2022 May/June · Paper 22 · Q1 (a, b(i), b(ii))8 marksHomeostasis: temperature & skin · Nervous system & reflex arc
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Practice questions
Original questions written by HomiLabs in the style of the exam, with answers and mark schemes. They are not
Cambridge past paper questions and have not been reviewed by Cambridge. Try each one before opening the answer.
Q1Eye & sense organs · Core · Paper 2 style · 4 marks
(a)State the function of each part: (i) cornea (ii) retina (iii) optic nerve.[3]
(b)Explain why no image is seen if light falls on the blind spot.[1]
Show answer
(a) (i) refracts / bends light (ii) contains light receptors that change light into impulses (iii) carries impulses to the brain
1 mark each
(b) There are no light receptors there (it is where the optic nerve leaves the eye).
B1
Q2Eye & sense organs · Standard · Paper 1 style · 1 mark
(a)[1]
Show answer
(a) B ciliary muscles relax, suspensory ligaments become tight, lens becomes thinner
For a distant object the ciliary muscles relax, the suspensory ligaments are pulled tight and the lens is pulled thinner, so light is refracted less. A is the change for a near object.
Q3Eye & sense organs · Standard · Paper 2 style · 5 marks
Ali walks out of a dark cinema into bright midday sunshine in Islamabad. His pupils quickly become smaller.
(a)Describe the changes in the iris that make the pupil smaller.[2]
(b)Explain why this response is useful.[1]
(c)State the type of response this is and give one feature of it.[2]
Show answer
(a) The circular muscles contract; the radial muscles relax.
B1 circular contract; B1 radial relax
(b) Less light enters, protecting the retina from damage.
B1
(c) A reflex action; it is automatic / involuntary / rapid / does not need conscious thought.
B1 reflex; B1 one feature
Q4Eye & sense organs · Standard · Paper 2 style · 5 marks
(a)Define the term sense organ.[1]
(b)Copy and complete: Stimulus | sense organlight | ?sound | ?chemicals in food | ?temperature change | ?[2]
(c)Explain how the eye sends information to the brain.[2]
Show answer
(a) A group of receptor cells that respond to a specific stimulus (e.g. light, sound, touch, temperature, chemicals).
B1
(b) eye; ear; tongue (and nose); skin
B2 all four; B1 two or three
(c) Light receptors in the retina are stimulated and produce electrical impulses; impulses travel along the optic nerve (sensory neurones) to the brain.
B1 receptors in retina stimulated / impulses; B1 along optic nerve
Q5Eye & sense organs · Challenge · Paper 2 style · 5 marks
A pharmacist looks at a distant shelf and then reads the small print on a medicine label held 25 cm from her eyes.
(a)Describe the changes in the eye that allow the label to be seen clearly.[3]
(b)As people age, the lens becomes less elastic. Suggest why older people often find it difficult to read small print but can still see distant objects clearly.[2]
Show answer
(a) Ciliary muscles contract; suspensory ligaments slacken / become loose; lens becomes thicker / more convex (and refracts light more).
1 mark each
(b) The lens cannot become fat / round enough on its own when the ligaments slacken; so light from near objects is not focused on the retina, whereas the thin lens shape for distant vision is still achieved.
B1 lens cannot become thicker / more convex; B1 near image not focused on retina
Q6Homeostasis: temperature & skin · Core · Paper 1 style · 1 mark
(a)What happens in the skin of a person who is too hot?[1]
Show answer
(a) C arterioles near the skin surface dilate
Vasodilation of arterioles supplying skin capillaries sends more blood near the surface, so more heat is lost by radiation. A (vasoconstriction) happens when the body is too cold.
Q7Homeostasis: temperature & skin · Core · Paper 2 style · 4 marks
(a)State the normal core body temperature of a human (the set point).[1]
(b)Define the term homeostasis.[2]
(c)Name the part of the body that monitors blood temperature.[1]
Show answer
(a) About 37 °C
B1
(b) Maintaining a constant internal environment; within set limits.
B1 constant internal environment / conditions; B1 within narrow limits / around a set point
(c) The brain (hypothalamus).
B1
Q8Homeostasis: temperature & skin · Standard · Paper 2 style · 5 marks
(a)Explain how sweating helps to cool the body.[2]
(b)Explain why sweating cools the body less effectively on a hot, humid day in Lahore during the monsoon.[2]
(c)Suggest why a person sweating heavily for a long time should drink water with a little salt.[1]
Show answer
(a) Water in sweat evaporates from the skin surface; evaporation uses heat energy from the skin, cooling it.
B1 evaporation of sweat; B1 takes heat (energy) from the body / skin
(b) Air already has a high water vapour content, so sweat evaporates more slowly; less heat is removed.
B1 less evaporation; B1 less heat lost
(c) Sweat contains water and salts, which must be replaced.
B1
Q9Homeostasis: temperature & skin · Standard · Paper 2 style · 5 marks
A cricketer's core temperature was measured every 10 minutes during a 30-minute run and the rest afterwards.time / min | 0 | 10 | 20 | 30 | 40 | 50 | 60temperature / °C | 37.0 | 37.2 | 37.6 | 38.1 | 37.9 | 37.4 | 37.1
(a)State the maximum rise in core temperature above the starting value.[1]
(b)Describe two changes in the skin that would have brought the temperature back down after 30 minutes.[2]
(c)Explain why the temperature rose during running.[2]
Show answer
(a) 1.1 °C
B1 38.1 − 37.0
(b) Vasodilation of arterioles near skin surface (skin looks flushed); increased sweating.
1 mark each
(c) Muscles respired more to release energy for contraction; respiration releases heat (as a by-product).
B1 more respiration in muscles; B1 releases heat
Q10Homeostasis: temperature & skin · Challenge · Paper 2 style · 6 marks
A mountaineer on K2 is exposed to very cold wind and her core temperature begins to fall below the set point.
(a)Describe and explain two ways in which the climber's body responds to reduce heat loss and increase heat production.[4]
(b)Explain how these responses are an example of negative feedback.[2]
Show answer
(a) Vasoconstriction: arterioles to skin capillaries narrow, so less blood flows near the surface and less heat is lost by radiation. Shivering: rapid muscle contractions increase respiration, releasing heat. (Also: less sweating; hairs raised trap insulating air.)
For each of two responses: B1 response, B1 explanation
(b) A fall in temperature below the set point is detected; responses act to bring the temperature back up towards the set point (reverse the change).
B1 change from set point detected; B1 response reverses the change / returns to set point
Q11Nervous system & reflex arc · Core · Paper 1 style · 1 mark
(a)Which neurone carries impulses from the central nervous system to an effector?[1]
Show answer
(a) C motor neurone
Motor neurones carry impulses from the CNS to effectors (muscles or glands). Sensory neurones carry impulses from receptors to the CNS.
Q12Nervous system & reflex arc · Core · Paper 2 style · 5 marks
(a)Put the parts of the reflex arc in the correct order: motor neurone, receptor, effector, relay neurone, sensory neurone.[2]
(b)Name the receptor and the effector when a hand is pulled away from a hot pan.[2]
(b) Receptor: (heat / pain) receptors in the skin. Effector: muscle in the arm (biceps).
B1 each
(c) In the central nervous system / spinal cord.
B1
Q13Nervous system & reflex arc · Standard · Paper 2 style · 5 marks
(a)Name the two parts of the central nervous system.[1]
(b)State two differences between a voluntary action and a reflex action.[2]
(c)Give one example of a reflex action and explain how it helps to protect the body.[2]
Show answer
(a) Brain and spinal cord
B1
(b) Voluntary: needs conscious thought / slower / involves the brain making a decision / can be learned. Reflex: automatic, fast, does not need conscious thought, same response every time.
1 mark each for any two differences
(c) Blinking when something approaches the eye — prevents damage to the eye (or withdrawing hand from a sharp pin — prevents injury).
B1 example; B1 protection explanation
Q14Nervous system & reflex arc · Challenge · Paper 4 style · 6 marks
Student A holds a 30 cm ruler at its top end. Student B places finger and thumb level with the 0 cm mark without touching it. A drops the ruler without warning and B catches it. The distance fallen is read where B catches it. Five trials gave: 16 cm, 14 cm, 13 cm, 11 cm, 10 cm.
(a)Calculate the mean distance the ruler fell.[1]
(b)Describe the trend in the results and suggest a reason for it.[2]
(c)Explain why catching the ruler is not a reflex action.[2]
(d)Suggest one way to improve this investigation.[1]
Show answer
(a) 12.8 cm
B1 (16+14+13+11+10) ÷ 5 = 12.8 cm
(b) The distance (reaction time) decreased with each trial; the student learned / anticipated the drop (practice effect).
B1 decreasing trend; B1 learning / practice / anticipation
(c) It involves a decision by the brain / conscious thought; the response can be changed or improved by learning.
B1 brain / conscious decision; B1 learned / not automatic
(d) Have practice trials first / use the same hand and starting position / do more repeats and find a mean / use different students.
B1
Q15Nervous system & reflex arc · Challenge · Paper 2 style · 6 marks
A boy walking barefoot in a field steps on a sharp acacia thorn and quickly lifts his foot.
(a)Describe the pathway of the nerve impulse from the moment the foot touches the thorn to the leg moving.[4]
(b)The boy feels the pain slightly after his foot moves. Suggest why.[2]
Show answer
(a) Pain receptor in the skin of the foot stimulated; impulse along sensory neurone to spinal cord; passes across synapse to relay neurone in spinal cord; then to motor neurone; to leg muscles (effector), which contract and lift the foot.
1 mark each for four of: receptor in skin; sensory neurone; spinal cord / relay neurone; synapse(s); motor neurone; muscle contracts
(b) The reflex arc passes through the spinal cord and does not need the brain; impulses to the brain travel further / through more synapses, so awareness comes later.
B1 reflex via spinal cord, not brain; B1 impulse to brain takes longer
Q16Tropisms & plant hormones · Core · Paper 2 style · 5 marks
(a)Define the terms (i) phototropism (ii) gravitropism.[2]
(b)State whether each response is positive or negative: (i) a shoot growing towards light (ii) a root growing downwards (iii) a shoot growing upwards in the dark.[3]
Show answer
(a) (i) a response in which part of a plant grows towards or away from the direction of light (ii) a response in which part of a plant grows towards or away from gravity
B1 each
(b) (i) positive phototropism (ii) positive gravitropism (iii) negative gravitropism
1 mark each
Q17Tropisms & plant hormones · Standard · Paper 1 style · 1 mark
(a)[1]
Show answer
(a) B auxin collects on the shaded side and stimulates cell elongation there
Auxin made in the shoot tip moves to the shaded side, where it causes cells to elongate more, so the shoot bends towards the light. A is a common misconception: light does not destroy auxin.
Q18Tropisms & plant hormones · Standard · Paper 2 style · 5 marks
(a)Explain the advantage to a seedling of its shoot growing upwards and its root growing downwards.[2]
(b)A bean seedling is laid on its side in the dark. Describe and explain how the shoot responds, in terms of auxin.[3]
Show answer
(a) Shoot grows up towards light for photosynthesis; root grows down into soil for water / mineral ions and anchorage.
(b) Auxin collects on the lower side of the shoot; stimulates cell elongation on the lower side; so the shoot curves upwards (negative gravitropism).
B1 auxin to lower side; B1 more elongation on lower side; B1 shoot bends upwards
Q19Tropisms & plant hormones · Challenge · Paper 4 style · 6 marks
Three maize seedlings were placed in a box with light coming from one side only.Seedling X: untreated — after 2 days it had bent towards the light.Seedling Y: tip cut off — no bending and very little growth.Seedling Z: tip covered with an aluminium foil cap — grew straight up.
(a)Explain the result for seedling X.[3]
(b)Explain the result for seedling Y.[1]
(c)Explain the result for seedling Z.[2]
Show answer
(a) Auxin is made in the tip; it moved to the shaded side; caused greater cell elongation on the shaded side, so the shoot bent towards the light.
B1 auxin from tip; B1 moves to shaded side; B1 cells on shaded side elongate more
(b) The tip, which makes auxin (and detects light), was removed, so no auxin and no bending / growth.
B1
(c) The foil cap stopped light reaching the tip; so auxin was not redistributed and the shoot grew straight up (evenly).
B1 tip cannot detect light; B1 auxin evenly distributed
Q20Tropisms & plant hormones · Challenge · Paper 2 style · 4 marks
(a)Suggest how a synthetic auxin weedkiller kills broad-leaved weeds such as thistles in a wheat field.[2]
(b)Suggest why the weedkiller does not kill the wheat.[1]
(c)Give one advantage of using a selective weedkiller rather than pulling out weeds by hand.[1]
Show answer
(a) It causes rapid, uncontrolled growth / elongation of the weeds; they cannot sustain this (use up food reserves), so they die.
(b) Wheat (narrow-leaved) absorbs less / is less sensitive to the weedkiller.
B1
(c) Quicker / cheaper for large areas / less labour.
B1
Q21Homeostasis: blood glucose · Standard · Paper 1 style · 1 mark
(a)Blood glucose concentration rises after a meal. Which response occurs?[1]
Show answer
(a) B the pancreas releases insulin and the liver converts glucose to glycogen
Insulin from the pancreas makes liver and muscle cells take up glucose and convert it to glycogen. A is the response to low blood glucose.
Q22Homeostasis: blood glucose · Standard · Paper 2 style · 5 marks
(a)Name the hormone that is released when blood glucose falls too low, and the organ that secretes it.[2]
(b)State how this hormone raises blood glucose.[1]
(c)Describe how type 1 diabetes is treated, and state one sign of the condition.[2]
Show answer
(a) Glucagon; pancreas.
B1 each
(b) It causes the liver to break down glycogen to glucose, which is released into the blood.
B1
(c) Treated by insulin injections (plus controlled diet / exercise and monitoring blood glucose). Sign: high blood glucose / glucose in urine / thirst / tiredness / weight loss.
B1 treatment; B1 sign
Q23Homeostasis: blood glucose · Challenge · Paper 2 style · 7 marks
A healthy student drank a glucose solution after fasting. Her blood glucose concentration was measured.time / min | 0 | 30 | 60 | 90 | 120blood glucose / mg per 100 cm³ | 90 | 150 | 135 | 105 | 92
(a)Calculate the percentage increase in blood glucose from 0 to 30 minutes.[2]
(b)Explain how the concentration returned to normal by 120 minutes.[3]
(c)Describe how the results would differ for a person with type 1 diabetes, and explain why.[2]
Show answer
(a) 66.7 %
M1 (150 − 90) ÷ 90 × 100; A1 66.7 %
(b) The rise was detected by the pancreas; it secreted insulin into the blood; insulin caused the liver / muscles to take up glucose and convert it to glycogen (and cells to respire more glucose).
B1 pancreas detects / secretes insulin; B1 insulin travels in blood to liver; B1 glucose → glycogen
(c) Glucose would rise higher and stay high for longer; because the pancreas does not produce (enough) insulin.
B1 higher / does not return to normal; B1 no / little insulin
Q24Synapses · Standard · Paper 2 style · 5 marks
(a)Describe how an impulse passes across a synapse.[4]
(b)Name the process by which the neurotransmitter crosses the gap.[1]
Show answer
(a) Impulse arrives at the end of the first neurone; vesicles release neurotransmitter into the gap; neurotransmitter diffuses across the gap; binds to receptor proteins on the next neurone; which starts an impulse in it.
1 mark each for any four of the five points
(b) Diffusion
B1
Q25Synapses · Challenge · Paper 1 style · 1 mark
(a)Why can nerve impulses cross a synapse in one direction only?[1]
Show answer
(a) B neurotransmitter is released only from the first neurone and receptors are only on the second neurone
Vesicles of neurotransmitter are only in the neurone before the gap, and receptor proteins are only on the neurone after it. D is wrong: the signal crosses the gap as a chemical, not electrically.
Q26Synapses · Challenge · Paper 2 style · 5 marks
A medicine, drug D, has a molecular shape very similar to a neurotransmitter but does not start impulses.
(a)Suggest how drug D affects transmission across a synapse.[2]
(b)Suggest why a drug that blocks the receptors at synapses between motor neurones and muscles could cause paralysis.[2]
(c)State one role of synapses in the nervous system.[1]
Show answer
(a) It has a similar shape to the neurotransmitter, so it binds to the receptors; this blocks the neurotransmitter, so fewer impulses are started in the next neurone.
B1 binds to / blocks receptors; B1 fewer / no impulses in next neurone
(b) Impulses cannot pass from motor neurones to muscles; so muscles do not contract.
B1 no impulse transmitted to muscle; B1 muscles do not contract
(c) Ensure impulses travel in one direction / allow impulses to be passed between neurones / allow connections with many neurones.
B1
Q27Hormones · Core · Paper 1 style · 1 mark
(a)Which gland secretes adrenaline?[1]
Show answer
(a) B adrenal gland
Adrenaline is secreted by the adrenal glands (above the kidneys). The pancreas secretes insulin and glucagon.
Q28Hormones · Standard · Paper 2 style · 7 marks
(a)State the meaning of the term hormone.[2]
(b)Copy and complete the table.hormone | glandinsulin | ?testosterone | ?oestrogen | ?[3]
(c)State two differences between nervous control and hormonal control.[2]
Show answer
(a) A chemical substance produced by a gland; carried by the blood; which alters the activity of one or more specific target organs.
B1 chemical made by gland; B1 transported in blood (to target organs)
(b) pancreas; testes; ovaries
1 mark each
(c) Nervous: electrical impulses, along neurones, very fast, short-lasting. Hormonal: chemical, in blood, slower, longer-lasting.
1 mark each for two valid differences
Q29Hormones · Challenge · Paper 2 style · 6 marks
A goalkeeper in a hockey match in Karachi feels nervous as a penalty shoot-out begins, and his adrenal glands secrete adrenaline.
(a)Describe three effects of adrenaline on the body.[3]
(b)Explain how two of these effects help the goalkeeper's muscles during the shoot-out.[3]
(b) Faster heart rate delivers more oxygen and glucose to muscles; more glucose in blood is available; so more aerobic respiration releases more energy for muscle contraction.
B1 more oxygen / glucose delivered; B1 more respiration; B1 more energy for contraction
Q30Hormones (option) · Challenge · Paper 2 style · 8 marks
(a)Compare the way in which the body responds to (i) touching a hot iron and (ii) a rise in blood glucose after a meal. Refer to the type of signal, how it travels, speed and duration.[6]
(b)Explain why the control of blood glucose is an example of homeostasis.[2]
Show answer
(a) (i) Nervous: electrical impulses; along neurones; very fast; short-lived response (muscle contracts). (ii) Hormonal: chemical (insulin); carried in the blood plasma; slower; longer-lasting; can affect several target organs (liver, muscles).
1 mark each for any six comparison points, at least one from each response: electrical vs chemical; neurones vs blood; fast vs slow; short vs long-lasting; specific effector vs target organs; reflex via spinal cord vs pancreas detects change
(b) It keeps the internal environment (blood glucose) constant within narrow limits; by negative feedback that reverses changes from the set point.
B1 constant internal conditions; B1 negative feedback / returns to normal
Similar questions
Questions that test the same subtopic in different years, grouped so you can work on one skill at a time.
References only: find each question in its paper (official link where available, otherwise through your school).
Eye & sense organsBanker24 questions · 9/9 sessions
