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C4.2.22—Recycling of all chemical elements

Recycling of all chemical elements explains how energy flow, matter cycling or carbon transfer is represented, measured or limited within ecosystems.

Syllabus
First assessment 2025
Objective
C4.2.22
Level
HL

Exam analysis

Chance of appearing4%of analysed past papers
Latest appearanceNovember 2020
Most common paperPaper3
Typical marks3–6

Common command terms

  • Identify
  • Describe
  • Outline
  • Explain
  • Suggest

Scoring notes

Common mistake
Confusing detritivores that ingest material with saprotrophs that digest externally.

Recent exam appearances

November 2020Paper3 ["HL"] · TZ019[ 6 ]C4.2.22—Recycling of chemical elements
November 2019Paper2 ["HL"] · TZ08(c)[ 7 ]C4.2.22—Recycling of all chemical elements
May 2018Paper2 ["HL"] · TZ27(c)[ 3 ]C4.2.22—Recycling of all chemical elements
May 2018Paper3 ["HL"] · TZ118[ 6 ]C4.2.22—Recycling of chemical elements
May 2016Paper3 ["HL"] · TZ014(b)[ 2 ]C4.2.22—Recycling of all chemical elements
Practice this objective

Coverage 2016–2020 · Updated 16 Jul 2026

Concept essentials

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