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Ecosystems and Energy Flow Paper 1: Basics
Ecosystems and Energy Flow Paper 1: Basics
Starting from food chains and trophic levels, practising the ten per cent rule and separating producers, consumers and decomposers.
Direct answers Answers and explanations for all ten questions
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: DSE Biology Ecosystems and Energy Flow |
| Level | Paper 1 (basics) |
02 Questions (10 items)
- FoundationIn the food chain grass, rabbit, fox, which trophic level is the rabbit?
- FoundationA producer fixes 20000 kJ of energy. Under the ten per cent rule, how much reaches the primary consumer?
- FoundationA producer holds 10 000 kJ. After passing through two consumer levels, how much does the secondary consumer get?
- IntermediateWhich organisms convert light energy into chemical energy in an ecosystem?
- IntermediateWhat is the main role of decomposers in energy flow?
- IntermediateWhy is an energy pyramid normally upright?
- ChallengeIn what form does the energy used in consumers respiration finally leave the ecosystem?
- ChallengeA field holds 10 000 kJ in producers. If there is only one consumer level, how much do the primary consumers receive?
- ChallengeWhy is net primary productivity usually high in tropical rainforests?
- Error redoError: a student says energy can be recycled in an ecosystem just like nutrients. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | The rabbit eats the producer, so it is a primary consumer at the second trophic level. | Numbering starts with the producer as level one, so the primary consumer is level two. |
| 2 | 2000.0 kJ. | Each level passes on roughly a tenth, the rest being lost to respiration and excretion. |
| 3 | 200 kJ. | Each level multiplies by 0.1, so two levels multiply by 0.01. |
| 4 | Producers, mainly green plants and algae, through photosynthesis. | Producers are the only entry point for new energy; everything else depends on them. |
| 5 | They break down organic matter in remains and waste, releasing inorganic nutrients back to the environment. | Decomposers release nutrients, not energy; at this step the energy is lost as heat. |
| 6 | Because energy is lost heavily at each transfer, so higher levels always have less total energy available. | An upright pyramid reflects falling energy, not body size or numbers. |
| 7 | Mostly as heat, which can no longer be used by living things. | Energy flows one way and heat cannot be recovered, which is why the pyramid must be upright. |
| 8 | 1000.0 kJ. | A short chain loses less, which is why eating plants costs less energy than eating animals. |
| 9 | Abundant light, warm temperatures and a steady water supply keep photosynthesis high all year. | Net primary productivity is gross production minus the producers own respiration. |
| 10 | Nutrients cycle, energy does not; energy flows one way along the food chain and ends as heat. | Confusing cycling with flow is the commonest conceptual error, so state the two separately. |
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.
Start at the producer and multiply by a tenth level by level; that is the safest routine.Tutor Registration →
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