Excretion — Edexcel International GCSE Science (Double Award)
What excretion is, and the excretory products of the lungs, kidneys and skin, such as carbon dioxide and urea.
Revision notes
1 short note, in the order of the specification. Each one in short:
Excretion is the removal from the body of the waste products of metabolism. In humans the lungs excrete carbon dioxide, a waste product of respiration. The kidneys excrete urea, a nitrogen-containing waste, with excess water and ions in urine. The skin loses water, salts and urea in sweat. Faeces are egested, not excreted.
Exam questions
2 exam-style questions (4 marks), each with its mark scheme.
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4 cards: flip them, mark what you knew, and practise the rest.
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The whole of structure and functions in living organisms on one page, so you can see where this subtopic fits.
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Quick check questions
Name the excretory product of the lungs.
Show answer
Carbon dioxide.
Name three substances lost from the skin in sweat.
Show answer
Water, salts (ions) and urea.
Frequently asked questions
What is the difference between excretion and egestion?
Excretion is the removal of the waste products of metabolism, such as carbon dioxide from the lungs and urea from the kidneys. Egestion is the removal of faeces, which are undigested food that was never part of the cells' chemistry. So faeces are not excretory products, but urine and the carbon dioxide we breathe out are.
Written and checked against the Edexcel IGCSE Science Double Award (4SD0) specification · Updated October 2026