15.2 pollutants. Thus pollutants are harmful solids,

Environmental pollution

              Our environment becomes
polluted day
by day, by the increased addition of industrial and domestic wastes to it. The air we breathe,
the water we drink and the place where we live in are  highly contaminated. Rapid
industrialization, unplanned urbanisation, population
explosion and deforestation are responsible for the pollution.

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“Pollution is an undesirable change in physical,
chemical or biological characteristics of air, water and soil that may
harmfully affect human, animal and the plant life.

 Environmental pollution
is usually caused by the addition of waste products of human activity. When the
waste products are not efficiently assimilated, decomposed, or otherwise
removed by the natural, biological and physical processes, adverse effects may
result on living things. The substances which cause pollution of environment are called
pollutants. Thus pollutants are harmful
solids, liquids or gaseous substances present in such concentration in the
environment which tend to be harmful for the whole
living biota.

ecological context, the pollutants are classified as bio-degradable and
non-biodegradable pollutants.

Bio-degradable pollutants :

pollutants are those which can be decomposed easily  by the natural biological process and also in
the engineered systems which enhance nature’s great capacity to decompose and
recycle. Such pollutants consists of animal and plant debris, domestic sewage ,etc Pollutants
which degrade rapidly are known as rapidly
degradable pollutants. Pollutants which degrade slowly are known as slowly degradable pollutants.

(2) Non bio-degradable pollutants :

bio-degradable pollutants are those which either do not degrade or degrade very
slowly in their natural environment. Such pollutants are mostly inorganic
compounds like Mercury and lead salts, phenolic compounds and pesticides like D.D.T, etc., Such pollutants
are harmful even in low concentration. These pollutants not only accumulate but
are often biologically magnified as they move along food chains. These
pollutants are not degraded naturally hence it is difficult to  eliminate from our environment.

15.3 Disturbance of Ecology
and Biosphere:

is the life zone on earth. It is the layer of soil, rock, water and air that
surrounds the earth along with the living organisms for which it provides support.
The biosphere extends from approximately six kilometers above the sea level to
about ten kilometers below the sea level.

A community
of organisms interacting with each other and with other non living surroundings
is called an Ecosystem. The Ecosystems
are the subdivision of the biosphere. The entire world’s ecosystem constitutes the
biosphere. The ecosystem can be classified as,






factors                              Biotic



            Producers                    Consumers                    Decomposers



                                                       Primary                      Secondary 

                                                   (Herbivores)          (Primary Carnivores)         (Secondary



The study   of inter relationship between the living
species and their non living environment is called ecology. In an ecosystem. the biological cycles are maintained by producers, consumers and
decomposers. Nature is capable of sustaining the producer- consumer –
decomposer cycle indefinitely with sun as energy source.


the ecological context, Disturbance is
regarded as an event of intense environmental stress occurring over a
relatively short period of time and causes large changes in the affected
ecosystem. Disturbance can be natural or by human activities.


disturbances is caused by force of nature. Forest fire (Natural lighting
strike), floods, winds, diseases, severe storms, volcanic eruptions, earth
quake ,etc., are some of the natural disturbances. The natural disturbances can be short lived
or long lived .Sometimes it takes a few months for an ecosystem to regain or it can take
decades. Natural disturbances are healthy for ecosystem.

Human disturbances

 Human activities like forest fire ignited by
humans, deforestation, pollution by toxic chemicals, nutrients or heat, etc., have
contributed a lot of disturbances in eco system.  Human activities like destruction of
tropical rain forests, pollution of rivers and streams, the introduction of
various chemicals into the atmosphere from industries are producing
dramatic ecological disturbances
in the world .The damaged ecosystems may fail to recover.

the basis of the type of environment, the pollution may  be classified 

                                        (i)  Air pollution

                                       (ii) Water pollution ; and

                                       (iii) Soil pollution