This free quiz has 21 multiple choice questions on homeostasis and excretion, all taken from OCR A Level Biology A exam papers. It marks itself, so you get your score as soon as you finish.
What the quiz covers (OCR A spec 5.1.1 and 5.1.2)
Communication systems and why multicellular organisms need them
Cell signalling in animals and plants
Homeostasis and negative feedback
Thermoregulation in endotherms and ectotherms
Structure and functions of the liver, including urea production
Water balance, ADH and the hypothalamus
Kidney failure and its treatments
Urine analysis, including pregnancy tests
How to use it
Before you start, draw a quick nephron and liver lobule and label the main regions, and sketch a negative feedback loop (stimulus, receptor, coordinator, effector, response). Use these to check each option rather than relying on memory alone.
Where students lose marks (from OCR examiners' reports and mark schemes)
Each point below is followed by wording that gained marks.
Cold slows enzymes, not denatures: Many students explained positive feedback in hypothermia correctly in principle but suggested responses such as sweating, or claimed that falling temperature denatures enzymes.
✔ Gains credit: A lower temperature reduces kinetic energy, so enzyme activity and metabolic rate fall, less heat is released by metabolism and body temperature falls further.
Define an endotherm using heat: Most answers gave only part of the definition, with few mentioning heat, and some students confused endotherms with ectotherms or used these terms inappropriately when comparing mammals.
✔ Gains credit: An endotherm uses heat produced internally by metabolism to maintain its body temperature, while ectotherms rely mainly on heat from the environment and behavioural responses.
Make thermoregulation comparisons explicit: When comparing animals, students often described only one, did not use comparative words such as 'more' or 'less', or mentioned a lack of fur without linking it to insulation. Disadvantages of being an ectotherm were not always linked to their consequence.
✔ Gains credit: Clearly comparative statements about body temperature, how narrowly it is kept and the use of behavioural versus physiological responses, and for ectotherms, slower metabolism and lower activity at low temperatures.
Why protein in urine means damage: Many students thought protein in urine was a reabsorption problem, used unclear phrases such as 'filtered out', or linked high protein to kidney failure without giving the cause.
✔ Gains credit: Large proteins such as albumin should stay in the blood because they are too large to pass through the basement membrane into the Bowman's capsule, so protein in urine suggests damage to the glomerulus, Bowman's capsule or basement membrane.
Renal, not adrenal, cortex and medulla: Some students labelled kidney regions as the adrenal cortex or adrenal medulla, swapped cortex and medulla, or named the pelvis as the ureter or renal artery. Drawings often had sketchy lines and showed structures that were not visible.
✔ Gains credit: Renal cortex on the outside, renal medulla (pyramids) inside and the pelvis where urine collects, drawn with clear continuous lines and only the visible structures.
Proximal versus distal tubule roles: A common error was confusing the roles of the proximal and distal convoluted tubules, and many students could not explain what the microvilli lining the tubule are for.
✔ Gains credit: The proximal convoluted tubule reabsorbs glucose, amino acids and ions, with microvilli and co-transporter proteins increasing surface area for reabsorption, while the distal convoluted tubule regulates named ions and water.
Explaining excretion properly: Many students understood excretion in general but struggled to explain it for a specific substance, and answers on losing body mass referred to breaking down fat from the diet rather than stored body fat.
✔ Gains credit: Identifying the substance as a metabolic waste product made in the body (for example bilirubin from haem, or carbon dioxide and water from respiring stored fat) that is then removed from the body.
Keep practising
Go on to the Neuronal and Hormonal Communication quiz, the Transport in Animals quiz or the Plant and Animal Responses quiz, or browse all our OCR A Level Biology quizzes. Our OCR A masterclasses (Year 12 on Wednesdays at 5.15pm, Year 13 on Tuesdays at 6.30pm) work through real exam questions on one topic each week.