IGCSE Biology: Excretion in Humans – Exam Tips & Revision Guide
This guide covers IGCSE Biology topic 13: excretion in humans. You will revise excretion (removal of waste), the kidneys (filtration, reabsorption, urine), the nephron, and the skin (sweat: water, salts, urea).
Key concepts to revise
- Excretion – Removal of waste products of metabolism (e.g. urea, CO2). Not the same as egestion (faeces).
- Kidneys – Filter blood; remove urea, excess water and salts; form urine. Know the role of filtration and reabsorption.
- Nephron – Filtration in glomerulus; reabsorption of useful substances (glucose, water, salts) in tubule; urine to bladder.
- Skin – Sweat glands excrete water, salts and a little urea; cooling by evaporation.
Exam tips and command words
- State – What excretion is; what the kidneys excrete (urea, excess water, salts).
- Describe – The path of urine (kidney to ureter to bladder to urethra); filtration and reabsorption in the nephron.
- Explain – Why reabsorption is needed (glucose and salts are useful; water balance).
- Label – Kidney (cortex, medulla, ureter); nephron (glomerulus, tubule).
Common mistakes
- Confusing excretion (urea, CO2) with egestion (faeces; undigested food).
- Saying the kidney produces urine without mentioning filtration and reabsorption.
- Not stating that glomerulus filters and tubule reabsorbs.
Revision checklist
- Define excretion and name the main excretory products (urea, CO2) and where they are removed.
- Describe the role of the kidney (filtration, reabsorption, urine formation).
- Label a diagram of the kidney and nephron; state the function of glomerulus and tubule.
- State what sweat contains and the role of skin in excretion and temperature regulation.
Next steps
Book a free trial with an IGCSE Biology tutor to practise excretion and kidney questions, or explore Tutopiya’s learning portal for more revision resources.
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