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D4.2.2—Requirements for stability

Ecosystem stability depends on continuing energy input, nutrient recycling, biological diversity, and abiotic conditions that do not exceed species tolerances.

Syllabus
First assessment 2025
Objective
D4.2.2
Level
HL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper2
Typical marks2–4

Common command terms

  • Outline
  • Describe

Scoring notes

Common mistake
Treating sustainability as a list of organisms only, without explaining energy input or nutrient recycling.

Recent exam appearances

May 2023Paper3 ["HL"] · TZ23(c)[ 2 ]D4.2.2—Requirements for stability
May 2019Paper2 ["HL"] · TZ17(c)[ 4 ]D4.2.2—Requirements for stability
Practice this objective

Coverage 2019–2023 · Updated 16 Jul 2026

Concept essentials

  • Energy must continually enter ecosystems because it is transferred and lost rather than recycled.
  • Decomposers support stability by returning inorganic nutrients from organic matter and wastes.
  • Limiting factors such as light, temperature, water, and nutrients restrict productivity when outside tolerance ranges.
ConceptIB Biology HL