Describe the roles of the lungs and the skin as organs of excretion in humans.

Pearson Edexcel International GCSE Biology (4BI1) — 2.13 Excretion: humans · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

The lungs remove the waste gas carbon dioxide produced during cellular respiration, and they also excrete water in the form of vapour.
The skin removes waste by excreting sweat, which contains water, urea and salts.

Examiner tips

  • Use the word "remove" or "excrete" to show function; mention both CO₂ and water for lungs, and sweat, urea, salts for skin.
  • Keep the answer concise – one sentence per organ – to fit the 4‑mark limit.

Common mistakes

  • Writing only one waste product for each organ; forgetting that lungs also excrete water.
  • Using vague terms like "eliminate" instead of "excrete"; not naming urea or salts in sweat.

Mark scheme (4 marks)

  1. The lungs excrete carbon dioxide (produced during respiration)
  2. The lungs also excrete water (vapour)
  3. The skin excretes sweat / sweat contains water and urea (and salts)
  4. Excretion is the removal of waste products of metabolism from the body

Key terms in this question

excretion · lungs · skin

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