Practise 34 exam-style questions on Control and coordination for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
34 questions
4–6 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
4 marks
Name two experimental observations that support the idea that auxin moves from the tip of the shoot downwards.
Model answer
Application of auxin to an intact tip restores growth; a tip placed on agar transfers activity that causes growth; removal of tip prevents downward effects; radioactively labelled auxin moves basipetally (down the stem).
Explanation
Experiments show auxin is produced at the shoot tip and moves downward: replacing a removed tip with an auxin source restores growth patterns; labelled auxin moves basipetally; auxin can be transferred via agar from tip to stem, and removing the tip stops these effects.
Mark scheme
1 mark
applying auxin to a decapitated tip restores normal growth/responses
Experimental replacement evidence.
1 mark
radioactive-labelled auxin detected moving down the stem
Tracer movement evidence.
1 mark
agar block under tip causes same response showing transfer from tip
Auxin diffuses into agar then into stem.
1 mark
cutting tip prevents responses that require downward auxin movement
Loss of tip removes source.
Question 2
4 marks
Explain how auxin transport inhibitors could be used to study the role of auxin in plant development.
Model answer
Apply auxin transport inhibitors to specific regions and observe developmental changes. Inhibitors block polar auxin flow, altering auxin gradients; resulting phenotypes (e.g., loss of apical dominance, altered organ positioning) reveal processes dependent on auxin transport.
Explanation
By locally blocking auxin transport, researchers can disrupt normal auxin distribution and monitor resulting developmental defects, allowing inference of which developmental events rely on directional auxin movement.
Mark scheme
1 mark
apply transport inhibitor to region(s) and compare to control
Experimental approach.
1 mark
inhibitor blocks polar auxin transport and alters auxin gradients
Mechanism of inhibitor.
1 mark
observe changes in development (apical dominance, organ initiation, tropisms)
Observable consequences.
1 mark
infer role of auxin transport from altered phenotypes
Interpretation step.
Question 3
5 marks
Describe how you would use a decapitation and auxin application experiment to show that auxin mediates phototropic curvature in coleoptiles.
Model answer
Arrange coleoptiles into: intact illuminated from one side (control), decapitated illuminated, decapitated with auxin paste applied to cut and illuminated. Keep conditions identical. Measure curvature. If curvature is mediated by auxin from tip, decapitated coleoptiles won't curve but decapitated+auxin will curve towards light.
Explanation
Decapitation removes the auxin source and abolishes phototropic bending; applying auxin to the cut stem restores bending in response to unilateral light, demonstrating that auxin from the tip mediates the curvature towards light.
Mark scheme
1 mark
three groups: intact, decapitated, decapitated+auxin
Experimental set.
1 mark
unilateral light for all groups and control variables kept same
Light and other conditions constant.
1 mark
measure curvature angle after fixed time
Measurement.
1 mark
expected: intact curves towards light; decapitated does not curve
Design an experiment to test whether auxin promotes cell elongation in stem segments. Include hypothesis, method, controls, measured variable and expected result.
Model answer
Hypothesis: auxin increases stem cell elongation. Method: take equal stem segments from same species/age. Place in agar with different auxin concentrations (including zero) for fixed time. Controls: same temperature, light, water. Measure change in length. Expected: greater elongation with increasing auxin up to optimal concentration.
Explanation
Use identical stem segments and treat with varying auxin concentrations (including no auxin). Keep all other conditions constant. Measure elongation after a set period. If auxin promotes elongation, treated segments should be longer than untreated controls, with a dose response up to an optimum.
