Nutrient Cycle

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  • Nutrient Cycle
    • Carbon cycle
      • Plants take up C from atmosphere as CO2 via stoma
        • C fixed in photosynthesis to organic molecuels
          • 1 Consumers eat producer and C compounds are digested absorbed then assimilated
            • 2 Consumer eats 1 Consumer and C compounds passed along food chain
              • Indigestible C egested as faeces
                • C in dead plants and animals broken down by decomposers
                  • Respiration by decomposers releases CO2
                    • Respiration of producers and consumers releases CO2
    • Nitrogen Cycle
      • Plants take up N in the soil as NO3 by active transport via root hair cells
        • Plants use N for proteins
          • Consumers eat plants and digest, absorb and assimilate N into new compounds
            • Primary consumers eaten by secondary and N passes along food chain
              • Plants and animals die, animals excrete waste
                • Saprobiotic decomposers break N containing compounds into NH3 (ammonification)
                  • NH3 converted to nitrites then nitrates by nitrifying bacteria (nitrification)
                    • Some nitrates converted to N gases by denitrifying bacteria (denitrification)
                      • N gases converted back to NH3 by nitrogen fixing bacteria (nitrogen fixation)
    • Long term CO2 fluctuations
      • Deforestation removes trees as carbon sinks reducing amount of CO2 taken up in photosynthesis
        • Slash and burn method releases CO2 when trees burn
      • Combustion of fossil fuels releases CO2, increased with the industrial revolution
    • Short term CO2 fluctuations
      • Day- more photosynthesis and less respiration by plants so decrease in CO2 levels
      • Night- More respiration and no photosynthesis so increase in CO2 levels
      • Little air movement causes a build up of CO2 at night
      • Seasons- In winter shorter days, cooler temp, loss of leaves means a decrease in CO2 levels so increase in CO2 levels
    • Global Warming
      • Green house effect is a natural process where energy from the sun is reflected back into the atmosphere but prevented from escaping due to green house gases
        • To much green house effect cause global warming
      • Increase in methane
        • Increase number of cattle, gut bacteria that break down cellulose produce CO2
        • Rice cultivation in paddy fields are ideal for anaerobic bacteria that produce methan
      • Crop yields may increase but other limiting factors may effect yield
      • Pest numbers increase as rate of biological reactions speed up so shorter life cycle
        • More generations of pest and more surviving winter
      • Change in distribution of plants and animals
  • Consumers eat plants and digest, absorb and assimilate N into new compounds
    • Primary consumers eaten by secondary and N passes along food chain
      • Plants and animals die, animals excrete waste
        • Saprobiotic decomposers break N containing compounds into NH3 (ammonification)
          • NH3 converted to nitrites then nitrates by nitrifying bacteria (nitrification)
            • Some nitrates converted to N gases by denitrifying bacteria (denitrification)
              • N gases converted back to NH3 by nitrogen fixing bacteria (nitrogen fixation)

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