Nutrient Cycling in Ecosystems

Steps:

• Identify the direction of energy flow: from producers to consumers, not reverse.
• Recognize nutrient recycling: decomposers break down organic matter, returning nutrients like carbohydrates to producers.
• Evaluate each option against energy flow and nutrient cycling principles.
• Select the option that accurately describes decomposer role in nutrient return.

Why D is correct:

• Decomposers recycle organic compounds like carbohydrates from dead matter back to producers via nutrient cycling, as defined in ecosystem dynamics.

Why the others are wrong:

• A: Carbohydrates flow from producers to herbivores, not the reverse.
• B: Energy flows from producers to herbivores to carnivores, not backward.
• C: Proteins flow from producers to primary consumers, with recycling via decomposers, not directly from consumers to producers.

Final answer: D