Energy Flow and the 10 Percent Rule

Energy Flow and the 10 Percent Rule

On average only 10 percent of energy available at one trophic level is passed on to the next. This is known as the 10 percent rule, and it limits the number of trophic levels an ecosystem can support.


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Biology, Ecology

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Every organism needs energy. They need it to grow and breathe. They get their energy from an ecosystem.

An ecosystem is like a community. It is made up of living and nonliving things. These include soil, plants and animals.

An ecosystem gets energy from the sun. Then, plants use sunlight to make biomass. That is a type of energy. It is the energy in living organisms.

Next, animals get energy from eating plants. Other animals get it from eating other animals. The energy moves all the way up the food chain. A food chain is like a path. It's how energy moves through an ecosystem.

Producers and Consumers

Food chains have different levels. These are called trophic levels.

Plants are at the bottom level. These organisms are called primary producers. They make their own food. Plants use photosynthesis. They do this with help from the sun. They use the sun, soil, air, and water to make nutrients. This is how plants turn the sun's energy into energy that living things can use.

The next level is made up of primary consumers. These are organisms that cannot make their own food. They have to eat other living things. They eat producers. Some consumers only eat plants. Others eat plants and animals.

The third level contains secondary consumers. They eat the primary consumers. Organisms at this level include carnivores. These are animals that only eat other animals. They are also called predators.

Organisms in the next level are called tertiary consumers. They eat the secondary consumers.

Moving Energy from One Level to the Next

Only so much biomass, or energy, can move from one trophic level to the next. Energy is lost at each step along the food chain.

An energy pyramid is a good way to think about energy loss. It shows you how energy moves from one level to the next. Each step of the pyramid is a different level. Producers are at the bottom. Tertiary consumers are at the top.

The size of the step relates to the amount of energy at each level. The steps get smaller as you go up the pyramid. That is because more energy is lost at each level. Eventually, the steps cannot get any smaller. So, the pyramid ends.

Only 10 percent of energy moves from one level to the next. This idea is called the 10 percent rule. Let's say a primary consumer eats a producer">primary producer. The consumer only gets 10 percent of the producer's energy. For example, an insect eats a plant. The insect only gets 10 percent of the energy from the plant. The animal that eats the insect would only get 10 percent of the energy from the insect. This continues all the way up the food chain.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Tyson Brown, National Geographic Society
National Geographic Society
Production Managers
Gina Borgia, National Geographic Society
Jeanna Sullivan, National Geographic Society
Program Specialists
Sarah Appleton, National Geographic Society, National Geographic Society
Margot Willis, National Geographic Society
Clint Parks
Roza Kavak
Last Updated

October 19, 2023

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