Food Supply Notes

Cambridge IGCSE Biology: Revision notes

Key facts

  • Production rises with machinery, fertilisers, insecticides, herbicides and selective breeding.
  • Monocultures raise short-term yield but cut biodiversity and risk disease.
  • Intensive livestock production raises yield and cuts cost but raises welfare and pollution concerns.
  • A sustainable resource is replaced as fast as it is removed.
  • Fish stocks are conserved by quotas, closed seasons, protected areas, mesh size, education and monitoring.

Raising food production

Machinery, chemicals and selective breeding have all raised the amount of food from each area of land.

  • Machinery works land faster and on a larger scale.
  • Chemical fertilisers add nitrates to the soil.
  • Insecticides kill insect pests.
  • Herbicides kill weeds that compete for light, water and nutrients.
  • Selective breeding picks individuals with desirable features, such as high yield or disease resistance.
  1. 1

    Choose

    parents with the desired characteristic

  2. 2

    Breed

    them together

  3. 3

    Select

    the best offspring

  4. 4

    Repeat

    over many generations

Then back to step 1

Selective breeding over generations

Why do farmers use herbicides?

Monocultures

A monoculture boosts short-term yield and efficiency, but it lowers biodiversity and leaves the crop open to disease.

A monoculture is the large-scale growing of a single crop species over a wide area. All plants need the same care at once, so machinery and labour are used efficiently. But the same nutrients are removed from the soil repeatedly, and one pest or disease can destroy the whole crop.

  1. 1

    One crop over a wide area

    machinery and labour used efficiently

  2. 2

    Same nutrients removed

    the soil is depleted repeatedly

  3. 3

    Low biodiversity

    no variety to limit pests

  4. 4

    Pest or disease spreads

    the whole crop can be lost

Why a monoculture is risky.

Advantages

  • Efficient use of machinery and labour
  • Easier to plan planting, spraying, harvesting
  • Higher short-term yields

Disadvantages

  • Reduces biodiversity
  • Depletes the same soil nutrients
  • Pests and disease spread rapidly

Why is a monoculture at risk from disease?

Intensive livestock

Keeping many animals in a small space gives cheap, high yields but raises welfare, disease and pollution concerns.

Intensive livestock production keeps large numbers of animals in a confined space. Feeding, temperature and disease treatment are easy to control, and food costs less. However, animals have little room to move, disease spreads quickly, and large amounts of waste can pollute local water.

  1. 1

    Many animals, small space

    feeding, temperature and treatment easy to control

  2. 2

    Higher yield, lower cost

    cheaper food

  3. 3

    Disease spreads quickly

    animals are close together with little room to move

  4. 4

    Waste builds up

    can pollute local water

Intensive livestock production: benefits and risks.

Advantages

  • Higher yield per unit area or cost
  • Easier to control feeding and disease treatment
  • Lower cost, so cheaper food

Disadvantages

  • Animal welfare concerns
  • Disease spreads rapidly
  • Waste pollutes water

Give one advantage and one disadvantage of intensive livestock production.

Sustainable resources

A resource is sustainable if it is replaced as fast as it is used, as with well-managed forests and fish stocks.

A sustainable resource is produced as rapidly as it is removed, so it does not run out. Forests and fish stocks can keep providing food and materials if harvesting does not exceed natural replacement.

Fish stocks are protected by a quota, closed seasons, protected areas, mesh size, education and monitoring.

  1. 1

    Fish stock breeds

    protected by closed seasons and reserves

  2. 2

    Catch within quota

    larger mesh lets small fish escape

  3. 3

    Enough fish left

    to breed and replace those removed

  4. 4

    Stock maintained

    it keeps providing food

Then back to step 1

A sustainable fishery: the harvest never exceeds natural replacement.

Closed seasons

  • Ban fishing during breeding

Protected areas

  • Marine reserves restrict fishing

Mesh size

  • Small fish escape to breed

Quotas

  • Limit the amount caught

Why is fishing banned during the breeding season?

Try an exam question

Explain how fish stocks can be conserved.

[4 marks]

That's the notes covered.

Carry on to the next subtopic.