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An ecosystem is a group of living and nonliving things interacting with each other. Ecosystems can vary in size ranging from something as small as a mud puddle to as large as the Earth. A classroom aquarium can be an example of an ecosystem with the plants, fish, rocks, water, and microorganisms working together to make the ecosystem. There are lots of other ecosystems that you may find around your school such as a pond or nearby woods.
An important aspect of an ecosystem is the interactions that occur between the organisms and their environment. Each member provides something important to the system. The sun is ultimately the source of the energy in the ecosystem. Some members of the ecosystem, called producers, are able to capture energy from the sun and use it to make their own food. They do this through the process of photosynthesis. Plants are usually the producers in ecosystems that occur on land while algae are the dominant producers in marine (saltwater) and freshwater ecosystems. Some kinds of bacteria are also able to act as producers by using chemicals from their environment to make their food. Consumers get their energy by eating other organisms. Sometimes consumers eat the plants or algae, sometimes they eat other animals. When plants and animals die, decomposers break down the chemicals found in their bodies and return them to the ecosystem. Bacteria and fungi are important decomposers in an ecosystem.
The number of organisms in an ecosystem and the kind of organisms present are determined by the resources that are available in that area. The amount of light and water, temperature range, and kind of soil present affect the kinds of organisms that live in a particular ecosystem. For example, in a forest ecosystem in western North Carolina where there is rich soil and temperatures ranging from below freezing in winter to the low 80 degrees F in the summer you could expect to find oak trees, rhododendron, red squirrels, foxes, and racoons. Along the coast where there is sand, salt water, and temperatures ranging from an average low of 35 degrees F in January to an average high of 86 degrees F in July, you could expect to find beach grass, wax myrtles, sand crabs, and a variety of bird life. Organims in these ecosystems interact to form a complex web of interdependence. Factors such as available resources, disease, and predation determine how large populations in an ecosystem can grow.
Humans can have dramatic affects on ecosystems. As the population of humans increases, we require more space and can encroach on the habitat and resources available for plants and animals in a given area. Humans also contribute to pollution of air, land, and water affecting the natural habitats for other living organisms. Pollution has led to issues such as ozone depletion, acid rain, and nutrient run off into streams and rivers.