Chapter 4: Ecosystem Structure and Function

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Chapter 4 Ecosystem Structure and Function
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Ecosystems

• Study of how organisms interact with each other
  and with the biotic EVR
• Organism -gt species-gt population -gt community -gt
  ecosystem
• Each species has a range of tolerance
  physical/chemical EVR, biotic/abiotic factors

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Ecosystems

• Purpose of an organism to reproduce
  successfully, ensure offspring reproduce
  successfully with genetic variation as the lowest
  energy cost
• Adaptations chemical/physical/behavioral
  changes to increase survival rates

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The earth can be divided into layers

• Atmosphere
• Trophosphere goes up 11 miles, greenhouse
  contains ozone
• Stratosphere ozone layer, filter out harmful
  UV rays
• Hydrosphere all the ice, H2O, and H2O vapor
• Lithosphere the land (crust/mantle)

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What sustains life on earth?

• The one-way flow of high-quality energy
• The cycling of matter or nutrients
• Gravity
• Allows the planet to hold onto its atmosphere
• Causes the downward movement of nutrients

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How does the sun sustain life on earth?

• Supplies light energy needed for photosynthesis
• Warms the earth
• Drives the weather systems that distribute heat
  and fresh water

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Principles of Ecosystem Functioning

• Ecosystems run on solar energy.
• Nutrients are recycled in an ecosystem.
• Ecosystems cannot support large numbers of top
  consumers
• the amount of energy is limited
• energy is lost as heat AND is used to keep
  consumers alive so the amount of energy available
  decreases as we move up the food chain

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Ecosystem Structure the living components of an
ecosystem

• The roles of organisms in an ecosystem
• Producer (autotrophs) make food plants, algae
• Consumer (heterotrophs) eat other organisms
• Decomposer eat dead organic matter bacteria
  and fungi

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Role of organisms

• Classes of Consumers
• Herbivore primary consumer eats plants
• Carnivores secondary meat eaters eat
  herbivores
• Tertiary feed on carnivores
• Omnivores eat plants/animals

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Role of Organisms

• Scavengers feed on dead organisms (vultures,
  flies, crows, lobsters)
• Detritus feeders organisms that extract
  nutrients from fragments of dead organisms into
  more simple organic waste (termites, earthworms,
  crabs)
• Decomposers organisms that digest parts of the
  dead organisms into simplest chemicals (bacteria,
  fungi)

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Ecosystem Function

• 1. Energy flow in an ecosystem is represented by
  a food web.

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• The amount of energy available to the organisms
  at each trophic level decreases as one moves up
  the food chain since
• energy is lost as heat and
• organisms use energy to sustain themselves
• Remember the laws of energy?

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• Because the amount of energy decreases at each
  successive trophic level, the number of organisms
  also decreases
• Only approximately 10 of the energy is
  transferred to the next trophic level.
• So, are there more producers or consumers on
  Earth?

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Energy and biomass pyramids
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The amount of energy available in an ecosystem
depends on the type of vegetation the area can
support.This is measured as an areas net
primary productivity (NPP).The higher the NPP,
the greater the diversity of animals in that
ecosystem.
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The net primary productivity of biomes
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Ecosystem Function (cont)

• 2. Nutrients are recycled within an ecosystem.
• Water Nitrogen
• Carbon Phosphorus
• Oxygen Sulfur

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Water Cycle

• condensation of water vapor in the air leads to
  precipitation
• evaporation returns water vapor to the atmosphere
• infiltration of rainwater replenishes groundwater
  supplies
• surface runoff of rainwater replenishes surface
  water supplies

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Carbon Cycle

• CO2 is taken up by plants during photosynthesis
• CO2 is released by organisms during respiration
  and decomposition fires, volcanoes
• CO2 is also released by autos and industries
• carbon, present in all organic molecules, moves
  through the food chain as one organism eats
  another

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Carbon Cycle

• Sinks
• - Lithosphere limestone (largest reservoir)
• - hydrosphere ocean (2nd largest)
• - Atmosphere in form of CO2
• - biosphere wood, plants, dead animals

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Oxygen Cycle

• Essential for animals during respiration,
  released by plants
• Cycles much like the carbon cycle
• What is threatening this cycle? Forest
  deforestation, ocean pollution, etc

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Nitrogen Cycle

• 78 of the volume of trophosphere
• Most complex cycle
• N2 gas cant be used as is it must be fixed
  so that organisms can use it
• Steps to the cycle b/c of complexity, no certain
  order
• N Fixation occurs in plant, by bacteria
• Ammonification
• Nitrification
• Assimilation
• Denitrification
• N2 gas is modified by nitrogen-fixing bacteria
  in legumes into ammonia (NH3) NITROGEN FIXATION
  aids in production of sugars/starches
• Bacteria turn wastes and detritus into ammonia
  AMMONIFICATION released into atm
• NH3 is converted into nitrite (NO2-) which is
  then used to produce nitrate (NO3-) -
  NITRIFICATION

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Nitrogen cycle (cont)

• Plant roots take up the ammonia and nitrate ions
  and converts it into amino acids, proteins,
  DNA/RNA Assimilation
• other bacteria convert nitrite (NO2-) into N2 gas
  - DENITRIFICATION
• nitrogen, present in proteins, moves through the
  food chain as one organism eats another

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Phosphorus Cycle

• phosphorus is released as rocks erode and plants
  assimilate this
• Very slow process
• phosphorus passes from one organism to another in
  the food chain
• decomposers release phosphorus during
  decomposition
• Mined for production of fertilizer. Mined in
  Tampa, FL

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Sulfur Cycle

• sulfur is released as rocks erode and plants
  assimilate this
• Mostly found under ground like phosphorus
• H2S is released by decomposers and during
  volcanic eruptions some H2S in soil is converted
  into sulfur by aerobic bacteria and plants
  assimilate this
• 99 of all sulfur in the atm is due to man
• SO2 gas is released by industries SO2 then
  reacts with water to form H2SO4 which falls to
  the earth as acid rain

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