Question 1 · MCQ · Analyse · 1 mark
Withdrawing a hand
Nervous system
A person pulls a hand away from a hot object before consciously describing the pain. Which explanation is most appropriate?
(A) The hand has no sensory receptors.
(B) A spinal reflex circuit can coordinate withdrawal before conscious interpretation.
(C) The muscles decide independently without nerves.
(D) Only hormones coordinate the immediate withdrawal.
Show answer and solution
Answer: (B) A spinal reflex circuit can coordinate withdrawal before conscious interpretation.
Worked solution: A reflex arc can route the sensory signal through the spinal cord to a motor neuron quickly. Signals also reach the brain for awareness.
Question 2 · MCQ · Analyse · 1 mark
A shoot bends towards a window
Tropic movements
A young shoot receives light from one side. Which distribution best explains bending towards the light?
(A) More auxin on the shaded side causes greater elongation there.
(B) More auxin on the lit side kills that side.
(C) Equal growth on both sides bends the shoot.
(D) Gravity stops all growth on the shaded side.
Show answer and solution
Answer: (A) More auxin on the shaded side causes greater elongation there.
Worked solution: In the standard shoot phototropism model, auxin accumulates on the shaded side and promotes greater cell elongation, bending the shoot towards light.
Question 3 · MCQ · Analyse · 1 mark
A rise in blood glucose
Animal hormones
After a carbohydrate-rich meal, which hormone normally helps bring elevated blood glucose towards its usual range?
(A) Adrenaline
(B) Thyroxine
(C) Insulin
(D) Testosterone
Show answer and solution
Answer: (C) Insulin
Worked solution: Insulin from the pancreas helps cells take up glucose and promotes its storage, reducing elevated blood glucose.
Question 4 · MCQ · Analyse · 1 mark
Balance while cycling
Brain and coordination
Which part of the brain is especially associated with coordinating precise movements and balance while cycling?
(A) Medulla only
(B) Hypothalamus only
(C) Spinal sensory neuron
(D) Cerebellum
Show answer and solution
Answer: (D) Cerebellum
Worked solution: The cerebellum coordinates voluntary muscle activity and helps maintain posture and balance.
Question 5 · A-R · Analyse · 1 mark
Signals cross a synapse
Nervous system
Assertion (A): A chemical synapse normally transmits the signal from a presynaptic neuron towards a postsynaptic neuron.
Reason (R): Neurotransmitters are released from the presynaptic ending and act on receptors on the postsynaptic side.
(a) Both A and R are true, and R correctly explains A.
(b) Both A and R are true, but R does not correctly explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show answer and solution
Answer: (A) Both A and R are true, and R correctly explains A.
Worked solution: The location of transmitter release and reception makes the transmission directional in a typical chemical synapse.
Question 6 · A-R · Analyse · 1 mark
Touch and growth
Plant responses
Assertion (A): Folding of Mimosa leaves on touch is a slow directional growth response towards the stimulus.
Reason (R): Mimosa leaf folding involves rapid changes in water content and turgor of specialised cells.
(a) Both A and R are true, and R correctly explains A.
(b) Both A and R are true, but R does not correctly explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show answer and solution
Answer: (D) A is false, but R is true.
Worked solution: The folding response is rapid and does not depend on directional growth. Turgor changes explain the movement.
Question 7 · VSA · Apply · 2 marks
Tracing a reflex pathway
Nervous system
Arrange these parts in the order of a simple withdrawal reflex: motor neuron, receptor, effector muscle, sensory neuron, spinal cord.
Show answer and solution
Answer: Receptor → sensory neuron → spinal cord → motor neuron → effector muscle.
Worked solution: The receptor detects the stimulus, the sensory neuron carries the signal to the spinal cord, and a motor signal reaches the muscle to produce withdrawal.
Question 8 · VSA · Apply · 2 marks
Iodine in the diet
Animal hormones
Explain why insufficient iodine can affect thyroxine production and lead to enlargement of the thyroid gland.
Show answer and solution
Answer: Iodine is needed to make thyroxine; deficiency can cause goitre.
Worked solution: The thyroid requires iodine for thyroxine synthesis. Persistent deficiency can reduce hormone production and stimulate enlargement of the gland.
Question 9 · SA · Analyse · 3 marks
Matching three growth responses
Plant hormones
A grower wants to explain (i) greater stem growth, (ii) cell division in developing tissue, and (iii) inhibition of growth during water stress. Name a plant hormone associated with each and state the relevant role.
Show answer and solution
Answer: (i) Gibberellins promote stem growth; (ii) cytokinins promote cell division; (iii) abscisic acid helps inhibit growth and promotes stomatal closure.
Worked solution: Different hormones coordinate plant responses. Gibberellins can stimulate stem elongation. Cytokinins are associated with cell division. Abscisic acid acts as a growth inhibitor and helps plants respond to water stress by promoting stomatal closure.
Question 10 · SA · Analyse · 3 marks
Comparing two messages
Nervous and hormonal coordination
Compare pulling a hand away from heat with the longer-lasting bodily changes during a stress response involving adrenaline. Give one difference in signal route, speed and duration.
Show answer and solution
Answer: Withdrawal uses a rapid nerve circuit; adrenaline travels in blood and can produce a more widespread, longer-lasting response.
Worked solution: Neural messages travel along neurons and act through synapses on specific targets, producing a very rapid response. Adrenaline is secreted by adrenal glands into blood, reaches several organs and acts through receptors. Its effects generally persist longer than one brief nerve impulse.
Question 11 · LA · Analyse · 5 marks
From stimulus to muscle response
Nervous system
Explain a withdrawal reflex using a hot-surface example. Include (i) receptor, (ii) sensory neuron, (iii) spinal integration, (iv) motor neuron and effector, and (v) the role of the brain.
Show answer and solution
Answer: Skin receptors detect heat; sensory signals enter the spinal cord; motor signals activate muscles; the brain receives information for awareness.
Worked solution: Receptors in the skin detect the harmful stimulus and initiate impulses. A sensory neuron carries them to the spinal cord, where the circuit connects, usually through an interneuron, to a motor neuron. The motor neuron activates an effector muscle, withdrawing the hand. Information also travels to the brain, so the person becomes consciously aware of the pain and can plan further action.
Question 12 · Case Study · Analyse · 4 marks
Changing the direction of light
Tropic movements
Two similar young seedlings grow vertically. P receives light from a side window; Q receives light equally from above. Water, temperature and soil conditions are kept similar.
Answer the following:
(i) Which shoot is more likely to bend sideways? [1 mark]
(ii) Name the response shown by P. [1 mark]
(iii) Explain the role of unequal cell elongation in P. [2 marks]
Show answer and solution
Answer: (i) P. (ii) Positive phototropism. (iii) More elongation on the shaded side bends the shoot towards the light.
Worked solution: A shoot’s auxin distribution becomes unequal when light comes mainly from one side. The shaded side elongates more, causing curvature towards the window. Equal overhead illumination gives no comparable lateral growth difference in Q.
