4bEcology and the Environment
Feeding relationships — Edexcel Linear - OL Revision Notes & Topical Questions
5 min read 7 parts Lesson 3 of 10 1 quiz
Lesson summary
Feeding relationships Edexcel O Level Linear Biology notes: understand the names given to different trophic levels, including producers, primary, secondary and tertiary consumers and decomposersFood chains rarely have more than 5 levels.Energy flows; nutrients cycle.Pyramids of e…
- Feeding relationships Edexcel O Level Linear Biology: what to do next
- Ecological pyramid
- Give / State / Name
- Evaluate / Assess
- Keywords the mark scheme looks for in this lesson
- How to get full marks (examiner guidance)
Part 1 of 6Key ideas
Key ideas
Food chains rarely have more than 5 levels.
Energy flows; nutrients cycle.
Pyramids of energy are never inverted.
Part 2 of 6Syllabus points
1
understand the names given to different trophic levels, including producers, primary, secondary and tertiary consumers and decomposers
2
understand the concepts of food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer
3
understand the transfer of substances and energy along a food chain
4
understand why only about 10% of energy is transferred from one trophic level to the next
Part 3 of 6Process & sequence
- Sun
- Producer
- Primary consumer
- Secondary consumer
- Tertiary consumer
Why energy is lost
Respiration (heat)
Undigested food
Parts not eaten
Excretion
Part 4 of 6Summary
Summary
About 10% of energy passes to the next level.
Producers are at trophic level 1.
Part 5 of 6Keep going
Feeding relationships Edexcel O Level Linear Biology: what to do next
These Feeding relationships Edexcel O Level Linear Biology notes covered the key ideas, worked examples and exam technique for this topic. Check your Feeding relationships Edexcel O Level Linear Biology understanding with the practice questions below, then reread any Feeding relationships Edexcel O Level Linear Biology point you were unsure about before moving on.
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Previous lesson: 4a The organism in the environment — Notes
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Next lesson: 4c Cycles within ecosystems — Notes
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Course: Edexcel Linear - OL — all units
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Official syllabus: Pearson Edexcel International GCSEs
Part 6 of 6Compare: Compare
| Level | Organism type | Example | Energy available | Energy lost as | Pyramid width |
|---|---|---|---|---|---|
| 1 | Producer | Grass | 10 000 kJ | Respiration, heat | Widest |
| 2 | Primary consumer | Grasshopper | 1 000 kJ | Heat, waste | — |
| 3 | Secondary consumer | Frog | 100 kJ | Heat, waste | — |
| 4 | Tertiary consumer | Snake | 10 kJ | Heat, waste | — |
| 5 | Quaternary | Hawk | 1 kJ | — | Narrowest |
Key terms
Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
Producer · Consumer · Trophic level · 10% rule · Food web · Decomposer · Biomass · Ecological pyramid
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.
How to get full marks (examiner guidance)
How to get full marks (examiner guidance)
Use specification keywords exactly (e.g. eukaryotic/prokaryotic, enzyme–substrate complex, active site, complementary).
Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
Do not extrapolate a graph line beyond the data or to zero unless asked.
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
Marked practiceQuizzes for this lesson
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