The term Biosphere was first used a century ago by the Austrian geologist Eduard Suess as a sphere of living organism or biological process lying at the interface between the atmosphere, lithosphere and hydrosphere.
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It was at that time an insignificant concept. Today, however the biosphere has become the most important problem faced by man. Replacement of the communities of nature by man made communities have to be observed if these man-made communities are to thrive. People must think less about conquering nature and more about learning to work with nature.
In addition, each person must realize his interdependence with the rest of nature, including his fellow human beings. To safeguard life on earth, people must learn to control and adjust the balances in nature that are altered by their activities. The distinguishing feature of the biosphere is that it supports life. It is estimated that the biosphere contains more than 350,000 species of plants including algae, fungi, mosses and higher forms of plants, from eleven million animal species ranging from uni-cellular protozoa to man. The biosphere supplies the essential species, namely light, heat, water, food and living space or habitats.
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The biosphere or the eco system , as it is generally called is the evolutionary system. It represents a stable equilibrium of various physical and biological factors which have been operating in the past. The organic continuity of the system rests on a delicate network of interdependent relationship. The air, the water, man and the animals, plants and planktons, the soil and bacteria are all invisibly interlinked in a life-sustaining system, we call the environment.
The eco system or the environment has a rhythm and movement of its own which depend upon a whole set of delicately balanced cycles. All living organisms- microbes, plants, animals, man – have survived by adjusting themselves to the environment and attuning their lives to its rhythm. It is therefore, absolutely necessary that these cycles should be maintained unimpaired.
Energy Cycle
What keeps the biosphere going is solar energy which comprise 99.98 % of the total energy supply of the biosphere. Sun pours out its energy in various forms. Light consists of bundles of energy called quanta. The energy content of a quantum of light is proportional to its frequency. The shorter the wavelength, the higher the frequency and the greater the energy content.
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The process by which solar energy is transferred to molecules is called photochemical process. In this process sunlight excites the electrons in a molecular and kicks them out. These released electrons par with other electrons from a neighboring atom or molecule and thus from electron-pair bonds. These new bonds create new molecules.
The most important photochemical activity in the biosphere is photosynthesis in plants. Photosynthesis is a complicated process. The light absorbed by chlorophyll molecules and by other pigments in plants is transferred to electrons in such a way as to create strong oxidants, that is, molecules that readily remove electrons from other molecules (oxides them), or reluctant, that is, molecules that readily supply electrons to other molecules (reduce them).
It is these oxidants and reluctant that assist plants in producing carbohydrates and oxygen, from molecules of carbon dioxide and water. Plants respire (give out) oxygen but retain carbohydrates which are converted to energy and stored in the form of chemical bonds, notably those of adenosine troposphere (ATP) which is the basic energy currency of all living cells. High energy phosphate bonds of ATP contain 12,000 calories and release 7,5000 calories when broken.
This energies is carried up the food chain by herbivores feeding on plants and carnivores feeding on herbivores. Omnivores like man draw their energy both from plant and animal sources. Much of the energy drawn by plants and animals (including man) is consumed and spent in maintaining the process of life.
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The energy that is not expended in the course of life is stored in dead matter. Decomposing bacteria break up the dead matter and convert it into humus or organic sediments, releasing carbon dioxide, water and heat into the biosphere. Thus the basic ingredients of life are returned to soil. The plants draw their nutrients from the soil and keep the cycle going.
Heat Cycle
Heat is one of the prime requisites of life. This is supplied by solar radiation. it is calculated that the solar heat reaching the Earth’s orbit (just above the atmosphere) amounts to about 2 calories per sq centimeter per minute. But the Earth gets only less then half the radiation reaching the top of the atmosphere.
About 2% is absorbed by the ozone layer in the atmosphere. Atmospheric water vapor, carbon dioxide and dust particles absorb around 18%. The clouds reflect back into space some 23%. About 22% is scattered by atmospheric dust. The Earth receives only the balance of 38%. But the story does not end there. Out of the 38% solar radiation received, the Earth re-radiates about 7% by long wave radiation, thus reducing the stock of terrestrial energy to 31%.
At the same, time out of the 22% scattered by the atmosphere, 16% ultimately reaches the Earth as diffuse radiation, the rest 6% being irretrievably lost in space. Thus, on the whole the Earth receives about 47% of the solar energy reaching the atmosphere. Meanwhile, the atmosphere acting as an intermediary between the Sun and the surface of Earth, retains about 5% of the energy as sensible heat and about 24% as latent heat in water vapor. it is essential that the absorption and re-radiation of heat should ultimately balance. Otherwise the Earth would experience a net increase in heat or a net decrease according as a surplus or deficit of heat results from radiation. The balance between absorption and re-radiation. The balance between absorption and re-ration is mainly regulated by water vapor in the atmosphere.
There is only very little amount of water in the atmosphere, about 0.0001%. This insignificant amount of atmospheric water exercises an influence on the climate of the Earth, out of all proportion to its total mass. besides keeping the balance between the absorption and radiation of heat, it controls the water cycle and determines our climatic condition.
Carbon Cycle
The biosphere contains a complex mixture of carbon compounds, in a continuous state of creation, transformation and decomposition. Practically all organic matter originates in the process of photosynthesis. The plants use the radiant energy of the sun to convert carbon dioxide and water into carbohydrates by splitting water to derive hydrogen, and by drawing in carbon dioxide from the air. In the process the plants release free oxygen (O2)f into the atmosphere.
While plants absorb carbon dioxide during photosynthesis, all living organisms respire and release carbon dioxide and decomposing bacteria do the same in regard to dead matter. but while respiration and decomposition go on all the time, photosynthesis takes place only during daytime. During daytime, carbon dioxide in atmosphere comes down from an average 320 parts per million to around 305 parts but at night it increases, going up to as much as 400 parts per million, near the ground level.
Apart from the daily production and consumption of carbon ( in the form of carbon dioxide), the Earth has a vast stock of carbon in permanent form. this stock consists of inorganic deposits (mainly carbonates like calcium carbonate etc). and organic fossil deposits (chiefly coal, shale and oil). When we burn fossil flues, we are merely adding more carbon dioxide to the atmosphere which has an excess supply already.
Oxygen Cycle
Oxygen not only supports life but also plays a fundamental role as a building block of practically all vital molecules accounting for about a fourth of all the atoms in living matter.
The most recent factor affecting the oxygen cycles of the biosphere and the oxygen budget of the earth is man himself. he inhales oxygen and exhales carbon dioxide, thus reducing the stock of oxygen and increasing the supply of carbon dioxide. He goes further and burns fossil fuels, depleting the oxygen supply still further. He reduces photosynthetic activity by cutting down forests and replaying them with cities.
Some astronomer think that the original supply of oxygen in the atmosphere came from the ultraviolet rays of the Sun which broke up the water molecules in the upper atmosphere into hydrogen and oxygen. whatever may be the initial source of the oxygen in the atmosphere, what is important is that the ply by photosynthesis. They are not only augmenting our oxygen supply but also reducing the total supply of carbon dioxide which is increasing to alarming dimensions.
Nitrogen Cycle
Nitrogen as it is obtained in the atmosphere cannot be used by the higher organisms. It has to be “fixed”, that is, incorporated into a chemical compound. Nitrogen, in other words, has to be converted into ammonia or amino acid, so as to be use to plants and animals.
Fixation of atmospheric nitrogen on land is carried our by organisms called diastrophism who posses the genetic code for the synthesis than 1%-contained in our rivers and fresh water lakes and in the subsoil. This meager stock of water is replenished by an even smaller stock of mobile water – less than 0.01% which circulates in the atmosphere as water vapor much of which ultimately falls down as rains. The water cycle of the biosphere depends on the reciprocity of evaporation and precipitation. Liquid water on the Earth goes into the atmosphere as vapor by evaporation and transpiration of the plants. The vapor is returned to earth as rain or snow.
Earth Day
April 22 is a day dedicated not just to recognize the beauty and riches of the Earth but also to make the Earth a healthier and safer place to live. Speeches, workshops, parades and demonstrations on the occasion of Earth Day have brought awareness about the dangers of overpopulation, energy waste, and other issues of vital concern. Earth Day was first observed on April 22, 1970 with the message “Give Earth A Chance” and intention to reclaiming the purity of the air, water and living environment.
World Environment Day
The UN General Assembly designated June 5 as World Environment Day, to depend public awareness the need to preserve and enhance the environment It was on that day the UN Conference on the Human Environment (Stockholm, 1972) started. The Assembly reconvened United Nation Conference on environment and Development (UNCED) after 20 years, in Rio de Janeiro, where nations took up the challenges of viable and equitable balance between environment and development and a sustainable future for the earth and its people.