Explain how the process of peristalsis moves food along the alimentary canal.

Pearson Edexcel International GCSE Biology (4BI1) — 2.11 Transport: humans · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

1. Muscles in the wall of the alimentary canal contract behind the bolus.
2. Muscles in front of the bolus relax.
3. This creates a wave‑like, squeezing movement.
4. The wave pushes the bolus forward along the digestive tract from mouth to anus.

Examiner tips

  • Use the exact terms ‘contract’ and ‘relax’ as the mark scheme expects.
  • Show the sequence of contraction behind and relaxation ahead to demonstrate the wave mechanism.
  • Mention the direction of movement (mouth to anus) to cover the final point.
  • Keep the answer brief – one sentence per point – to fit the 4‑mark allocation.

Common mistakes

  • Confusing the order of contraction and relaxation (e.g., saying muscles relax behind the bolus).
  • Using vague phrases like ‘pushes food along’ without specifying the wave mechanism.
  • Omitting the direction of movement from mouth to anus.

Mark scheme (4 marks)

  1. Muscles in the wall of the alimentary canal contract (behind the bolus)
  2. Muscles relax in front of the bolus / ahead of the food
  3. This produces a wave-like / squeezing movement that pushes the bolus forward
  4. This moves the bolus along the alimentary canal / digestive tract from mouth towards the anus

Key terms in this question

peristalsis · alimentary canal

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