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					Ecosystems

 Chapter 30
            Ecosystem

An array of organisms and their physical
environment, interconnected through a
one-way flow of energy and cycling
of raw materials
         Modes of Nutrition

• Photoautotrophs
  – Capture sunlight or chemical energy
  – Primary producers

• Heterotrophs
  – Extract energy from other organisms or
    organic wastes
  – Consumers, decomposers, detritivores
  Simple    Energy
            input from
Ecosystem   sun



  Model
                           Producers
                  Autotrophs (plants and other
                    self-feeding organisms)



                           Nutrient
                           Cycling



                          Consumers
               Heterotrophs (animals, most fungi,
                 many protists, many bacteria)



            Energy output (mainly metabolic heat)
Simple Ecosystem Model




   The role of organisms in an ecosystem
                            fifth trophic level
                               top carnivore
            marsh hawk   (fourth-level consumer)

                            fourth trophic level
                                 carnivore
          crow            (third-level consumer)

                            third trophic level
                                 carnivore
          garter snake   (second-level consumer)

                          second trophic level
                               herbivore
                          (primary consumer)
          cutworm
                            first trophic level
                                autotroph
flowering plants           (primary producer)
                                                   Fig. 30-3, p.528
Tall-Grass Prairie Food Web
          marsh hawk




    sandpiper          crow




  snake


  frog
                                         weasel   badger   coyote
            spider

                              sparrow

                                        vole      pocket     ground
 earthworms, insects                              gopher     squirrel



                              grasses, composites
                          marsh hawk
                                                Connections in a
                                                tallgrass prairie food web
Higher
Trophic                       crow
Levels
              upland
              sandpiper
               garter snake



                frog



                                              weasel        badger coyote
              spider
Second
Trophic
                                 sparrow
 Level
          earthworms, insects          prairie vole   pocket gopher    ground squirrel

 First
Trophic                       grasses, composites
 Level

                                                                               Fig. 30-4, p.529
           Which statement about ecosystems is false?


1.   energy flows in a cycle
     between producers and
                                     25%   25%    25%   25%
     consumers
2.   nutrients are recycled by
     passing from producers to
     consumers and back again
     via decomposers
3.   in most ecosystems, energy
     flow begins with the capture
     of solar energy by
     photosynthesizers
4.   heterotrophs include bacteria
     and fungi

                                     1      2       3    4
Rain Forest




 Rain-forest food web
           Energy Losses

• Energy transfers are never 100%
  efficient
• Some energy is lost at each step
• Limits number of trophic levels in an
  ecosystem
                                   Grazing         Detrital
                                   Food Web        Food Web
                    Two Types of Food Webs
                   Energy Input:      Energy Input:

      Transfers:                                    Transfers:
                 Producers                                           Producers
             (photosynthesizers)                                 (photosynthesizers)



                                                                                       energy
energy                              energy          energy                             losses
in organic                          losses          in organic       decomposers       as metabolic
wastes,
                  herbivores                        wastes,
                                                                     decomposers
                                                                                       heat
                                    as metabolic
remains                             heat            remains                            and as net
                                    and as net                                         export
                                    export                                             from
                  carnivores        from                              detritivores
                                                                       detritivores    ecosystem
                                    ecosystem



                 decomposers




       Energy                                              Energy
       Output                                              Output
        Ecological Pyramids

• Primary producers are bases for
  successive tiers of consumers
• Biomass pyramid
  – Dry weight of all organisms

• Energy pyramid
  – Usable energy decreases as it is
    transferred through ecosystem
               Biomass Pyramid
• Aquatic ecosystem, Silver Springs, Florida
• Long-term study of a grazing food web

                               third-level carnivores
                   1.5         (gar, large-mouth bass)


                   1.1         second-level consumers
decomposers,
                               (fishes, invertebrates)
detritivores
(bacteria,                     first-level consumers
crayfish)          37          (herbivorous fishes,
                               turtles, invertebrates)

                         809   primary producers (algae,
 5                             eelgrass, rooted plants)
                 Energy Pyramid
    • Primary producers trapped about 1.2% of
      the solar energy that entered the
      ecosystem
    • 6–16% passed on to next level


top carnivores           21       decomposers + detritivores = 5,080
carnivores
                   383
herbivores
                  3,368
producers         20,810 kilocalories/square meter/year
Silver Springs Study




    Energy flow at Silver Springs
      Biogeochemical Cycle

• Flow of an essential substance from the
  environment to living organisms and
  back to the environment
• Main reservoir is in the environment
• Geologic processes, decomposers aid
  cycles
  Three Categories

• Hydrologic cycle
  – Water

• Atmospheric cycles
  – Nitrogen and carbon

• Sedimentary cycles
  – Phosphorus and other
    nutrients
                     Hydrologic Cycle
                            atmosphere

                        wind-driven water vapor             precipitation
                                 40,000                      onto land
                                                              111,000
evaporation precipitation        evaporation from land
from ocean into ocean         plants (evapotranspiration)
  425,000     385,000                   71,000
                                                                     surface and
                                                                     groundwater
                                                                     flow 40,000



        ocean                                                           land
             Watershed


• A region where
  precipitation is
  funneled into a
  single stream
  or river
    Hubbard Brook Experiment

• A watershed was experimentally
  stripped of vegetation
• All surface water draining from
  watershed was measured
• Deforestation caused six-fold increase
  in calcium content of runoff water
          Global Water Crisis
• Limited amount of fresh water
• Desalinization is expensive and requires
  large amounts of energy
• Aquifers are being depleted
• Groundwater is contaminated
• Sewage, agricultural runoff, and industrial
  chemicals pollute rivers
Aquifer Depletion
 Hawaiian
             Alaska
 Islands
  When the Earth's waters move from ocean to
atmosphere to land and back again, it is called the
                  _____ cycle.
                            25%   25%   25%    25%
 1. water
 2. hydrologic
 3. hydrodynamic
 4. precipitation



                             1     2      3      4
           A watershed is _____.
1.   a stream or river
                                 25%   25%   25%   25%
2.   a river that discharges
     water directly into the
     ocean
3.   a region where
     precipitation becomes
     funneled into a single
     stream or river
4.   a region where
     precipitation becomes
     funneled into a reservoir
     for use in human            1      2     3     4
     communities
           Carbon Cycle

• Carbon moves through atmosphere,
  food webs, ocean, sediments, and rocks
• Sediments and rocks are the
  main reservoir
• Combustion of fossil fuels changes
  natural balance
 diffusion between
 atmosphere and ocean




       bicarbonate and               combustion of fossil fuels
         carbonate in
         ocean water


   photosynthesis     aerobic
                    respiration

         marine food
           webs

                  death,
incorporation sedimentation
into sediments                    uplifting
                                                    sedimentation
         marine sediments



               Carbon Cycle: Marine
                                 atmosphere


        volcanic action                               combustion of
                                                       fossil fuels

                      photosynthesis     aerobic combustion
        terrestrial                    respiration of wood
          rocks


                                           deforestation
       weathering           land food
                              webs

        soil water
                                                       peat,
                            death, burial,             fossil
leaching,                   compaction over            fuels
  runoff                    geologic time




            Carbon Cycle: Land
        My Carbon Cycle
1. I eat carbohydrate molecules.
– These are molecules of fuel which I will
  “burn”.
– Some of the energy released when I burn
  them will be trapped for me to use. The
  rest will be lost as heat.
2. The waste products of burned fuel
   are carbon dioxide and water. I
   breathe these out.
3. Plants (or other producers) take in
   carbon dioxide from the atmosphere
   and use it to make carbohydrate.
  According to the last slide, why do I
         eat carbohydrates?
1. Because they                               25% 25% 25% 25%
   taste good.
2. Because they
   contain lots of
   vitamins.
3. Because they
   contain lots of
   energy.




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     Energy saved from burning up my
       fuel is saved in the form of :
1.   Muscle                25%       25%   25%   25%
2.   ATP
3.   Fat
4.   Heat



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 The only reason I need to breathe in
             oxygen is :
1. I need oxygen to                             25% 25% 25% 25%
   “burn” fuel
   molecules.
2. All living things
   need oxygen.
3. Oxygen + carbon
   = carbon dioxide.




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            Breathing out :

1. Helps me regulate                          25% 25% 25% 25%
   my body
   temperature.
2. Gets rid of excess
   fuel molecules.
3. Burns extra
   calories.
4. Gets rid of the




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                                                                G
 The carbon in the plants I eat comes
                from :
1.   The atmosphere.                      25% 25% 25% 25%
2.   The food they eat.
3.   The soil.
4.   Water.




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  The carbon in the steak I eat comes
                 from :
1. Supplements in                       25% 25% 25% 25%
   animal feed.
2. Vitamins.
3. The cow’s
   drinking water.
4. The plants eaten
   by the cow.



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       Greenhouse Effect

• Greenhouse gases impede escape of
  heat from Earth’s surface
        Global Warming
Long-term increase in temperature of
      Earth’s lower atmosphere
     Carbon Dioxide Increase

• Carbon dioxide levels fluctuate
  seasonally
• Average level is steadily increasing
• Burning of fossil fuels and deforestation
  are contributing to the increase
     Other Greenhouse Gases

• CFCs: synthetic gases used in plastics
  and in refrigeration
• Methane: released by natural gas
  production, livestock
• Nitrous oxide: released by bacteria,
  fertilizers, and animal wastes
Greenhouse Gases Increasing
Table 30-1, p.537
           Nitrogen Cycle

• Nitrogen is used in amino acids and
  nucleic acids
• Main reservoir is nitrogen gas in the
  atmosphere
• Nitrogen gas can’t enter food web
Fig. 30-16, p.538
       Nitrogen Fixation

• Plants cannot use nitrogen gas
• Nitrogen-fixing bacteria convert
  nitrogen gas into ammonia (NH3)
• Ammonia and ammonium can be
  taken up by plants
             Air Pollution
• Effects of nitrogen oxides released by
  burning fossil fuels

				
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posted:10/23/2011
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