The primary importance of the hydrosphere is that it contains water, which sustains a variety of life forms and plays an important role in regulating the atmosphere and surrounding ecosystems. The hydrosphere includes all water located on the surface of the Earth. It contains freshwater, saltwater and frozen water as well, including groundwater and water in the lower levels of the atmosphere.
The water in the hydrosphere vary in texture and consistency, but shares the important function of sustaining human, plant, animal and bacterial life on Earth. Living organisms contain approximately 75 percent water. Cells within living beings rely on water to carry out important life functions. Water also allows cells to carry out critical chemical reactions, which otherwise would not happen, and therefore cause life to cease.
In addition to existing within organisms, water exists in habitats where plants and animals live. Water helps to regulate climates and atmospheric conditions and facilitates human activities, such as irrigation. The hydrosphere contains bodies of water around the world. Most of its composition derives from oceans, which have water trapped in layers of sedimentary rock. Oceans, lakes, rivers and ice include the main geographical features in the hydrosphere, and exist in places around the world. Of these features, ice makes up the smallest portion of the hydrosphere, contributing only one percent to the total.
