2 What is the Nitrogen Cycle? Facts:Nitrogen (N) is an essential constituent of protein, DNA, RNA, and chlorophyll.Nitrogen is the most abundant gas in the atmosphere (78%), but it must be fixed or converted into a usable form.
3 How is Nitrogen Fixed? Nitrogen Fixation Methods: High energy fixation- a small amount of atmospheric nitrogen is fixed by lightening. The high energy combines N and H2O resulting in ammonia (NH3) and nitrates (NO3). These forms are carried to Earth in precipitation.Biological fixation: achieves 90% of the nitrogen fixation. Atmospheric nitrogen (N2) is split and combined with hydrogen (H) atoms to eventually form ammonia (NH3).
4 Who Performs Nitrogen Fixation? Symbiotic bacteria (eg. Rhizobium spp.) living in association with leguminous (plants in the pea/bean family). - free-living anaerobic bacteria - blue-green algae (cyanobacteria)Ammonification: Once NH3 is in the soil it combines with H+ ions to form ammonium ion (NH4), or without it to form NO3. NH4+ and NO3 are readily absorbed by plants.Nitrification: is the biological oxidation of ammonia with oxygen into nitrite followed by the oxidation of these nitrites into nitrates (bacteria)Denitrification: Bacteria reduces nitrates and nitrites back into gaseous nitrogen (N2)
6 What is the Carbon Cycle? All life is based on the element carbon.Carbon is the major chemical constituent of most organic matter, from fossil fuels to the complex molecules (DNA and RNA) that control genetic reproduction in organisms.Yet by weight, carbon is not one of the most abundant elements within the Earth's crust. In fact, the lithosphere is only % carbon by weight.In comparison, oxygen and silicon respectively make up 45.2 % and 29.4 % of the Earth's surface rocks.
8 Where is Carbon Stored Living Organisms (organic molecules) Sedimentary Rock (limestone, dolomite)Shells of marine organisms (calcium carbonate)Fossil FuelsCarbon Dioxide in our atmosphereOrganic matter in our soils
9 What is the Phosphorus Cycle? Component of DNA, RNA, ATP, proteins and enzymesCycles in a sedimentary cycle - A good example of how a mineral element becomes part of an organism.The source of Phosphorus (P) is rock.It is released into the cycle through erosion or mining.It is soluble in H2O as phosphate (PO4)It is taken up by plant roots, then travels through food chains.It is returned to sediment