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Grade 7 · unit review

Review: Food-web energy, cycling matter, and bounded predictions

Combine feeding relationships with quantitative energy models and distinguish matter cycling.

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Bring the unit skills together

Use these 4 new cases to check your reasoning. Choices are temporary and are not saved to an account, sent to staff or recorded as school grades. Download your current review choices before leaving or reloading.

Unit review questions
1. New relationships say algae is eaten by snails and snails by fish. With food-to-consumer arrows, which path is correct?
2. A growth-energy model supplies 400 kJ to herbivore growth from 2,000 kJ producer growth. What is the fraction?
3. A carbon map returns animal carbon to air through respiration. Which statement is careful?
4. Fish eat snails and insect larvae; birds eat fish. Snails decline. What information helps bound an indirect bird-food prediction?

The download contains your current choices and any checked feedback. Keep the separate transfer-task work in your own document; downloading its instructions does not mark it complete.

Use the skills in a new task

Write an ecosystem briefing from this fictional model: algae → snail → fish → bird and larvae → fish. Algae-growth energy is 900 kJ; snail growth receives 180 kJ and fish growth on that route receives 36 kJ. A separate carbon map includes organism respiration returning CO₂ to air. Calculate two transfer percentages, trace energy and carbon separately, and discuss reduced snails.

Work on paper or in your own document. Explain the choices you made.

  • Use the food-to-consumer arrow direction.
  • Calculate 20% for each transfer and 4% overall from algae to fish growth.
  • Explain that respiration cycles carbon without cycling all usable energy.
  • Make a conditional fish/bird prediction and name larval availability as missing evidence.
Compare with a model response

Energy follows algae → snail → fish → bird. Snail growth gets 180/900 = 20%, and fish growth gets 36/180 = 20%; overall 36/900 = 4%. The separate respiration arrows return carbon matter as CO₂, while energy is transferred and partly disperses thermally. Reduced snails could reduce fish food and then bird food, but larvae remain a fish food route. Its availability and fish feeding amounts are needed before estimating population changes.

A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.