IGCSE · Practice questions · Food supply

Yield up, biodiversity down.

Six original Cambridge-style questions on how humans have increased food production and on weighing up monocultures and intensive livestock farming, including yield data.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Name the method, then the reason.

Machinery: larger areas, more efficiently.
Fertilisers: mineral ions, better yields. Insecticides: fewer insect pests. Herbicides: less competition from weeds.
Selective breeding: crops and livestock with higher production.
Every advantage has a cost: biodiversity, disease spread, pollution, animal welfare.

Recall

[4 marks]

State four ways in which humans have increased food production and give one reason each method raises yield.

Agricultural machinery: one farmer can farm a larger area of land efficiently. ✓
Chemical fertilisers: supply mineral ions such as nitrate, so plants grow more. ✓
Insecticides: kill insect pests, so less of the crop is damaged. ✓
Herbicides: kill weeds that compete with the crop for light, water and ions. (Also accept selective breeding: higher-yielding varieties or breeds.) ✓

Explain

[4 marks]

Describe two advantages and two disadvantages of growing a crop as a large-scale monoculture.

Advantage: machinery can be used easily for planting, spraying and harvesting. ✓
Advantage: high yield of a uniform crop at low cost per tonne. ✓
Disadvantage: low biodiversity, because hedgerows and other plants are removed, so fewer habitats and food sources. ✓
Disadvantage: pests and diseases of that crop spread quickly; heavy pesticide and fertiliser use can pollute nearby water. ✓

Data

[3 marks]

A field produced 3.0 tonnes of wheat per hectare. After fertiliser was added the yield was 4.5 tonnes per hectare. (a) Calculate the percentage increase in yield. (b) Suggest why the farmer must also take care not to add too much fertiliser.

(a) Increase = 4.5 − 3.0 = 1.5 t/ha; (1.5 ÷ 3.0) × 100 = 50%. ✓
(b) Excess fertiliser is wasted money and is not taken up by the crop. ✓
It can be washed by rain into rivers and lakes, causing water pollution (eutrophication). ✓

Explain

[4 marks]

Discuss the advantages and disadvantages of intensive livestock production.

Advantage: large amounts of meat, eggs or milk produced from a small area of land, so food is cheaper. ✓
Advantage: animals kept warm and with little movement waste less energy, so more of their food is converted into growth. ✓
Disadvantage: animals are crowded, so diseases spread easily and antibiotics are often used; animal welfare is poor. ✓
Disadvantage: large amounts of waste can pollute water; land is still needed to grow their feed. ✓

Analysis

[3 marks]

A farmer says: "Spraying insecticide over my whole monoculture is the best way to protect it." Give three reasons why this may harm the wider ecosystem.

Insecticides can kill useful insects too, such as pollinators and predators of the pests. ✓
Removing insects reduces food for birds and other animals, altering food chains and food webs. ✓
Insecticide can be washed into water and harm aquatic organisms (or build up along food chains). ✓

Recall

[2 marks]

Explain how selective breeding is used to improve milk production in dairy cattle.

Cows that produce the most milk (and bulls whose mothers did) are chosen as parents and bred together. ✓
Offspring with the highest milk yield are chosen to breed again, repeated over many generations. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.