LEARNING OBJECTIVES

1. To make the reader aware about the environment, its importance and basic components.

2. To develop an understanding about the concept, scope and importance of the discipline

     Environmental Studies.

3. To discuss the concept and necessity of multidisciplinary approach of the subject.

4. Readers will be aware of the historic milestones of the environmentalism and

    environmental education

5. To make the readers know about the origin of the concept of ‘Sustainability’ and

   ‘Sustainable Development’.

1. Components of Environment

Planet earth is the only known planet in the universe having diversity of life. As earlier

mentioned, life could have been possible on the planet only because of the healthy

‐ 2 ‐

interactions between biotic and abiotic components in such a manner where the flow of

Energy and Biogeochemical cycle follows a well-defined path. The planet earth is categorized

into different spheres which represent solid (rock/soil), liquid (water) and gaseous (air)

Phases. The overlapping zone of the three spheres, where life is available, is called the

Biosphere. A brief description of the spheres is given below:

Lithosphere: (Greek: means rock) Earth’s structure can be stratified into outer crust,

middle mantle and inner core regions (Fig. 1). Lithosphere is the outermost layer of the crust

Which represents the land mass of the planet. It consists of rocks, soil, sediments and

Minerals. Various geological structures or landforms like high mountains, plateau, deep

Valleys and sea beds make the surface of lithosphere uneven. Mount Everest is the highest

Point on the lithosphere. Various geological processes like weathering & erosion, volcanic

Eruptions,  take place Different terrestrial

Ecosystems like forests, grasslands, deserts etc. are found on the lithosphere.

Lithosphere

Hydrosphere: (Greek: means water) Hydrosphere represents water masses on the

planet present in solid (ice cover, glaciers etc.), liquid (water bodies) and gaseous (water

Vapors) phases. Hydrosphere covers almost three-fourth of the total surface area of the earth.

Oceans and seas represent marine ecosystem which contains 97 percent of the total water

Content (having very high concentration of salts) of the planet. Remaining 3 percent of the

water resources are freshwater present in the form of glaciers, rivers, lakes, ponds etc. (Figure

2). Hydrosphere is an integral part of the water cycle and plays a crucial role in maintaining

Normal climatic, meteorological, physical, chemical and biological functions on the planet.

Oceans and seas are the largest sink of carbon in the environment.

Figure 2: Distribution of Water Resources on the Earth

Atmosphere: (Greek: Atmos means vapor) the thin sheet of gaseous mixture which envelops

The planet earth is called atmosphere. Content of water vapor, density of the air mass and

Atmospheric pressure decreases rapidly with the increase in altitude. The composition of dry

air is as follows:

Component Volume (%)

Nitrogen 78.084

Oxygen 20.946

Argon 0.934

Carbon oxide 0.04

Gases in traces Remaining

The rate of change of temperature with the altitude is called lapse rate. The atmosphere has

been stratified into major four layers where temperature decreases (negative lapse rate) or

Increases (positive lapse rate). Brief description of atmospheric layers is as follows:

1 Troposphere: the altitude of this layer varies from 16 km on Equator to 8 km at poles.

Largest percentage of the air mass found in this region. The upper layer is called

Tropopause. Temperature decreases with increase in altitude (-6.4 0C per km) in this  varies from 15 0C (ground Level) to – 56 0C (tropopause).

4. Thermosphere: ionic oxygen atoms and other ions in this layer absorb short wave solar

radiation which increases the temperature in this layer rapidly from -96 (0C) (lower

Boundary) to 1200 0C (upper layer).

Table 2: Layers of atmosphere and their composition

Chemistry 

Layer Average Altitude

(km)

Temperature Variation

(0C)

Prominent Chemical

S

Figure 3: Layers of atmosphere and temperature change with

 Britannica 

Encyclopedia.

Figure 4: Biosphere (Source: Britannica Encyclopedia;