Nitrogen and Carbon Cycles.ppt by yurtgc548

VIEWS: 23 PAGES: 39

									            Nature Cycles
• Plants, animals, and soil interact to make up the
  basic cycles of nature.
Simple Carbon Cycle
Complex Carbon Cycle
            The Carbon Cycle
• Carbon atoms continually
  move through living
  organisms, the oceans,
  the atmosphere, and the
  crust of the planet. This
  movement is known as
  the carbon cycle.
• The paths taken by
  carbon atoms through
  this cycle are extremely
  complex, and may take
  millions of years to come
  full circle.
1.   In the carbon cycle, plants absorb       •   Ultimately, the same carbon atom
     carbon dioxide from the atmosphere           can move through many
2.   Animals, such as the rabbit pictured         organisms and even end in the
     here, eat the plants and use the             same place where it began.
     carbon to build their own tissues.       •   The same carbon atoms can be
3.   Other animals, such as the fox, eat          recycled forever!
     the rabbit and then use the carbon
     for their own needs.
4.   These animals return carbon dioxide
     to the earth when they breathe, and
     when they die, since the carbon is
     returned to the soil during
     decomposition.
5.   The carbon atoms in the soil may
     then be used by small
     microorganisms, decomposers, who
     also return carbon dioxide to the air.
6.   Carbon atoms may also become
     stuck in the soil. They are packed
     down, making fossil fuels.
   The Story of a Carbon Atom
• Consider, for example,
  the journey of a "typical"
  carbon atom that existed
  in the atmosphere as part
  of a carbon dioxide
  molecule some 360
  million years ago.... That
  molecule drifted into the
  leaf of a large fern
  growing in the extensive
  tropical swamp forests of
  that time…
        How is coal made????
•   Through photosynthesis, oxygen was
    released back into the air
•   The sugar molecule made during
    photosynthesis, which contains
    carbon, was transformed into a long-
    lived structural part of one of the plant
    cells.
•    Soon after, the fern died and the
    remains sank into the muck at the
    bottom of the swamp.
•   Over thousands of years, more plants
    grew in the swamp and their remains
    also sank into the swamp, forming a
    layer of dead plant material many
    meters thick.
•   Gradually, the climate changed,
    becoming drier and less tropical.
•    Sand, dust, and other materials slowly
    covered the ancient swamp and
    sealed the decaying vegetation under
    an ever-thickening layer of sediment.
•   The sediment hardened, turning to
    sedimentary rock.
•   The carbon atom stayed trapped in the
    remains of the long-vanished swamp
    while the pressure of the layers above
    slowly turned the material into coals.
                                     • The process of burning
                                       released the energy stored in
                                       the carbon compounds in the
                                       coal and reunited the carbon
• Some 360 million                     atom with 2 oxygen atoms,
  years later, in the                  forming carbon dioxide.
  1900s, the coal bed
  was mined by
  humans and burned
  to fuel industrial
  civilization.
  Walk-Through of the Carbon Cycle
  http://www.windows.ucar.edu/earth/climate/carbon_cycle.html
                  Finding Connections
   What is the connection between a car
    driving down the road, a tree growing in a
    forest, and global warming?




                   CO2     CO2       CO2




2007 AERA Annual Meeting                         9
We believe that it is vital to understand how the carbon
cycle works in order to see the danger of it not working.

  • Carbon dioxide (CO2) is the
    major gas involved in the
    greenhouse effect, which          Deforestation of
    causes global warming. All the      Tropical Rain
                                           Forests
    things that produce CO2 (like a
    car burning gas) and the things
    that consume CO2 (growing
    plants) are involved in the
    "global carbon cycle."
  • Deforestation increases the
    amount of CO2 and other trace
    gases in the atmosphere.
    When a forest is cut down,
    there are fewer trees available
    to use the CO2 in the
    atmosphere.
  GREENHOUSE
    EFFECT




http://www.teachersdomain.org/resources/phy03/sci/ess/watcyc/co2
               Tracing Carbon’s Path
   • Example: Grandma Johnson




                                          ?



        Describe the path of a carbon atom from Grandma Johnson’s remains, to
          inside the leg muscle of a coyote. NOTE: The coyote does not dig up
          and consume any part of Grandma Johnson’s remains.
2007 AERA Annual Meeting                                                        12
Answer: “Grandma
Johnson's remains
decay and
decomposers use
respiration and turn       Grandma
                                              Decomposers
it to carbon dioxide.      Johnson
The plants absorb the
carbon dioxide.
Rodents eat the plants
and then the coyote         Plants             Herbivores
eats the rodent.”


                                     Coyote




2007 AERA Annual Meeting
     The
Nitrogen Cycle
Nitrogen Cycle
What is nitrogen?
           Nitrogen is an
         element. It is an
              essential
           component of
          DNA, RNA, and
           proteins—the
         chemical building
         blocks found in al
           living things .
Where is nitrogen found
 in the environment?
The largest single source of nitrogen is in the
                atmosphere.

     Nitrogen makes up 78% of our air!
            It is one of
           nature’s great
             ironies…
Although the majority of the
 air we breathe is nitrogen,
 most living organisms are
unable to use nitrogen as it
 exists in the atmosphere!
                N
        N

   Atmospheric
                                        N
nitrogen needs to                           N

be converted to a
form living things
     can use.
            N
    N
                    How does this happen?
Nitrogen is changed in
  the first step of the
    nitrogen cycle…
   Nitrogen Fixation!
                     (1) Nitrogen Fixation

          Nitrogen
          Cycle
“Nitrogen Fixation” is the process that changes
nitrogen gas from the air into a form of nitrogen that
organisms can actually use.

                          Oxygen
      N
              N
                             Oxygen
 N                    +               =
 N                N         Oxygen
          N



Nitrogen gets “fixed” when it is combined with oxygen
or hydrogen.
There are three ways
 that nitrogen gets
      “fixed”!
 (a) Atmospheric Fixation


       (b) Industrial Fixation



     (c) Biological Fixation

                                 Bacteria
                               Lightning “fixes” Nitrogen!


   Atmospheric Fixation
    (Only 5 to 8% of the
                                      N
     Fixation Process)                    N   O
  The enormous energy of                             Nitrogen
                                                     combines
lightning fixes the nitrogen                         with Oxygen
 and enables the nitrogen                 Nitrogen oxides forms
   atoms to combine with         (N2O)            Nitrogen
oxygen. The fixed nitrogen       (NO3)            oxides dissolve
falls to the ground with the                      in rain and
                                                  change to
             rain.                                nitrates

                                               Plants use
                                               nitrates to grow!
                            NN
                                       H


 Industrial Fixation        N
                                H3
Under great pressure,
 at a temperature of
600 degrees Celsius,                 Industrial Plant combines
atmospheric nitrogen                 nitrogen and hydrogen
 (N2) is fixed to form                     Ammonia is formed
                           (NH3)
   ammonia (NH3).
Ammonia can be used
    as a fertilizer.


                         Ammonia is used a fertilizer in soil
              Biological Fixation
 (where MOST nitrogen fixing is completed)
There are two types of “Nitrogen Fixing Bacteria”




Free Living Bacteria
(“fixes” 30% of N2)    Symbiotic Relationship Bacteria
                            (“fixes” 70% of N2)
                Free Living Bacteria
Highly specialized bacteria live in the soil and have
       the ability to fix atmospheric nitrogen.
        N
    N             H

            NH3
Free-living bacteria live
in soil and fix nitrogen




                                     Bacteria
                             Legume plant
                                roots
      Symbiotic
    Relationship
       Bacteria
  Bacteria live in the
roots of legume family
plants and provide the
plants with nitrogen in
   exchange for the
 plant’s carbon and a
   protected home.
                          Roots have nodules
    What type of          where bacteria live
 symbiosis is this?
Microscope picture
  of nitrogen-fixing
  bacteria
(Magnified 39,000
  times with a TEM)
How do plants and animals get the
        “fixed” nitrogen?
• Plants absorb the nitrogen from the soil
  through their roots.
• Animals eat the plants to get the nitrogen.
• Plants and animals die and are broken
  down by decomposers.
• The nitrogen is now returned to the soil.
 How does
  nitrogen
reenter the
atmosphere
   in the
  nitrogen
   cycle?
 Through the opposite
  process of nitrogen
     fixation called
    denitrification!
                  Nitrogen Fixation
Denitrification
 What does
denitrification
     do?
Denitrification converts nitrogen in the soil to
atmospheric nitrogen (N2), replenishing the
                 atmosphere.
                       Nitrogen in atmosphere (N2)




           Nitrates (NO3)
           in Soil
 How does
     the
denitrificatio
 n process
   work?

                 Nitrates in soil
Denitrifying bacteria live deep in soil. The denitrifying
bacteria change the nitrogen in the soil into nitrogen
gas which goes back to the atmosphere. They close
                  the nitrogen cycle!

                                  Nitrogen in atmosphere
                                  closes the nitrogen cycle!

                                                         (N2)



                                                         (NO3)

                                  Denitrifying bacteria live
                                  deep in soil.
         Q. What is Nitrogen?
• A. Nitrogen is essential to life on earth.
  Nitrogen gas makes up 78 percent of the
  air we breathe, but we cannot get
  nitrogen directly from the air!!!
• Nitrogen, in various forms, passes from
  the air, to the soil, to all living things, and
  then back into the air.
 Q. What is the Nitrogen Cycle?
• A. The nitrogen cycle is the continuous
  movement of nitrogen from the air to the
  soil, to plants, and ultimately to sustain all
  animal life.
• http://www.ext.vt.edu/resources/4h/virtualf
  arm/flash_mov/nitrogencycleintro.swf
• Nitrogen is essential to all living systems.
• Nitrogen passes through the food chain from
  plants to herbivores to carnivores.
• When plants and animals eventually die, the
  nitrogen compounds are broken down giving
  ammonia (ammonification).
• Some of the ammonia is taken up by the plants;
  some is dissolved in water or held in the soil
  where bacteria convert it to nitrates (nitrification).
• Nitrates may be stored or leached from the soil
  and carried to lakes and streams. It may also be
  converted to free nitrogen (**denitrification) and
  returned to the atmosphere.
  **dentrification is the loss of nitrogen

								
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