Nutrient Cycles

• decomposers


  break down dead plant and animal material and gain the chemical energy
• 2 main groups of decomposers

  bacteria and fungi
• How do decomposers break down the waste?

  -secrete digestive enzymes on to the surface of the dead organism

  -dead matter broken down into small soluble food molecules

  -absorbed by decomposers
• Nitrogen fixation

  atmospheric nitrogen gas converted to ammonia by nitrogen-fixing bacteria
• Ammonification


  decomposers convert waste products and dead organisms into ammonia-forms ammonium ions in the soil
• Nitrification

  ammonium ions in soil are converted by nitrifying bacteria into nitrates
• Denitrification


  denitrifying bacteria uses nitrates in the soil during respiration, produces nitrogen which returns to the atmosphere
• The phosphorus cycle

  Weathering-phosphorus in rocks id slowly released by the breaking down and erosion of rocks

  -Phosphate ions taken up by plants

  -Transferred to consumers during feeding

  -Ions in waste products released to soil by decomposers

  -Phosphate ions can be used again by producers
• Role of fertilisers

  replacing the minerals lost when organisms aren't left to decompose and provide soil with minerals
• Natural fertilisers

  made up of organic matter which is gradually decomposed so provides a gradual release of nutrients in a low concentration
• Artificial fertilisers

  made up of inorganic matter that contain pure chemical compounds, higher concentration so less needed
• Leaching


  transportation of mineral ions from fertilisers into bodies of water and waterways, more likely with artificial fertilisers
• what can leaching cause?

  Eutrophication
• Eutrophication


  -mineral ions leach into waterways and cause the rapid growth of algae on the surface of the water

  -Tlocks sunlight and prevents photosynthesis

  -Aquatic plants die and bacteria feed on the dead organic matter and rapidly increase in number

  -The bacteria use up all of the oxygen in the water and fish are unable to survive.