C4.2.1—Ecosystems as open systems
Ecosystems as open systems explains how energy flow, matter cycling or carbon transfer is represented, measured or limited within ecosystems.
- Syllabus
- First assessment 2025
- Objective
- C4.2.1
- Level
- HL
Exam analysis
Chance of appearing5%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper1
Typical marks1–2
Common command terms
- Describe
- Identify
- Distinguish
- Outline
- Compare
- Contrast
- State
- Explain
Scoring notes
- Common mistake
- Saying energy is recycled instead of flowing through and leaving ecosystems as heat.
Recent exam appearances
May 2023Paper1 ["HL"] · TZ215[ 1 ]C4.2.1—Ecosystems as open systems
November 2018Paper3 ["HL"] · TZ014(a)[ 1 ]C4.2.1—Ecosystems as open systems
May 2018Paper1 ["HL"] · TZ222[ 1 ]C4.2.1—Ecosystems as open systems
November 2017Paper3 ["HL"] · TZ016(b)[ 3 ]C4.2.1—Ecosystems as open systems
May 2017Paper2 ["HL"] · TZ14(b)[ 2 ]C4.2.1—Ecosystems as open systems
Practice this objective
Coverage 2013–2023 · Updated 16 Jul 2026
Concept essentials
- Ecosystems as open systems must be linked to the correct source, store, transfer or loss process.
- The evidence for ecosystems as open systems depends on distinguishing energy flow from matter cycling.
- Ecosystems as open systems is clearer when arrows, units and trophic positions match the biological process.
- Data or diagrams for ecosystems as open systems need interpretation as ecosystem transfer evidence.