Follow Matter on a Different Map

Supplied materials

• Use the supplied fictional observations or model. Paper and pencil are optional; spoken answers are welcome. No equipment or real experiment is needed.

Learn the idea

A diagram’s arrow key matters. A food-chain arrow can track energy transferred by eating. A different diagram can track matter, such as atoms in soil nutrients moving into a plant and later returning through waste or dead material. Matter can be reused in an ecosystem; the useful energy flow is not a loop that endlessly powers itself.

Use this simplified matter map: soil nutrients → grass → rabbit; grass waste and dead grass → decomposers; rabbit waste and dead rabbit → decomposers; decomposers return some mineral nutrients → soil. These arrows mean material moves, not that every substance takes exactly this route. Plants also obtain much of their carbon from air, so soil is not their only matter source.

1. Write the arrow key “movement of matter.”
2. Trace soil → grass → rabbit.
3. Add a route from rabbit waste through decomposers back to soil nutrients.
4. Compare this loop with sunlight → grass → rabbit energy flow.

Check your reasoning

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Take it further

Remove the decomposer-to-soil arrow from the paper map. The revised diagram no longer represents that return route; it does not prove decomposers have stopped working in every real ecosystem.

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