A farmer grows wheat plants in two different fields. Field A has fertile soil and receives plenty of sunlight. Field B has poor soil and is shaded by nearby trees. The wheat plants in Field A are taller and produce more grain than those in Field B. Explain why the wheat plants in Field A photosynthesise at a greater rate, and explain how this leads to greater growth.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A farmer grows wheat plants in two different fields. Field A has fertile soil and receives plenty of sunlight. Field B has poor soil and is shaded by nearby trees. The wheat plants in Field A are taller and produce more grain than those in Field B.
Model answer (5 marks)
Field A receives more light, so the light intensity available for photosynthesis is higher.
Light is a key reactant in the light‑dependent reactions; increased light raises the rate of photosynthesis.
Higher photosynthetic rate produces more glucose (and oxygen) per unit time.
Glucose is taken up by cells and used in cellular respiration to release ATP, which powers cell division and growth.
Glucose is also a precursor for synthesising cellulose, proteins and other macromolecules that build new plant tissue, leading to taller plants and more grain.
Light is a key reactant in the light‑dependent reactions; increased light raises the rate of photosynthesis.
Higher photosynthetic rate produces more glucose (and oxygen) per unit time.
Glucose is taken up by cells and used in cellular respiration to release ATP, which powers cell division and growth.
Glucose is also a precursor for synthesising cellulose, proteins and other macromolecules that build new plant tissue, leading to taller plants and more grain.
Examiner tips
- Use the exact terms: light intensity, photosynthesis, glucose, respiration, ATP, cellulose, proteins.
- Show the causal chain: more light → higher photosynthesis → more glucose → energy for growth and building material.
- Keep answer concise – one sentence per point.
- Mention both energy release and biosynthesis as reasons for growth.
Common mistakes
- Confusing photosynthesis with respiration; forgetting that glucose is produced in photosynthesis.
- Using vague phrases like ‘more energy’ without linking to ATP or cell division.
- Omitting the role of light intensity or the specific products (glucose, oxygen).
Mark scheme (5 marks)
- Plants in Field A receive more light / greater light intensity
- Light is needed for / increases the rate of photosynthesis
- Photosynthesis produces glucose (and oxygen)
- Glucose is used in respiration to release energy for growth / cell division
- Glucose is also used to make cellulose / proteins / other biological molecules needed for growth
Key terms in this question
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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