towards it using the suggestions provided below.
Comments about Including the Science and Engineering Practice
This lesson directly engages students in using a computer model of photosynthesis. The science and engineering practices represent both knowledge and skills to be mastered by students. To be successful in this lesson, students must learn to manipulate the model and the included parameters and to make sense of the information communicated by the model. The lesson text provides a great deal of scaffolding to help students make sense of the model, but teachers should be prepared to provide additional support. In particular, slowing down the model can reduce potential confusion while viewing the model. Students may benefit from other activities that allow them to directly generate or interact with evidence of matter and energy flows occurring during photosynthesis. The model provides students with qualitative, but not quantitative, evidence of the inputs, outputs, and rate of photosynthesis. Students may benefit from additional learning activities that provide an opportunity to collect and analyze such data. Teachers should also note that this lesson leaves two important gaps in addressing the practice cited above. First, the lesson does not call for students to develop or revise a model. Teachers might address this aspect of the practice by asking students to develop and revise their own model after studying the computer model. Student models could include diagrams, chemical equations, or conceptual models. If students engage in hands-on investigations, then evidence from those investigations could be used to develop and support the student models. Second, the lesson does not call for students to predict relationships between components of the photosynthetic system. This aspect of the practice could be addressed through a combination of hands-on investigation and student model development. For example, students might use their models to predict the outcomes of student-designed experiments that explore how different variables (e.g., light intensity, light color, or CO2 concentration) affect photosynthesis in plants. A final important consideration is the need to engage students in examining the strengths and limitations of any model they use in science. Here are some points to consider with this lesson. The strengths of the model lie in the representation of the overall flows of matter and energy into and out of the process of photosynthesis and in the fact that the model highlights the role of the chloroplasts in converting light energy to chemical energy. As is the case with all models, there are several important limitations. (1) The model shows a single leaf, rather than a whole plant. Teachers can help students think about how the concepts here translate to the full plant, including the metabolic needs and processes of the plant and the different processes occurring in the leaves, stems, and roots. (2) The model provides a macroscopic view of photosynthesis without delving into the cellular and biochemical processes. This can be seen as a strength and limitation. In classes in which students are ready to move beyond this conceptual view, teachers will need to design or select additional learning experiences. (3)The model is certainly based on evidence, but the model does not provide students with direct access to that evidence.