A stream flows through a forest. Its clear water rushes over rocks and swirls into deep pools. The water looks empty, but it is not. A stream is home to many plants and animals. Many more live along its banks.
The plants, the animals, and the stream itself are all part of a small ecosystem, a community of living and nonliving things. Fish, insects, birds, and other living things that are part of this community depend on the stream and one another to survive. Every part of the ecosystem has a role to play. Even the sunlight that filters through the trees is important.