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Biogeochemical Cycles

Biogeochemical Cycles. Geochemical Cycles. Carbon Cycle Early atmosphere of Earth 95% CO 2 . Photosynthetic plants removed some of the CO 2 and added O 2 . Today’s atmosphere is 0.04% CO 2 !

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Biogeochemical Cycles

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  1. Biogeochemical Cycles

  2. Geochemical Cycles Carbon Cycle • Early atmosphere of Earth 95% CO2. Photosynthetic plants removed some of the CO2 and added O2. Today’s atmosphere is 0.04% CO2! • Reactions of photosynthesis and cellular respiration couldn’t take place without carbon. These two reactions form a continuous cycle. • Two important sources of Carbon are the ocean (since CO2 dissolves easily in H20) and rocks (such as coal, ore and limestone formed from dead organisms) Carbon is found in the atmosphere primarily as CO2 Photosynthesis: Plants taking CO2 out of the atmosphere and using it to produce sugar. Cellular Respiration: Organisms take that sugar and in the process of burning energy release CO2 back into the atmosphere.

  3. And, another way to look at the carbon cycle:

  4. Humans affect the Carbon Cycle • Burning of fossil fuels, (oil, coal and natural gas). • Fossil fuels were formed very long ago and is “fixed”: essentially locked out of the carbon cycle. • By burning fossil fuels the carbon is released back into the cycle.

  5. Humans affect the Carbon Cycle • We presently release more carbon into the air than can be reabsorbed by photosynthetic organisms, thereby we have a net INCREASE of carbon in the cycle. • This atmospheric carbon has a role to play in the warming of the atmosphere.

  6. Geochemical Cycles Nitrogen Cycle • Organisms require Nitrogen to form amino acids for the building of proteins. • Lots of N2 in our atmosphere • Unfortunately, most organisms CANNOT use atmospheric nitrogen. • Nitrogen-fixing bacteria CAN use N2 from the atmosphere. Nitrogen-fixing bacteria live in the soil and in roots of legumes.

  7. Nitrogen Cycle Continued … • Nitrogen-fixing bacteria convert atmospheric N2 into ammonia (NH4) which is a form of nitrogen that plants CAN use. • These bacteria also form nitrites (NO2) and nitrates (NO3); which are compounds containing N and O. • Nitrate is the most common source of N for plants. • Animals get N from the proteins they eat. • Decomposers return N to the soil in the form of ammonia and the cycle repeats. • So, the nitrogen cycle does not require the N to be returned to atmospheric form!

  8. Nitrogen Cycle Summary • All living organisms require nitrogen – to form amino acids to build proteins. • Proteins are important for locomotion, reproduction, defense, and structure. • Nitrogen makes up 78% of atmosphere as N2 • Nitrogen-fixing bacteria are very important - N2 needs to be “fixed” before it can be used by most living things.

  9. Sheep NITROGEN CYCLE N2 Fertilizer Production Lightning Denitrification (GAS) Nitrogen Fixation Crops Legume Nitrogen-Fixing Bacteria in soil & roots Decomposers Ammonia Nitrates Nitrites

  10. Humans affect the Nitrogen Cycle • From the production and use of nitrogen fertilizers to the burning of fossil fuels in automobiles, power plants, and industries, humans impact this cycle. • Excessive nitrogen additions can pollute ecosystems

  11. Humans affect the Nitrogen Cycle • Increased global concentrations of nitrous oxide (N2O), a potent greenhouse gas, in the atmosphere • Increased concentrations of nitric oxide, (NO) that drive the formation of smog along with N2O

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