C4.2.5—Supply to decomposers
Supply to decomposers explains how energy flow, matter cycling, trophic transfer or carbon movement is represented, measured or limited within ecosystems.
- Syllabus
- First assessment 2025
- Objective
- C4.2.5
- Level
- SL
Exam analysis
Chance of appearing4%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper2
Typical marks2
Common command terms
- State
- Explain
- Describe
- Outline
- Suggest
Scoring notes
- Common mistake
- Reversing food-web arrows instead of showing energy transfer direction.
Recent exam appearances
November 2025Paper2 ["SL"] · TZ35(b)[ 2 ]C4.2.5—Supply to decomposers
May 2019Paper2 ["SL"] · TZ18(a)[ 4 ]C4.2.5—Supply to decomposers
May 2019Paper3 ["SL"] · TZ12(b)[ 2 ]C4.2.5—Supply to decomposers
May 2017Paper2 ["SL"] · TZ12(d)[ 2 ]C4.2.5—Supply to decomposers
November 2015Paper2 ["SL"] · TZ02(d)(ii)[ 1 ]C4.2.5—Supply to decomposers
Practice this objective
Coverage 2015–2025 · Updated 16 Jul 2026
Concept essentials
- Supply to decomposers must be linked to the correct source, store, transfer or loss process.
- The evidence for supply to decomposers depends on distinguishing energy flow from matter cycling.
- Supply to decomposers is clearer when arrows, units and trophic positions match the biological process.
- Data or diagrams for supply to decomposers need interpretation as ecosystem transfer evidence.