energy pyramids

energy pyramids

When an herbivore eats a plant, the energy in the plant tissues is used by the herbivore. But how much of that energy is transferred to the herbivore? Remember that plants are producers, bringing the energy into the ecosystem by converting sunlight into glucose. Does the plant use some of the energy for its own needs? Recall the energy is the ability to do work, and the plant has plenty or "work" to do. So of course it needs and uses energy. It converts the glucose it makes into ATP through cellular respiration just like other organisms. After the plant uses the energy from glucose for its own needs, the excess energy is available to the organism that eats the plant. The herbivore uses the energy from the plant to power its own life processes and to build more body tissues. However, only about 10% of the total energy from the plant gets stored in the herbivores body as extra body tissue. The rest of the energy is used by the herbivore and released as heat. The next consumer on the food chain that eats the herbivore will only store about 10% of the total energy from the herbivore in its own body. This means the carnivore will store only about 1% of the total energy that was originally in the plant. In other words, only about 10% of energy of one step in a food chain is stored in the next step in the food chain. The majority of the energy is used by the organism or released to the environment. Every time energy is transferred from one organism to another, there is a loss of energy. This loss of energy can be shown in an energy pyramid. An example of an energy pyramid is pictured below ( Figure 1.1). Since there is energy loss at each step in a food chain, it takes many producers to support just a few carnivores in a community. Each step of the food chain in the energy pyramid is called a trophic level. Plants or other photosynthetic organisms ( autotrophs) are found on the first trophic level, at the bottom of the pyramid. The next level will be the herbivores, and then the carnivores that eat the herbivores. The energy pyramid ( Figure 1.1) shows four levels of a food chain, from producers to carnivores. Because of the high rate of energy loss in food chains, there are usually only 4 or 5 trophic levels in the food chain or energy pyramid. There just is not enough energy to support any additional trophic levels. Heterotrophs are found in all levels of an energy pyramid other than the first level.

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instructional diagrams

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questions

plants convert glucose into atp through photosynthesis.

a. true

-->  b. false

because of the constant loss of energy, there can be a maximum of 7 trophic levels in a food chain.

a. true

-->  b. false

how much of the original energy of the producers is available to an organism in the third trophic level?

a) 10%

-->  b) 1%

c) 0.1%

d) 10 grams

which of the following organism would be in the first trophic level?

a) mouse

b) caterpillar

-->  c) maple tree

d) bee

what trophic level has autotrophs?

-->  a) only the first level

b) the first and second levels

c) all levels except the first

d) only the last level

what trophic level has heterotrophs?

a) only the first level

b) only the second level

-->  c) all levels except the first

d) only the last level

in what trophic level would you find a shark?

a) the first level

b) the second level

c) all levels except the first

-->  d) the last level

diagram questions

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