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Practice · Biology · 2025 syllabus · B4.2

IB Biology B4.2 Ecological niches: practice questions

7 exam-style questions on B4.2 Ecological niches, SL and HL: 3 multiple choice, 2 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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B4.2-01 · Paper 1A style · multiple choice · 1 mark

Feeding on dead matter

Which describes saprotrophic nutrition? [1]

  1. Ingesting food, then digesting and absorbing it inside the body
  2. Photosynthesizing in light and also ingesting other organisms
  3. Secreting digestive enzymes onto dead organic matter and absorbing the products
  4. Oxidizing inorganic chemicals to release energy for making organic compounds
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Answer: C. C is correct. Saprotrophs, such as many fungi and bacteria, digest dead organic matter outside their bodies by secreting enzymes onto it and then absorb the small molecules produced; they act as decomposers. A describes holozoic nutrition, used by animals. B describes mixotrophic nutrition, as in Euglena. D describes chemoautotrophic nutrition, found in some bacteria and archaea, which are autotrophs, not heterotrophs.

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The 7 questions in B4.2

  1. B4.2-01 Feeding on dead matterPaper 1A style · multiple choice · 1 mark
  2. B4.2-02 Two kinds of mixotrophPaper 1A style · multiple choice · 1 mark
  3. B4.2-03 Two water fleas in one tankPaper 1A style · multiple choice · 1 mark
  4. B4.2-04 Two sedges competingPaper 2 style · short answer · 5 marks
  5. B4.2-05 Leaf hairs and caterpillarsPaper 1B style · data-based · 7 marks
  6. B4.2-06 A protist that feeds two waysPaper 1B style · data-based · 8 marks
  7. B4.2-07 Niches, nutrition and herbivoryPaper 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.