2(i) Excretion
Pearson Edexcel International GCSE Biology · 4BI1
Paper 2 | Whole paper: All content including bold B statements
Removing the waste products of metabolism, and the kidney's role in controlling water as well.
Specification coverage
Topic 2 Structures and functions in living organisms (i) Excretion — statements 2.71–2.78B (includes bold B statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2. Suggested learning time: 60 minutes.
Required knowledge
- The excretory products of the lungs, kidneys and skin
- The structure of the urinary system and of a nephron
- Bold B statements: how the kidney carries out excretion and osmoregulation, including ultrafiltration and selective reabsorption
Required skills
- Distinguish excretion from egestion in every answer
- Explain the composition of filtrate at different points along a nephron
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
Common mistakes
- Calling faeces an excretory product. Undigested food has never been part of metabolism, so removing it is egestion.
- Saying the kidney 'filters blood' and stopping. Ultrafiltration and selective reabsorption are two separate processes, and both are examinable.