Matter and Energy in Ecosystems

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Matter and Energy in Ecosystems

• Almost all energy in the ecosystem comes
  originally from the sun.
• Food chains show the direction of
• energy transfer.
• Example Algae ? Fish ? Heron

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Drawing a Food Chain
Food chains represent the flow of energy as
one organism is consumed by another. The
arrow should be drawn from the organism being
consumed to the consumer.
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• Trophic level
• a step in the food chain.
• What type of organism is always at the 1st
  trophic level?
• autotroph/producer
• What type(s) of organism can be at the 2nd
  trophic level?
• herbivore or omnivore

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Ecological Pyramid

• When you compare the biomass (mass of living
  things) at each level of a food chain, it forms a
  pyramid.
• The greatest mass is always the autotrophs
  (producers) with decreasing amounts at higher
  trophic levels.

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• The Law of Conservation of Energy states that
  matter can not be created or destroyed. Yet the
  energy pyramid shows that less energy is
  available as you move up a food chain. What
  happens to the rest of the energy?

Much of the energy that an organism consumes is
given off in the form of heat.
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• Implications of the Energy Pyramid
• It takes approximately 16 x more energy to
  produce a pound of beef as it does to produce a
  pound of soybeans, since much of the energy
  consumed by the cow is transformed to heat.

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Bioaccumulation and Biomagnification

• Bioaccumulation a toxin that remains in body
  tissue.
• Toxins that bioaccumulate include PCBs, DDT and
  mercury.
• Biomagnification an increase in the
  concentration of a substance in organisms higher
  up the food chain.
• This occurs because each step in the food chain
  must consume a greater amount of the previous
  level.

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Concentration of a toxin increases up a food
chain.
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• King mackerel is a fish that tends to be high
  in mercury, tilapia is a fish that is usually low
  in mercury contamination. Predict what that
  indicates about their roles in the food chain.
• Fish that are high in mercury contamination
  tend to be fish at the top of the food chain
  (king mackerel, shark).

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Food Webs

• Many heterotrophs feed on more than one type of
  organism.
• So most communities have energy flow in a food
  web, made of interacting food chains.

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Population Growth Patterns

• Under ideal conditions, the reproductive rates of
  species allows for exponential growth.
• Exponential growth is growth in which the rate
  of change is proportional to the amount (and
  therefore increases by an increasing amount,
  forming a J-shaped curve).

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Population Growth Patterns

• Most populations must compete for limited
  resources and their growth levels off after a
  period of exponential growth.
• This pattern forms an S-shaped graph and is
  called logistic growth.

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Carrying Capacity

• Carrying capacity is the maximum number of a
  species that a particular environment can
  normally support.