Biosphere: A Giant Ecosystem

Biosphere: A Giant Ecosystem

What is Biosphere?

Biosphere is a combination of two Greek words, 'Hos' (= life) and 'sphaira' (= sphere). Biosphere means the sphere where life exists. It is the sphere of action between an organism and its environment.

Thus, that part of the earth in which living organisms are known to exist, comprising the common part of the lithosphere, hydrosphere, and atmosphere, is called the Biosphere.

The biosphere is mostly found in the relatively narrow zones of contact among the:

• Lithosphere (exactly, a fraction of the crust)

• Hydrosphere (exactly, a limited part of the hydrosphere)

• Atmosphere (exactly, the lower region—troposphere—of the atmosphere)

Extension of Biosphere

• The biosphere extends to any place where life of any kind exists.

• According to Irish biogeographer Ioytivy (1924–95), the 'Organic world' or biosphere is that part of the earth containing living organisms—the biological inhabited soil (land), air, and water.

• The average thickness of the biosphere or life-supporting layer of the Earth, consisting of land (soil), water, and air, is approximately 30 km (– up to 9 km deep in the water + 9 km over the land surface + up to 12 km above in the air roughly).

• Most living organisms live within a small area in the biosphere, from 500 metres below the surface of the ocean to 6,000 metres above sea level.

The biosphere is absent at extremes of the North & South poles, at the highest mountains, and in the deepest oceans, because of existing hostile conditions that do not support life. Occasionally, spores of bacteria and fungi are found at great height beyond 8,000 metres, but they are not metabolically active, so they represent dormant life only.

Upper Limit (in Air)

• The upper limit of the biosphere is determined by the availability of oxygen, moisture, temperature, and air pressure.

• With an increase in height in the atmosphere, these factors limit the upper boundary of the biosphere.

Though NASA has detected the presence of bacteria up to the height of 15 km in the atmosphere, the lower layer of the atmosphere up to a few thousand meters accounts for most of the living organisms because favourable environmental conditions are available for the growth and development of living organisms in the lower part of the atmosphere.

Lower Limit of Biosphere

(a) Over Land

The lower limit of the biosphere is determined by the availability of the required amount of oxygen and light, which can sustain life. Thus, the depth of the biosphere over the land is:

• Depth of the deepest roots of the trees

• The depth at which the burrowing organism

• The depth at which lie the parent bedrocks

(b) In Water

The existence of life has been detected up to a depth of 9 km in the deep oceanic trenches and deep-sea plants.

Diagrammatic Representation of Biosphere

A diagrammatic representation of the biosphere is given below -

From the above-mentioned diagram, it is very clear that the biosphere is not a separate or fourth sphere of the Earth, as many think, but it is the common part of the lithosphere, hydrosphere, and atmosphere where life exists.

Our Earth is a unique planet in having a biosphere. The biosphere is a life-supporting layer that surrounds the Earth and makes the life of organisms possible without any protective device.

Variety of Organisms in the Biosphere

There are a variety of organisms in the biosphere. They are broadly divided into plants, animals, and microbes. More than 3 lakh plant species and 10 lakh animal species are known to exist.

These organisms exist in the zones of contact among the lithosphere, hydrosphere, and atmosphere. There is an exchange of matter and energy among these three constituents of physical environments and the organisms in the biosphere.

Importance of Biosphere

Though the biosphere is a relatively thin layer of the Earth, it has great significance to our lives:

• The biosphere provides a variety of food and also raw materials, which provide clothing, shelter, and other needs of humans.

Therefore, it is necessary to understand the relationship of organisms to one another and to their physical environment.

Biosphere and Ecosystem

• Plants, animals, and other organisms, together with the physical environment with which they interact, constitute the Ecological system, in short, the Ecosystem.

• The term ecosystem was coined by English botanist Arthur Tansley in 1935.

Final Thoughts

The biosphere is the only life-supporting layer on Earth, making it vital for the survival of all living organisms. It is a thin yet essential zone that connects the lithosphere, hydrosphere, and atmosphere through a continuous exchange of matter and energy.

Understanding the limits of the biosphere, from deep ocean trenches to high mountain peaks, helps us realize the fragility of life. Despite its vast diversity, the biosphere is highly sensitive to environmental changes and human interference. It provides food, raw materials, and shelter, forming the foundation of human civilization.

Protecting the ecosystem balance within the biosphere is crucial for sustainable living and ensuring the well-being of future generations. Every plant, animal, and microbe plays a unique role in maintaining this delicate system, and recognizing our dependence on the biosphere should inspire collective efforts toward environmental conservation.