Page 97 - SST Class 07

graphy Environment
Geo
q Components of environment
q Human environment
Introduction
The word environment means surroundings or
conditions in which a person, animal or plant lives
or operates. It includes everything on, in and
around the earth and how each of these elements
affect the others. The existence, survival and
growth of a living being depend on the things or
conditions that surround it. If these conditions or
things are removed, the existence, survival and
growth of that living being will become impossible.
COMPONENTS OF ENVIRONMENT
The environment is a whole unit, but it can be
divided into two parts—natural environment and
human environment.
The natural environment includes all things, both
living and non-living or biotic and abiotic. Biotic
components include all biological or living beings
such as plants, animals, insects etc. Abiotic
components include all physical or non-living
things such as land, minerals, soil, water and
climate.
The human environment includes constructed
surroundings or built up areas like buildings,
roads, machines and social and cultural factors,
like family and school.
F ind Outind Out
Which day is celebrated as the World Environment
Day?
NATURAL ENVIRONMENT
Land, water, air, plants and animals are the
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q Natural environment
elements of natural environment. Natural
environment provides us the base for our
existence, like land to live on, air to breathe,
water to drink and food to eat. It consists of four
realms—lithosphere , atmosphere , hydrosphere
and biosphere .
Activity
Visit a garden and zoo. Take photographs of five
animals and five plants living there. These are
biotic elements. Try to find out how plants and
animals are interdependent. Also find out how
biotic and abiotic elements are related.
Lithosphere
The thin and solid upper covering of the earth is
known as lithosphere . It is made up of rocks and
minerals and covered with a thin layer of soil. The
average thickness of lithosphere is about 100 km.
The lithosphere comprises both continents (29%)
and ocean beds (71%). Lithosphere has two
layers—the sial and the sima . Sial are rocks of the
continents rich in silica and aluminium. So it is
called sial, taking si from silica and al from
aluminium. Sima rocks form the ocean basin.
These rocks have materials rich in silica and
magnesium. So it is called sima, taking si from
silica and ma from magnesium.
Lithosphere is very important for all sorts of life
form. It provides us forests, grasslands, agricultural
land and land for human settlement. It is a source
of minerals wealth because all kinds of minerals
and metals are embedded in the rock strata.
Hydrosphere
The water which forms about three-fourths of our
Environment
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