Practise 32 exam-style questions on Plant organ system 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.
32 questions
2–5 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
2 marks
Explain why measuring leaf temperature (infrared thermometer) might be useful in transpiration experiments.
Model answer
Leaf temperature indicates evaporative cooling from transpiration — cooler leaves suggest higher transpiration. It helps detect stress or stomatal closure affecting transpiration without contact.
Explanation
Evaporation cools leaves; measuring temperature gives indirect evidence of transpiration rate and plant stomatal behaviour.
Can indicate stomatal closure or stress and is non-contact measurement
Question 2
3 marks
Give one safety precaution and one ethical consideration when collecting wild plant samples for stomatal counts.
Model answer
Safety: wear gloves/handle glass slides carefully and avoid cuts; ethical: don't overcollect from rare populations / get permission and minimise habitat damage.
Explanation
Safety reduces risk of injury in the field and lab. Ethically, researchers must avoid harming plant populations or protected areas and obtain permission to collect samples.
Mark scheme
1 mark
Safety: wear gloves, use tools safely, avoid slippery leaves, eye protection if needed
Any sensible laboratory safety precaution
2 marks
Ethical: minimise impact on population (take few samples), obtain permission, avoid protected species or habitats
Award 2 marks for mention of permission and minimise harm; 1 mark for only one of these
Question 3
4 marks
A graph of transpiration vs light intensity shows saturation at high light. Explain the meaning of 'limiting factor' using this graph.
Model answer
A limiting factor is a variable that, when in short supply, restricts the rate of a process. On the graph, after stomata/opening and light are sufficient, another factor (eg water supply, CO2 or temperature) limits further increase so the rate levels off.
Explanation
A limiting factor is whichever component currently restricts the process. When light rises beyond the point where it affects rate, another factor limits photosynthesis/transpiration, causing saturation.
Mark scheme
1 mark
Define limiting factor: factor that limits the rate when its level is low
1 mark
Graph shows rate levels off (saturates) at high light indicating light is no longer limiting
1 mark
Another factor (temperature or CO2 or water supply) becomes limiting
1 mark
Therefore increasing light further does not increase rate
Question 4
5 marks
Explain how you would use a balance and ruler to estimate surface area and volume of a cylindrical plant stem segment, and why these measurements might be useful in plant transport experiments.
Model answer
Measure length and diameter with ruler to calculate cylinder surface area (2prh) and volume (pr^2h). A balance gives mass which with volume yields density or water content. Surface area/volume are useful because transport and evaporation scale with surface area while storage and transport capacity relate to volume.
Explanation
Use ruler dimensions to compute cylinder geometry. Mass gives density or water content. Surface area vs volume helps interpret transport and exchange processes and normalise rates.
Mark scheme
1 mark
Measure length and diameter / radius with ruler
1 mark
Calculate surface area = 2prh and volume = pr^2h (show formulas)
1 mark
Weigh on balance to get mass (optionally determine density = mass/volume)
1 mark
Surface area relates to exchange/evaporation/absorption; volume relates to storage/transport capacity
1 mark
Useful to normalise transpiration or transport rates per unit area or volume for fair comparisons
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