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Our World of WaterLiving Things Depend on WaterWater is an essential part of every living thing. Plants use water in deriving some of their nutrients from minerals in the soil. These minerals have to be dissolved in water in order to be absorbed by the plants. This is why a desert can be mineral-rich, yet support very little plant life except during brief rainy periods. To illustrate how much of a plant is actually water, imagine burning a log in a fireplace. The ash that remains after the log is burnt contains nearly all of the nutrients. The greatest part of the log went up the chimney as smoke. This smoke consisted of water vapor and organic material manufactured by the leaves. Not all of the water taken in by the plant remains there. Much is transpired, or given off, by the leaves. At night, little water is lost, but during a hot, dry day there is much water given back to the air. In fact, this is one of the major ways in which water is returned to the atmosphere. For example, an acre of corn (20,000 to 25,000 plants) gives off about 3,000 to 4,000 gallons of water each day. Water is taken into the body by eating plants and meats and by drinking beverages. Humans can go for a month without eating but will die in 3 to 5 days without water because our bodies are made up of about 70 percent water. (That is about 15 gallons for an adult.) The body uses water in maintaining its temperature, breathing, digesting food, and lubricating moving joints.
Since water is so important for all living things, you can understand the concern over pollution of any kind. When we refer to pollution we mean the addition of harmful substances that make an undesirable change in the physical state of clean water. Polluted water cannot safely be used by living things because dissolved substances or water-borne disease organisms may interfere with cell chemistry, causing sickness or death. Poor water management encourages pollution.
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