It provides the level occupied by the species in the process of energy transfer through the ecosystem. Plants occupy the first feeding or trophic level as they make food directly from the sun's energy. Herbivores eat the plants and are at the second trophic level. A raccoon is at the second feeding or trophic level when consuming nuts and at the third trophic level when eating a crayfish. An ecosystem reuses water through the water cycle.
Water enters the atmosphere as vapour from bodies of water and from the soil.
Plants lose water through the pores in their leaves. Water vapour in the atmosphere condenses and forms clouds. The water droplets return to the earth as rain, snow, sleet, or hail and are used again by plants and animals and the cycle continues.