What this practice covers
These questions are drawn from past CIE 0654 Co-ordinated Sciences papers and filtered to excretion in humans. You answer, you find out immediately whether you were right, and you get the reasoning for the correct option and for each distractor. Wrong answers go to a mistakes locker so you can come back to exactly those.
Practice is free. You need an account only so your progress and your mistakes are still there next time.
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What examiners see students get wrong here
These are the errors that cost marks on excretion in humans, taken from our own topic notes. Read them before you practise and you will recognise the traps in the questions.
- Calling egestion excretion.
- Forgetting that the lungs are an excretory organ, and that carbon dioxide is an excretory product.
- Saying the kidney makes urea. The liver makes it.
- Saying urea is made from carbohydrate or fat. It is made from surplus amino acids.
- Confusing the ureter with the urethra.
- Saying the kidney filters out only the waste. It filters out all small molecules and then reabsorbs the useful ones.
- Saying protein is filtered into the urine. Protein molecules are too large to pass through.
- Saying blood leaving the kidney has less glucose. All the glucose is reabsorbed, so it is unchanged.
Revise it first
If any of the above is unfamiliar, work through the notes before practising: Excretion in humans revision notes.