Feeding the human race

What you'll learn

• What food security means: reliable access to enough safe, nutritious food.
• Why a larger population, changing diets and environmental change make feeding people harder.
• How farming methods can increase yield — the amount of food produced.
• How selective breeding (choosing parents with desired features) and genetic engineering (changing DNA, the molecule carrying genetic information) can help, and what risks to consider.

Some of this topic is separate Biology J247 only, especially the detail about food-security factors and biotechnological solutions. Because you are doing J247, it is worth learning the whole story.

The big problem: food security

A population needs food containing carbohydrates, proteins, lipids, vitamins, minerals, fibre and water. If food supply is unreliable, people may suffer from malnutrition, deficiency diseases or starvation.

To grow crops, plants need light, carbon dioxide, water, mineral ions and suitable temperatures. Anything that reduces plant growth, reduces livestock health, or makes food too expensive can reduce food security.

Factors that affect food security

A pest is an organism that damages crops or livestock. A pathogen is an organism or virus that causes disease. Both can reduce food production.

Important factors include:

• Increasing human population — more people need more food.
• Changing diets in wealthier populations — people often eat more meat and dairy, which requires more land, water and animal feed.
• New pests and pathogens — these can spread through global trade or environmental change.
• Environmental change — drought, flooding, climate change and soil erosion can reduce crop yields.
• Cost of agricultural inputs — agricultural inputs are things farmers must put into farming, such as seeds, fertilisers, pesticides, water, fuel, machinery and labour.
• Sustainability — a sustainable method can continue long-term without using up resources or causing serious ecosystem damage.

Agricultural solutions

Agricultural solutions aim to increase food yield, reduce losses, or make production more reliable.

Hydroponics

Hydroponics can control water, mineral ion concentration, pH and sometimes temperature. It can be used where soil is poor or space is limited. However, it can be expensive to set up and may need energy for pumps and lighting.

Fertilisers

A fertiliser is a substance added to soil or water to provide mineral ions needed for plant growth, such as nitrates for making proteins. Fertilisers can increase yield because they replace minerals removed when crops are harvested.

The risk is that fertilisers can be washed into rivers and lakes, causing algal growth and oxygen depletion. This can harm aquatic ecosystems.

Pesticides and biological control

A pesticide is a chemical used to kill pests. Pesticides can reduce crop losses, but may also harm non-target organisms, build up in food chains, or lead to resistant pest populations.

Biological control can reduce the need for chemical pesticides, but it must be carefully tested because the control organism could damage other species or become invasive.

Selective breeding

Selective breeding uses existing variation within a species. Variation means differences between individuals. Some variation is caused by genes, so it can be inherited by offspring.

To selectively breed food plants or domesticated animals:

1. Choose parents with desirable characteristics, such as high yield, disease resistance, fast growth or good milk production.
2. Breed them together.
3. Select the offspring with the best characteristics.
4. Repeat over many generations.

This can greatly improve food production. For example, wheat may be bred for higher grain yield, and cattle may be bred for higher milk production.

However, selective breeding can reduce genetic diversity because many individuals become genetically similar. This can increase the risk of inherited disorders in animals and can make crops more vulnerable to a new disease.

Genetic engineering and GM organisms

A genome is all the genetic material in an organism. Genetic engineering involves modifying an organism’s genome to introduce a desirable characteristic. An organism produced this way is often called a genetically modified organism, or GM organism.

A GM crop might be engineered to resist insect pests, tolerate drought, grow in salty soil, or contain extra nutrients.

This bit is Higher Tier only: you need to know the main steps in the process of genetic engineering.

Higher Tier process: the main steps

Key terms first:

• A restriction enzyme is an enzyme that cuts DNA at a specific base sequence.
• Sticky ends are short, unpaired DNA bases left after certain restriction enzymes cut DNA. Matching sticky ends can pair up.
• A vector is something used to transfer genetic material into a cell.
• A plasmid is a small circular piece of DNA found in bacteria, often used as a vector.
• Ligase is an enzyme that joins pieces of DNA together.
• A host bacterium or host cell is the cell that receives the new DNA.
• An antibiotic resistance marker is a gene that lets transformed cells survive on an antibiotic, so scientists can identify which cells took up the vector.

The basic process is:

1. Identify and cut out the desired gene using restriction enzymes.
2. Cut a plasmid vector using the same restriction enzyme, creating matching sticky ends.
3. Use ligase to join the desired gene into the plasmid, making a recombinant plasmid.
4. Insert the recombinant plasmid into host bacteria or plant cells.
5. Use antibiotic resistance markers to select the cells that successfully took up the plasmid.
6. Grow the selected cells into organisms with the desired characteristic.

Benefits and risks of gene technology

Gene technology means using techniques that alter or use genetic material. In agriculture, this often means genetic modification of crops or livestock. This is also a biotechnological solution, because biotechnology uses living organisms or biological processes to make useful products.

Possible benefits include:

• Higher crop yields.
• Reduced losses from pests and diseases.
• Crops that survive drought, salty soil or changing climates.
• Improved nutritional content, such as extra vitamins.
• Possible reduced use of some chemical pesticides.

Possible risks and concerns include:

• GM genes may spread to wild relatives through cross-pollination.
• Resistant pests or weeds may evolve.
• Non-target organisms could be affected.
• Farmers may become dependent on expensive seeds from companies.
• Some people have ethical concerns about altering organisms or want clear food labelling.
• Long-term ecosystem effects can be difficult to predict.