Why is an ecosystem considered to be a self supporting system

Why is an ecosystem considered to be a self supporting system?

An example of a ecosystem is a tropical forest and it is self supporting because the rain forest gas sunlight produce food from a process known as photosynthesis and then the animals eat the food which at one point be eaten by other animals.

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the secretary of state, appointed by the president with the advice and consent of the senate, is the president's chief foreign affairs adviser. the secretary carries out the president's foreign policies through the state department and the foreign service of the united states.