Q.1 Define environment. Explain different types of environment. (AKTU. - 2009-10, 10 - 11)
Related Questions -
Q. Discuss in brief four segments of atmosphere. (AKTU. - 2008-09)
Q. What is environment? Enumerate and discuss the various segments of environment in brief. (AKTU. - 2012 - 13)
Ans. The term environment is derived from the french word environner which means ‘surrounding’. It refers to an aggregate of all conditions that affect the existence, growth, and welfare of an organism or group of organisms. The term may be defined in a number of ways:
- Environment is the sum total of all social, economical, biological, physical, and chemical factors which constitute the surroundings of humans, who are both the creator and moulders of the environment.
- Environment is the sum total of influences which modify and determine the development of life and its characteristics.
Therefore, environment is a complex system that includes physical, chemical, biological, social, and cultural elements; all these elements are inter-linked to each other in a complicated manner similar to a spider web and the disturbance of any one of these elements will threaten the structure of the environment. Thus, for the stability and sustenance of the environment, it is important that all these elements are preserved and left undisturbed.
Natural environment includes components such as air, water, soil, land, forest, wildlife, flora, fauna, etc. This environment operates through a self-regulating mechanism; therefore, any change brought about by one component of the environment is counter-balanced by some other changes in another component of the environment. The natural environment is never static; the changes may sometimes be negligible, while at other times, they may be drastic. These changes may be either beneficial or harmful to the living organisms in the environment.
The four realms of Earth are lithosphere, hydrosphere, atmosphere, and biosphere (Fig. 1).
Lithosphere: - The lithospher includes the solid part of the Earth’s crust. It has two parts, the crust and the upper mantle. The crust includes rocks, minerals, and soil. There are two parts of the crust: continental and oceanic. Directly below the crust is the mantle. The mantle makes up the largest volume of the Earth’s interior and has two parts, an upper layer and a lower layer.
Hydrosphere: - The hydrosphere includes all the water on earth, most of which is contained in the oceans. The availability of water on earth is a unique feature and is the factor responsible for the existence of life on the planet. The presence of water on earth gives it the name ‘blue solid (ice), liquid (water), and gas (water vapour) on earth.
Atmosphere: - The layer of gases surrounding earth is called the atmosphere. The atmosphere of earth is composed of several distinct layers such as troposphere, stratosphere, mesosphere and inosphere.
Biosphere: - The biosphere is that part of Earth which includes air, land surface rocks and water and all components within which life occurs. It is the life-zone of earth and includes all loving organisms. The biosphere can be divided into distinct ecosystems that represent the interactions between different groups of organisms.
Q.2 Classify the atmosphere on the basis of temperature variation. (AKTU. - 2008-09)
Ans. Four Segments of Environment: -
On the basis of temperature profile and other related phenomena, atmosphere is divided into four major layers or shells, as follows: -
(i) Troposphere: -
The lowest layer of atmosphere in which living organisms operated is called troposphere. It extends upto about 8 km at the poles and 16 km at the equator. It is the region of strong air movements and cloud formations. It contains about three fourth of the atmospheric mass and is the above of clouds and stroms and convective motion. This layer is of greatest interest in pollution control, since this is the layer in which most living things exist and also the air which we breath is the air in the troposphere. One of the more recent changes in troposphere involves the phenomenon of acid rains.
(ii) Startosphere: -
After troposphere next layer is startosphere. In this layer temperature is nearly constant upward to about 20 km and then increases upto a maximum of 00C near its outer limit, startopause, due to absorption of ultraviolet radiation by ozone. Moreover, it serves as a blanket in reducing the cooling rate of earth. The outer limit of the startosphere has a mean altitude of about 50 km.
(iii) Mesosphere: -
Above to startosphere is the mesosphere in which there is cold temperature and low atmosphere pressure. The temperature decreases slowly with the altitude but then sharply to a minimum of about - 750C near the Mesopause, at 80 km.
(iv) Thermosphere: -
In the thermosphere, the temperature again rises to very high values and approaches 20000C and even more at about 500 km depending upon solar activity. Coinciding with the lower portion of the thermosphere is the ‘Ionosphere’. Above the ionosphere, the portion is called ‘Exophere’ till the edge of space.
