The Oxygen Cycle

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The Oxygen Cycle

• Desarea Williams
• Jeremy Roca

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Definition of Oxygen

• Oxygen a colorless, odorless, tasteless gas
• Denser than air
• Poor conductor of heat and electricity

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Step One of Oxygen Cycle

• Plant release oxygen into the atmosphere as a
  by-product of photosynthesis.

oxygen
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Step Two of Oxygen Cycle

• Animals take in oxygen through the process of
  respiration.
• Animals then break down sugars and food.

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Step Three in Oxygen Cycle

• Carbon dioxide is released by animals and used in
  plants in photosynthesis.
• Oxygen is balanced between the atmosphere and the
  ocean.

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History of Oxygen

• Early evolution of Earth, oxygen released from
  H2O vapor by UV radiation and accumulated in the
  atmosphere as the hydrogen escaped into the
  earth's atmosphere
• Photosynthesis became a source of oxygen
• Oxygen released as organic carbon and gets buried
  in sediments.

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Photosynthesis

• Definition- process in which green plants use the
  energy from the sun to make carbohydrates from
  carbon dioxide and water in the presence of
  chlorophyll.

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How is Photosynthesis Carried Out?

• Photosynthesis only occurs in plants containing
  chlorophyll
• Water is absorbed by the roots and carried to the
  leaves by the xylem
• Carbon dioxide is obtained from air that enters
  the leaves through the stomata and diffuses to
  the cells containing chlorophyll.
• Chlorophyll is uniquely capable of converting the
  energy from light into a dormant form that can be
  stored and used when needed.

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Steps in Photosynthesis

• The light energy strikes the leaf, passes into
  the leaf and hits a chloroplast inside an
  individual cell
• The light energy, upon entering the chloroplasts,
  is captured by the chlorophyll inside a grana.
• Inside the grana some of the energy is used to
  split water into hydrogen and oxygen.
• The oxygen is released into the air.
• The hydrogen is taken to the stroma along with
  the grana's remaining light energy.

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Steps Continued

• Carbon dioxide enters the leaf and passes into
  the chloroplast.
• In the stroma the remaining light energy is used
  to combine hydrogen and carbon dioxide to make
  carbohydrates.
• The energyrich carbohydrates are carried to the
  plant's cells.
• The energyrich carbohydrates are used by the
  cells to drive the plant's life processes.

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Respiration

• Process by which an organism exchanges gases with
  its environment
• Process ? oxygen is abstracted from air,
  transported to cells for the oxidation of organic
  molecules while CO2 and H2O, the products of
  oxidation, are returned to the environment

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Earths Layers

• The lithosphere is Earth's surrounding layer,
  composed of solids such as soil and rock.
• The atmosphere is the surrounding thin layer of
  gas.
• The hydrosphere refers to liquid environments
  such as lakes and oceans that lie between the
  lithosphere and atmosphere.
• The biosphere's creation and continuous existence
  results from chemical, biological, and physical
  processes.

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Today

• The Earths atmosphere consists of
• 21 Oxygen
• The Earths lithosphere consists of
• 99.5 Oxygen
• The Earths hydrosphere consists of
• 46.60 Oxygen
• The Earths biosphere consists of
• 0.01 Oxygen

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Biological Importance of Oxygen

• Humans need it to breathe
• Needed for decomposition of organic waste
• Water can dissolve oxygen and it is this
  dissolved oxygen that supports aquatic life.

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Ecological Importance of Oxygen

• Without oxygen at the bottom of the water body,
  anaerobic bacteria (those that live without
  oxygen) produce acids. These acids not only
  increase acidity, but also cause a massive
  release of phosphorus and nitrogen, two major
  fertilizers, from the organic sediment and into
  the water column.
• These same anaerobic bacteria put toxic gases in
  the water including hydrogen sulfide (that rotten
  egg smell), ammonia, carbon dioxide and methane.
  These gases are all toxic to fish, beneficial
  bacteria and insects.
• Lack of bottom oxygen is the cause of odors
  produced by anaerobic bacteria.

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Ecological Importance of Oxygen Cont.

• Lack of fish enables disease-hosting mosquitoes
  to thrive, as mosquitoes are natural food for
  fish.
• Without oxygen at the bottom at all times,
  beneficial bacteria and insects cannot biodegrade
  the organic sediment. Large accumulations of
  organic sediment follow.

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Bibliographies

• http//dictionary.reference.com/browse/oxygen
• http//www.windows.ucar.edu/tour/link/earth/past/
  oxygen_buildup.html
• http//www.wisedude.com/science_engineering/compos
  ition_earth.htm
• http//water.me.vccs.edu/concepts/oxycycle.html