Ponds and lakes are large bodies of freshwater that are found in all types of environments and on all continents. Generally the center of the pond reaches depths of about 10 feet with little emergent vegetation and the edges are shallow with emergent grasses and sedges. Ponds and lakes support animals living in that area with fresh drinking water and therefore are a vital system to support wildlife. Rivers and streams may run into or out of the pond eventually merging with other bodies of water.
Wetlands are found on every continent but Antarctica usually at the edges of ponds, lakes, rivers and streams. Other terms for wetland include marsh, bog, flood plain, prairie pothole and swamp. Wetland characteristics include shallow water with emergent vegetation surrounding lakes and ponds. This habitat supports many animals like amphibians, exotic birds, reptiles and some mammals and fish. Wetlands are important because they prevent the flooding of ponds, lakes streams and rivers by acting much like a sponge releasing water when areas get low and absorbing it when it get to high. Common plants found in the wetland are grasses, sedges, and water lilies.
Rivers and streams are constantly in motion running from ponds, lakes, or draining wetlands. Because this environment is in constant motion fish are very strong and able to swim up and downstream. Rivers may have varied water levels depending on the time of year. Many rivers and streams may only run during the spring and summer because melting snow forms them. Most rivers and streams eventually reach the ocean where some migratory fish may live part of their life in freshwater rivers and then the other half in the ocean.