1. Nutrient Cycles

2. Learning Objectives Understand the role of organic breakdown in nutrient cycles Be able to draw a diagram of the carbon cycle Understand the main processes in the nitrogen cycle – nitrogen fixation / nitrification / putrefaction and denitrification Be able to name bacteria associated with nitrogen fixation and nitrification Understand the agricultural practices of ploughing and maintaining well drained soils

3. Nutrient Cycles Carbon and nitrogen move in cycles between the physical environment and living organisms. Saprophytes are responsible for the breakdown of organic matter – decomposition.

4. Carbon Cycle Fossilisation – coal / oil / gas Calciferous rocks – limestone and chalk

5. Atmospheric CO2 – 0.03% Biomass Bicarbonate ions / carbonic acid

6. PHOTOSYNTHESIS (plants and Algae): 6CO 2 + 6H 2 O  (sunlight)  C 6 H 12 O 6 + 6O 2 RESPIRATION (all life) C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O (+ energy!) Where: C 6 H 12 O 6 = sugar O 2 = oxygen CO 2 = carbon dioxide H 2 O = water(PUT THIS IN NOTES)

8. Nitrogen Cycle Nitrogen Fixation N2 in the atmosphere is reduced to NH3 Carried out by free living Azotobacter or mutualistic bacteria – Rhizobium in an oxygen deficient environment (leghaemoglobin or high metabolic rate) Uses enzyme nitrogenase (AA’s host & bacterium or soil)

9. Putrefaction (ammonification) Carried out by decomposers Nitrogen containing compounds to ammonium ions (dead organisms, faeces and urine) Nitrification Oxidation of ammonium ions to nitrite then nitrate ions Ammonium ions to Nitrite - Nitrosomonas Nitrite ions to Nitrate ions- Nitrobacter Carried out by chemoautotrophs Needs well aera ted soil

10. Denitrification Denitrifying bacteria predominate in water logged and trampled soils.