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Ecosystems are comprised of a community of organisms that interact with one another. Organisms depend on each other for food. The food supplies energy needed to carry out the biological processes that are required each day. Organisms are made of matter, so within ecosystems, you can begin to see a relationship between energy and matter. Because organisms are made of matter, they have energy trapped within them. If you remember from Lesson 1.02, chemical energy is the energy trapped within the bonds of matter. This means that all living things have the potential to be a source of energy for other living things.

To better see the relationship between energy and matter, scientists often represent the energy and biomass present in an ecosystem in the form of an ecological pyramid or energy pyramid.

Energy pyramids are used to show how much energy is available in each of the different trophic levels. Because the amount of energy is proportional to the amount of matter in an ecosystem, these pyramids can also show how much matter or biomass is available in each trophic level. When you examine an energy pyramid, you see that the base of the pyramid is bigger than the levels above it, and each individual level is smaller than the one below. The base is always bigger because this makes the entire structure stable.

Energy pyramids are set up with the organisms with the most available energy at the bottom.

  • The first level is the producer trophic level.
  • The second level is made up of the primary consumers.
  • The third level is the secondary consumers, and
  • the fourth level is the tertiary consumers.
Since they are the base of the pyramid, the producers are the level within ecosystems that have the most energy available-followed by the primary consumers, secondary consumers, and then the tertiary consumers. Since matter and energy are directionally proportional (as the amount of energy increases, the amount of matter/biomass increases), the producer level has the greatest biomass and the tertiary consumers have the least biomass.

Therefore, it can be stated that there are a greater number of organisms that are producers than there are the number of tertiary consumers. If something occurs where there are more primary consumers than producers, an ecosystem becomes unstable and likely to have problems or even collapse. More primary consumers than producers could mean that the primary consumers will deplete all of the energy resources/food available to them. When this happen, the primary consumers will begin to die off creating less food and energy available for the secondary consumers. Unless stopped, this will eventually affect the primary consumers and the whole ecosystem could disappear.

Visit the following interactive on energy pyramids to learn more.

Not all of the energy in a trophic level is available to the level above it. About 90% of the energy in a trophic level is used by the organisms in that level for biological process, such as growth, reproduction, and hunting. This means that only about 10% of the energy in a trophic level is available to the next level above it. This is the case for each trophic level. This is why the number of individual organisms is lower than the trophic level below it.

To get an estimate of how much energy in one trophic level is available to the next trophic level, you multiply the amount of energy (expressed in Joules) by 0.10. This will show you the approximate amount of available energy.

Available Energy= Energy X 0.10. So if there are 10,000 J of energy located in the producers level of an ecosystem, you would do the following: 10,000 X 0.10= 1,000 Joules of energy that can be passed to the primary consumers. How much energy would be available to the secondary consumers? 1,000 X 0.10= 100 Joules.

Discovery Education Streaming

View the following video clip to see how and why energy and matter are distributed within an ecosystem. Login Instructions

 

 

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