MS-LS2-3 model: matter and energy in ecosystems

MS-LS2-3 asks students to develop a model describing how matter cycles and energy flows through an ecosystem. The key insight is that living organisms and the nonliving environment exchange matter and energy continuously. Photosynthesis brings carbon from the atmosphere into living tissue. Respiration releases carbon back to the atmosphere. Decomposition recycles matter from dead organisms into the soil and air. All three processes are essential to how ecosystems function.

The carbon-cycle simulation lets students observe the cycling of matter and energy among living and nonliving ecosystem parts. Students adjust the balance of photosynthesis, respiration, and decomposition, then watch how carbon moves between the atmosphere, living organisms, soil, and water. The model responds dynamically, showing students what happens when one process increases or decreases. This interaction helps them see that matter is conserved. Carbon is neither created nor destroyed, only transformed and moved.

Start by asking students what happens to carbon from a plant or animal after it dies. Their initial guesses often stop at decomposition without connecting to the atmosphere or to photosynthesis. The simulation reveals the full cycle. In the predict phase, students make a hypothesis about how changing respiration rate affects carbon in the atmosphere. In the explore phase, they run the model and gather evidence. In the explain phase, they use the simulation to trace carbon's journey through photosynthesis, respiration, and decomposition. The assessment phase includes auto-graded questions that check whether students can identify which process moves carbon between specific parts of the ecosystem.