NCERT Environmental Studies (EVS) important notes Part 11 for AEES, KVS, NVS, DSSSB, UPTET, REET, CTET, BTET, MPTET, HTET and All other Teaching Exams

• Environment is our basic life support system. It provides the air we breath, the water we drink, the food we eat and the land where we live.

 

 

• The place, people, things and nature that surround any living organism is called environment. It is a combination of natural and human made phenomena. 
• While the natural environment refers to both biotic and abiotic conditions existing on the earth, human environment reveals the activities, creations and interactions among human beings.

 

Biotic
The world of living organisms. e.g. plants and animals.

 

Abiotic
The world of non-living elements. e.g. land. 

 

 

NATURAL ENVIRONMENT 

 

Domains of Environment

 

(i) Lithosphere is the solid crust or the hard top layer of the earth. It is made up of rocks and minerals and covered by a thin layer of soil. It is an irregular surface with various landforms such as mountains, plateaus, plains, valleys, etc. Landforms are found over the continents and also on the ocean floors. 

Lithosphere is the domain that provides us forests, grasslands for grazing, land for agriculture and human settlements. It is also a source of mineral wealth.

 

(ii) The domain of water is referred to as hydrosphere. It comprises various sources of water and different types of water bodies like rivers, lakes, seas, oceans, etc. It is essential for all living organisms.

 

(iii) The atmosphere is the thin layer of air that surrounds the earth. The gravitational force of the earth holds the atmosphere around it. It protects us from the harmful rays and scorching heat of the sun. It consists of a number of gases, dust and water vapour. The changes in the atmosphere produce changes in the weather and climate.

 

(iv) Plant and animal kingdom together make biosphere or the living world. It is a narrow zone of the earth where land, water and air interact with each other to support life.

 

• Ecosystem: It is a system formed by the interaction of all living organisms with each other and with the physical and chemical factors of the environment in which they live, all linked by transfer of energy and material.
• All plants, animals and human beings depend on their immediate surroundings. Often they are also interdependent on each other. This relation between the living organisms, as well as the relation between the organisms and their surroundings form an ecosystem. 
• There could be an ecosystem of large rain forest, grassland, desert, mountains, lake, river, ocean and even a small pond.
• On 5 June every year World Environment Day is celebrated. 
• Barter System: It is a trade in which goods are exchanged without the use of money.

 

HUMAN ENVIRONMENT

Human beings interact with the environment and modify it according to their need. Early humans adapted themselves to the natural surroundings. They led a simple life and fulfilled their requirements from the nature around them. With time needs grew and became more varied. Humans learn new ways to use and change environment. They learn to grow crops, domesticate animals and lead a settled life. The wheel was invented, surplus food was produced, barter system emerged, trade started and commerce developed. Industrial revolution enabled large scale production. Transportation became faster. Information revolution made communication easier and speedy across the world. 

Have you ever thought why you love eating a juicy watermelon in summer and hot roasted peanuts in winter? A perfect balance is necessary between the natural and human environment. Humans must learn to live and use their environment in a harmonious way. 

 

 

Questions and Answers

 

Ques 1 Which is not a natural ecosystem? 

(a) Desert 

(b) Aquarium 

(c) Forest 

Ans- (i) Aquarium

Ques 2 Which is not a component of human environment? 

(a) Land 

(b) Religion 

(c) Community 

Ans- (a) Land

 

Ques 4 Which is a human made environment? 

(a) Mountain 

(b) Sea 

(c) Road 

Ans- (c) Road 

 

Ques 5 Which is a threat to environment? 

(a) Growing plant 

(b) Growing population 

(c) Growing crops

Ans- (b) Growing population

 

 

• The deepest mine in the world, is in South Africa. It is about 4 km. deep. In search for oil engineers have dug a hole about 6 km. deep.
• To reach to the centre of the earth (which is not possible!) you will have to dig a hole 6000 km. deep on the ocean floor.

 

 

• The uppermost layer over the earth’s surface is called the crust. It is the thinnest of all the layers. It is about 35 km. on the continental masses and only 5 km. on the ocean floors.
• The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina). The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium). 
• Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust.
• The innermost layer is the core with a radius of about 3500 km. It is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous i.e. iron). The central core has very high temperature and pressure.
• The crust forms only 0.5 per cent of the volume of the earth, 16 per cent consists of the mantle and 83 per cent makes the core.
• The radius of the earth is 6371 km. 

 

ROCKS AND MINERALS

 

• The earth’s crust is made up of various types of rocks. Any natural mass of mineral matter that makes up the earth’s crust is called a rock. Rocks can be of different colour, size and texture.
• There are three major types of rocks: igneous rocks, sedimentary rocks and metamorphic rocks.
• Igneous: Latin word Ignis meaning fire. 
• Sedimentary: Latin word sedimentum meaning settle down. 
• Metamorphic: Greek word metamorphose meaning change of form.
• Fossils: The remains of the dead plants and animals trapped in the layers of rocks are called fossils.
• When the molten magma cools, it becomes solid. Rocks thus formed are called igneous rocks. They are also called primary rocks. There are two types of igneous rocks: intrusive rocks and extrusive rocks.
• Lava is actually fiery red molten magma coming out from the interior of the earth on its surface. When this molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. They have a very fine grained structure. For example, basalt. The Deccan plateau is made up of basalt rocks. 
• Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks. Since they cool down slowly they form large grains. Granite is an example of such a rock. Grinding stones used to prepare paste/powder of spices and grains are made of granite.
• Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments. 
• These sediments are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks. 
• For example, sandstone is made from grains of sand. These rocks may also contain fossils of plants, animals and other micro�organisms that once lived on them. 
• Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure. For example, clay changes into slate and limestone into marble.
• Rocks are very useful to us. The hard rocks are used for making roads, houses and buildings. You use stones in many games. For example, seven stones (pitthoo), hop-scotch (stapu/kit kit), five stones (gitti).
• The Red Fort is made of red sandstone.
• The Taj Mahal is made of white marble.

 

 

• This process of transformation of the rock from one to another is known as the rock cycle.
• When the molten magma cools; it solidifies to become igneous rock. These igneous rocks are broken down into small particles that are transported and deposited to form sedimentary rocks. When the igneous and sedimentary rocks are subjected to heat and pressure they change into metamorphic rocks. The metamorphic rocks which are still under great heat and pressure melt down to form molten magma. This molten magma again can cool down and solidify into igneous rocks.
• Rocks are made up of different minerals. Minerals are naturally occurring substances which have certain physical properties and definite chemical composition. Minerals are very important to humankind. Some are used as fuels. 
• For example, coal, natural gas and petroleum. They are also used in industries – iron, aluminium, gold, uranium, etc, in medicine, in fertilisers, etc.

 

Questions and Answers

 

Ques 1 The rock which is made up of molten magma is

(a) Igneous 

(b) Sedimentary 

(c) Metamorphic

Ans- (a) Igneous 

 

Ques 2 The innermost layer of the earth is 

(a) Crust 

(b) Core 

(c) Mantle 

Ans- (b) Core

 

Ques 3 Gold, petroleum and coal are examples of 

(a) Rocks 

(b) Minerals 

(c) Fossils 

Ans- (b) Minerals

 

Ques 4 Rocks which contain fossils are 

(a) Sedimentary rocks 

(b) Metamorphic rocks 

(c) Igneous rocks 

Ans- (a) Sedimentary rocks

 

Ques 5 The thinnest layer of the earth is 

(a) Crust 

(b) Mantle 

(c) Core

Ans- (a) Crust

 

 

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