Study guide: Food chains, matter, and model boundaries
Trace energy and matter while recognizing the limits of a food-chain diagram.
Ideas to explain in your own words
- Explain where food-chain energy begins and distinguish energy flow from recycling.
- Distinguish a matter-cycle arrow from an energy-transfer arrow.
- Calculate energy available at successive steps of a model.
- Use a food web to make a bounded claim about food availability.
Watch your reasoning
- Grass uses sunlight to make energy-rich food. Feeding can transfer some of this stored energy to the rabbit and then to the fox. The model does not say energy is created by an animal or endlessly recycled.
- The map returns some mineral nutrients to soil. Matter recycling does not mean energy is endlessly recycled, and plants also use carbon from air.
- 600 × 1/10 = 60 for rabbit growth, then 60 × 1/10 = 6 for fox growth.
- The berry-plant arrow still reaches rabbits. The diagram supplies no amounts or population rule.
A worked review example
Trace Energy in a Food Chain: In a second model, sunlight → bean plant → caterpillar → bird, the sunlight supplies energy to the plant, and feeding transfers some stored food energy to the animals. Follow Matter on a Different Map: One matter route is soil nutrients → grass → rabbit waste → decomposers → soil nutrients. Decomposers help return nutrients; they do not recreate the sunlight that supplied the food-chain energy. Use a Stated Transfer Fraction: Grass 1,000 → rabbit 100 → fox 10 growth-energy units. Fox growth is one hundredth of the starting grass-growth value in this deliberately simplified two-transfer model. Add an Alternative Feeding Route: Removing grass leaves berry plant → rabbit → fox. That is a remaining represented energy route, not proof that the populations will stay the same.
Make a practice plan
- Try the supplied lesson problems without looking at the answers.
- Compare your method with the worked examples and explain any correction.
- Use the new review cases, then complete the transfer task on paper or in your own document.