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IGCSEBiology
Trial Class

Original practice · 5 questions · 16 marks · about 18 minutes

Breathing Mechanics Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your ability to describe the mechanics of breathing: how air is moved in and out of the lungs by changes in thorax volume and pressure.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 4 Both 4 marks Difficulty 3/5

    Describe the changes that occur in the thorax during inhalation (inspiration).

    Show model answer and marking guidance
    1. External intercostal muscles contract: ribs move up and out.
    2. Diaphragm contracts: flattens / moves downward.
    3. Volume of the thorax increases.
    4. Pressure inside the thorax decreases (below atmospheric): air is drawn into the lungs.

  2. Question 2

    Paper 4 Both 4 marks Difficulty 3/5

    Describe the changes that occur during exhalation (expiration) at rest.

    Show model answer and marking guidance
    1. Internal intercostal muscles contract (or external intercostals relax): ribs move down and in.
    2. Diaphragm relaxes: returns to dome shape / moves upward.
    3. Volume of the thorax decreases.
    4. Pressure inside the thorax increases (above atmospheric): air is pushed out of the lungs.

  3. Question 3

    Paper 4 Extended 3 marks Difficulty 4/5

    Explain why breathing rate increases during vigorous exercise.

    Show model answer and marking guidance
    1. Muscles require more energy so respiration rate increases.
    2. More oxygen is needed for aerobic respiration and more CO₂ is produced.
    3. Faster breathing increases the rate of gas exchange: more O₂ in, more CO₂ out.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 1/5

    Name the two sets of muscles involved in breathing.

    Show model answer and marking guidance
    1. Intercostal muscles (between the ribs).
    2. Diaphragm (sheet of muscle below the lungs).

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 3/5

    A bell jar model uses a rubber sheet and balloons to demonstrate breathing. State one limitation of this model.

    Show model answer and marking guidance
    1. The bell jar has rigid walls: the real thorax has a flexible rib cage that moves.
    2. The model has no intercostal muscles: only the diaphragm (rubber sheet) is represented.
    3. The balloons do not have alveoli: real lungs have millions of tiny air sacs.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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