5. Food production

• An increase in human population requires an increase in food yield.
• There are two common ways to increase crop yield:

  • Pesticides - Chemicals used to kill pests that damage crops
  • Fertilisers - A substance added to the soil to increase its fertility
• Pesticides are chemicals that are sprayed onto crops.
• However, pesticides sprayed onto crops can accumulate bodies of organisms over a length of time. As they are passed along the food chain, the toxicity builds up and they become lethal.
• We can use genetically modified (GM) crops as an alternative to pesticides.
• Biological control can be used as an alternative to pesticides. This reduces pests through the use of natural predators.
• A fertiliser is a substance containing extra supplies of the nutrients required by growing plants. This allows an increase in crop yield.
• Fertilisers can be natural by adding compost or manure to your crops.
• Fertilisers can be artificial by using nitrate fertilisers.
• We can use genetically modified (GM) crops as an alternative to fertilisers. Crops can be genetically modified to increase their yield, without the need for chemicals.
• Nitrates dissolved into soil water are absorbed by roots.
• Nitrates are used to produce amino acids which are synthesised into plant proteins.
• Animals then consume plants or other organisms to obtain amino acids for protein synthesis.
• Fertilisers are added to soil to increase the nitrate content of the soil.
• Fertilisers can leach into fresh water, causing an algal bloom.
• Algal bloom leads to reduction in oxygen levels.
• Stages of Algal bloom:

  1. Fertilisers leach into fresh water, adding extra, unwanted nitrates.
  2. This increases the algal population, causing algal bloom.
  3. This reduces light levels, killing aquatic plants.
  4. Bacteria feeds on the dead plants, as well as dead algae, so the bacteria increase greatly in numbers.
  5. The bacteria use up great quantities of oxygen, reducing the oxygen available for other organisms.