Calentamiento globar

The atmosphere is a layer of gases that protects the earth from excessive ultraviolet radiation and allows the existence of life. It is a gaseous mixture of nitrogen, oxygen, hydrogen, carbon dioxide, water vapor, and other elements like dust particles. Water is essential for every one, plants, animals and humans need it: life would be impossible without water.
Carbon dioxide is used by plantsduring photosynthesis to make sugar, which may either be consumed in respiration or used as the raw material to produce other organic compounds needed for plant growth and development.
Each one of those elements on the planet has a different function in relation to other but, destruction or bad use of one or more of them can produce a dangerous imbalance which threatens our planet and thereforefuture generations. Water is the most abundant element in our planet and consequently the most important for our life and health; Aproximately 97% of water is found in oceans, 2% is ice and the remaining 1% is fresh water from rivers and lakes.
“Water pollution refers to the changes in the physical, biological, and chemical conditions of any body of water which harmfully disrupts the balance ofthe ecosystem.” (ezinearticles.com); every day water becomes dirty and polluted due to developing nations needing a greater level of water for industrialization, then after the water is used it is often contaminated and thrown back into the rivers or the sea. For instance pathogens are a type of pollution that prove very harmful.  They can cause many illnesses that range from typhoid anddysentery to minor respiratory and skin diseases.  Pathogens include such organisms as bacteria, viruses, and protozoan.  These pollutants enter waterways through untreated sewage, storm drains, septic tanks, runoff from farms, and particularly boats that dump sewage.  Though microscopic, these pollutants have a tremendous effect evidenced by their ability to cause sickness.
Another example comes fromnatural sources, like mercury that occurs naturally in the Earth and oceans pollutes as do hydrocarbons and many other products, nevertheless natural pollution sources are widely dispersed and do not cause high levels of pollution. Contamination human origin, however, focuses on specific areas and it is much more dangerous than naturally occurring sources.
Ships produce various types of pollution,especially oil spills, accidental or not, cause great ecological damage, “Chemicals commonly used to clean up oil spills make oil far more toxic to fish, particularly for eggs and young fish, according to new research” (abc.net.au): When a ship spills oil on water sources it is difficult to choose what is better: clean the river and murder a lot of animals and their eggs or forget the issue andallow pollution to increase. For example Exxon Valdez Oil spill disaster with total of 11,000,000 gallons of Alaska North Slope crude oil leaked from the ruptured hull of the ship, impaled by the jagged rocks of Bligh Reef. Within two months, the oil had been driven along a path stretching 470 miles to the southwest, the initial cleanup of the spill took three years, and the cost was over $2.1billion. (explorenorth.com)
Water pollution is also due to agriculture, because are use of pesticides and fertilizers the organic remains of animals and plants are which also a big source of water pollution. In addition, water contamination is caused by chemicals like acids, salts and toxic metals like mercury and lead. Nitrates and phosphates are water soluble substances that plants need fortheir development, but if found in excessive amounts they induce excessive growth of algae, when these algae and other plants die to cause water pollution
The presence of so much domestic waste, fertilizers, pesticides and industrial wastes alter the aquatic flora and fauna. In unpolluted waters there is a balance between animals and plants, which is broken by the presence of foreign material,...