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The second strand of "Global challenges" is food. The human population is rising, and feeding everyone — now and in the future — is one of the great challenges of biology. This lesson defines food security and the threats to it, then surveys the biological tools we use to produce more food: selective breeding and genetic engineering of crops, biotechnology (mycoprotein from a fungus, and bacteria engineered to make human insulin), sustainable fishing, and the efficiency argument for eating more plants and fewer animals. Several of these ideas extend topics from B5, applied here to the food-security context.
By the end of this lesson you should be able to define food security and its threats, describe selective breeding and genetic engineering with their benefits and concerns, explain how mycoprotein and GM insulin are produced, describe methods of sustainable fishing, and explain why eating lower down the food chain is more efficient.
Food security means having enough safe, nutritious food to feed a population, both now and in the future. Many factors threaten it:
Tackling food security therefore means producing more food, more reliably, and more sustainably — which is where the biology in the rest of this lesson comes in.
Exam Tip: "Food security" is about having enough nutritious food for the future, not just today. When listing threats, give a range (population, changing diets, pests/pathogens, environmental change, cost) rather than repeating one idea.
Selective breeding (artificial selection) is choosing, over many generations, the individual plants or animals with the most useful characteristics to breed together. Farmers have used it for thousands of years to produce, for example, crops with higher yields or disease resistance, and animals that produce more meat or milk.
The steps are always the same:
A drawback is reduced variation (inbreeding): repeatedly breeding similar individuals reduces genetic variety, which can make a population more vulnerable to disease or to inherited problems.
Genetic engineering transfers a gene for a desired characteristic from one organism into the cells of another, so that the second organism develops that characteristic. Applied to crops, this produces genetically modified (GM) crops. Examples include crops engineered to be resistant to insect pests, resistant to herbicides, or to have improved nutritional value. GM is far faster and more targeted than selective breeding because a single useful gene can be introduced directly.
In the food-security context, the benefits and concerns of GM are an important debate:
| Benefits of GM crops | Concerns about GM crops |
|---|---|
| Higher yields, helping feed a growing population | Possible effects on wild plants and wildlife (e.g. on insect populations) |
| Pest- and disease-resistant crops reduce losses and pesticide use | Some worry about long-term effects on health, although GM foods are tested |
| Crops can be improved nutritionally (e.g. added vitamins) | Concerns about control of seeds by large companies, and cost to farmers |
| Can grow in harsher conditions, extending where food is produced | Possible reduction in biodiversity if one engineered crop dominates |
Exam Tip: A common question asks you to give the benefits and concerns of GM crops. Give a balanced answer with points on both sides, and link the benefits explicitly to food security (higher yields, pest resistance) for full credit.
Producing more food is not only about better varieties of crop — it is also about helping the crops you grow to thrive and protecting them from the pests and diseases that destroy yields.
Plants need mineral ions from the soil — especially nitrates (for making proteins and so for growth), as well as phosphates and potassium. Where crops are grown intensively year after year, the soil's supply of these minerals runs down. Fertilisers replace them, so that crops grow faster and give higher yields. They can be natural (such as manure or compost) or artificial (manufactured to contain a known mix of nitrogen, phosphorus and potassium).
Fertilisers have a clear benefit for food security but also a well-known drawback. If too much fertiliser is used, rain can wash the excess minerals off fields and into rivers and lakes. There, the extra nutrients make algae and water plants grow rapidly; when these die, microorganisms decomposing them use up the oxygen in the water, and fish and other animals can suffocate. This process — eutrophication — is the main reason fertiliser use has to be managed carefully.
Pests (such as insects, fungi and weeds) reduce yields by damaging crops or competing with them. There are two broad approaches:
A modern, balanced strategy often combines methods (sometimes called integrated pest management), using biological control and careful, targeted pesticide use together to protect yields while limiting harm to the wider ecosystem.
Exam Tip: For pest control, be ready to compare chemical pesticides with biological control: pesticides are fast but can harm other species and lead to resistance; biological control is more sustainable but slower and riskier to manage. Linking either back to food security (protecting yields) earns credit.
Microorganisms can be grown on a large scale in fermenters to produce food and useful substances. Two examples are required.
Mycoprotein is a protein-rich food made from the fungus Fusarium. The fungus is grown in large fermenters with a supply of glucose (food) and oxygen, at a controlled temperature and pH. The fungus respires and grows, and the mycoprotein is then harvested, purified and processed into meat-substitute foods. It is suitable for vegetarians and is high in protein and fibre but low in fat.
People with type 1 diabetes need insulin. Genetically modified bacteria are used to produce human insulin on a large scale: the human gene for insulin is inserted into bacteria, which then make human insulin as they grow in fermenters. The insulin is harvested and purified. This provides a reliable, large-scale supply of insulin that is identical to human insulin — a clear example of genetic engineering benefiting medicine.
Fish are a major source of protein, but overfishing — catching fish faster than they can reproduce — can cause fish populations to collapse. Sustainable fishing aims to keep fish stocks at a level where they can recover, so that fishing can continue into the future. Methods include:
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