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Practice · Biology · 2025 syllabus · C4.2

IB Biology C4.2 Transfers of energy and matter: practice questions

6 exam-style questions on C4.2 Transfers of energy and matter, SL and HL: 3 multiple choice, 1 data-based, 1 short answer and 1 extended response. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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C4.2-01 · Paper 1A style · multiple choice · 1 mark

Nutrition of a chemoautotroph

Iron-oxidising bacteria live in water draining from old mines, where they convert iron(II) ions to iron(III) ions.

Which row describes how these bacteria obtain energy and carbon? [1]

  1. Energy: oxidation of inorganic ions; carbon: carbon dioxide
  2. Energy: absorption of light; carbon: carbon dioxide
  3. Energy: oxidation of carbon compounds from dead organisms; carbon: the same carbon compounds
  4. Energy: oxidation of inorganic ions; carbon: carbon compounds from other organisms
Show the answer and the reasoning

Answer: A. A is correct. Iron-oxidising bacteria are chemoautotrophs. Oxidising iron(II) ions releases energy, which the bacteria use to fix carbon dioxide into carbon compounds, so they are autotrophs that do not need light. B describes photoautotrophs such as plants and algae. C describes saprotrophs, heterotrophs that feed on dead organic matter. D is wrong because an organism that takes its carbon compounds from other organisms is a heterotroph, whatever its source of energy; autotrophs make their own carbon compounds from carbon dioxide.

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The 6 questions in C4.2

  1. C4.2-01 Nutrition of a chemoautotrophPaper 1A style · multiple choice · 1 mark
  2. C4.2-02 Feeding at two trophic levelsPaper 1A style · multiple choice · 1 mark
  3. C4.2-03 Seasonal carbon dioxide swingsPaper 1A style · multiple choice · 1 mark
  4. C4.2-04 Primary production in four biomesPaper 2 style · short answer · 7 marks
  5. C4.2-05 Energy flow in a streamPaper 1B style · data-based · 9 marks
  6. C4.2-06 Carbon cycling and energy flowPaper 2 style · extended response · 15 marks

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.