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Ecosystem Services in EnviroAtlas | US EPA

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These benefits underpin almost every aspect of human well-being, including our food and water, security, health, and economy.

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This article was most recently revised and updated by

Ecosystem, the complex of living organisms, their physical environment, and all their interrelationships in a particular unit of space.

Bryan and Cherry Alexander

A brief treatment of ecosystems follows. For full treatment, see biosphere.

An ecosystem can be categorized into its abiotic constituents, including minerals, climate, soil, water, sunlight, and all other nonliving elements, and its biotic constituents, consisting of all its living members. Linking these constituents together are two major forces: the flow of energy through the ecosystem, and the cycling of nutrients within the ecosystem.

The fundamental source of energy in almost all ecosystems is radiant energy from the Sun. The energy of sunlight is used by the ecosystem's autotrophic, or self-sustaining, organisms. Consisting largely of green vegetation, these organisms are capable of photosynthesis-i.e., they can use the energy of sunlight to convert carbon dioxide and water into simple, energy-rich carbohydrates. The autotrophs use the energy stored within the simple carbohydrates to produce the more complex organic compounds, such as proteins, lipids, and starches, that maintain the organisms' life processes. The autotrophic segment of the ecosystem is commonly referred to as the producer level.

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Follow the energy flow of a given ecosystem from the light-synthesizing autotrophs to the higher heterotrophs Encyclopædia Britannica, Inc. See all videos for this article

Organic matter generated by autotrophs directly or indirectly sustains heterotrophic organisms. Heterotrophs are the consumers of the ecosystem; they cannot make their own food. They use, rearrange, and ultimately decompose the complex organic materials built up by the autotrophs. All animals and fungi are heterotrophs, as are most bacteria and many other microorganisms.

Together, the autotrophs and heterotrophs form various trophic (feeding) levels in the ecosystem: the producer level, composed of those organisms that make their own food; the primary consumer level, composed of those organisms that feed on producers; the secondary consumer level, composed of those organisms that feed on primary consumers; and so on. The movement of organic matter and energy from the producer level through various consumer levels makes up a food chain. For example, a typical food chain in a grassland might be grass (producer) → mouse (primary consumer) → snake (secondary consumer) → hawk (tertiary consumer). Actually, in many cases the food chains of the ecosystem overlap and interconnect, forming what ecologists call a food web. The final link in all food chains is made up of decomposers, those heterotrophs that break down dead organisms and organic wastes. A food chain in which the primary consumer feeds on living plants is called a grazing pathway; that in which the primary consumer feeds on dead plant matter is known as a detritus pathway. Both pathways are important in accounting for the energy budget of the ecosystem.

The Editors of Encyclopaedia Britannica Adam Augustyn, Managing Editor, Reference Content.

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ecosystem | Definition, Components, Examples, Structure, & Facts

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Ecosystem, the complex of living organisms, their physical environment, and all their interrelationships in a particular unit of space. An ecosystem can be categorized into its abiotic constituents, including minerals, climate, soil, water, and sunlight, and its biotic constituents, consisting of all living members.

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Feed the Dingo: An Ecosystem Game

Players strive to create a balanced desert ecosystem in which each animal has enough food to survive over a period of 12 days, in this interactive game from PLUM LANDING. Players see how the different species of plants and animals in a desert depend on one another. They also experiment with how changing the amount of one resource affects the whole ecosystem.

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Players strive to create a balanced desert ecosystem in which each animal has enough food to survive over a period of 12 days, in this interactive game from PLUM LANDING. Players see how the different species of plants and animals in a desert depend on one another.

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ecosystem interactive game for 5th grade

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also review skills on abiotic and biotic components of ecosystems

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Ecosystem interactive game for 5th grade

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Ecosystem interactive game for 5th grade, food chain activities 5th grade, feeding relationships / food chains, also review skills on abiotic and biotic components of ecosystem.

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Teaching Tools | Resources for Teachers from Scholastic

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We're All in This Together

Everything in the natural world is connected. An ecosystem is a community of living and non-living things that work together. Ecosystems have no particular size.

An ecosystem can be as large as a desert or a lake or as small as a tree or a puddle. If you have a terrarium, that is an artificial ecosystem. The water, water temperature, plants, animals, air, light and soil all work together. If there isn't enough light or water or if the soil doesn't have the right nutrients, the plants will die. If the plants die, animals that depend on them will die. If the animals that depend on the plants die, any animals that depend on those animals will die. Ecosystems in nature work the same way. All the parts work together to make a balanced system!

The More the Merrier

A healthy ecosystem has lots of species diversity and is less likely to be seriously damaged by human interaction, natural disasters and climate changes. Every species has a niche in its ecosystem that helps keep the system healthy. We are learning about new species every day, and we are just figuring out the roles they play in the natural world. By studying and maintaining biodiversity, we help keep our planet healthy.

Life in a Lake

In a lake ecosystem, the sun hits the water and helps the algae grow. Algae produces oxygen for animals like fish, and provides food for microscopic animals. Small fish eat the microscopic animals, absorb oxygen with their gills and expel carbon dioxide, which plants then use to grow. If the algae disappeared, everything else would be impacted. Microscopic animals wouldn't have enough food, fish wouldn't have enough oxygen and plants would lose some of the carbon dioxide they need to grow.

Getting Along

Ecosystems have lots of different living organisms that interact with each other. The living organisms in an ecosystem can be divided into three categories: producers, consumers and decomposers. They are all important parts of an ecosystem.

Producers are the green plants. They make their own food. Consumers are animals and they get their energy from the producers or from organisms that eat producers.

There are three types of consumers: herbivores are animals that eat plants, carnivores are animals that eat herbivores and sometimes other carnivores and omnivores are animals that eat plants and other animals.

The third type of living organism in an ecosystem is the decomposers. Decomposers are plants and animals that break down dead plants and animals into organic materials that go back into the soil, which is where we started!

Parts and Pieces

What are the major parts of an ecosystem? An ecosystem includes soil, atmosphere, heat and light from the sun, water and living organisms.

Getting Down and Dirty

Soil is a critical part of an ecosystem. It provides important nutrients for the plants in an ecosystem. It helps anchor the plants to keep them in place. Soil absorbs and holds water for plants and animals to use and provides a home for lots of living organisms.

Give Me a Little Air

The atmosphere provides oxygen and carbon dioxide for the plants and animals in an ecosystem. The atmosphere is also part of the water cycle. Without the complex interactions and elements in the atmosphere, there would be no life at all!

Getting Some Sun

The heat and light from the sun are critical parts of an ecosystem. The sun's heat helps water evaporate and return to the atmosphere where it is cycled back into water. The heat also keeps plants and animals warm. Without light from the sun there would be no photosynthesis and plants wouldn't have the energy they need to make food.

Water Everywhere

Without water there would be no life. Water is a large percentage of the cells that make up all living organisms. In fact, you may have heard that humans can go longer without food than they can without water. It's true! Without water all life would die. In addition to being an important part of cells, water is also used by plants to carry and distribute the nutrients they need to survive.

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Everything in the natural world is connected. An ecosystem is a community of living and non-living things that work together. Ecosystems have no particular size. An ecosystem can be as large as a desert or a lake or as small as a tree or a puddle.