1 (d) Energy Pyramid

Energy Pyramids
When an organism in an ecosystem eats, it obtains energy. The organism uses some of this energy to move, grow, reproduce, and carry out other life activities. This means that only some of the energy it obtains will be available to the next organism in the food web.

A diagram called an energy pyramid shows the amount of energy that moves from one feeding level to another in a food web. You can see an energy pyramid in Figure 3. The most energy is available at the producer level of the pyramid. As you move up the pyramid, each level has less energy available than the level below. An energy pyramid gets its name from the shape of the diagram—wider at the base and narrower at the top.

In general, only about 10 percent of the energy at one level of a food web is transferred to the next higher level. The other 90 percent of the energy is used for the organism’s life processes or is lost to the environment as heat. Since about 90 percent of the energy is lost at each step, there is not enough energy to support many feeding levels in an ecosystem.

The organisms at higher feeding levels of an energy pyramid do not necessarily require less energy to live than do the organisms at lower levels. Since so much energy is lost at each level, the amount of energy available at the producer level limits the number of consumers that the ecosystem is able to support. As a result, there are usually few organisms at the highest level in a food web.

R.C.P.  Why is the pyramid shape useful for showing the energy available at each of the levels of the food web?