The human population is increasing at an exponential rate. This is the shape of the graph below.
The exponential growth of the human population
More people means more demand for resources including food. Traditional and modern farming techniques are used to help supply this food.
Selective breeding
This process has occurred for thousands of years. Farmers have naturally known to breed large bulls with large cows to get large calves. This is the process of selective breeding:
- Decide which characteristics are important enough to select.
- Choose parents that show these characteristics from a mixed population. They are bred together.
- Choose the best offspring with the desired characteristics to produce the next generation.
- Repeat the process continuously over many generations, until all offspring show the desired characteristics.
Genetic modification
Genetic modification is a more recent technology than the process of selective breeding. It involves moving a gene for a desirable characteristic from one organism to another. This is the process of genetic modification:
- Restriction enzymes are used to isolate the required gene leaving it with sticky ends. Sticky ends are short strands of unpaired bases.
- A vector, which is usually a bacterial plasmid or a virus, is cut by the same restriction enzyme leaving it with corresponding sticky ends.
- The vector and the isolated gene are joined together by ligase enzyme.
- The vector inserts the gene into required cells.
- The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics.
Some people disagree with genetic modification for ethical reasons. Other people believe this process could help feed millions of starving people in poorer parts of the world.
Intensive farming
Intensive farming is a series of techniques that maximise the yield of animal or plant crops. Examples of intensive farming are shown in the table below.
Action | Treatment | Explanation | Side effects |
---|---|---|---|
Remove competing plants from the crop growing area | Herbicide spray | Allows more energy to be transferred to the crop | Reduces biodiversity. May have harmful effect on health. |
Remove animals that feed on the crop | Pesticide spray | Prevents energy being transferred from the crop to consumers | Reduces biodiversity. May poison helpful organisms. |
Keep animals indoors | ‘Battery’ farming | Reduces energy transferred to environment so more energy available for growth | Increased risk of disease. Lower quality product. Ethical concerns. |
Biological control
Biological control is an alternative to using pesticides. By releasing a natural predator into the crop growing area, the number of pests can be reduced. This can have unforeseen consequences as the numbers of different organisms in the food web are changed. There have been examples of the predator becoming a more serious pest than the original problem.