1
Triple only
[3 marks]Explain one advantage and one disadvantage of using fertilisers to increase crop yields.
Show mark scheme
- advantage: supply mineral ions / nitrates that plants need for growth (1)
- so crop yield increases (1)
- disadvantage: can be washed into rivers / lakes (1)
- causing water pollution / harm to wildlife (1)
- allow disadvantage: costly (1) so increases the farmer's costs (1)
- Max 3
2
Triple only
[3 marks]Ladybirds can be released in a greenhouse to control aphids. Explain one advantage and one disadvantage of using biological control instead of chemical pesticides.
Show mark scheme
- advantage: no chemical residue on the food / chemical pesticides not needed (1)
- so less harm to people or other organisms / the ladybirds target only the pest / keep working over a long time (1)
- disadvantage: slower / may not remove all the pests (1)
- allow disadvantage: the control organism may become a pest / eat other organisms (1)
- Max 3
3[2 marks]
In a practice data set, a non-GM crop yields 5.0 tonnes per hectare. A GM crop yields 6.5 tonnes per hectare. Calculate the percentage increase in yield.
Show mark scheme
- (6.5 − 5.0) ÷ 5.0 × 100 (1)
- 30% (1)
4[6 marks]
Evaluate the use of genetic engineering and selective breeding in modern agriculture. Include practical and ethical implications in your answer.
Show mark scheme
| Level | Marks | What the answer does |
|---|---|---|
| 3 | 5–6 | A balanced evaluation which covers benefits and risks of both methods, includes practical and ethical implications, and reaches a justified conclusion. |
| 2 | 3–4 | A partly balanced evaluation covering benefits and risks of both methods, or giving more detail for one method. Some practical or ethical implications are given. |
| 1 | 1–2 | A basic answer with one or two valid points. There is little or no evaluation. |
Indicative content
- selective breeding: higher yield, disease resistance, better quality food
- selective breeding: takes many generations, reduces genetic variation, so risk of disease affecting all
- genetic engineering: new characteristics such as insect resistance or higher nutritional value
- genetic engineering: quicker and more precise than selective breeding
- genetic engineering: costly, unknown effects on the environment or health, genes may spread to wild species
- ethical: some people think it is wrong to alter genes / interfere with nature
- ethical: concerns about animal welfare
- a justified conclusion, for example weighing increased food production against risks