C4.2.12—Energy reductions
Energy reductions explains how energy flow, matter cycling, trophic transfer or carbon movement is represented, measured or limited within ecosystems.
- Syllabus
- First assessment 2025
- Objective
- C4.2.12
- Level
- HL
Exam analysis
Chance of appearing6%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper3
Typical marks1–3
Common command terms
- Identify
- Explain
- Outline
- Calculate
- State
- Deduce
- Distinguish
- Suggest
- Discuss
Scoring notes
- Common mistake
- Reversing food-web arrows instead of showing energy transfer direction.
Recent exam appearances
May 2023Paper3 ["HL"] · TZ115(d)[ 2 ]C4.2.12—Energy reductions
November 2019Paper3 ["HL"] · TZ014(a)[ 2 ]C4.2.12—Energy reductions
May 2019Paper2 ["HL"] · TZ25(a)[ 2 ]C4.2.12—Energy reductions
May 2018Paper3 ["HL"] · TZ214(b)[ 3 ]C4.2.12—Energy reductions
May 2016Paper2 ["HL"] · TZ07(b)[ 3 ]C4.2.12—Energy reductions
Practice this objective
Coverage 2012–2023 · Updated 16 Jul 2026
Concept essentials
- Energy reductions must be linked to the correct source, store, transfer or loss process.
- The evidence for energy reductions depends on distinguishing energy flow from matter cycling.
- Energy reductions is clearer when arrows, units and trophic positions match the biological process.
- Data or diagrams for energy reductions need interpretation as ecosystem transfer evidence.