A farmer grows crops in a greenhouse. During winter, the farmer uses a gas heater inside the greenhouse to keep the plants warm. Explain why the plants inside the greenhouse grow faster in winter than plants of the same species growing outside.

Eduqas GCSE Biology — 1.5.2 Photosynthesis · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

The gas heater burns fuel, producing carbon dioxide as a combustion product.
Carbon dioxide is a reactant in photosynthesis, so the higher CO₂ concentration inside the greenhouse increases the rate of photosynthesis compared with plants outside.
A higher photosynthetic rate means more glucose is produced, giving the plants more energy and building material for growth, so they grow faster in winter than the same species outdoors.

Examiner tips

  • Use the word ‘because’ to link the heater’s CO₂ release to the higher photosynthetic rate. Mention the key reactant (CO₂) and the result (more glucose).
  • Show the causal chain: heater → CO₂ ↑ → photosynthesis ↑ → glucose ↑ → growth ↑.

Common mistakes

  • Failing to state that the heater releases CO₂. Confusing the heater’s heat with CO₂ as the limiting factor. Omitting the link between increased glucose and faster growth.

Mark scheme (4 marks)

  1. The gas heater releases carbon dioxide (as a product of combustion)
  2. Carbon dioxide is a raw material / reactant for photosynthesis
  3. So the rate of photosynthesis increases (compared to outside plants)
  4. More glucose is produced, providing more energy / materials for growth

Related

More Photosynthesis questions

▶ Try answering this question with AI marking (free) →