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CAIE A Level Biology 9700

Homeostasis questions

Exam-style questions on Homeostasis, ordered from foundation to challenge. Pick one, write your answer the way you would in the exam, and it comes back marked against the mark scheme, point by point.

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Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.

  1. Describe5 marksStandardA gardener notices that during a prolonged dry spell, the leaves of a tomato plant wilt and the stomata are observed to be closed, even during daylight hours. Using your knowledge of homeostasis in plants, describe the…
  2. Outline5 marksStandardA gardener notices that during a period of drought, the leaves of a tomato plant wilt and the stomata close. Outline the mechanism by which guard cells control stomatal aperture, including the role of abscisic acid…
  3. Describe5 marksStandardWhen a plant is short of water, abscisic acid (ABA) is produced and triggers a signalling pathway that results in stomatal closure. Describe the role of ABA and calcium ions in this process.
  4. Explain4 marksStandardA tomato plant is subjected to drought stress for several days. In these dry conditions, the plant synthesises abscisic acid (ABA). Explain how ABA brings about the closure of stomata, and why this closure is…
  5. Outline4 marksStandardA longitudinal section of a human kidney reveals several distinct structural regions. Outline the main structural regions visible in such a section and state a function of each region.
  6. Describe5 marksStandardDescribe the sequence of events that leads to the closure of stomata in a plant experiencing water stress. In your answer, include the roles of abscisic acid (ABA) and calcium ions.
  7. Outline4 marksStandardScientists investigated stomatal aperture in two plant species, X and Y, under well-watered and water-stressed conditions. Stomatal aperture (width in μm) was measured at three times of day. The results are shown in…
  8. Outline4 marksStandardThe table shows the mean stomatal aperture of leaves from well-watered and water-stressed plants of a shrub species, measured at midday. Condition Mean stomatal aperture / µm Well-watered 8.2 Water-stressed (soil water…
  9. Describe5 marksStandardA student examines a stained longitudinal section of a mammalian kidney under a light microscope. The outer region (cortex) appears darker due to many glomeruli, the inner region (medulla) contains loops of Henle and…
  10. Explain4 marksStandardAfter consuming a meal rich in protein, the body absorbs amino acids. Any excess amino acids cannot be stored. Explain why the liver converts the amino groups from these excess amino acids into urea and how this…
  11. Explain5 marksStandardA plant leaf is exposed to light. The guard cells surrounding a stoma actively take up potassium ions. Explain how this uptake of potassium ions leads to the opening of the stoma.
  12. Outline5 marksStandardThe diagram shows a nephron with structures labelled A–E. A is the glomerulus B is the Bowman's capsule C is the proximal convoluted tubule D is the loop of Henle E is the collecting duct Using your knowledge of kidney…
  13. Describe4 marksStandardA student measured her blood glucose concentration at intervals after eating a carbohydrate-rich meal. The results are shown in the table below. Time after meal (minutes) Blood glucose concentration (mmol dm^-3) 0 4.5…
  14. Describe4 marksStandardA person becomes dehydrated after prolonged exercise without drinking water. Describe the sequence of events that occur in the body in response to a decrease in blood water potential, including the roles of the…
  15. Explain5 marksStandardExplain how the movement of potassium ions into and out of guard cells controls the opening and closing of stomata. In your answer, refer to the role of abscisic acid (ABA) and calcium ions during water stress.
  16. Outline5 marksStandardThe table below shows the blood glucose concentration of a healthy human after eating a meal containing carbohydrate. Time after meal (min) Blood glucose concentration (mg/100ml) 0 90 30 145 60 120 90 100 120 90 Using…
  17. Describe5 marksStandardDescribe the sequence of events that occurs when the water potential of the blood falls below normal, including the role of ADH and its effect on the kidney.
  18. Outline4 marksStandardA study investigated stomatal aperture in leaves of a drought-sensitive plant species. The table shows the mean stomatal aperture (µm) at different times of day for plants grown under well-watered conditions and plants…
  19. Describe4 marksStandardThe table below shows the mean stomatal aperture (width of the stomatal pore in micrometres) measured in leaves of a plant species over a 24-hour period under natural conditions. Time (hours) Stomatal aperture (μm) 0…
  20. Explain5 marksStandardIn a laboratory experiment, hepatocytes (liver cells) were exposed to a very low concentration of glucagon, resulting in only a small number of glucagon molecules binding to their receptors. Despite this, a large…
  21. Explain4 marksStandardExplain how the uptake of potassium ions into guard cells leads to the opening of a stoma.
  22. Explain4 marksStandardA small number of glucagon molecules can cause the rapid breakdown of a large amount of glycogen in liver cells. Explain how this amplification is achieved in the glucagon signalling cascade.
  23. Outline4 marksStandardThe table below shows the blood glucose concentration of a healthy mammal at intervals after a meal. Time after meal (min) Blood glucose concentration (mmol dm^-3) 0 4.5 30 6.2 60 5.8 90 5.0 120 4.5 Outline the…
  24. Outline5 marksStandardA tomato plant in a garden is observed on a hot, dry afternoon. The leaves appear wilted, but by the evening they have fully recovered. A biologist explains that the stomata closed during the day to reduce water loss…
  25. Outline4 marksStandardIn response to low blood glucose, the pancreas releases a small amount of glucagon into the blood. Outline how this small signal is amplified inside a liver cell to bring about a rapid breakdown of glycogen.
  26. Describe4 marksStandardThe table below shows the mean stomatal aperture (width in micrometres) measured every 2 hours over a 24-hour period in leaves of a soybean plant (Glycine max) under normal conditions (light from 06:00 to 18:00, dark…
  27. Explain5 marksStandardExplain the sequence of events that occur in the body when the water potential of the blood decreases, leading to increased water reabsorption in the kidney.
  28. Outline5 marksStandardBroad bean (Vicia faba) plants typically have stomata that open during the day and close at night. When the soil becomes dry, the roots produce abscisic acid (ABA), which is transported to the leaves and causes…
  29. Describe5 marksStandardA patient consumes a diet very high in protein, resulting in an excess of amino acids that cannot be stored. Describe the process by which the liver handles these excess amino acids and forms urea, and include why this…
  30. Explain4 marksStandardA student uses glucose test strips to estimate the concentration of glucose in urine samples. The strips contain glucose oxidase, peroxidase, and a chromogen. After adding the urine, the strip is left for 30 seconds…
  31. Outline5 marksStandardThe table below shows the colour results obtained when a glucose test strip is dipped into solutions containing different concentrations of glucose. The strip contains glucose oxidase, peroxidase, and a colourless…
  32. Explain5 marksStandardIn an experiment, leaf epidermal peels from a species of tomato were placed in a solution containing 100 mmol dm⁻³ KCl and exposed to blue light. Within 10 minutes, stomatal apertures increased significantly. Explain…
  33. Describe5 marksChallengeWhen blood glucose concentration falls, the pancreas secretes glucagon. Glucagon binds to receptors on liver cells, initiating a signalling cascade that rapidly releases glucose from glycogen stores. Describe how this…
  34. Outline7 marksChallengeA researcher investigated the effect of water stress on stomatal aperture in leaves of a shrub species. Plants were either kept well-watered or subjected to water stress by withholding water. The table shows mean…
  35. Explain6 marksChallengeThe nephron is the functional unit of the kidney. The proximal convoluted tubule (PCT), loop of Henle, and the action of antidiuretic hormone (ADH) on the collecting duct are all essential for the production of…
  36. Explain6 marksChallengeResearchers studying the stomatal behaviour of a drought-tolerant shrub observe that during the early morning, guard cells accumulate potassium ions and the stomata open. By midday, if the soil is dry, abscisic acid…
  37. Describe5 marksChallengeTable 1 shows the mean stomatal aperture (width of the pore) in leaves of a plant species over a 24-hour period under normal conditions (adequate water, alternating light/dark cycle, with light from 06:00 to 18:00)…
  38. Describe5 marksChallengeA patient with diabetes mellitus uses a blood glucose meter that employs test strips based on the enzyme glucose oxidase. The table below shows the colour change observed on the test strip for different glucose…
  39. Outline7 marksChallengeExcess amino acids are deaminated in the liver, producing ammonia which is converted to urea. Outline how the body removes this nitrogenous waste, including: the formation of urea the roles of the kidney nephron…
  40. Describe5 marksChallengeA person consumes a high-protein meal. Describe the process by which the body removes excess amino acids from the blood, including the roles of the liver and kidneys, and explain why this process is important for…
  41. Outline7 marksChallengeA student measured her blood glucose concentration at intervals after eating a carbohydrate-rich meal. The results are shown in the table. Time after meal (minutes) Blood glucose concentration / mmol l^-1 0 5.0 30 7.8…
  42. Explain6 marksChallengeThe table below shows the blood glucose concentration of a healthy individual after eating a meal at time 0. Time (minutes) Blood glucose concentration (mmol dm⁻³) 0 5.0 30 7.5 60 6.5 90 5.5 120 5.0 Explain how…
  43. Describe5 marksChallengeAfter prolonged exercise, a person becomes dehydrated, causing a decrease in blood water potential. Describe the sequence of events that leads to an increase in water reabsorption in the kidneys, including the roles of…
  44. Explain6 marksChallengeA researcher investigates glucagon signalling in hepatocytes. She adds a very low concentration of glucagon (10⁻¹¹ mol dm⁻³) to a culture of normal hepatocytes and measures the glucose released into the medium. Despite…
  45. Outline7 marksChallengeOutline the role of the kidney in osmoregulation in mammals. In your answer, refer to the structure of the nephron and the action of antidiuretic hormone (ADH).
  46. Describe5 marksChallengePlants experiencing water shortage close their stomata to reduce water loss. This closure is regulated by the hormone abscisic acid (ABA) and involves calcium ions (Ca²⁺) as a second messenger. Describe the sequence of…
  47. Explain6 marksChallengeIn an experiment, plants of a drought-tolerant species were subjected to soil drying. Within 30 minutes, the concentration of abscisic acid (ABA) in the leaves increased significantly. Soon after, the stomata closed…
  48. Explain6 marksChallengeA diabetic patient uses a glucose test strip that contains the enzyme glucose oxidase, a peroxidase enzyme, and a colourless chromogen. A droplet of blood is placed on the test strip. After 30 seconds, the strip is…
  49. Outline7 marksChallengeIn an experiment, leaves of the plant Commelina communis were treated with a solution containing abscisic acid (ABA). Within minutes, the stomatal apertures decreased significantly. Outline the mechanism by which ABA…
  50. Outline7 marksChallengeTable 1 shows the mean stomatal aperture of a plant species measured at different times of day under well-watered and water-stressed conditions. Time of day Well-watered Water-stressed 06:00 2.1 1.2 12:00 8.7 2.8 18:00…
  51. Outline7 marksChallengeGuard cells are specialised cells that surround stomata. Their cell walls are thicker on the inner side (adjacent to the stoma) and thinner on the outer side. They also contain chloroplasts. Outline how guard cells…
  52. Describe5 marksChallengeThe table below shows the mean stomatal aperture (width of the stomatal pore, in arbitrary units) measured on the lower surface of leaves of a tomato plant over a 24-hour period under constant temperature and adequate…
  53. Explain6 marksChallengeThe diagram shows a longitudinal section of a mammalian kidney. The outer region (cortex) contains the glomeruli and Bowman's capsules; the inner region (medulla) contains loops of Henle and collecting ducts; the renal…
  54. Describe5 marksChallengeAn experiment is conducted using leaves from a well-watered plant and a plant that has been deprived of water for 48 hours. Microscopic examination of the lower epidermis reveals that the stomata of the water-deprived…
  55. Explain6 marksChallengeA botanist observes that a plant growing in a drying soil closes its stomata during the day, even though sunlight is available for photosynthesis. Explain how the plant's response to water stress reduces water loss but…
  56. Describe5 marksChallengeThe table below shows the mean stomatal aperture (width in µm) of leaves of a plant species measured every two hours over a 24-hour period. The plant was kept under a natural light-dark cycle (light from 06:00 to…
  57. Outline7 marksChallengeDuring a hot day, a mammal loses water through sweating and panting, leading to a decrease in blood water potential. Outline the sequence of events that occur to restore blood water potential to normal, starting with…
  58. Describe5 marksChallengeThe Bowman's capsule and the proximal convoluted tubule (PCT) are two important parts of a nephron. Describe how the structure of the Bowman's capsule is adapted for ultrafiltration and how the structure of the…
  59. Explain6 marksChallengeA student investigates the response of stomata in leaves of a tomato plant. Under normal daylight conditions, the stomata are open. When the plant is subjected to drought stress, the stomata close. Explain the cellular…