What this practice covers
These questions are drawn from past CIE 9700 Biology papers and filtered to homeostasis. 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 homeostasis, taken from our own topic notes. Read them before you practise and you will recognise the traps in the questions.
- Defining homeostasis as keeping conditions exactly the same, rather than within narrow limits about a set point.
- Describing a positive feedback loop and calling it negative feedback. Ask whether the response opposes or reinforces the change.
- Saying the kidney makes urea. The liver makes it by deamination; the kidney removes it.
- Explaining ultrafiltration without the narrower efferent arteriole, so the source of the high hydrostatic pressure is never given.
- Saying proteins are reabsorbed. They never enter the filtrate in the first place.
- Calling reabsorption in the proximal convoluted tubule simple diffusion, or forgetting that the sodium-potassium pump is what makes the co-transport of glucose possible.
- Saying ADH causes water to be pumped out of the collecting duct. It increases permeability by inserting aquaporins, and the water moves by osmosis.
- Saying ADH is made in the pituitary. It is made in the hypothalamus and released from the posterior pituitary.
Revise it first
If any of the above is unfamiliar, work through the notes before practising: Homeostasis revision notes.