Biology  by Bradford
IB Biology 2025 · Theme D · Continuity and change

D3.3 Homeostasis. Practice questions with markscheme.

45 original IB-style questions on D3.3, written from the 2025 guide: 22 multiple-choice, 16 short-answer, 4 data-based, 1 extended-response part, 1 labelling, 1 drawing. Below is a 20-mark standard-level practice paper built from them, ready to hand out as a class quiz or homework, or to sit yourself and mark against the scheme. Print it, project it, or build a fresh one on the same topic.

What the guide asks for

6 statements at SL and HL, 5 additional higher level.

  1. D3.3.1SL / HL Homeostasis as maintenance of the internal environment of an organism
  2. D3.3.2SL / HL Negative feedback loops in homeostasis
  3. D3.3.3SL / HL Regulation of blood glucose as an example of the role of hormones in homeostasis
  4. D3.3.4SL / HL Physiological changes that form the basis of type 1 and type 2 diabetes
  5. D3.3.5SL / HL Thermoregulation as an example of negative feedback control
  6. D3.3.6SL / HL Thermoregulation mechanisms in humans
  7. D3.3.7HL Role of the kidney in osmoregulation and excretion
  8. D3.3.8HL Role of the glomerulus, Bowman’s capsule and proximal convoluted tubule in excretion
  9. D3.3.9HL Role of the loop of Henle
  10. D3.3.10HL Osmoregulation by water reabsorption in the collecting ducts
  11. D3.3.11HL Changes in blood supply to organs in response to changes in activity

In the bank for D3.3

  • 22 multiple-choice
  • 16 short-answer
  • 4 data-based
  • 1 extended-response part
  • 1 labelling
  • 1 drawing
  • 15 higher level only

Every question is original and tagged to a guide statement. See the whole bank →

Make your own

The practice paper

Take it on screen → Build a fresh paper Paper code BbB-EAAAAAAAEBQAO8xC
Biology · topic quiz
Standard level · topic practice, not an exam format
30 minutes20 marks

Paper code: this paper was generated, so the code is its recipe. Enter it at biologybybradford.com/exam-maker to rebuild this exact paper and its markscheme.

Covers D3.3 Homeostasis
Name:
1.

During a marathon, a runner's blood glucose stays fairly steady despite heavy use by muscles. Which hormones maintain it?

[1]
  1. Melatonin and ADH
  2. Progesterone and oestrogen
  3. Insulin alone, raising glucose
  4. Glucagon and adrenaline
2.

Lizards bask on warm rocks in the morning and retreat to shade at midday. What does this behaviour show?

[1]
  1. Shivering to generate heat
  2. Lizards are true endotherms
  3. Homeostasis is impossible in reptiles
  4. Behavioural thermoregulation
3.

The diagram shows the control of uterine contractions during birth. How does this control differ from the control of blood glucose?

[1]
Baby's head pushesagainst the cervixStretch receptors in cervixsend impulses to the brainPituitary gland releasesmore oxytocin into bloodUterine muscle contractsmore strongly+each turn amplifies the lastBirth: the stimulus is removedand the loop stops
  1. It returns the controlled variable to a set point after each contraction of the uterus ends
  2. Each response increases the stimulus, so the change accelerates until birth removes the stimulus
  3. It uses hormones carried in the blood, whereas blood glucose is controlled only by nerve impulses
  4. It involves stretch receptors, whereas the control of blood glucose does not involve any receptors
4.

What is homeostasis?

[1]
  1. Keeping internal conditions within preset limits despite external change
  2. Growth of the body to a genetically determined set size
  3. Activation of defence responses against internal infection
  4. Keeping every internal variable exactly constant throughout life
5.

The diagram shows how the concentration of glucose in the blood is kept close to a set point.

Blood glucose at set point≈ 5 mmol dm⁻³Blood glucose rises(e.g. after a meal)β cells of pancreassecrete insulinLiver and muscle take upglucose; glycogen madeglucose falls backBlood glucose falls(e.g. during exercise)α cells of pancreassecrete glucagonLiver breaks glycogendown; glucose releasedglucose rises backabovebelow
(a)Outline the response to a rise in blood glucose concentration after a meal.[3]
(b)Explain why homeostasis relies on negative rather than positive feedback.[2]
6.

Newborn babies cannot generate much heat by shivering. Explain how a newborn's body generates heat in cold conditions.

[3]
7.

Six healthy volunteers sat still in a bath of water at 15 °C for 30 minutes. Core (rectal) temperature, skin temperature on the forearm and the rate of oxygen consumption were recorded every 10 minutes. The table shows the mean values.

Time in water / minCore temperature / °CForearm skin temperature / °COxygen consumption / cm³ kg⁻¹ min⁻¹
037.033.53.5
1036.922.46.8
2036.619.89.4
3036.318.910.1
(a)State the fall in core temperature over the 30 minutes.[1]
(b)Calculate the percentage increase in oxygen consumption between 0 and 30 minutes.[2]
(c)Compare the changes in core temperature and skin temperature during the immersion.[2]
(d)Explain the rise in oxygen consumption.[2]
(e)Explain how the large difference between skin and core temperature helps the body to conserve heat.[1]

Original practice questions © Biology by Bradford · CC BY-NC-SA 4.0 · Not affiliated with or endorsed by the International Baccalaureate Organization.
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Show the markscheme

Markscheme BbB-EAAAAAAAEBQAO8xC

One mark per point; / separates alternative wording within a point, OR separates alternative answers, words in brackets are not required, underlined words are essential. OWTTE = or words to that effect.

1. D3.3.3 [1]
  • D: falling glucose triggers glucagon (α-cells) and adrenaline, mobilizing glycogen (and other fuels); insulin release is suppressed;
2. D3.3.5 [1]
  • D: ectotherms regulate temperature largely by behaviour (basking, shade, orientation); endotherms generate heat metabolically;
3. D3.3.2 [1]
  • B: this is positive feedback: the response strengthens the stimulus rather than reversing it, so it is useful only for a process that must run to completion, unlike homeostasis;
4. D3.3.1 [1]
  • A: regulated variables (e.g. blood glucose, core temperature, water balance) oscillate within tolerable ranges around set points, maintained by (negative) feedback;
5. D3.3.2, D3.3.3
  • (a) [3 max]
    • detected by β cells of the pancreas (islets), which secrete insulin;
    • insulin is transported in the blood to target cells (liver and muscle);
    • target cells take up more glucose / liver and muscle convert glucose to glycogen;
    • blood glucose falls back towards the set point;
  • (b) [2]
    • negative feedback reverses a change, returning the variable to the set point from above or below;
    • positive feedback would amplify the change, driving the variable further from the set point, OWTTE;
6. D3.3.6 [3 max]
  • newborns have (abundant) brown adipose tissue (around the neck/shoulders/kidneys);
  • in its (numerous) mitochondria, fat/fatty acids are oxidized with respiration uncoupled from ATP synthesis;
  • (so) the energy released is dissipated directly as heat instead of being captured in ATP (heat production without muscle contraction);
  • (the response is switched on by the nervous system in response to cold, compensating for the newborn's inability to shiver effectively), OWTTE;
7. D3.3.5, D3.3.6
  • (a) [1]
    • 0.7 °C;
  • (b) [2]
    • (10.1 − 3.5) / 3.5 × 100;
    • 189 % (accept 188–189 %);
  • (c) [2]
    • both fall, but skin temperature falls far more (14.6 °C) than core temperature (0.7 °C);
    • skin temperature falls rapidly in the first 10 minutes and then levels off, whereas core temperature falls slowly and steadily throughout, OWTTE;
  • (d) [2 max]
    • thermoreceptors / hypothalamus detect the fall in (core) temperature and trigger shivering;
    • shivering is (rapid, involuntary) contraction of skeletal muscle, which requires ATP from (aerobic) cell respiration, so oxygen consumption rises;
    • respiration releases heat (as a by-product), which helps to maintain core temperature, OWTTE;
  • (e) [1 max]
    • vasoconstriction of arterioles supplying the skin reduces blood flow to the skin, so less heat is carried from the core to the surface and lost to the water;
    • cooler skin means a smaller temperature difference with the water, so heat is lost more slowly, OWTTE;

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