Resource Library

ENCYCLOPEDIC ENTRY

ENCYCLOPEDIC ENTRY

Food Chain

Food Chain

The food chain describes who eats whom in the wild.

Grades

5 - 12+

Subjects

Biology, Ecology

Powered by
Morgan Stanley

The food chain describes who eats whom in the wild. Every living thing—from one-celled algae to giant blue whales—needs food to survive. Each food chain is a possible pathway that energy and nutrients can follow through the ecosystem.

For example, grass produces its own food from sunlight. A rabbit eats the grass. A fox eats the rabbit. When the fox dies, bacteria break down its body, returning it to the soil where it provides nutrients for plants like grass.

Of course, many different animals eat grass, and rabbits can eat other plants besides grass. Foxes, in turn, can eat many types of animals and plants. Each of these living things can be a part of multiple food chains. All of the interconnected and overlapping food chains in an ecosystem make up a food web.

Trophic Levels

Organisms in food chains are grouped into categories called trophic levels. Roughly speaking, these levels are divided into producers (first trophic level), consumers (second, third, and fourth trophic levels), and decomposers.

Producers, also known as autotrophs, make their own food. They make up the first level of every food chain. Autotrophs are usually plants or one-celled organisms. Nearly all autotrophs use a process called photosynthesis to create “food” (a nutrient called glucose) from sunlight, carbon dioxide, and water.

Plants are the most familiar type of autotroph, but there are many other kinds. Algae, whose larger forms are known as seaweed, are autotrophic. Phytoplankton, tiny organisms that live in the ocean, are also autotrophs. Some types of bacteria are autotrophs. For example, bacteria living in active volcanoes use sulfur compounds to produce their own food. This process is called chemosynthesis.

The second trophic level consists of organisms that eat the producers. These are called primary consumers, or herbivores. Deer, turtles, and many types of birds are herbivores. Secondary consumers eat the herbivores. Tertiary consumers eat the secondary consumers. There may be more levels of consumers before a chain finally reaches its top predator. Top predators, also called apex predators, eat other consumers.

Consumers can be carnivores (animals that eat other animals) or omnivores (animals that eat both plants and animals). Omnivores, like people, consume many types of foods. People eat plants, such as vegetables and fruits. We also eat animals and animal products, such as meat, milk, and eggs. We eat fungi, such as mushrooms. We also eat algae, in edible seaweeds like nori (used to wrap sushi rolls) and sea lettuce (used in salads).

Detritivores and decomposers are the final part of food chains. Detritivores are organisms that eat nonliving plant and animal remains. For example, scavengers such as vultures eat dead animals. Dung beetles eat animal feces.

Decomposers like fungi and bacteria complete the food chain. They turn organic wastes, such as decaying plants, into inorganic materials, such as nutrient-rich soil. Decomposers complete the cycle of life, returning nutrients to the soil or oceans for use by autotrophs. This starts a whole new food chain.



Food Chains

Different habitats and ecosystems provide many possible food chains that make up a food web.

In one marine food chain, single-celled organisms called phytoplankton provide food for tiny shrimp called krill. Krill provide the main food source for the blue whale, an animal on the third trophic level.

In a grassland ecosystem, a grasshopper might eat grass, a producer. The grasshopper might get eaten by a rat, which in turn is consumed by a snake. Finally, a hawk—an apex predator—swoops down and snatches up the snake.

In a pond, the autotroph might be algae. A mosquito larva eats the algae, and then perhaps a dragonfly larva eats the young mosquito. The dragonfly larva becomes food for a fish, which provides a tasty meal for a raccoon.

Fast Fact

Carnivorous . . . Plants?
Most plants on Earth take energy from the sun and nutrients from the soil. A few plants, however, get their nutrients from animals. These carnivorous plants include pitcher plants, Venus flytraps, and bladderworts. These plants attract and trap preyusually insectsand then break them down with digestive enzymes.

Fast Fact

Links in the Chain
Organisms consume nutrients from a variety of different sources in the food chain.

  • Xylophages eat wood. Termites and bark beetles are xylophages.
  • Coprophages eat animal feces. Dung beetles and flies are coprophages.
  • Geophages eat earth, such as clay or soil. Parrots and cockatoos are geophages.
  • Palynivores eat pollen. Honeybees and some butterflies are palynivores.
  • Lepidophages are fish that eat the scales (but not the body) of other fish. Some piranha and some catfish are lepidophages.
  • Mucophages eat mucus. Usually, these tiny organisms live in the gills of fish.
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.

Writers
Kim Rutledge, Kim Rutledge
Melissa McDaniel, Melissa McDaniel
Santani Teng, Santani Teng
Hilary Hall, Hilary Hall
Tara Ramroop, Tara Ramroop
Erin Sprout, Erin Sprout
Jeff Hunt, Jeff Hunt
Diane Boudreau, Diane Boudreau
Hilary Costa, Hilary Costa
Illustrators
Mary Crooks, National Geographic Society,
Tim Gunther, Tim Gunther
Editors
Jeannie Evers, Emdash Editing, Emdash Editing
Kara West, Kara West
Educator Reviewer
Nancy Wynne,
Producer
National Geographic Society, National Geographic Society
other
Last Updated

May 20, 2022

For information on user permissions, please read our Terms of Service. If you have questions about licensing content on this page, please contact ngimagecollection@natgeo.com for more information and to obtain a license. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. She or he will best know the preferred format. When you reach out to him or her, you will need the page title, URL, and the date you accessed the resource.

Media

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

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

Interactives

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

Related Resources