Ecosystems

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					Ecosystems

 Chapter 30
              Ecosystem

• Definition: An array of organisms
  together with their physical environment.

• Interconnected through:
  – one-way flow of energy
  – cycling of raw materials


• Needs continual energy inputs
  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)
                Consumers

                                           fruits             SPRING
•   Herbivores              rodents,
                                                    insects

                            rabbits
•   Carnivores                                       birds


•   Parasites
•   Omnivores                          fruits                 SUMMER


•   Decomposers and      rodents,
                         rabbits                    insects

    Detritivores                       birds



                      seasonal variation in the diet of an
                      omnivore (red fox)
                            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
                          marsh hawk


Higher
Trophic                       crow                   Connections in a
Levels                                          tallgrass prairie food web
              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
Pyramid of Energy
  Biological Magnification

Nondegradable or slowly degradable
substances become more and more
concentrated in tissues of organisms at
higher trophic levels of a food web
  DDT in Food Webs
• Synthetic pesticide banned in
  United States since 1970s
• Carnivorous birds accumulate
  DDT in their tissues, produce
  brittle egg shells
      Primary Productivity

• Gross primary productivity is
  ecosystem’s total rate of photosynthesis

• Net primary productivity is rate at which
  producers store energy in tissues in
  excess of their aerobic respiration
     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 and decomposition
  continues the 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
Water and Climate
             Watershed

• A region where
  precipitation is
  funneled into a
  single stream or
  river
Ogallala aquifer
First used for irrigation
in 1911.
Widely used after
1930’s.

Now produces
irrigation for 20% of
Midwest crops.

Water table has
dropped as much as 5
feet in some places.
             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
           Carbon Cycle

• Carbon moves in gaseous form

• Main source in sediments and rocks.

• Ocean water, soil, atmosphere, and
  biomass also produce carbon.
 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
                                 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
Fossil Fuels
      Greenhouse Effect

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


        CO2           Methane




       CFCs
                        N 2O
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
• Nitrogen fixation – bacteria convert nitrogen to
  useable forms like ammonia; further converted
  to ammonium and nitrate
Fig. 30-16, p.538
       Phosphorus Cycle

• Phosphorus is part of phospholipids,
  nucleotides, NADH, ATP

• Main limiting factor in ecosystems

• Reservoir is Earth’s crust; no gaseous
  phase
                                                mining          FERTILIZER
  excretion                GUANO
                                                                                          agriculture
                uptake     weathering                                         uptake
                  by                                                            by
              autotrophs                                                    autotrophs
                                            weathering
  MARINE             DISSOLVED                                  DISSOLVED IN             LAND
   FOOD               IN OCEAN                                  SOIL WATER,              FOOD
   WEBS                 WATER                                  LAKES, RIVERS             WEBS
              death,                                                      death,
          decomposition                                               decomposition
                            settling
sedimentation                 out                        leaching, runoff

                                            uplifting
        MARINE SEDIMENTS                                         TERRESTRIAL ROCKS
                                        over geologic time
              Eutrophication
• Runoff from
  phosphate fertilizers
  accelerates algal
  growth in waterways

• Resulting dense algal
  blooms cause system
  overload and death

				
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