ECOSYSTEM ECOLOGY

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ECOSYSTEM ECOLOGY
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Objective

• I will be able to explain how energy flows
  through ecosystems while matter is recycled.

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Ecosystem Ecology

• Ecosystem the sum of all the organisms living
  within its boundaries and all the abiotic factors
  with which they interact.
• Ecosystems are all about the flow of energy and
  cycling of matter.
• The Laws of Thermodynamics explain the flow of
  energy and cycling of matter.

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Flow of Energy in Ecosystems

• Food Chain a linear model that shows how energy
  moves through an ecosystem.
• Food Web consists of two or more food chains.
• Trophic level position an organism occupies in
  a food chain.
• (trophic feeding)
• Primary producers autotrophs (self-feeders).
• Primary consumers through tertiary consumers
  heterotrophs (other-feeders).
• Detritivores or decomposers get their energy from
  dead organisms, feces, and wood.
• Found on all trophic levels.

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Food Chain
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Food Web
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10 Rule

• Energy transfer between trophic levels is
  typically only 10 efficient.
• 90 of energy at each trophic level is used for
• life processes (growth, cellular respiration,
  reproduction, movement, etc.),
• some energy is converted to heat.
• Heat is energy that cannot be harnessed by
  organisms to do work and thus represents unusable
  energy that cannot be recycled.

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The 10 RULE . . .
There isnt much ENERGY left near the top.
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Pyramid of Numbers
It takes over 5 million primary producers to
support 3 tertiary consumers.
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• Draw an example of an energy pyramid with four
  trophic levels.
• Label the trophic levels and indicate the amount
  of energy available at each level.

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Recycling of Matter in Ecosystems

• Biochemical or nutrient cycles describe the
  cycling of essential elements in ecosystems.
• Most important biochemical cycles
• Water cycle.
• Carbon cycle.
• Nitrogen cycle.
• Phosphorus cycle.

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Review of the Water Cycle
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Carbon Cycle

• Carbon is required for the building of
  carbohydrates, lipids, proteins, nucleic acids,
  and other organic molecules.
• CO2 from the air is taken in by plant leaves and
  incorporated into sugars (photosynthesis).
• Plants are eaten by animals.
• C is returned into air by
• Respiration and decomposition,
• Burning of fossil fuels (made from decayed
  plants).

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Nitrogen Cycle

• Nitrogen is required for the manufacture of
  proteins and nucleic acids.
• N2 makes up 78 of air but N2 is unusable for
  plants and animals.
• N2 must be converted into usable nitrogen
  containing compounds
• ammonium NH4 and nitrate NO3-.
• Nitrogen fixation N2 ? NH3 (ammonia)? NH4
• Nitrification NH4 ? NO2- (nitrite) ? NO3-
• This happens
• 1. naturally by bacteria living in roots of
  legumes or by lightening,
• 2. in labs (chemical fertilizers).
• Plants absorb NH4 and NO3- through roots
  (assimilation).
• Animals eat plants.
• Nitrogen is returned to soil when organisms
  release waste or die.
• Bacteria change NO3- to N2 (denitrification) and
  return it to the air.

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Phosphorus Cycle

• Phosphorus is required to make ATP, nucleic
  acids, cell membranes, and bones.
• No gaseous form found in rocks.
• Released by weathering, absorbed by plant roots.
• Plants are eaten by animals.
• P is released into the soil when organisms
  release waste or die.
• Artificial supply fertilizers.
• Biochemical cycles of other minerals, such as
  calcium and magnesium, are similar to the
  phosphorus cycle.

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Remember

• Energy flows
• Matter cycles

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Math Connection

• Carbon Flow in a Grassland Ecosystem
• How much carbon (in g/m2) is released into the
  atmosphere as a result of the metabolic activity
  of herbivores? Give your answer to the nearest
  whole number.

Respiration 4 g/m2
Respiration  
125 g/m2
5 g/m2
Herbivores
Grass
Predators
60 g/m2
125 g/m2 (Litter)
1 g/m2
250 g/m2 (Roots)
Respiration 336 g/m2
Soil/Decomposers
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Summary/Short Essay

• Use the 1st and 2nd laws of thermodynamics to
  compare the flow of energy and recycling of
  matter in ecosystems.