What is a Decomposer? - Definition & Examples

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  • 0:00 What Are Decomposers?
  • 0:45 Job Categories of Organisms
  • 1:40 How Do Decomposers Work?
  • 2:55 How People Use Decomposers
  • 3:50 Lesson Summary
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Lesson Transcript
Terry Dunn

Terry has a master's degree in environmental communications and has taught in a variety of settings.

Expert Contributor
Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

Decomposers are an often overlooked part of the natural world, but their job is an important one. Learn what decomposers are, what role they have in the environment and how people use them.

What are Decomposers?

Imagine this scene... bodies are piled high, everything from birds and mammals to lizards and frogs. Mixed in are leaves, branches, feces, and even dead people. The stench is overwhelming. You try to turn away, but you are surrounded. It sounds like a horror movie, but at this show, you can't even have a grilled cheese sandwich with a glass of wine while watching the horrors unfold. Where are you? In a world without decomposers.

It may be unpleasant to think about, but decomposers do the natural world's dirty work. They are responsible for eliminating dead and dying organisms, and in the process, they release nutrients into the soil.

Job Categories of Living Organisms

There are three categories of jobs that living organisms have in the environment. Producers are green plants that produce their own food using the sun's energy. Consumers need to eat other living things, such as plants or animals (or both), to get their energy. Decomposers have the job of 'recycling' dead organisms and waste into non-living elements.

Examples of decomposers include bacteria, fungi, some insects, and snails, which means they are not always microscopic. Fungi, such as the Winter Fungus, eat dead tree trunks.

Decomposers can break down dead things, but they can also feast on decaying flesh while it's still on a living organism. Dung beetles, as you may have accurately concluded from their name, break down feces from other animals. Some decomposers, like snails and worms, can also be consumers because they sometimes eat plants.

How Do Decomposers Work?

Often, when an animal dies, a scavenger, such as a vulture or hyena, will consume larger chunks of the body, but while scavengers do break down dead animals, they aren't decomposers, because they're not reducing the animal into chemicals that become part of the soil. Decomposers reduce dead animals, plants, and feces into chemicals such as nitrogen and carbon. Those chemicals become part of the soil and those nutrients can then be used by living plants and the animals that consume them.

Soil is teeming with bacteria and fungi spores ready to spring into action when there is something to decompose. For plants, the rate of decomposition is highly dependent on moisture and temperature. Generally, environments that are moister and warmer have much faster decomposition rates. A dead leaf in the tropics may last a matter of weeks while in the Arctic it could last years.

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Additional Activities

Decomposers In Action

This scavenger hunt activity will allow students to locate and identify different decomposers in their environment. To do this, students should have access to outside areas, such as a park or backyard. For example, students might find a decomposing leaf in the grass. Even though no decomposers are visually present, there is still bacteria doing the job that we can't see. They would fill out their table as follows:

DecomposerLocationDescriptionWhy It's a DecomposerRole in the Ecosystem
Bacteria The backyard near our tree A leaf was found on the ground and is damp and clearly decomposing into the soil The bacteria is breaking down the leaf and that's what decomposers do To recycle organic matter, such as leaves and other things on the forest floor back into the soil for plants to use

Student Directions

As you now know, decomposers are an essential type of organism in the ecosystem. Although you may be picturing decomposers in the dark, damp corners of the forest, the truth is that decomposers are all around us. In this scavenger hunt you will find three decomposers in your environment and explain why you think each is a decomposer and their role in the ecosystem. If you're stuck on where to start, look back at the lesson and recall the different types of decomposers. After you complete the table, then move on to answer the questions.

DecomposerLocationDescriptionWhy It's a DecomposerRole in the Ecosystem


  1. Which type of decomposer did you find most often? Why do you think that is?
  2. Are there decomposers that wouldn't be immediately visible to you? Why or why not?
  3. What do you think would happen if there were no more decomposers?
  4. What do you think is the effect of polluting the environment with things decomposers can't break down, such as plastic?

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