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Primary General Studies: Food Chains and Ecology (Paper 2 (intermediate))
Primary General Studies: Food Chains and Ecology (Paper 2 (intermediate))
Paper two focuses on food webs, decomposers and changes in numbers, training multi-step working and percentage reasoning.
Direct answers In a multi-step question, write each step with its meaning first and combine them only at the end.
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: Primary General Studies: Food Chains and Ecology |
| Level | parts of a closed circuit, conductors against insulators, series against parallel, adding up battery voltage, and electrical safety |
02 Questions (10 items)
- FoundationBacteria and fungi break down dead leaves and bodies. What are they called in an ecosystem?
- FoundationWhat does the arrow in grass to rabbit mean?
- FoundationBesides living things, what non-living factors does an ecosystem include?
- IntermediateA meadow holds 400 grasshoppers. Eight frogs eat 30 each in a month. How many are left?
- IntermediateA wood covers 5 000 square metres with 3 plants per square metre. If 100 plants feed one rabbit, how many rabbits can it support?
- IntermediateGrass holds 50 000 kJ. A cow keeps one tenth and a person eating the cow keeps one tenth of that. How much does the person get?
- ChallengeAfter snakes are heavily hunted, mice rise from 200 to 500. What is the percentage increase?
- ChallengeThe base of a pyramid holds 20 000 insects and each level keeps one tenth. How many are on the fourth level?
- ChallengeFertiliser runoff makes algae bloom and oxygen falls from 8 mg/L to 2 mg/L. What is the percentage drop?
- Error redoA classmate says decomposers only clear rubbish and are optional. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | They are called decomposers. | Decomposers turn dead material into nutrients that plants can take up again. |
| 2 | It means energy flows from the grass to the rabbit, which eats it. | The arrow shows the direction of energy flow, not that the rabbit turns into grass. |
| 3 | It includes sunlight, water, air and soil. | Living things and the non-living environment affect each other, and together they form an ecosystem. |
| 4 | 160 are left. | 8 times 30 is 240 eaten, and 400 minus 240 is 160. |
| 5 | It can support 150 rabbits. | 5 000 times 3 is 15 000 plants, and 15 000 divided by 100 is 150. |
| 6 | The person gets 500 kJ. | 50 000 times 0.1 is 5 000, and 5 000 times 0.1 is 500. |
| 7 | The increase is 150 per cent. | The rise is 300 mice, and 300 divided by 200 is 1.5, which is 150 per cent. |
| 8 | There are 20 on the fourth level. | Divide by ten three times: 20 000, 2 000, 200, then 20. |
| 9 | It drops by 75 per cent. | The loss is 6 mg/L, and 6 divided by 8 is 0.75, which is 75 per cent. |
| 10 | Without decomposers nutrients never return to the soil, harming plants and the whole chain. | Decomposers are a key part of the nutrient cycle, not an optional service. |
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.
Then try paper three, using voltage and current to work out power and resistance.Tutor Registration →
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