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Author(s): Deanne Erdmann MS

Water Cycle

The water or hydrologic cycle refers to the continuous circulation of moisture on earth, particularly between the atmosphere and the earth's surface. Solar radiation provides the energy for the water cycle. Water changes between gaseous and liquid states through the processes of transpiration, evaporation, and precipitation. Transpiration is the loss of water vapor by plant parts (mostly through tiny pores, known as stomata). Only a small amount of water is involved in a chemical process that occurs during photosynthesis (hydrogen and oxygen are split).

All living things require water.