Agricultural solutions to the demands of a growing population
The human population is increasing at an A set of numbers that increase more and more rapidly. rate. This is the shape of the graph below.
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 An artificial process in which organisms with desired characteristics are chosen as parents for the next generation.:
- 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 The basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production. 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 The way in which genetic material is transferred from a donor to a recipient e.g. plasmids and artificial chromosomes. , which is usually a bacterial The small circular genetic material present in bacterial cells and used in DNA recombinant technology. 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 Relating to right and wrong, eg ethical companies are often ones that act in a responsible way. 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 The mass of a crop produced. 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 pests | Reduces biodiversity. May harm helpful organisms. |
| Maximise growth of farm animals | Keep animals indoors or in smaller pens | Reduces energy transferred to environment so more energy available for growth which maximises yield | Increased risk of disease |
| Action | Remove competing plants from the crop growing area |
|---|---|
| Treatment | Herbicide spray |
| Explanation | Allows more energy to be transferred to the crop |
| Side effects | Reduces biodiversity. May have harmful effect on health. |
| Action | Remove animals that feed on the crop |
|---|---|
| Treatment | Pesticide spray |
| Explanation | Prevents energy being transferred from the crop to pests |
| Side effects | Reduces biodiversity. May harm helpful organisms. |
| Action | Maximise growth of farm animals |
|---|---|
| Treatment | Keep animals indoors or in smaller pens |
| Explanation | Reduces energy transferred to environment so more energy available for growth which maximises yield |
| Side effects | Increased risk of disease |
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 may be changed. There have been examples of the predator becoming a more serious pest than the original problem.