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.


2 - 12


Biology, Ecology

NGS Resource Carousel Loading Logo
Loading ...
Selected text level

All organisms need energy to live. They need it to grow and breathe. They get this energy from an ecosystem.

Ecosystems are like communities. They are made up of all the living and nonliving things in an area. These include soil, plants, and animals.

First, an ecosystem gets most its energy from the sun. Next, plants change the sun's energy into biomass. Biomass is the energy in living organisms. Then, the energy moves to animals that eat the plants. As organisms eat other organisms, the energy moves all the way up the food chain. A food chain is a path that energy takes through an ecosystem.

Producers and Consumers

Living things in food chains are grouped into categories. These are called trophic levelsOrganisms are grouped based on how they obtain their food.

Organisms in the first trophic level are called primary producers. Producers are organisms that make their own food. Plants are common producers. They use photosynthesis to make their food. Plants do this with help from the sun. They use the sun, soil, air, and water to make nutrients. This is how plants convert the sun's energy into energy that living things can use.

Organisms in the second trophic level are called primary consumers. Consumers can't make their own food. They have to eat other living things to survive. They eat producers. Some consumers eat only plants. Others eat both plants and animals.

The third trophic level contains secondary consumers. They eat the primary consumers. Organisms in this trophic level include carnivores. These are animals that only eat other animals.

Tertiary consumers make up the fourth tropic level. 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 shows the flow of energy between trophic levels. Each step of the pyramid is a different trophic level. The producers are at the bottom level. The tertiary consumers are at the top level.

The size of each step shows how much energy moves between levels. The steps get smaller as you travel up the pyramid. This is because energy is lost at every level in the food chain. Eventually, the step can't get any smaller. This is where the pyramid ends.

Only 10 percent of energy moves from one trophic level to the next. This is known as the 10 percent rule. For example, let's say a primary consumer eats a producer">primary producer. The consumer only gets 10 percent of the producer's energy. So, if an insect eats a plant, it only gets 10 percent of the energy from the plant. The animal that eats the insect would only receive 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

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.


If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.


Text on this page is printable and can be used according to our Terms of Service.


Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.