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S3 Science: Ecosystems and Energy Flow (Paper 4: mistake clinic)
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S3 Science: Ecosystems and Energy Flow (Paper 4: mistake clinic)
This last paper revisits three frequent errors: treating the top of a pyramid as the largest, applying the ten per cent rule only once, and treating energy as something that cycles.
Direct answers Spend three seconds checking those three points after each question, which beats rereading the notes.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S3 Science: Ecosystems and Energy Flow |
| Level | S3 Science |
02 Questions (10 items)
- FoundationIs a producer always a green plant?
- FoundationWhat kind of organism does a primary consumer eat?
- FoundationWhat do decomposers turn organic matter into?
- IntermediateProducers fix 500 kJ. How much reaches the secondary consumer at ten per cent transfer?
- IntermediateProducers fix 8 000 kJ. How much reaches the third trophic level?
- IntermediateIn what form is energy mainly lost during transfer?
- ChallengeIf the transfer efficiency is twenty per cent, how much of 2 500 kJ reaches the primary consumer?
- ChallengeWhy can the same field feed more people with maize than with cattle?
- ChallengeIn a food web, what do grass to rabbit to fox and grass to rabbit to eagle represent?
- Error redoA student answers that energy grows towards the top of a pyramid. What should the answer be?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | No, algae and some bacteria can also be producers | Algae in water and bacteria that use chemical energy also make their own food. |
| 2 | Producers | A primary consumer feeds directly on producers and takes the second place in a food chain. |
| 3 | Inorganic substances such as carbon dioxide, water and minerals | Decomposers break organic matter in dead bodies into inorganic substances and return them to the environment. |
| 4 | 5 kJ | The chain runs 500 to 50 to 5 kJ. |
| 5 | 80 kJ | The chain runs 8 000 to 800 to 80 kJ. |
| 6 | As heat from respiration | Most of the energy becomes heat during respiration and cannot be used again. |
| 7 | 500 kJ | Twenty per cent of 2 500 kJ is 500 kJ. |
| 8 | There is one transfer fewer between the plants and the people, so less energy is lost | Maize eaten directly involves one feeding step, while passing through cattle adds another loss. |
| 9 | Two different food chains inside one food web | The rabbit is eaten by two predators, so the two chains share the same producer and primary consumer. |
| 10 | Energy falls towards the top, keeping about one tenth at each step | Energy is lost as heat at every level, so it decreases upwards. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Keep three columns in the error log: question, cause, corrected steps. The three commonest slips are putting the most energy at the top of a pyramid, applying the ten per cent rule only once, and treating energy as something that cycles.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.