Feeding Levels

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Feeding Levels

• Science 10

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Every ecosystem is made up of different tropic
(feeding) levels.

• The first tropic level contains the producers
  (plants, trees, etc).
• The second tropic level contains the primary
  consumers (herbivores).

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Tropic levels continued

• The third tropic level contains the secondary
  consumers (omnivores).
• The fourth tropic level contains the top
  predators (tertiary consumers/carnivores).

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What about the scavengers?

• Decomposers (fungi, bacteria) are not represented
  by these trophic levels.
• They feed at all levels on dead plants and
  animals, as well as on waste.

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30 kJ thermal energy to the environment
Food eaten 100kJ
10 kJ energy to body tissues (heat)
60 kJ energy to decomposers

• Most of the energy entering each tropic level is
  wasted. It is either changed into heat and
  released or used for bodily functions
  (reproduction, digestion).

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How much is passed on?

• Only 10 of energy that is taken in is passed on
  to the next trophic level.

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• Therefore, higher tropic levels have less energy
  available due to waste at lower levels. This is
  why top predators are rare.

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Pyramid diagrams are used to represent organisms
in an ecosystem.

• Pyramid of numbers shows how many of each
  organism is in an ecosystem.
• Pyramid of biomass shows what weight of each
  organism is in an ecosystem.
• Pyramid of energy flow shows how much energy is
  at each trophic level in an ecosystem.

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Pyramid of Numbers

• The concept that numbers of organisms generally
  decrease as one progresses towards the top of a
  food chain.

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Pyramid of Biomass

• The concept that the mass (or weight) of all the
  organisms in each tropic level usually decreases
  as one progresses towards the top of a food chain.

1.5 g/m2 tertiary consumers 11 g/m2 secondary
consumers 37 g/m2 primary consumers 809 g/m2
producers
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Pyramid of Energy Flow

• The concept that the energy available to
  organisms at each trophic level ALWAYS decreases
  as one progresses towards the top of a food chain.

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The Calculation

• In the following food chain, if the grass
  contains 5000kJ of energy, how much gets passed
  on to the organisms and how much do they use?
• Grass ? Deer ? Wolf

Organism Energy Available (kJ) Energy Used (kJ) Energy Stored (kJ)
Grass
Deer
Wolf
Then draw the pyramid!