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 qualities –
These qualities enable the life to exist on this planet.
This is a very small portion of the earth where life exists. Beyond this narrow space of the earth, there is no life forms found.
What is so special about this narrow zone of the earth which made life possible?
It is because of right mixture of many things – energy, some living beings and some non-living things and their interaction.
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. Now this living planet is in danger. This is mainly due to unsustainable human intervention.
Our Father of Nation, Mahatma Gandhi has rightly said “Earth has everything to meet human needs but not its greed.” It we want to save this unique living planet, then we have to control our greed and change our life style and behaviour pattern.
Biosphere refers to the narrow zone of the earth in which all life forms exist. It has all the three essentials things which are required for sustenance of life ( in a right mixture ).
They are land (lithosphere), air (atmosphere) and water (hydrosphere)
In other words, this narrow zone is a place where lithosphere, atmosphere and hydrosphere meet.
We must appreciate that how narrow this zone is!!
It extends vertically into the atmosphere to about 10km, 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 thermophillic.
- Algae which is supposed to be one of the earliest forms of life can exist even in the most hostile environment such as frozen Antarctica.
- Thermophillic (heat loving) bacteria usually inhabit deep sea volcanic vents having a temperature of more than 3000C. In fact, these bacteria can not survive in a temperature below boiling point.
The situation was not like this when the life form began. About 700 million years ago, it is believed to have been only a narrow discontinuous land encompassing only shallow parts of the oceans. As per the trend of expansion of area in terms of the availability of life form, it can be predicated that may be after a few million years, the expanse of the biosphere gets extended beyond the upper troposphere.
This shows that biosphere has been evolving over the time.
Though the life may not be possible in some of the hottest and the coldest parts. 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 (say 6,550M above sea levels). When it extends beyond this line, life forms become very limited.
Bibliography : NIOS Geography Book