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APES Ch. 3, part 2
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APES Ch. 3, part 2


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  • 1. Giraffes eat the grass Lions eat the giraffes And when they die, they become part of the soil and feed the grass
  • 2. Wait…seriously…this is mind blowing stuff!  Everything here has always been here  I know.  Wait? What?
  • 3. Biogeochemical Cycles  Water  Carbon  Nitrogen  Phosphorus  Sulfur
  • 4. Does any of this look familiar?
  • 5. The Water Cycle  Water comes down as precipitation, goes into the earth (groundwater) or the oceans, and is taken up by plants. It returns to the air by evaporation and transpiration.  Earth to plants (geo and bio) transpiration The water that comes out of plants!
  • 6. Water gets cleaned through this cycle  Evaporation leaves the other stuff behind  Flowing water naturally filtered - mostly by decomposers
  • 7. Human Impact 1. We take too much fresh water - faster than it can be replenished naturally
  • 8. 2. We clear plants and replace with concrete - this increases soil erosion and landslide risk, increases flooding risk, reduces groundwater replenishment, decreases transpiration
  • 9. Carbon, Carbon, everywhere  The carbon cycle is a series of processes through which all carbon atoms in existence rotate  All the carbon on earth and in living things gets recycled over and over again.
  • 10. Where is the Carbon?  Carbon is found in the environment as: – CO² gas in the atmosphere (air) – dissolved CO2 in the oceans (water) – Carbon in organic molecules in every living thing – Carbon is in fossil fuels and sedimentary rocks
  • 11. Carbon moves from the air into plants  Carbon moves from the atmosphere into plants through a process called photosynthesis
  • 12. Review - Photosynthesis Plants take CO2 + water + energy from the sun And make Glucose (sugar) and oxygen CO2 + H2O C6H12O6 + O2
  • 13. Carbon is in animals Animals get their carbon when they eat
  • 14. How does carbon get back into the air?  Carbon is returned to the atmosphere when an organism does cellular respiration  All living things give off CO2
  • 15. Decomposers When decomposers break down dead things, they return the carbon in those dead organisms to the air
  • 16. Summing it up  What is the GEO part of this cycle (where is the carbon on earth?)  What is the BIO part of this cycle?  In other words, what are the reservoirs of carbon?
  • 17.  If an organism dies and is buried very quickly, before decomposers can get to it, the carbon in the organism may turn into coal, gas, or oil.  We call this fossil fuel.
  • 18. Human Impact  When fossil fuels are burned, the carbon in them is released into the atmosphere
  • 19.  When we burn trees, we release the carbon in them.  The carbon gets put into the air.
  • 20. Carbon diffuses into water  Carbon in the atmosphere diffuses into the oceans  Forms carbonic acid – CO2 + H20  H2CO3  Too much CO2 in oceans leads to ocean acidification
  • 21. Human Impact  Removal of trees and other plants reduces the amount of CO2 that can be removed from the atmosphere through photosynthesis Alaska Brazil
  • 22. Let’s Review  How does Carbon get into the atmosphere? – every living thing gives off CO2 – burning of organic matter like wood – burning of fossil fuels like coal and oil – through the decomposition of dead plants and animals  How does carbon get out of the atmosphere? – By plants through photosynthesis
  • 23. Diagram the Carbon Cycle  Work in pairs to diagram the carbon cycle  Include:  Respiration  Burning/Combustion  Fossil fuels  Decomposition  Photosynthesis  Exchange with oceans/ocean acidification  Digestion  LABEL all processes with arrow that show the direction carbon is moving
  • 24. Do nowDo now 1. Get out the Carbon Cycle Game 2. Fill in as much as you can about the waterwater and carboncarbon cycles on your graphic organizer. Cycle Name Reservoirs Major Processes How it moves from the earth into living things How it is returned to the earth Human Impact on the cycle/Environmental Concerns Water Cycle Carbon Cycle Nitrogen Cycle Phosphor us Cycle Sulfur Cycle
  • 25. The Nitrogen Cycle
  • 26. Where is the nitrogen?  Most of the nitrogen (the main reservoir) is in the air. – 78% of our air is nitrogen gas  The nitrogen is the air cannot be used as it is by most organisms – It has to be “fixed” first.
  • 27. How does the nitrogen get fixed?  There are 2 ways: – Lightning can fix the nitrogen in the air – Lightning causes nitrogen and oxygen in the air to combine into nitric oxide (NO) and nitrogen dioxide (NO2). This will fall with the rain to the soil.
  • 28. Fixing Nitrogen  Most of the nitrogen that is fixed is done by special bacteria  These bacteria live in the roots of legumes – Legumes are plants like alfalfa, clover, and soybeans  The bacteria live in root nodules of these plants.  There, they fix nitrogen into a usable form for the plant
  • 29. Nitrogen Fixation  Nitrogen Fixation: Lighting = 10% Bacteria = 90% – N2 is combined with H to make ammonia – Bacteria use some, put the rest in the soil for plants – Plants can convert ammonia (NH3) to ammonium (NH4 + ) – Remaining ammonia goes through nitrification
  • 30. Nitrification  Ammonia in soil (NH3) &ammonium (NH4 + ) converted by bacteria to nitrate ions (NO3 - ), which plants happily take up
  • 31. Because crop plants generally require large amounts of nitrogen for growth, nitrogen frequently becomes the limiting soil nutrient for plant growth.
  • 32. Nitrogen needs  Farmers and gardeners add nitrogen back into the soil by commercial fertilizers and, more naturally, by crop rotation.
  • 33.  Plants take up nitrates and convert it to amino acids, nucleic acids, vitamins. Animals acquire all of their nitrogen when they eat plants (and other animals).
  • 34. All living things need nitrogen. Plants use nitrogen to make important molecules such as proteins, nucleic acids (DNA) and other major cellular components
  • 35. Returning Nitrogen to the Earth  When animals and plants die nitrogen is released back to the soil by decomposers.  This process is known as ammonification
  • 36. Ammonification Animal waste products (urine and manure) also return nitrogen to the soil. Urine from animals contains excess nitrogen which is returned to the soil. When an organism dies, the nitrogen molecules return to the soil. Plants reuse these nitrates and ammonia molecules
  • 37.  Denitrification  The usual form of nitrogen returned to the soil in animal waste or by decomposers is ammonia. The ammonia is somewhat toxic, but is converted into nitrates by nitrate bacteria. The nitrate can be then be used by plants and the cycle continues.
  • 38. What returns nitrogen to the air? Bacteria that are called denitrifying bacteria act on nitrate molecules and put nitrogen back into the air as N2. Atmospheric Nitrogen N2 NO3 -
  • 39. Human Impact Algae bloom resulting from excess nitrates from farm runoff (manures). Burning fossil fuels puts NO2 & HNO3 into the air = acid deposition
  • 40.  Just as nitrogen acts as an excellent fertilizer for agricultural crops, it also acts as a fertilizer in aquatic ecosystems. When too much nitrogen is washed into a waterway, it promotes an explosion of plant and algae growth, knocking the system out of balance. The plants and algae grow very fast and deplete the available oxygen supply.  The worst-case scenario is the creation of so-called dead zones, where nothing can live. The Gulf of Mexico, Chesapeake Bay, and Black Sea all have dead zones, with devastating consequences to marine life and the livelihoods of those who depend on the fisheries.
  • 41. Human Impact  Put N2O into the atmosphere when anaerobic bacteria feed on animal waste and fertilizer  This is a greenhouse gas  This breaks down the ozone layer
  • 42. Take a few minutes To fill in as much as you can about the nitrogen cycle on your table.
  • 43. The Phosphorus Cycle
  • 44. Where is the phosphorus?  A major difference with this cycle is that there is nothere is no atmospheric component.atmospheric component.  This process tends to be slow and local in nature.
  • 45. Where is the phosphorus?  Most of our phosphorus is stored in rocks andstored in rocks and sedimentsediment.  It is released through weathering and erosion. Plants can then take itPlants can then take it up through the soilup through the soil and water.
  • 46. What about us?  All consumers get theirAll consumers get their phosphorus through their foodphosphorus through their food.  Phosphorus is used to build bonesused to build bones and teeth in animals, and DNAand teeth in animals, and DNA in all living things
  • 47. Decomposers  Decomposers also help put phosphorus inDecomposers also help put phosphorus in the soilthe soil and water by breaking down dead organisms and their waste.  Phosphatizing bacteria are important in converting this phosphorus into a more usable form for plants.
  • 48. Waste  Waste productsWaste products,, especially fish eating bird guano, is highhigh in phosphorusin phosphorus and contributes a little bit to the overall cycle.
  • 49. Trapped phosphorus  Weathering andWeathering and erosion washerosion wash phosphorusphosphorus from rocks intofrom rocks into the oceanthe ocean.  There it can sink to the bottom, become part of the sediment, and be trapped out of circulation for some time.
  • 50. Problems associated with the phosphorus cycle  Since phosphorusphosphorus is needed for plant growth, it is often added inin the form of fertilizersfertilizers.  Just like nitrogen, too much phosphorus can pollute waterwayspollute waterways and lead to euthrophication (dead zones).
  • 51. Take a few minutes To fill in as much as you can about the phosphorus cycle on your table.
  • 52. The Sulfur Cycle  Most of the sulfur is stored underground in rocks and minerals (sulfate ions - SO4 2- )
  • 53. Sulfur to the air  From volcanoes and anaerobic decomposers in wet ecosystems (swamps, etc)  As H2S - hydrogen sulfide - rotten egg  As SO2 - suffocating
  • 54. Sulfur and clouds  Some plankton make dimethyl sulfide (DMS or CH3SCH3) – These serve as nuclei for condensation of water into droplets in clouds – So changes in DMS = changes in clouds!
  • 55. Completing the cycle  Bacteria in low oxygen environments convert sulfate ions to sulfide ions (S2- )  Sulfide reacts with metals to make metallic sulfides which form rocks
  • 56. Human Impacts  Burning coal and oil puts sulfur into the atmosphere  We refine sulfur containing petroleum which puts sulfur into the air  We convert sulfur containing mineral ores into metals like copper, zinc, lead and out sulfur into the air  All this = acid deposition
  • 57. Take a few minutes To fill in as much as you can about the sulfur cycle on your table.
  • 58. Human Impact on Ecosystems 1. Nutrient enrichment – adding excess nutrients to aquatic ecosystems 2. Acid precipitation – pH less than 5.6, harms trees, aquatic ecosystems, 3. Biological magnification – toxins accumulate in the tissues of organisms, PCBs and DDT 4. Rising atmospheric CO2– global warming 5. Depletion of the ozone layer – CFCs, burns leaves and skin