food production

• nitrogen is essential for all organisms
• Nitrates dissolved in soil water are absorbed (taken in by) into plants and are used to produce amino acids which are used to make plant proteins

  Animals consume plants or other animals to obtain amino acids for protein synthesis
• Nitrogen is recycled through a set of processes called the nitrogen cycle
• bacteria and fungi are vital to the nitrogen cycle
• When crops are harvested (collected), nitrogen is taken out of the soil which needs to be replaced using artificial fertilisers, compost or manure

  Fertilisers provide chemicals such as nitrates which increase crop yield (how much crop can be harvested) to provide more food for the increasing human population

  Genetically modified (GM) crops can be used to reduce the use of fertilisers
• Plants and animals which reduce (lower) crop yield can be killed by pesticides

   Pesticides are sprayed onto crops and can build-up in the bodies of organisms over time

  o As the pesticides are passed along food chains, toxicity (harmfulness) increases and can reach

  lethal (deadly) levels

  o This is known as bioaccumulation
• Biological controls can be used instead of pesticides

   They can be natural predators which will prey on (eat) the pest species or a disease which only

  affects the pest species
• formation of an algal bloom

  1. fertilisers can leach into fresh water which increase the nutrient content
  2. this causes an algal bloom to form
  3. algal bloom reduces how much light enters the water which kills aquatic plants
  4. the dead plants and algae provides more food for the bacteria
  5. the bacteria increase in numbers
  6. the bacteria reduce the oxygen concentration reducing how much is available for the other organisms ( killing them)
  7. this causes a decrease in biodiversity