Food production

• Fertilisers provide chemicals such as nitrates which increase crop yield.
• Plants and animals which reduce crop yield can be killed by pesticides.
• Why are nitrates so important to plants?

  Nitrates dissolved in soil water are absorbed into plants. Nitrates are used to produce amino acids which are synthesised into plant proteins
• Describe the process of leaching and explain how it can affect aquatic life

  Fertilisers can leach into fresh water, adding extra, unwanted nitrates. This will increase algal populations which can cause algal blooms.

  Algal blooms reduce light levels, killing aquatic plants.

  These dead plants, as well as dead algae, become food for bacteria which increase greatly in number.

  The bacteria use up large quantities of oxygen, reducing the oxygen availability for other organisms.
• Animals consume plants or other animals to obtain amino acids for protein synthesis.
• Fertilisers can be added to soil to increase the nitrate content of the soil.
• Genetically modified (GM) crops can be used to reduce the use of fertilisers.
• Pesticides sprayed onto crops can accumulate in the bodies of organisms over time.

  As they are passed along food chains, toxicity increases and can reach lethal levels
• The build-up of toxic substances in living organisms is known as bioaccumulation.
• Give two examples of biological control

  1.Myxomatosis to kill rabbits

  2. using ladybirds to control greenfly populations