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Practice · Biology · 2025 syllabus · A2.3

IB Biology A2.3 Viruses: practice questions

5 exam-style questions on A2.3 Viruses, HL only: 3 multiple choice, 1 data-based and 1 short answer. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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A2.3-01 · Paper 1A style · multiple choice · 1 mark · HL

Diversity of virus structure

Which correctly describes a virus? [1]

  1. Bacteriophage lambda: single-stranded RNA and not enveloped
  2. Coronavirus: single-stranded RNA and enveloped
  3. HIV: double-stranded DNA and enveloped
  4. Bacteriophage lambda: double-stranded DNA and enveloped
Show the answer and the reasoning

Answer: B. Coronaviruses have single-stranded RNA and an envelope taken from host cell membrane. A and D are both wrong about lambda: it has double-stranded DNA and no envelope, just a protein capsid and tail. C is wrong because HIV's genetic material is single-stranded RNA, which it copies into DNA with reverse transcriptase after infection.

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The 5 questions in A2.3

  1. A2.3-01 Diversity of virus structurePaper 1A style · multiple choice · 1 mark · HL
  2. A2.3-02 Copying a prophagePaper 1A style · multiple choice · 1 mark · HL
  3. A2.3-03 Several origins of virusesPaper 1A style · multiple choice · 1 mark · HL
  4. A2.3-04 Drug resistance in influenzaPaper 2 style · short answer · 8 marks · HL
  5. A2.3-05 Phage growth on a log scalePaper 1B style · data-based · 8 marks · HL

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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.