Lec 9 - Lecture 8 BIS2b Fall 2009 The Carbon Cycle The...

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Lecture 8 BIS2b Fall 2009 The Carbon Cycle
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The earth’s atmosphere has been built slowly by life, by photosynthesis and respiration. It is now being changed rapidly by human influence, by burning of fossil fuels and agricultural activities.
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If carbon is ‘King’ then nitrogen is ‘Queen,’ and H, O, P, & S are members of the ‘Royal Court.’ Mancinelli, 2003
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Earth has but a thin atmosphere 50% of the atmosphere by mass is below an altitude of 5.6 km. 90% of the atmosphere by mass is below an altitude of 16 km. The common cruising altitude of commercial airliners is about 10 km. 99.99997% of the atmosphere by mass is below 100 km (almost all of it). The highest plane flights reach an altitude of ca 110 km. Mean radius of earth = 6,371.0 km Atmosphere thickness is 100/6371 = 0.016 of earth’s radius. Huge surface area, small atmospheric volume. Modest rates of pollution can foul the atmosphere.
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Carbohydrate, CH 2 O, Sugars
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GPP is Gross Primary Productivity. In moles of fixed carbon, GPP equals the number of moles of O 2 produced by the plant or by vegetation in an area per unit time (look at the equation for photosynthesis to understand this equivalence). NPP = GPP – plant respiration, the energy used by the plant in its metabolism and to fuel growth. NPP is the calories in wood, leaves, flowers, nectar, seeds, and roots at the end of the growing season. Much NPP decomposes quickly (if it is not buried away from oxygen). NPP is about 50% of GPP globally.
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The shorthand of “CH 2 O” means carbohydrate, aka “fixed carbon.” Fixed carbon means that C has been combined with oxygen and hydrogen and lots of energy to form glucose, a simple sugar. Plants transform glucose into complex sugars, cellulose, lignin, and ultimately thousands of other compounds.
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Photosynthesis results in GPP and then NPP, the accumulation of fixed carbon, food for animals, and ultimately biodiversity.
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Oxygenic photoautotrophs split (oxidize) water with energy from the sun, captured by chlorophyll, and the products are: O 2 , , oxygen free in the atmosphere, virtually all of which is from photosynthesis, and fixed carbon in the form of glucose. Glucose is a simple carbohydrate from which plants make complex sugars, cellulose, lignin, and ultimately all other biomolecules.
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From simple carbohydrates, plants make cellulose and lignin, the most enduring forms of fixed carbon. These resist breakdown by microbes. The plant cell wall is composed of cellulose. Wood is composed of lignin.
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http://en.wikipedia.org/wiki/Detritus Photosynthesis fixes carbon Decomposition reverses the reaction, releasing CO 2 nutrients O 2 CO 2
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light energy e input of energy Chlorophyll 8.1 , p 161 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 Respiration & decomposition are oxidation of fixed C: 7.1, p. 140, upper left 6 CO 2 + 6 H 2 O + e C 6 H 12 O 6 + 6 O 2 Shorthand for biogeochemical calculations. CO
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This note was uploaded on 04/21/2010 for the course BIS 2C BIS 2C taught by Professor Rizzo during the Winter '09 term at UC Davis.

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Lec 9 - Lecture 8 BIS2b Fall 2009 The Carbon Cycle The...

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