For an Ecosystem to be Stable, Materials Must be Cycled Water Cycle Carbon – Oxygen Cycle Nitrogen Cycle CO2 and O2 Photosynthesis CO2 O2 Cellular Respiration Fossil Fuel Burning Water Cycle Evaporation Condensation Precipitation *Transpiration from Plants *Respiration Nitrogen Cycle Nitrogen is needed for amino acids, proteins and DNA N2 Nitrogen Gas – 80% of Earth’s atmosphere *Most Organisms cannot use N2 directly Plants – can use NH3 (ammonia) and NO3 (nitrate) Animals – must ingest plants and other animals for nitrogen Decomposers play a very important role in the Nitrogen Cycle Nitrogen in the air nitrogen fixing plant eg pea, clover animal protein plant made protein root nodules (containing nitrogen fixing bacteria) dead plants & animals urine & faeces denitrifying bacteria nitrates absorbed decomposition by bacteria & fungi nitrates bacteria (nitrifying bacteria) ammonia nitrites bacteria The nitrogen fixing bacteria are found in lumps on the roots called root nodules. The bacteria and the plant have a symbiotic relationship: the bacteria benefits by having food and shelter from the plant and the plant benefits by having nitrates produced by the bacteria. Roots of a legume plant (peas, beans and clover).
