Food production: crop plants — Edexcel International GCSE Biology
How glasshouses, fertilisers, pesticides and biological control are used to increase the yield of crop plants.
Revision notes
2 short notes, in the order of the specification. Each one in short:
Glasshouses and polythene tunnels increase crop yield by letting the farmer control the conditions plants grow in. They trap heat, let light in and allow carbon dioxide to be added, so photosynthesis is faster and more glucose is made for growth. Adding carbon dioxide or heat only helps if that factor is limiting the rate of photosynthesis.
Fertilisers replace the mineral ions, such as nitrate, phosphate and potassium, that crops take from the soil, so plants grow bigger and the yield rises. Pests reduce yield, so farmers control them with pesticides, which are chemicals that kill pests, or biological control, which uses a living organism such as ladybirds eating aphids.
Exam questions
6 exam-style questions (19 marks), each with its mark scheme.
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8 cards: flip them, mark what you knew, and practise the rest.
Practise the cardsMind map
The whole of use of biological resources on one page, so you can see where this subtopic fits.
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Quick check questions
Name two ways a glasshouse can increase the yield of a crop.
Show answer
Any two from: higher temperature, added carbon dioxide, extra light, protection from pests and weather.
Why does adding carbon dioxide increase yield?
Show answer
If carbon dioxide is limiting, photosynthesis is faster, so more glucose is made for growth.
What do fertilisers supply to crop plants?
Show answer
Mineral ions, such as nitrates, phosphates and potassium.
Give one disadvantage of using pesticides.
Show answer
Any one from: kill non-target organisms, build up in food chains, pests become resistant, pollute water.
What is biological control?
Show answer
Using a living organism to reduce the population of a pest.
Frequently asked questions
How do glasshouses increase crop yield?
Glasshouses increase crop yield by controlling the conditions for photosynthesis. They trap heat, let light in and allow carbon dioxide to be added, so plants make more glucose and grow faster. They also protect crops from wind, frost and many pests, and allow a longer growing season than growing outside.
How does carbon dioxide affect the rate of photosynthesis in a glasshouse?
Adding carbon dioxide increases the rate of photosynthesis if carbon dioxide is the limiting factor. The plants make more glucose, grow faster and give a higher yield. If light intensity or temperature is limiting instead, extra carbon dioxide gives no further benefit, so the cost of the fuel or gas is wasted.
Why do farmers use fertilisers?
Farmers use fertilisers to replace the mineral ions removed from the soil when a crop is harvested. Fertilisers supply ions such as nitrate, needed to make proteins, as well as phosphate and potassium. With more mineral ions available, plants grow faster and bigger, so the crop yield is higher.
What are the advantages and disadvantages of biological control?
Biological control uses no chemicals, so it leaves no harmful residues, usually targets only the pest, and pests do not become resistant as they do to pesticides. However, it is slower and rarely removes the pest completely, and the control organism may become a pest itself or feed on other species.
Written and checked against the Edexcel IGCSE Biology (4BI1) specification · Updated October 2026