4. Matter continuously cycles through an ecosystem. A simplified carbon cycle is depicted below. Organic Molecules CO, (a) Identify the key metabolic process for step I and the key metabolic process for step II, and briefly explain how each process promotes movement of carbon through the cycle. For each process, your explanation should focus on the role of energy in the movement of carbon. (b) Identify an organism that carries out both processes. 1. What overall process uses carbon dioxide as a reactant and produces organic molecules (labeled I) ?