Biosphere: Biosphere and Its Limit, Components of Biosphere

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  • Our earth is the only planet where life is found. That is why this planet is also known as living planet or sphere of life. This sphere contains those qualities, atmosphere, lithosphere and hydrosphere. They all enable the life to exist on this planet. But this is a very small portion of the earth where life exists. Beyond this narrow space of the earth, there are no life forms found.

  • For millions of years, nature has provided some checks and balances which sustain these life forms without any problems. But today the situation has changed. This is mainly due to unsustainable human intervention. If we want to save this unique living planet, then we have to control our greed and change our lifestyle and behaviour pattern.


The major objectives of this chapter are:

  • To state the elements of biosphere and its interrelationships with lithosphere, atmosphere, and hydrosphere

  • To give reasons for the unique nature of biosphere

  • To define the key concepts like ecology, ecosystem, global warming, ozone layer depletion, acid rain, and sustainable development

  • To state the ecological processes in the ecosystem

  • To understand the interactions of the biosphere with different types of environments

  • To appreciate the importance of balance, interdependence, and energy flow in different ecosystems

  • To identify the causes of climatic changes as global warming, ozone layer depletion, acid rain, and also those caused by human activities

  • To explain the need and importance of sustainable development

Biosphere and Its Limit

  • Biosphere refers to the narrow zone of the earth in which all life forms exist. This is the zone in which all the three essentials things which are required for sustenance of life are found in a correct combination. They are land or the lithosphere, air or the atmosphere, and water or the hydrosphere. This narrow zone is a place where lithosphere, atmosphere and hydrosphere meet. It extends vertically into the atmosphere to about 10 km, downward into the ocean to depths of about 10.4 km and into about 27,000 ft of the earth’s surface where maximum living organism have been found. There are some life forms which are found in extreme conditions. Two examples of this type are algae and thermophilic. Algae which are supposed to be one of the earliest forms of life can exist even in the most hostile environment such as frozen Antarctica. On the other extreme side, thermophilic bacteria usually inhabit deep sea volcanic vents having a temperature of more than 300oC. In fact, these bacteria cannot survive in a temperature below boiling point.

  • However, most living things are confined to a narrow band which permits the capture of solar energy through the process of photosynthesis, which is essential for any organic life. This narrow region extends from about 180-200 feet below sea level to the highest value of snowline in tropical and sub-tropical mountain ranges i.e., 6,550M above sea levels.



Components of Biosphere

Biosphere has three basic components. These are as follows:

  • Abiotic Components: These components broadly consist of all non-living elements which are essential for the survival of all living organisms. These are lithosphere (solid part of the earth crust), atmosphere and hydrosphere. Mineral nutrients, certain gases, and water are the three basic requirements of organic life. Soils and sediments constitute the chief reservoir of mineral nutrients. Atmosphere constitutes the chief reservoir of gases essential for organic life. Ocean constitutes the chief reservoir of liquid water. The upper layer of the soil and shallow parts of the ocean constitute the most important areas, sustaining organic life.

  • Biotic Components: Plants, animals and human beings including microorganisms constitute the three biotic components of environment.

  • Plants: Plants are the only primary producers as they produce their own food through the process of photosynthesis and hence are called autotrophs. Plants not only produce all kinds of organic matter but also help in cycling and recycling of organic matters and nutrients. Therefore, plants are the major source of food as well as energy for all organisms.

  • Animals: Animals are the main consumers. Therefore, animals are heterotrophs. There are three main functions of animals:

    • To use organic matter made available by plants as food

    • To transform the food into energy

    • To utilise the energy for growth and development

  • Micro-Organisms: These consist of a variety of micro-bacteria, fungi etc. Their numbers are unlimited and are popularly known as decomposers as these organisms decompose the dead plants and animals and other organic matters. It is through this process they obtain their food. Through this process of decomposition, they differentiate and separate the complex organic matter, so that the same could be put to reuse by the primary producers i.e., the plants.

  • Energy: This is the third and vital component of the biosphere without which life could not have been possible on this planet. It is essential for generation and reproduction of all biological life on this planet. All organisms in the biosphere are like machines which use energy to work and also to convert one form of energy into another. Sun is the major source of energy without which we cannot think about the existence of the biosphere.

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