Energy Flow in Ecosystems

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Chapter 3

• Energy Flow in Ecosystems

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Activity

• Ingredients
• ½ bathtub of oxygen
• 50 glasses of water
• ½ cup sugar
• ½ cup calcium
• 1/10 thimbleful of salt
• Some assorted elements K, N, Ph, Su, Mg, etc.
• Mystery ingredient?

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Energy Transfer

• In the transfer of energy, organisms are one of
  two things
• Producers
• Consumers
• A producer is an organism that can make its own
  food.
• A consumer is an organism that gets it energy by
  eating other organisms.

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The Sun

• Almost all organisms get their energy from the
  sun
• Producers get it directly from the sun.
• Consumers get it indirectly from the sun.
• The exception to this rule is deep ocean
  Ecosystems.

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What Eats What?

• Herbivores Consumers that eat only producers.
• Carnivores Consumers that eat only other
  consumers.
• Omnivores Consumers that eat both consumers and
  producers.
• Decomposers Consumers that get their food by
  breaking down dead organisms, causing them to rot.

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Burning the Fuel

• Photosynthesis The process by which producers
  turn water and CO2 into sugar and oxygen.
• Photosynthesis
• 6CO2 6H20 ? C6H12O6

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Burning the Fuel

• Cellular Respiration The process of breaking
  down food to yield energy.
• Cellular Respiration
• C6H12O6 O2 ? 6CO2 6H2O energy.

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Food Chains and Food Webs

• Every time one organism eats another, a transfer
  of energy occurs.
• A food chain is a sequence in which energy is
  transferred from one organism to the next as each
  organism eats the other.

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Food Chains and Food Webs

• Is a food chain as accurate as we can get?
• No, there are many more species of organisms
  present in an ecosystem at any given time
• A food web shows many of the food relationships
  in an ecosystem.

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Trophic Levels

• Each step in the transfer of energy through an
  ecosystem is known as a trophic level.
• Each time energy is transferred, less of it is
  available to organisms at the next trophic level.
  
• Where is the energy going?

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Trophic Levels

• Some of the energy is lost while converting food
  to energy.
• Much of the rest is used in carrying out the
  functions of living.
• Regulating body temperature, producing new cells,
  moving around.

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Trophic Levels
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Trophic Levels

• Think of it like this
• You buy a CD for 15.oo ? the store keeps a large
  amount for handling and storing ? the record co.
  gets some for producing and distributing ? the
  agent gets some for promoting ? finally the band
  gets some.

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The Cycling of Materials

• Three main cycles of the ecosystem
• The Water Cycle
• The Carbon Cycle
• The Nitrogen Cycle

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The Water Cycle

• Water is essential to life.
• Water moves between the earths surface and the
  atmosphere in a process called the water cycle.

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The Water Cycle

• Heat from the sun evaporates water from oceans,
  lakes, etc. ?
• water cools in the atmosphere ?
• the water condenses and forms tiny droplets in
  clouds ?
• when the clouds meet cold air, the droplets fall
  as precipitation.
• Precipitation rain, sleet or snow.

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The Carbon Cycle

• Carbon is an essential component of the proteins,
  fats, and carbohydrates necessary for life.
• The Carbon cycle is the movement of carbon
  between the earths surface and atmosphere.

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The Carbon Cycle

• Producers take in carbon from the atmosphere
  during photosynthesis ?
• Consumers eat the producers ?
• During cellular respiration, the carbon is
  released back out as CO2 ?
• The process starts again.

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How are we affecting the carbon cycle?
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The Nitrogen Cycle

• All organisms need N2 to build proteins.
• N2 gas makes up 78 percent of the earths
  atmosphere.

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The Nitrogen Cycle

• Only nitrogen-fixing bacteria can use the N2
  directly from the atmosphere.
• The fix the N2 into a form that the ecosystem
  can use.
• The bacteria have a mutualistic relationship with
  plants.
• They fix N2 for the roots while the plant
  provides sugar for the bacteria.

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The Nitrogen Cycle

• Lightning also fixes some N2 which then falls to
  earth.

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The Nitrogen Cycle

• So how does the N2 get back into the atmosphere?
  
• Bacteria and fungi act as decomposers and break
  down wastes and dead organisms.
• This returns the N2 back to the soil.
• Once back in the soil, bacteria again turn in
  back into gas and return in to the atmosphere,
  completing the cycle.

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How Ecosystems Change

• Changes in an ecosystem are called succession.
• Succession is a regular pattern of changes over
  time in the type of species in a community.
• The process may take hundreds or thousands of
  years.

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Succession
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Succession

• Each new community that arises makes it more
  difficult for the previous one to survive.
• Pine tree example.
• The community that eventually forms if the land
  is left undisturbed is called the climax
  community.

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Secondary Succession

• Succession that occurs on a surface where an
  ecosystem has previously existed is called
  secondary succession.
• For example, consider Mount St. Helens

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Secondary Succession
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Secondary Succession
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Secondary Succession
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Secondary Succession

• Another example is old-field succession.
• When a farmer stops planting and cultivating,
  grasses and weeds quickly move in.
• These plants are called pioneers, the first
  organisms to colonize any newly available area
  and start the succession.

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Fire Maintained Communities

• Natural fires caused by lightning are a necessary
  part of secondary succession in some communities.
• Some pines (The Jack) pine need the heat of the
  fire to release their seeds.
• Fire clears out dead wood and brush that could
  cause larger fires.
• Animals feed on the vegetation that sprouts after
  a fire has passed.

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Primary Succession

• Succession that occurs on surfaces where no
  ecosystem existed before is called primary
  succession.
• This occurs on new lands created by volcanoes or
  when a glacier retreats.
• It is much slower than secondary because it
  begins where there is no soil.
• Bacteria and lichens are usually the first to
  inhabit a new area, they dont need soil to live.

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Primary Succession

• A lichen is actually composed of two organisms in
  a mutualistic relationship.
• A fungus
• An algae
• The algae photosynthesizes for the fungus and the
  fungus absorbs nutrients from the rock.
• Together they break down the rock.

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