• use of nitrogen in plants and animals (animals eat plants)

  • nitrogen cycle stages

  • nitrogen fixation

  • ammonification

  • saprobiotic nutrition

  • nitrification

  • denitrification

  • use of phosphorus in plants and animals

  • phosphorus cycle

  • why are nutrients lost in crop harvesting

  • environmental problems when using fertilisers

  • leaching

  • eutrophication