C4.2.18—Carbon sinks and sources
Carbon sinks and sources explains how energy flow, matter cycling or carbon transfer is represented, measured or limited within ecosystems.
- Syllabus
- First assessment 2025
- Objective
- C4.2.18
- Level
- SL
Exam analysis
Chance of appearing4%of analysed past papers
Latest appearanceNovember 2022
Most common paperPaper1
Typical marks1
Common command terms
- Identify
- Explain
- Describe
Scoring notes
- Common mistake
- Reversing photosynthesis and respiration arrows in carbon-cycle diagrams.
Recent exam appearances
November 2022Paper1 ["SL"] · TZ019[ 1 ]C4.2.18—Carbon sinks and sources
May 2018Paper1 ["SL"] · TZ118[ 1 ]C4.2.18—Carbon sinks and sources
November 2017Paper2 ["SL"] · TZ07(c)[ 4 ]C4.2.18—Carbon sinks and sources
November 2014Paper1 ["SL"] · TZ020[ 1 ]C4.2.18—Carbon sinks and sources
May 2013Paper1 ["SL"] · TZ220[ 1 ]C4.2.18—Carbon sinks and sources
Practice this objective
Coverage 2013–2022 · Updated 16 Jul 2026
Concept essentials
- Carbon sinks and sources must be linked to the correct source, store, transfer or loss process.
- The evidence for carbon sinks and sources depends on distinguishing energy flow from matter cycling.
- Carbon sinks and sources is clearer when arrows, units and trophic positions match the biological process.
- Data or diagrams for carbon sinks and sources need interpretation as ecosystem transfer evidence.