The Plants unit (approximately 16 hours of instructional time), part of the Carbon TIME curriculum, builds on student learning about organic and inorganic materials in the Systems and Scale unit as well as the processes learned in the Animals Unit, including how all systems exist at multiple scales and the transformation of materials and energy during chemical change. In the Plants Unit students learn how the process of photosynthesis converts light energy from the sun into chemical energy stored in glucose, how the process of cellular respiration transforms organic materials to inorganic materials and chemical energy to energy for function and movement of organisms, and how the process of biosynthesis transforms food molecules into the biomass of an organism during growth.
This review focuses on lesson 4 (3-4 hours of instructional time) in which students use molecular models to learn how matter and energy are transformed in plants during photosynthesis and cellular respiration. The focus of this lesson is on developing explanations for how plants make food, move, and function in the light and in the dark. This lesson helps middle school and high school students understand why plants “breathe” (i.e., exchange gasses with the air) differently in the light and in the dark and how the mass of plants can come mostly from the air. As they model photosynthesis, students learn how to explain plant gas exchange and growth in a way that follows the key rules about matter and energy—atoms last forever and energy lasts forever (in chemical changes). As students model cellular respiration, they learn how to explain this carbon-transforming process that makes food energy available to plant cells.