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C4.2.2—Sunlight as principal energy source

Sunlight as principal energy source explains how energy flow, matter cycling or carbon transfer is represented, measured or limited within ecosystems.

Syllabus
First assessment 2025
Objective
C4.2.2
Level
SL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceMay 2024
Most common paperPaper2
Typical marks1–8

Common command terms

  • State
  • Explain

Scoring notes

Common mistake
Skipping the conversion of light energy into chemical energy by producers.

Recent exam appearances

May 2024Paper2 ["SL"] · TZ16(c)[ 7 ]C4.2.2—Sunlight as principal energy source
November 2016Paper2 ["SL"] · TZ07(a)[ 8 ]C4.2.2—Sunlight as principal energy source
November 2011Paper2 ["SL"] · TZ03(b)(ii)[ 1 ]C4.2.2—Sunlight as principal energy source
Practice this objective

Coverage 2011–2024 · Updated 16 Jul 2026

Concept essentials

  • Sunlight as principal energy source must be linked to the correct source, store, transfer or loss process.
  • The evidence for sunlight as principal energy source depends on distinguishing energy flow from matter cycling.
  • Sunlight as principal energy source is clearer when arrows, units and trophic positions match the biological process.
  • Data or diagrams for sunlight as principal energy source need interpretation as ecosystem transfer evidence.
ConceptIB Biology SL