Exam skills
What the paper asks you to do
- Distinguish excretion from egestion
- Trace filtrate through a nephron
- Explain ADH responses using feedback
Human systems
Excretion
Explain removal of metabolic waste, kidney function and regulation of water concentration.5090 syllabus routeConcept · skill · exam language
What to know
Build the topic around four anchors.
- 01Definition of excretion
- 02Urea formation
- 03Kidney and nephron function
- 04Water balance and ADH
Common mistakes
Where marks disappear
- Calling faeces an excretory product
- Saying all filtered glucose is excreted
- Reversing ADH effects on water reabsorption
Structured practice
Answer these without looking back.
For each prompt, write the biological chain clearly enough that every mark-worthy link is visible.
- 01Explain why urea must be removed.
- 02Describe selective reabsorption.
- 03Predict ADH change after heavy sweating.
Continue learning
Read the connected explanation.
A complete mental model for receptors, control centres, effectors and the return toward a normal range.
This independent teaching resource follows the Cambridge O Level Biology 5090 syllabus direction and is not endorsed by Cambridge International Education.