An ecosystem can be explained to kids as the plants and animals found in a particular area that rely on each other to survive. The balance of an ecosystem is delicate, occurring in a specific pattern. Taking any organism out of this pattern disrupts the ecosystem.
An ecosystem also involves how the living organisms interact with the nonliving environment, which includes things such as the weather, earth, sun, soil and atmosphere. Every object in an ecosystem has a specific role to play.
An example of an ecosystem could be a small pond in a yard. The chain of the ecosystem would begin with the water, which insects rely on for a place to lay their eggs. Frogs in the ecosystem rely on the water for insects to eat and to keep them moist so the sun does not kill them. Fish also rely on the water to live in and the insects eggs to eat. The frogs and the fish then both supply food for the birds in the area. If any of these things were taken out, the whole system would fall apart; without the frogs and fish, the insect population would outnumber the space of water, and without the insects, the fish and frogs would die from hunger.