Responding to stimuliAQA A-Level Biology: Topic test

20 questions, 54 marks

AQA A-Level Biology

Responding to stimuli topic test

Total 54 marks

Name

Class

Date

1
A student applies a paste containing indoleacetic acid (IAA) to one side of the shoot of an upright seedling kept in complete darkness. She applies the same paste to one side of the root of a second upright seedling, also in the dark.
(a)
What happens to the shoot?
[1 mark]
AIt bends towards the paste side, because IAA inhibits elongation in shoots.
BIt bends away from the paste side, because IAA stimulates elongation of the cells on the paste side.
CIt stays straight, because IAA only affects roots.
DIt bends towards the paste side, because IAA stimulates elongation on the opposite side.
(b)
What is meant by describing IAA as a growth factor?
[1 mark]
AIt is a nutrient that is built into new cell walls.
BIt is a hormone made only in the roots.
CIt is an enzyme that digests cell walls.
DIt is a chemical made in growing regions that moves to other tissues and regulates their growth.
(c)
Predict the response of the root to the paste and explain it.
[2 marks]
Total for question 1: 4 marks
2
A woman has a rare inherited condition in which the cones in her retinas do not work. Her rods are normal. She can see in dim light, but her vision is poor in bright light, she cannot distinguish colours and she cannot see fine detail.
(a)
Which feature of rods helps to explain why she can see in dim light?
[1 mark]
AEach rod has its own separate connection to the optic nerve.
BRods contain three different types of optical pigment.
CMany rods are connected to one bipolar neurone, so their generator potentials can add together to reach the threshold.
DRods are concentrated in the fovea.
(b)
Why can she not distinguish colours?
[1 mark]
AThe rods all contain the same type of optical pigment, so they cannot tell wavelengths apart.
BRods are not sensitive to any light.
CRods are connected to separate bipolar neurones.
DRods contain the pigment that is found in cones.
(c)
Explain why her visual acuity is poor.
[2 marks]
Total for question 2: 4 marks
3
A patient takes a drug that blocks the effect of the sympathetic nerve on her sinoatrial node. During exercise her heart rate rises from 65 to 105 beats per minute. Without the drug, her heart rate rises from 65 to 155 beats per minute during the same exercise.
(a)
Calculate the percentage reduction in the increase in heart rate during exercise that is caused by the drug. Give your answer to two significant figures.
[3 marks]
(b)
Explain how the heart rate normally increases during exercise.
[4 marks]
Total for question 3: 7 marks
4
A man stands up quickly from a chair. His blood pressure falls briefly and, within seconds, his heart rate rises. The heart is myogenic: it can beat without any nerve stimulation.
(a)
Explain how the nervous system increases the heart rate in response to the fall in blood pressure.
[6 marks]
(b)
Describe how a wave of electrical activity from the sinoatrial node leads to a coordinated contraction of the heart.
[6 marks]
Total for question 4: 12 marks
5
Euglena is a single-celled organism with chloroplasts. When it is placed in a dish lit from one side, it swims directly towards the light. Springtails are small soil animals. In a warm zone they move faster and turn more often than in a cool zone, but not in any particular direction.
(a)
What is the swimming of Euglena towards the light an example of?
[1 mark]
AA kinesis
BA simple reflex
CA tropism
DPositive phototaxis
(b)
Why is the behaviour of the springtails an example of a kinesis?
[1 mark]
ATheir speed and rate of turning change with the intensity of the stimulus, but the direction of movement is not related to it.
BThey move directly towards the favourable stimulus.
CThey grow towards the stimulus.
DThey respond through a three-neurone pathway.
(c)
Suggest how the response of Euglena increases its chance of survival.
[2 marks]
Total for question 5: 4 marks
6
A scientist isolates a Pacinian corpuscle from a mammal and presses on it with a fine probe. When the probe presses lightly, the sensory neurone at its centre produces a small change in membrane potential and no impulses. When it presses harder, a larger change is recorded and impulses are produced at a high frequency.
(a)
What causes the change in membrane potential when the corpuscle is pressed?
[1 mark]
ALight opens potassium ion channels in the membrane.
BPressure deforms the membrane, opening stretch-mediated sodium ion channels so that sodium ions enter.
CPressure closes sodium ion channels so that the membrane becomes more negative.
DChemicals released from the lamellae open calcium ion channels.
(b)
Why are impulses produced more frequently when the probe presses harder?
[1 mark]
AThe action potentials are larger.
BFewer sodium ion channels open.
CA larger generator potential is produced, so the threshold is reached more often.
DThe threshold potential falls.
(c)
Explain why a Pacinian corpuscle does not produce a generator potential when light shines on it.
[2 marks]
Total for question 6: 4 marks
7
Blowfly larvae were placed in a choice chamber with one half in the dark and the other half lit from above. The two halves had the same temperature and humidity. Thirty larvae were placed in the centre. After 10 minutes, 24 larvae were in the dark half and 6 were in the light half.
(a)
Calculate the chi-squared (χ²) value for these results, assuming the larvae were equally likely to be in either half. Show your working.
[3 marks]
(b)
The critical value of χ² at p = 0.05 with one degree of freedom is 3.84. State and explain the conclusion, and suggest two ways in which the student could make the investigation valid.
[4 marks]
Total for question 7: 7 marks
8
A person blinks when a speck of dust lands on the surface of the eye. This corneal reflex is a simple reflex that works through a three-neurone pathway.
(a)
Describe the pathway of this reflex and explain how the reflex helps to protect the person.
[6 marks]
(b)
Compare the way the nervous system controls the blink reflex with the way it controls heart rate.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).