KENDRIYA VIDYALAYA SANGATHAN: HYDERABAD REGION
OPEN TEXT-BASED ASSESSMENT MATERIAL FOR CLASS VII (Science)
Theme
1.FORESTS - OUR LIFELINE
“A Nation grows with its trees,
Save the trees ,save the nation”
ABSTRACT
Forests are considered the “green gold of a country. The very survival of humans
and other living beings is dependent on trees on plants which are a major source of
oxygen-the vital gas for our respiration. They also act as a “sink” for the
carbondioxide exhaled by humans and animals released from the chimneys and by
the automobiles.
Forest play a vital role in sustaining our life and the nation’s economy. They
provide oxygen without which life is not possible on earth. They maintain healthy
gaseous balance in the atmosphere. They are great moderators of climate.Plants
increase the humidity of water vapour from their exposed surfaces by way of
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transpiration.As one may be aware, forests extensively control soil erosion and
land slides.Forests in hilly areas keeps the soil of river banks intact with their
extensive root system.It is ironical that in the name of progress we are depleting
our forest and disturbing our ecological balance. A large number of species and
sub-species of animals are under threat of extinction.
THE CONTEXT
A forest is a large area of land covered with trees or other woody vegetation.
Forests are the dominant terrestrial ecosystem on Earth. Human society and forests
influence each other in both positive and negative ways. Forests provide ecosystem
services to humans, but also impose economic, environmental, health and aesthetic
costs. Human interactions with the forest, including harvesting forest resources,
affect the forest ecosystem.
Significance of forests
Forests serve different purposes. Forests are a very important natural resource
provided to us. It is very important for every country to have 30% land covered by
forests.
Forests maintain water cycle on earth. Plants in forests absorb water from the soil
through their roots. Transpiration involves the release of water vapour into the
environment thereby cooling the hot air. This helps in regulating the
temperature in atmosphere.
Prevention of global warming:
Carbon dioxide is considered to be a greenhouse gas. Its increased level in the
atmosphere results in greenhouse effect thereby causing global warming.
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Trees in the forests absorb carbon dioxide from the environment during
photosynthesis and regulate its levels in the atmosphere. Global warming is
prevented by forests.
Prevention of dust storms and soil erosion:
Trees in the forest hold the soil firmly with their roots which bind with the soil
particles and prevent it from erosion.
Forests and their products:
Forests provide us with rich quality of wood.
Different products provided by forests are elucidated.
 Trees provide us with variety of vegetables and fruits, medicinal products any
diseases Trees provide raw material for paper industry, matchstick industry, coir
industry etc.
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Trees provide us with latex, gums ,resins and lac
Trees support bee-hives which in turn provide us honey and bee wax.
Forests provide us with spices and oils.
Forests and food chains:
Forests inhabit many animals and plants. Living organisms based on their
nutrition are classified into different types namely producers, consumers and
decomposers.
Deforestation
Destruction of trees in the forest area and converting large area of land as a habitat for
human beings is called as deforestation. Deforestation has many ill-effects on the
environment.
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Loss of forest products provide by plants and animals living in the forests
Loss of different species of animals and plants. Food chains are disturbed due to their
loss.
Soil is eroded easily by wind and water.
Increase of carbon dioxide levels in the atmosphere due to the absence of trees for
absorbing this gas.
Increased CO2 levels lead to global warming which inturn cause melting of polar
icecaps.
Rainfall becomes scanty as there are no trees.
Afforestation
Afforestation is planting of trees in barren lands to increase the area under forests.
 Afforestation influences the climate of a particular area and shows positive effect on
the environment. Afforestation helps in restoring balance in the environment.
 Government has to insist on everybody planting trees in their lifetime.
Government has to take necessary actions in converting waste lands into forests.
It is ironical that in the name of progress we are depleting our forest and disturbing our
ecological balance. Urbanization, rarely accompanied by large-scale, long –range
planning, has turned many urban and sub-urban areas into commercial jungles. A serious
consequence of this land misuse is the loss of various life-forms. Urban growth, spread of
agriculture , building of dams and loss of forests have destroyed wild life habitats.
A large number of species and sub-species of animals are under threat of extinction.
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Environment is the priceless gift of Nature. Protection of environment and
maintenance of ecological balance is our prime duty. We must keep the earth lush
green so that we all can live together in an environment free from pollution. We have
to protect our environment to protect ourselves. Otherwise the day is not far when man
himself may become endangered species
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