CogKnoSys

Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.

Physical

Food Chains

A food chain is a single path through a food web, showing how energy passes from producers to the animals that eat them.

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The idea

A food chain shows who eats whom in nature, one link at a time. It usually begins with a producer, such as grass or algae, that makes its own food. It often ends with an apex predator, such as a grizzly bear or killer whale, or with decomposers, such as fungi and bacteria, that break down dead matter. A food chain is one straight path through a food web, the larger network of feeding links in an ecosystem.

Each step in a food chain is called a trophic level, from a Greek word for food or nourishment. Plants and other producers are at level 1, herbivores are at level 2, and carnivores are at level 3 or higher. Apex predators usually sit at level 4 or 5. Scientists often describe a chain by its length, which is the number of links between a consumer and the base of the chain.

Energy enters a food chain through the producers and then moves up through the levels. Living things use up much of the energy they take in, so less is passed on at each step and long chains are rare. Food chains can also be fragile. Removing even one member can push other species toward extinction, especially if it is a keystone species with a large effect on its environment.

Check yourself

Question 1 of 2

At which trophic levels do apex predators usually sit?

Pick one. The first pick counts.

Composition

what it's made of

  • Producers — Plants, algae and other autotrophs that make their own food and start the chain.
  • Herbivores — Plant eaters at trophic level 2.
  • Carnivores — Meat eaters at trophic level 3 or higher.
  • Apex predators — Top hunters, such as killer whales, usually at trophic level 4 or 5.
  • Decomposers — Fungi and bacteria that break down dead matter and can end a chain.

Connection

how it relates

Under Ecosystems

Related

  1. Energy Formsstrength 70 of 100

    A food chain is a path along which energy stored in food moves from one living thing to the next.

  2. Chinook Salmonstrength 60 of 100

    Chinook salmon are a link in many food chains: they eat smaller fish and are eaten by killer whales, bears and people.

  3. Digestive Systemstrength 40 of 100

    Digestion is how an animal breaks down the food it eats and takes in the energy passed along the chain.

Change

how and why it evolves

Past
Ecologists first described feeding relationships as simple chains, and later showed that chains link together into larger food webs.
Now
Today ecologists pay special attention to keystone species, because losing one could upset the balance of a whole food chain.
Next
As climate and habitats change, scientists will likely keep tracking how losing or adding species reshapes food chains.

Knowledge you can walk. Read the idea, then step up, across or down.

Food Chains

A food chain is a single path through a food web, showing how energy passes from producers to the animals that eat them.

Learn, discuss, create, buy or invest

The idea

A food chain shows who eats whom in nature, one link at a time. It usually begins with a producer, such as grass or algae, that makes its own food. It often ends with an apex predator, such as a grizzly bear or killer whale, or with decomposers, such as fungi and bacteria, that break down dead matter. A food chain is one straight path through a food web, the larger network of feeding links in an ecosystem.

Each step in a food chain is called a trophic level, from a Greek word for food or nourishment. Plants and other producers are at level 1, herbivores are at level 2, and carnivores are at level 3 or higher. Apex predators usually sit at level 4 or 5. Scientists often describe a chain by its length, which is the number of links between a consumer and the base of the chain.

Energy enters a food chain through the producers and then moves up through the levels. Living things use up much of the energy they take in, so less is passed on at each step and long chains are rare. Food chains can also be fragile. Removing even one member can push other species toward extinction, especially if it is a keystone species with a large effect on its environment.

Check yourself

2 quick questions, instant feedback.