Sources of Food
Plant needs, limiting factors, raising food production, environmental impacts and sustainable farming.
Before you begin
Begin with what plants need, then match a production method to the problem it addresses. Weigh its benefit against possible costs. The diagram traces environmental pathways to examine alongside changes in food output.
Learning goals
- Requirements for plant growth
- Why production must improve
- Fertilisers
- Pesticides and herbicides
- Slash-and-burn
- Fertiliser pollution
- Pesticide and herbicide pollution
- Slash-and-burn damage
- Biological control
- Improved varieties
- Intensive farming
- Uses of plant hormones
Syllabus statements covered
- state that plants need air, light, water, nutrients and appropriate pH for photosynthesis and growth
- show an understanding that the increase in world population and the limitation in space to grow food lead to the need to improve food production
- describe how the following methods improve crops produced: — use of fertilisers
- describe how the following methods improve crops produced: — use of pesticides and herbicides
- describe how the following methods improve crops produced: — slash-and-burn
- describe the environmental problems associated with the following methods: — use of fertilisers (water contamination leading to increased growth of algae and water weeds)
- describe the environmental problems associated with the following methods: — use of pesticides and herbicides (soil and water contamination leading to transfer of harmful substances along the food chain)
- describe the environmental problems associated with the following methods: — slash-and-burn method (haze leading to breathing difficulties and deforestation leading to soil erosion)
- explain how the use of biological control reduces the need for pesticides (limited to control of prey by their predators)
- describe how food production can be improved by: — improving varieties of plants and animals
- describe how food production can be improved by: — intensive farming methods for crops and farm animals (e.g. chicken, fish) [details of technologies are not required]
- state that plant hormones are used as weed killers, and in regulating growth and ripening of fruits
Lessons
Work through them in order.
- What plants need to growExplain the roles of air, light, water, mineral nutrients and pH, and judge plant-growth evidence from a fair test.
- Increasing food productionMatch fertilisers, pesticides, herbicides and slash-and-burn to the production problem each tackles.
- Environmental impacts of food productionTrace how fertiliser runoff, pesticides and land clearing can affect water, food chains, air and soil.
- Biological control of crop pestsExplain how predators can reduce pest numbers, crop damage and the need for pesticides, and evaluate the limits of the evidence.
- Varieties, intensive farming and plant hormonesDistinguish improved plant and animal varieties, intensive farming and agricultural uses of plant hormones by their purposes.
Practise and check
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