Agricultural solutions for a growing populationSpec 4.13BTriple only
The human population is growing, so more food is needed. Two agricultural solutions are the use of fertilisers and biological control.
Fertilisers
Fertilisers add mineral ions, such as nitrates, to the soil. Plants need these to grow well, so crop yields are higher.
- Advantage: increased growth and yield, so more food is produced from the same land.
- Disadvantage: fertilisers can be washed off fields into rivers and lakes, which can harm wildlife and pollute water.
- Disadvantage: they cost money, so the farmer's costs go up.
Biological control
Biological control is the use of living organisms to control pests. For example, ladybirds can be released to eat aphids.
- Advantage: no chemical residues are left on the food, and harmful chemical pesticides are not needed.
- Advantage: the control organism usually targets only the pest, and can keep working over a long time.
- Disadvantage: it is slower than pesticides and may not completely remove the pest.
- Disadvantage: the control organism might itself become a pest, or might eat other organisms, harming the ecosystem.
Evaluating genetic engineering and selective breedingSpec 4.14
'Evaluate' means weigh up benefits and risks, including practical and ethical implications, and reach a judgement. Here are the main points for agriculture and medicine.
| Benefits | Risks and implications | |
|---|---|---|
| Selective breeding | Higher yields and better quality food; no special equipment needed; produces useful animals and plants | Takes many generations; reduces genetic variation; inbreeding can cause health problems in animals |
| Genetic engineering in agriculture | Crops with new characteristics such as insect resistance or greater nutritional value; quicker than selective breeding | Unknown effects on the environment and human health; genes may spread to wild species; some people think it is wrong to alter genes |
| Genetic engineering in medicine | Medicines such as human insulin can be made in large amounts from GM organisms | Possible unforeseen effects; ethical concerns about changing the genes of organisms, especially animals |
Practical implications include time, cost, skill and the chance that it does not work. Ethical implications are about what people think is right or wrong, such as animal welfare and whether humans should change the genes of living things.
Interpreting yield data (practice data)
A farmer grows a non-GM crop with a yield of 4.0 tonnes per hectare, and a GM crop with a yield of 5.0 tonnes per hectare. Calculate the percentage increase in yield with the GM crop.
- Increase = 5.0 − 4.0 = 1.0 tonnes per hectare
- Percentage increase = increase ÷ original × 100
- 1.0 ÷ 4.0 × 100 = 25%
Answer: 25% increase.
Quick check
What does 'evaluate' require you to do in a question about genetic engineering?
Show answer
Weigh up benefits and risks, including practical and ethical implications, and reach a judgement.
Name one practical and one ethical implication of genetic engineering.
Show answer
Practical: it is costly or may not work. Ethical: some think it is wrong to alter the genes of organisms.
Give one risk of selective breeding.
Show answer
It reduces genetic variation, or inbreeding causes health problems.