To present the planet Earth without water very difficult. By the way, only on our planet this substance is in the liquid state. Water in liquid state — a necessary condition for existence of life.
Conditions for water
Liquid state of water is maintained on Earth thanks to set of many factors: the planet size thanks to what there is necessary force of an attraction holding the atmosphere; distance to the Sun because of what on the planet the necessary temperature keeps; the quantity of the atmosphere withheld by an attraction and creating the necessary pressure at a surface; rotation of Earth round its pivot-center thanks to which there is a circulation of atmospheric streams. There are no them, water on the earth would not be. On the basis of these factors the others which promote maintenance of life follow.
The main use of water living organisms consists only in one — for maintenance of functioning of the living cells making fabrics of which these organisms consist, including also the person. Animals and the person use water as well for other requirements. Maintenance of purity, cooling of a body from the increased surrounding temperature, for digestion of food, and as universal thinner.
Life without water
Existence of the world without water on the earth is, more or less, visible on the example of life in deserts. The scorching sun and dryness of air, forces all live to take cover in any ways somewhere. Reptiles bury under the Earth's surface, look for various shady places, change the appearance helping them to hold a moisture reserve during evolution. Plants extend the roots which are deeply going to more cool bottom to water, leaves replace with prickles for smaller expenditure of moisture. The people living in desert conditions are also protected from excess expenditure of water. Know sources and distances between them that at movement to calculate a consumption of water and then it to fill up in time. The bedouins who are completely wrapping up bodies in black fabric, thus, maintain the necessary amount of moisture of a body that provides the necessary temperature. Their measured, slow movements do not cause excess wasting of energy for recovery of whom water is also necessary. And if to speak about use by the person of water in the industry then it is obvious that without it no development of a civilization would happen. And in the future, if for any reasons of water on the earth becomes less (not to mention its disappearance), difficulties of mankind will be inevitable. In the distant future Earth will appear without conditions supporting water existence. And then the planet will turn into not the living, cold stone world which is monotonously flying to eternal distances of space.