In any ecosystem, some organisms can absorb energy and use it to produce food. This food is in the form of sugars. These organisms are called producers.

Plants are producers. They use the sun's energy to make sugars using photosynthesis.

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Animals however can not make their own food.

They must eat plants and other animals to get energy.

Animals are called consumers. They must get their food from other sources.

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Decomposers are organisms that break down dead organisms and their waste products. They get their energy from the organic materials they break down.

They also return important nutrients to the soil. Energy flows only one-way through an ecosystem.

Plants use the sun's energy to produce sugars.Animals than consume theplants for energy. Decomposers than get their energy from the dead plants and animals and their wastes.

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A Food Chain arranges organisms that feed on each other in a sequence, or series. Food chains always start with the producers. Producers are the plants and other photosynthetic organisms that produce food that all other organisms eat.

Organisms in an ecosystem usually belong to more than one food-chain.Food chains in an ecosystem normally cross over one another. Animals in one food chain often eat animals in another food chain. This is called a Food Web

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Relationships between organisms in a food web can also be important. Many times organisms live in such close relationships that at least one organism is helped by the other organism in a symbiotic relationship. This is called symbiosis. More on symbiosis can be found when we look more closely at organisms.