14147666 NCERT Book Social Science Our Environment Class VII

Contents

FOREWORD iii

1.1.1.1.1. Environment 1

2.2.2.2.2. Inside Our Earth 7

3.3.3.3.3. Our Changing Earth 12

4.4.4.4.4. Air 20

5.5.5.5.5. Water 30

6.6.6.6.6. Natural Vegetation and Wildlife 39

7.7.7.7.7. Human Environment – Settlement,Transport and Communication 47

8.8.8.8.8. Human Environment InteractionsThe Tropical and the Subtropical Region 55

9.9.9.9.9. Life in the Temperate Grasslands 65

10.10.10.10.10. Life in the Deserts 71

APPENDIX 78

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After the long vacation, when Ravi started going to schoolagain, he noticed that the only playground next to his schoolwas dug up. People said that a huge building with manyflats will be constructed there. Ravi was almost in tears,when he realised that the big playground with its softgrass, marigolds and butterflies is gone for ever. He sharedhis feelings with his classmates. In the assembly, thePrincipal too sadly observed, “See how our environmentis changing.”

In the class Ravi asked his teacher, “What isenvironment?” “Whatever you see in your surroundings,”said the teacher.

Ravi thought aloud, “That means, the school building,tables, chairs in the classroom, even that open field, theroad, the garbage, my friends – all are parts of ourenvironment”!

“Yes” said the teacher, “but wait….. Some objects arecreated by nature – for example, mountains, rivers, trees,animals. Others are made by people – for example roads,cars, clothes, books”.

Now work in pairs. Make a list with your classmatesitting next to you, of the creations of nature and byhuman beings.

Environment is ourbasic life supportsystem. It providesthe air we breath, thewater we drink, thefood we eat and theland where we live.

How do humanbeings modify thisnatural environment?The car fumes pollutethe air, water iscollected in a pot,food is served invessels and land isused to buildfactories.

Human beingsmake cars, mills,factories andmanufacturecontainers. This ishow human beingsmodify naturalenvironment.

1 Environment

Ravi, Paramjeet, Jessy, Mustafa, Asha were all excitedabout making the list. “Why is our environment changing?”asked Iqbal. “It’s all because of our needs. They are

2 OUR ENVIRONMENT

NaturalHumanmade

Humanmade

Human

Componentsof

Environment

Water(Hydrosphere)

Air

(Atmosp

here)

Land(Lithosphere)

Living Things(Biosphere)

Parks

Buildings Bridges

Roads

Industries Monuments

Individual

Family

Community

Religion Educational

Economic

PoliticalSituation

Fig. 1.1: Components of Environment

increasing day by day; we are therefore modifying andat times even destroying our natural surroundings”, theteacher replied.

From the above conversation youunderstand that the place, people, things andnature that surround any living organism iscalled environment. It is a combination ofnatural and human made phenomena. Whilethe natural environment refers to both bioticand abiotic conditions existing on the earth,

BioticThe world of

livingorganisms.e.g. plants

and animals.

AbioticThe world of

non-livingelements.e.g. land.

ENVIRONMENT 3

Let’s do

Fig. 1.2: Domains of the Environment

Hydrosphere

Lithosphere

Biosphere

Atmosphere

Let’s do

human environment reveals the activities, creations andinteractions among human beings.

NATURAL ENVIRONMENT

Land, water, air, plants and animals comprise the naturalenvironment. You are familiar with the meaning oflithosphere, hydrosphere, atmosphere and biospherefrom your previous class. Let us learn some more factsabout these domains.

Lithosphere is the solid crust or the hard top layer ofthe earth. It is made up of rocks and minerals and coveredby a thin layer of soil. It is an irregular surface withvarious landforms such as mountains, plateaus, plains,valleys, etc. Landforms are found over the continentsand also on the ocean floors.

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

Look at yoursurroundings. Make alist of uses that theland in yourneighbourhood isbeing put to.

Let’s do

Where does the wateryou use in your homeand school comefrom? Make a list ofdifferent uses ofwater in our daily life.Have you seen anyonewasting water? How?

Observe the sky whilecoming to school.Make a note whetherthe day is cloudy,rainy, sunny, foggy etc.

The domain of water is referred to as hydrosphere. Itcomprises various sources of water and different types ofwater bodies like rivers, lakes, seas, oceans, etc. It isessential for all living organisms.

The atmosphere is the thin layer of air thatsurrounds the earth. The gravitational force of theearth holds the atmosphere around it. It protects us

Word Origin

Environment: Frenchword “Environer/Environner” meaning“neighbourhood”.

4 OUR ENVIRONMENT

Glossary

Fig. 1.3: A Pond Ecosystem

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 inthe weather and climate.

Plant and animal kingdom together make biosphereor the living world. It is a narrow zone of the earthwhere land, water and air interact with each other tosupport life.

What is ecosystem?At an NCC camp that Ravi’s class was attending, Jessyexclaimed, “What a heavy downpour. It reminds me ofmy home in Kerala. You should come and see how itpours and pours and pours over the lush green fieldsand coconut plantations.”

Heera from Jaisalmer exclaimed, “We get no rains.We see only ‘kikar’ and sand, as far as the eyes cansee.” “But you also find camels”, said Ravi.

Let’s do

Sketch or bringphotographs of yourplace like thestudents in the story.

Ecosystem: It is asystem formed by theinteraction of allliving organisms witheach other and withthe physical andchemical factors ofthe environment inwhich they live, alllinked by transfer ofenergy and material.

ENVIRONMENT 5

Glossary

Let’s do

Barter System:It is a trade in whichgoods are exchangedwithout the use ofmoney.

Talk to some elderlyperson in yourneighbourhood andcollect informationabout–• The trees in his/

her neighbourhoodwhen he/ she wasyour age.

• The indoor gameshe/she played.

• His/her favouritefruit at your age.

• How did they makethemselvescomfortable duringhot summers andcold winters?

Display your answerson a wall/bulletinboard.

Heera says, “Not just camels. If you visit our desert,you will see snakes, lizards and many insects too.”

Ravi wondered, “Why do the animals, the vegetationand the way people live vary from place to place? Arethey all related to each other?”

“Oh yes, very much so”, the teacher replied.

All plants, animals and human beings depend ontheir immediate surroundings. Often they are alsointerdependent on each other. This relation between theliving organisms, as well as the relation between theorganisms and their surroundings form an ecosystem.There could be an ecosystem of large rain forest,grassland, desert, mountains, lake, river, ocean and evena small pond.

Do you think the park in which Ravi and his friendsplayed formed an ecosystem?

HUMAN ENVIRONMENT

Human beings interact with the environment and modifyit according to their need. Early humans adaptedthemselves to the natural surroundings. They led asimple life and fulfilled their requirements from thenature around them. With time needs grew and becamemore varied. Humans learn new ways to use and changeenvironment. They learn to grow crops, domesticateanimals and lead a settled life. The wheel was invented,surplus food was produced, barter system emerged, tradestarted and commerce developed. Industrial revolutionenabled large scale production. Transportation becamefaster. Information revolution made communicationeasier and speedy across the world.

Have you ever thought why you love eating a juicywatermelon in summer and hot roasted peanuts inwinter? A perfect balance is necessary between thenatural and human environment. Humans must learnto live and use their environment in a harmonious way.

Nurie, a girl from Mizoram from Ravi’s class often talksabout the lush green surroundings of her place. SeeingRavi upset at having lost his playground, Nurie invitedhim to visit her home state during the coming vacation.Ravi’s teacher asked the students to draw the landscape,houses and activities of the people and places they visitduring the holidays.

Do you know?

On 5 June every yearWorld EnvironmentDay is celebrated.

6 OUR ENVIRONMENT

1. Answer the following questions.

(i) What is an ecosystem?

(ii) What do you mean by natural environment?

(iii) Which are the major components of the environment?

(iv) Give four examples of human made environment.

(v) What is lithosphere?

(vi) Which are the two major components of biotic environment?

(vii) What is biosphere?

2. Tick the correct answer.

(i) Which is not a natural ecosystem?(a) Desert (b) Aquarium (c) Forest

(ii) Which is not a component of human environment?(a) Land (b) Religion (c) Community

(iii) Which is a human made environment?(a) Mountain (b) Sea (c) Road

(iv) Which is a threat to environment?(a) Growing plant(b) Growing population(c) Growing crops

3. Match the following.

(i) Biosphere (a) blanket of air which surrounds the earth

(ii) Atmosphere (b) domain of water

(iii) Hydrosphere (c) our surroundings

(iv) Environment (d) narrow zone where land water and air interact

4. Give reasons.

(i) Man modifies his environment(ii) Plants and animals depend on each other

5. Activity.

Imagine an ideal environment where you would love to live. Draw the picture ofyour ideal environment.

Exercises

The earth, our homeland is a dynamic planet. It isconstantly undergoing changes inside and outside. Haveyou ever wondered what lies in the interior of the earth?What is the earth made up of?

INTERIOR OF THE EARTH

Just like an onion, theearth is made up ofseveral concentriclayers with one insideanother (Fig. 2.1). Theuppermost layer overthe earth’s surface iscalled the crust. It is thethinnest of all thelayers. It is about 35 km.on the continentalmasses and only 5 km.on the ocean floors.The main mineralconstituents of thecontinental mass aresilica and alumina. It isthus called sial (si-silicaand al-alumina). Theoceanic crust mainlyconsists of silica andmagnesium; it is thereforecalled sima (si-silica andma-magnesium) (Fig. 2.2).

Just beneath the crustis the mantle whichextends up to a depth of2900 km. below the crust.

2 Inside Our Earth

Do you know?

• The deepest mine inthe world, is inSouth Africa. It isabout 4 km. deep. Insearch for oilengineers have dug ahole about 6 km.deep.

• To reach to thecentre of the earth(which is notpossible!) you willhave to dig a hole6000 km. deep onthe ocean floor.

CrustLithosphere

Core-mantleboundary

Mantle

Outercore

Inner core

Fig. 2.1: Interior of the Earth

ContinentalCrust

Fig. 2.2: Continental Crust and Oceanic Crust

Continent OceanOceanicCrust

8 OUR ENVIRONMENT

Glossary

The innermost layer is the core with a radius of about3500 km. It is mainly made up of nickel and iron and iscalled nife (ni – nickel and fe – ferrous i.e. iron). Thecentral core has very high temperature and pressure.

ROCKS AND MINERALS

The earth’s crust is made up of various types of rocks.Any natural mass of mineral matter that makes up theearth’s crust is called a rock. Rocks can be of differentcolour, size and texture.

There are three major types of rocks: igneous rocks,sedimentary rocks and metamorphic rocks.

When the molten magma cools, it becomes solid.Rocks thus formed are called igneous rocks. They arealso called primary rocks. There are two types of igneousrocks: intrusive rocks and extrusive rocks.

Can you imagine lava coming out from the volcanoes?Lava is actually fiery red molten magma coming out fromthe interior of the earth on its surface. When this moltenlava comes on the earth’s surface, it rapidly cools downand becomes solid. Rocks formed in such a way on thecrust are called extrusive igneous rocks. They have avery fine grained structure. For example, basalt. TheDeccan plateau is made up of basalt rocks. Sometimesthe molten magma cools down deep inside the earth’scrust. Solid rocks so formed are called intrusive igneousrocks. Since they cool down slowly they form largegrains. Granite is an example of such a rock. Grindingstones used to prepare paste/powder of spices and grainsare made of granite.

Rocks roll down, crack, and hit each other and arebroken down into small fragments. These smaller particlesare called sediments. These sediments are transported

and deposited by wind, water, etc. These loosesediments are compressed and hardened to formlayers of rocks. These types of rocks are calledsedimentary rocks. For example, sandstone ismade from grains of sand. These rocks may alsocontain fossils of plants, animals and other micro-organisms that once lived on them.

Igneous and sedimentary rocks can changeinto metamorphic rocks under great heat andpressure (Fig. 2.3). For example, clay changes intoslate and limestone into marble.

Fig. 2.3: Sedimentary rock turnedinto a Metamorphic rock

Fossils: The remainsof the dead plants andanimals trapped inthe layers of rocks arecalled fossils.

Word Origin

Igneous: Latin wordIgnis meaning fire.

Sedimentary: Latinword sedimentummeaning settle down.

Metamorphic: Greekword metamorphosemeaning change of form.

Do you know?

• The crust forms only0.5 per cent of thevolume of the earth,16 per cent consistsof the mantle and83 per cent makesthe core.

• The radius of theearth is 6371 km.

INSIDE OUR EARTH 9

Let’s do

The Taj Mahal is made of white marbleThe Red Fort is made of red sandstone

Collect pictures of some monuments and find out which are the rocksused to build them. Two pictures have been collected for you.

Rocks are very useful to us. The hard rocks are usedfor making roads, houses and buildings. You use stonesin many games. For example, seven stones (pitthoo), hop-scotch (stapu/kit kit), five stones (gitti). Find out somemore such games by asking your grand parents, parents,neighbours, etc.

You will be surprised to know that one type of rockchanges to another type under certain conditions in acyclic manner. This process of transformation of the rockfrom one to another is known as the rock cycle. Youhave already learnt when themolten magma cools; it solidifiesto become igneous rock. Theseigneous rocks are broken downinto small particles that aretransported and deposited toform sedimentary rocks. Whenthe igneous and sedimentaryrocks are subjected to heatand pressure they changeinto metamorphic rocks. Themetamorphic rocks which are stillunder great heat and pressuremelt down to form molten magma.This molten magma again cancool down and solidify intoigneous rocks (Fig. 2.4). Fig. 2.4: Rock Cycle

10 OUR ENVIRONMENT

Let’s do

What are theminerals found inyour state?

Collect some samplesto show in your class.


(i) What are the three layers of the earth?

(ii) What is a rock?

(iii) Name three types of rocks.

(iv) How are extrusive and intrusive rocks formed?

(v) What do you mean by a rock cycle?

(vi) What are the uses of rocks?

(vii) What are metamorphic rocks?


(i) The rock which is made up of molten magma is(a) Igneous (b) Sedimentary (c) Metamorphic

(ii) The innermost layer of the earth is(a) Crust (b) Core (c) Mantle

(iii) Gold, petroleum and coal are examples of(a) Rocks (b) Minerals (c) Fossils

(iv) Rocks which contain fossils are(a) Sedimentary rocks(b) Metamorphic rocks(c) Igneous rocks

(v) The thinnest layer of the earth is(a) Crust (b) Mantle (c) Core


(i) Core (a) Changes into slate

(ii) Minerals (b) Used for roads and buildings

(iii) Rocks (c) Made of silicon and alumina

(iv) Clay (d) Has definite chemical composition

(v) Sial (e) Innermost layer

Rocks are made up of different minerals. Mineralsare naturally occurring substances which have certainphysical properties and definite chemical composition.Minerals are very important to humankind. Some areused as fuels. For example, coal, natural gas andpetroleum. They are also used in industries – iron,aluminium, gold, uranium, etc, in medicine, infertilisers, etc.

Exercises

INSIDE OUR EARTH 11

4. Give reasons.

(i) We cannot go to the centre of the earth.

(ii) Sedimentary rocks are formed from sediments.

(iii) Limestone is changed into marble.

5. For fun.

(i) What are the minerals most commonly used in the following objects?

(ii) Identify some more objects made up of different minerals.

Karhai Ornaments

Pan/Tava

Bell

Hammer

Lamp

Activity

Take a small colouredpaper pellet and put itin a beakerhalf filledwith water.Place thebeaker on atripod standand heat it. As thewater warms up, youwill observe that thepaper pellet is movingupward along with thewarm layers of waterand thensinks backalong withthe coolerlayers of water. Themolten magma insidethe earth moves in asimilar manner.

The lithosphere is broken into a number of plates knownas the Lithospheric plates. You will be surprised to knowthat these plates move around very slowly – just a fewmillimetres each year. This is because of the movementof the molten magma inside the earth. The molten magmainside the earth moves in a circular manner as shown inthe activity.

The movement of these plates causes changes on thesurface of the earth. The earth movements are dividedon the basis of the forces which cause them. The forceswhich act in the interior of the earth are called asEndogenic forces and the forces that work on the surfaceof the earth are called as Exogenic forces (Fig. 3.1).

3 Our Changing Earth

Glossary

Lithospheric plates:The earth’s crustconsists of severallarge and some small,rigid, irregularly-shaped plates (slabs)which carrycontinents and theocean floor.

Fig. 3.1: Evolution of Landforms

Earth movements

Endogenic forces Exogenic forces

Sudden forces Diastrophic forces Erosional and Depositional

Building mountainsEarthquake

Volcano

Landslides

River

Wind

Sea-waves

Glaciers

Endogenic forces sometimes produce sudden movementsand at the other times produce slow movements. Suddenmovements like earthquakes and volcanoes cause massdestruction over the surface of the earth.

Crater

Lava

tube

Vent

Lava

Gases and ash

Crust

MantleMagmaChamber

Word Origin

Fig. 3.2: A Volcano

Epicentre Seismic waves radiateout in all directions

Plate boundary

Focus – this is where theearthquake occurs. It is theorigin of the seismic energy

A volcano is a vent (opening) in theearth’s crust through which moltenmaterial erupts suddenly (Fig. 3.2).

Fig. 3.3: Origin of an Earthquake

Activity

Take a container, fillit with water andclose it with a lid. Putthe water to boil. Nowput some peas, spoonand beads on top onthe lid. What do younotice? As the waterboils the lid begins toshake. The thingswhich you have puton the lid alsovibrate. The beads rolldown and the spoonvibrates to make asound. In the samemanner, the earthvibrates when anearthquake occurs.

Do you know?

There are three typesof earthquake waves.1. P waves or

longitudinal waves2. S waves or

transverse waves3. L waves or surface

wavesTry to find out theproperties of thesewaves from anencyclopedia.

Similarly, when the Lithospheric plates move, thesurface of the earth vibrates. The vibrations can travelall round the earth. These vibrations are calledearthquakes (Fig. 3.3). The place in the crust where themovement starts is called the focus. The place on thesurface above the focus is called the epicentre.Vibrations travel outwards from the epicentre as waves.Greatest damage is usually closest to the epicentre andthe strength of the earthquake decreases away fromthe centre.

Endo(inside)Exo(outside)

Endogenic

Exogenic

+ genic(origin)

13OUR CHANGING EARTH

.

14 OUR ENVIRONMENT

Activity

Do you know?

An earthquake ismeasured with amachine called aseismograph. Themagnitude of theearthquake ismeasured on theRichter scale. Anearthquake of 2.0 orless can be felt only alittle. An earthquakeover 5.0 can causedamage from thingsfalling. A 6.0 orhigher magnitude isconsidered verystrong and 7.0 isclassified as a majorearthquake.

A Seismograph

EARTHQUAKE PREPAREDNESS

Where to take shelter during an earthquake —Safe Spot – Under a kitchen counter, table or desk,against an inside corner or wall.Stay Away from – Fire places, areas around chimneys,windows that shatter including mirrors and pictureframes.Be Prepared – Spread awareness amongst your friendsand family members and face any disaster confidently.

Fig. 3.3a: Destructioncaused by an Earthquake

at Bhuj

1. Read the ‘Earthquake – A case study’ given in theform of headlines that appeared in the newspapersafter the quake. Arrange the events in the rightsequence of their happening.

2. Imagine if a quake suddenly shook in the middle ofthe school day, where would you go for safety?

Although earthquakes cannot be predicted, theimpact can certainly be minimised if we are preparedbefore-hand.

Some common earthquake prediction methodsadopted locally by people include studying animalbehaviour; fish in the ponds get agitated, snakes cometo the surface.

EARTHQUAKE HITS BHUJA massive earthquake measuring 6.9 on Richterscale hit Bhuj Town on 26th January 2001.

Fire in the city

Hundreds of firesstarted as charcoal,cookers overturned.

Emergency declaredin quake zone

The President declaresa state of emergency.

Atleast 971 students

and 31 teachers are

feared to have lost

their lives following

the collapse of

school buildings.

School worstaffected

CM’S APPEAL TO THE CENTRE

Gujarat appeals forfinancial help. TheChief Minister ofGujarat has launched

an appeal for theCentre to deal withthe disaster.

Destruction of BhujPhone lines, waterpipelines and powerstations transmissionlines were knocked out.

1

2 3

4

5

6

7

BHUJ RELIEF EFFORTBLIGHTED..

Three days after thequake, concern roseabout food, blankets

and medical suppliesnot reaching everyone.

Earthquake – A Case Study


Fig. 3.5: Features made by a river in a flood plain

Do you know?MAJOR LAND FORMS

The landscape is being continuously worn away by twoprocesses – weathering and erosion. Weathering is thebreaking up of the rocks on the earth’s surface. Erosionis the wearing away of the landscape by different agentslike water, wind and ice. The eroded material is carriedaway or transported by water, wind, etc. and eventuallydeposited. This process of erosion and deposition createdifferent landforms on the surface of the earth.

Work of a RiverThe running water in the river erodes the landscape. Whenthe river tumbles at steep angle over very hard rocks ordown a steep valley side it forms a waterfall (Fig. 3.4).

• There arethousands of smallwaterfalls in theworld. The highestwaterfall is AngelFalls of Venezuelain South America.The other waterfallsare Niagara fallslocated on theborder betweenCanada and USA inNorth America andVictoria Falls onthe borders ofZambia andZimbabwe in Africa.

The Niagra falls

Hard rock

Softer rock undercutby the power ofthe water

Fig. 3.4: Waterfall

As the river enters the plain it twists and turns forminglarge bends known as meanders. Due to continuouserosion and deposition along the sides of the meander,the ends of the meander loop come closerand closer. In due course of time themeander loop cuts off from the river andforms a cut-off lake, also called an ox-bowlake. At times the river overflows its banks.This leads to the flooding of theneighbouring areas. As it floods, itdeposits layers of fine soil and othermaterial called sediments along itsbanks. This leads to the formationof a flat fertile floodplain. The raisedbanks are called levees. As the riverapproaches the sea, the speed of theflowing water decreases and the

16 OUR ENVIRONMENT

river begins to break upinto a number of streamscalled distributaries. Theriver becomes so slow thatit begins to deposit its load.Each distributary forms itsown mouth. The collectionof sediments from all themouths forms a delta.

Work of Sea WavesThe erosion and deposition ofthe sea waves gives rise tocoastal landforms. Seawavescontinuously strike at therocks. Cracks develop. Overtime they become larger andwider. Thus, hollow like cavesare formed on the rocks. Theyare called sea caves. As thesecavities become bigger andbigger only the roof of thecaves remain, thus forming seaarches . Further, erosionbreaks the roof and only walls

are left. These wall like features are called stacks.The steep rocky coast rising almost vertically abovesea water is called sea cliff. The sea waves depositsediments along the shores forming beaches.

Work of IceGlaciers are “rivers” of ice whichtoo erode the landscape bybulldozing soil and stones toexpose the solid rock below.Glaciers carve out deep hollows.As the ice melts they get filledup with water and becomebeauti ful lakes in themountains. The material carriedby the glacier such as rocks bigand small, sand and silt getsdeposited. These deposits formglacial moraines.

Let’s do

Can you find outnames of some riversof the world that forma delta?

Fig. 3.8: Glacier

Main river Distributary

Fig. 3.6: Delta

Sea Cave

Sea Arch

Stack

Fig. 3.7: Features made by sea waves


Work of windHave you ever visited a desert? Try to collect somepictures of sand dunes.

An active agent of erosion and deposition in the desertsis wind. In deserts you can see rocks in the shape of amushroom, commonly called mushroom rocks. Windserode the lower section of the rock more than the upperpart. Therefore, such rocks have narrower base and widertop. When the wind blows, it lifts and transports sandfrom one place to another. When it stops blowing thesand falls and gets deposited in low hill – like structures.These are called sand dunes (Fig. 3.9). When the grainsof sand are very fine and light, the wind can carry it oververy long distances. When such sand is deposited inlarge areas, it is called loess. Large deposits of loess isfound in China.Fig. 3.9: Sand Dunes

Exercises


(i) Why do the plates move?

(ii) What are exogenic and endogenic forces?

(iii) What is erosion?

(iv) How are flood plains formed?

(v) What are sand dunes?

(vi) How are beaches formed?

(vii) What are ox bow lakes?


(i) Which is not an erosional feature of sea waves?(a) Cliff (b) Beach (c) Sea cave

(ii) The depositional feature of a glacier is:(a) Flood plain (b) Beach (c) Moraine

(iii) Which is caused by the sudden movements of the earth?(a) Volcano (b) Folding (c) Flood plain

(iv) Mushroom rocks are found in:(a) Deserts (b) River valleys (c) Glaciers

(v) Ox bow lakes are found in:(a) Glaciers (b) River valleys (c) Deserts

18 OUR ENVIRONMENT


(i) Glacier (a) Sea shore

(ii) Meanders (b) River of ice

(iii) Beach (c) Rivers

(iv) Sand dunes (d) Vibrations of earth

(v) Waterfall (e) Hard bed rock

(vi) Earthquake (f) Deserts

4. Give reasons.

(i) Some rocks have a shape of a mushroom.

(ii) Flood plains are very fertile.

(iii) Sea caves are turned into stacks.

(iv) Buildings collapse due to earthquakes.

5. Activity.

Observe the photographs given below. These are various features made by ariver. Identify them and also tell whether they are erosional or depositional orlandforms formed by both.

Photograph Name of theFeature

Type(Erosional or Depositional or Both)


Down

1. Rise and fall of water caused by frictionof wind on water surface

3. Flow of water in channel

5. Steep perpendicular face of rock alongsea coast

6. Debris of boulder and coarse materialcarried by glacier

8. Crescent shaped lake formed by rivermeander

10. Fine sand deposited by action of wind

13. Isolated mass of rising steep rock nearcoastline

14. Alluvial tracts of land at mouth of riverformed by river deposits

Across

2. Loop like bend of river

4. Solid form of water

7. Moving mass of ice

9. Sudden descent of water in bed of river

11. Natural cavity on weak rocks formed byaction of waves

12. Embankment on river that keeps riverin its channel

13. Large body of sea water

14. Dry area where sand dunes are found

15. Small hill of sand piled by action of wind

16. Flat plain formed by river deposits duringtime of flood

6. For fun.

Solve the crossword puzzle with the help of given clues.

Our earth is surrounded by a huge blanket of aircalled atmosphere. All living beings on this earthdepend on the atmosphere for their survival. Itprovides us the air we breathe and protects us fromthe harmful effects of the sun’s rays. Without thisblanket of protection, we would be baked alive by theheat of the sun during day and get frozen duringnight. So it is this mass of air that has made thetemperature on the earth liveable.

COMPOSITION OF THE ATMOSPHERE

Do you know that the air we take in while breathing isactually a mixture of many gases? Nitrogen and oxygenare two gases which make up the bulk of the

atmosphere. Carbondioxide, helium,ozone, argon andhydrogen are foundin lesser quantities.Apart from thesegases, tiny dust

particles are alsopresent in the air. The

pie chart gives you thepercentage of different

constituents of air (Fig. 4.1).Nitrogen is the most

plentiful gas in the air. Whenwe inhale, we take someamount of nitrogen into ourlungs and exhale it. Butplants need nitrogen for theirsurvival. They can not take

4Air

Fig. 4.1: Constituents of Air

Do you know?

Carbon dioxidereleased in theatmosphere creates agreen house effect bytrapping the heatradiated from theearth. It is thereforecalled a greenhousegas and without it theearth would have beentoo cold to live in.However, when itslevel in theatmosphere increasesdue to factory smokeor car fumes, the heatretained increases thetemperature of theearth. This is calledglobal warming. Thisrise in temperaturecauses the snow incoldest parts of theworld to melt. As aresult the sea levelrises, causing floods inthe coastal areas.There may be drasticchanges in the climateof a place leading toextinction of someplants and animals inthe long run.

nitrogen directly from the air. Bacteria, that live in thesoil and roots of some plants, take nitrogen from theair and change its form so that plants can use it.

Oxygen is the second most plentiful gas in the air.Humans and animals take oxygen from the air as theybreathe. Green plants produce oxygen duringphotosynthesis. In this way oxygen content in the airremains constant. If we cut trees then this balancegets disturbed.

Carbon dioxide is another important gas. Greenplants use carbon dioxide to make their food andrelease oxygen. Humans or animals release carbondioxide. The amount of carbon dioxide released byhumans or animals seems to be equal to the amountused by the plants which make a perfect balance.However, the balance is upset by burning of fuels, suchas coal and oil. They add billions of tons of carbondioxide into the atmosphere each year. As a result, theincreased volume of carbon dioxide is affecting theearth’s weather and climate.

Read and Ponder: Is global warming a serious issue in today’s world?

Do you know?

When air is heated, itexpands, becomeslighter and goes up.Cold air is denser andheavy. That is why ittends to sink down.When hot air rises,cold air fromsurrounding arearushes there to fill inthe gap. That is howair circulation takesplace.

AIR 21

22 OUR ENVIRONMENT

STRUCTURE OF THE ATMOSPHERE

Our atmosphere is divided into five layers starting fromthe earth’s surface. These are Troposphere,Stratosphere, Mesosphere, Thermosphere andExosphere (Fig. 4.2).

Troposphere: This layer is the most important layer ofthe atmosphere. Its average height is 13 km. The air

we breathe exists here.Almost all the weatherphenomena like rainfall,fog and hailstorm occur inthis layer.

Stratosphere: Above thetroposphere lies thestratosphere. It extends upto a height of 50 km. Thislayer is almost free fromclouds and associatedweather phenomenon,making conditions mostideal for flying aeroplanes.One important feature ofstratosphere is that itcontains a layer of ozonegas. We have just learnthow it protects us fromthe harmful effect of thesun rays.

Mesosphere: This is thethird layer of theatmosphere. It lies abovethe stratosphere. It extendsup to the height of 80 km.Meteorites burn up inthis layer on entering fromthe space.

Thermosphere: Inthermosphere temperaturerises very rapidly withincreasing height.Ionosphere is a part of thislayer. It extends between

10

20

30

40

50

60

70

80

90

100

Hei

ght

(km

)

Aeroplane

Mesopause

Stratopause

Tropoapuse

TROPOSPHERE

OZONE

Mt. Everest

THERMOSPHERE

MESOSPHERE

STRATOSPHERE

EXOSPHERE

Fig. 4.2: Layers of Atmosphere

AIR 23

Do you know?

You will be surprisedto know that theearth receives only 1in 2,000,000,0000parts of the sun’senergy.

80-400 km. This layer helps in radio transmission. Infact, radio waves transmitted from the earth are reflectedback to the earth by this layer.

Exosphere: The upper most layer of the atmosphereis known as exosphere. This layer has very thin air.Light gases like helium and hydrogen float into thespace from here.

WEATHER AND CLIMATE

“Is it going to rain today?” “Will it be bright and sunnytoday?” How many times have we heard this fromanxious cricket fans speculating the fate of a One Daymatch? If we imagine our body to be a radio and themind its speaker, weather is something that fiddleswith its control knobs. Weather is this hour-to-hour,day to day condition of the atmosphere. A hot or humidweather may make one irritable. A pleasant, breezyweather may make one cheerful and even plan for anouting. Weather can change dramatically from day today. However, the average weather condition of a placefor a longer period of time represents the climate of aplace. Now do you understand why we have dailyweather forecasts.

TemperatureThe temperature you feel everydayis the temperataure of theatmosphere. The degree of hotnessand coldness of the air is knownas temperature.

The temperature of theatmosphere changes not onlybetween day and night but alsofrom season to season. Summersare hotter than winters.

An important factor thatinfluences the distribution oftemperature is insolation.Insolation is the incoming solarenergy intercepted by the earth.

The amount of insolationdecreases from the equatortowards the poles. Therefore, the

Let’s do

For ten days notedown weather reportfrom a localnewspaper andobserve the changesoccurring in theweather.

Wind Vane: Shows thedirection of the wind

Rain Gauge: Measuresthe amount of rainfall

Thermometer:Measuresthe temperature

Barometre: Measuresatmospheric pressure

Fig. 4.3: Weather Instruments

24 OUR ENVIRONMENT

temperature decreases in the same manner. Now doyou understand why poles are covered with snow? Ifthe earth’s temperature rises too high, it would becometoo warm for some crops to grow. Temperature in citiesis much higher than that of villages. The concrete andmetals in buildings and the asaphalt of roads getheated up during the day. This heat is released duringthe night.

Also, the crowded high rise buildings of the citiestrap the warm air and thus raise the temperature ofthe cities.

Air PressureYou will be surprised to know that air above us pressesus with a great force on our bodies. However, we don’teven feel it. This is because the air presses us from alldirections and our body exerts a counter pressure.

Air pressure is defined as the pressure exerted by theweight of air on the earth’s surface. As we go up thelayers of atmosphere, the pressure falls rapidly. The airpressure is highest at sea level and decreases with height.Horizontally the distribution of air pressure is influencedby temperature of air at a given place. In areas wheretemperature is high the air gets heated and rises. Thiscreates a low-pressure area. Low pressure is associatedwith cloudy skies and wet weather.

In areas having lower temperature, the air is cold. Itis therefore heavy. Heavy air sinks and creates a highpressure area. High pressure is associated with clear andsunny skies.

The air always moves from high pressure areas to lowpressure areas.

WindThe movement of air from high pressure area to lowpressure areas is called wind. You can see wind at workas it blows dry leaves down the pavement or uprootstrees during a storm. Sometimes when the wind blowsgently you can even see it blowing away smoke or finedust. At times wind can be so strong that it is difficultto walk against it. You must have experienced it is noteasy to hold an umbrella on a windy day. Think ofsome other examples when strong winds have created

Do you know?

On the moon there isno air and hence noair pressure.

Astronauts have towear specialprotective space suitsfilled with air whenthey go to the moon. Ifthey did not wearthese space suits, thecounter pressureexerted by the body ofthe astronauts wouldmake the blood vesselsburst. The astronautswould bleed.

Do you know?

The standard unit ofmeasuringtemperature is degreeCelsius. It wasinvented by AndersCelsius. On theCelsius scale thewater freezes at 0°Cand boils at 100°C.

Do you know?

A wind is named afterthe direction fromwhich it blows, e.g.the wind blowing fromthe west is calledwesterly.

AIR 25

Sub-Polar Low PressureSub-Polar Low Pressure

Sub - Tropical High Pressure (Horse Latitudes)Sub - Tropical High Pressure (Horse Latitudes)

Sub - Tropical High Pressure (Horse Latitudes)Sub - Tropical High Pressure (Horse Latitudes)

Sub-Polar Low PressureSub-Polar Low Pressure

High Pressure

High Pressure

Equatorial Low Pressure (Doldrums)Equatorial Low Pressure (Doldrums)

P o l a r E a s t e r l i e s

P r e v a i l i n g W e s t e r l i e s

N o r t h e a s t T r a d e W i n d s

S o u t h e a s t T r a d e W i n d s

P o l a r E a s t e r l i e s

P r e v a i l i n g W e s t e r l i e s

60°S

23.5°N30°N

35°N

0°

60°N

23.5°S30°S

35°S

90°N

90°S

T r o p i c o f C a n c e rT r o p i c o f C a n c e r

Tropic of CapricornTropic of Capricorn

Fig. 4.4: Major Pressure Belts and Wind System

problems for you. Winds can bebroadly divided into three types.

1. Permanent winds – The tradewinds, westerlies and easterliesare the permanent winds.These blow constantlythroughout the year in aparticular direction.

2. Seasonal winds – Thesewinds change their directionin different seasons. Forexample monsoons in India.

3. Local winds – These blowonly during a particularperiod of the day or year in asmall area. For example, landand sea breeze. Do you recall thehot and dry local wind of northernplanes of India? It is called loo.

CYCLONE – NATURE’S FURY

Orissa, located on the easternseacoast of India is prone tocyclones that originate in theBay of Bengal. On 17-18October 1999, cyclone hit fivedistricts of the state. Anothersupercyclone occurred on the29 October 1999, thatdevastated large portions of thestate. The damages causedwere mainly due to threefactors: wind velocity, rain andtidal surge. The winds of upto260 km. per hour lasted for over 36 hours. These high velocity windsuprooted trees and damaged the kutcha houses. Roof tops of severalindustrial sheds and other houses were also blown away. Power supplyand telecom lines snapped completely. Heavy rain occurred under theinfluence of the cyclone for three days continuously. These rains led toflooding in the major rivers of Orissa. The cyclonic winds caused tidalwaves that swept 20 km. inland and brought massive destruction to thecoastal areas. The 7 to 10 m high tidal wave intruded suddenly andcaused massive damage to the standing paddy crops.

Destruction caused by cyclone

26 OUR ENVIRONMENT

The cyclone originated as a “depression” in the Gulf of Thailand,near east of Port Blair, on 25 October 1999 and gradually moved in anorthwestward direction. It intensified into a supercyclone and hit the areabetween Erasama and Balikuda in Orissa on 29 October at 10.30 a.m.

The supercyclone swept entire the coast of Orissa including thecities of Bhubaneshwar and Cuttack and 28 coastal towns. About 13million people were affected. A large number of livestock were killed.Standing crops of paddy, vegetables and fruits were heavily damaged.Due to salinisation caused by tidal surge, large tracts of agriculturalland have turned infertile. Large tracts of sal, teak and bambooplantations have disappeared. The mangrove forests between Paradeepand Konark vanished.

MoistureWhen water evaporates from land and differentwater bodies, it becomes water vapour. Moisturein the air at any time, is known as humidity.When the air is full of water vapour we call it ahumid day. As the air gets warmer, its capacityto hold the water vapour increases and so itbecomes more and more humid. On a humidday, clothes take longer to dry and sweat fromour body does not evaporate easily, making usfeel very uncomfortable.

When the water vapour rises, it starts cooling.The water vapour condenses causing formationof droplets of water. Clouds are just masses ofsuch water droplets. When these droplets of waterbecome too heavy to float in air, then they comedown as precipitation.

Jet planes flying in the sky leave a white trailbehind them. The moisture from their enginescondenses. We see trails of this condensedmoisture for some time when there is no airmovement to disturb it.

Precipitation that comes down to the earthin liquid form is called rain. Most of the groundwater comes from rainwater. Plants help preservewater. When trees on hill sides are cut, rainwaterflows down the bare mountains and can causeflooding of low lying areas. On the basis ofmechanism, there are three types of rainfall: theconvectional rainfall, the orographic rainfall andthe cyclonic rainfall (Fig. 4.5).

Cyclonic Rainfall

Convectional Rainfall

Relief (Orographic) Rainfall

Fig. 4.5: Types of Rainfall

Warmair

Coldair

Moistair

Warmair

AIR 27

Exercises


(i) What is atmosphere?

(ii) Which two gases make the bulk of the atmosphere?

(iii) Which gas creates green house effect in the atmosphere?

(iv) What is weather?

(v) Name three types of rainfall?

(vi) What is air pressure?


(i) Which of the following gases protects us from harmful sun vays?(a) Carbon dioxide (b) Nitrogen (c) Ozone

(ii) The most important layer of the atmosphere is(a) Troposphere (b) Thermosphere (c) Mesosphere

(iii) Which of the following layers of the atmosphere is free from clouds?(a) Temperature (b) Air pressure (c) Wind direction

(iv) As we go up the layers of the atmosphere, the pressure(a) Increases (b) Decreases (c) Remains the same

(v) When precipitation comes down to the earth in the liquid form,it is called(a) Cloud (b) Rain (c) Snow


(i) Trade Winds (a) Seasonal wind

(ii) Loo (b) Horizontal movement of Air

(iii) Monsoon (c) Permanent wind

(iv) Wind (d) Local wind

4. Give reasons.

(i) Wet clothes take longer time to dry on a humid day?

(ii) Amount of insolation decreases from equator towards poles?

Do you know?

Other forms ofprecipitation aresnow, sleet, hail.

Rainfall is very important for the survival of plants andanimals. It brings fresh water to the earth’s surface. Ifrainfall is less – water scacity and drought occur. On theother hand if it is more, floods take place.

28 OUR ENVIRONMENT

Down1. Amount of water vapour in air

2. Condensation of water vapours arounddust particles in atmosphere

3. Example of local wind blowing in summerin northern india

4. Short term changes in atmosphere

5. Precipitation in liquid form

7. Blanket of air around the earth

9. Instrument to measure pressure

10. Incoming solar radiation

13. Reduces visibility in winters

17. It is ....... time when sun is overhead

Across6. An Indian tree having extraordinary

quality of providing oxygen round theclock

8. Gas present in atmosphere occupyingonly 0.03% by volume

11. Outermost layer of atmosphere

12. Mixture of many gases

14. Life giving gas

15. Air in motion

16. An indian tree valued highly formedicinal properties

18. Gas protecting us from harmful sunrays

19. Low pressure area

5. For fun.

(i) Solve this Crossword puzzle with the help of given clues:

AIR 29

1.

2.

3.

4.

5.

6.

7.

Sunny day

Day Weather

(ii) Make a weather calendar for one week. Use pictures or symbols to showdifferent types of weather. You can use more than one symbol in a day, ifthe weather changes. For example, the sun comes out when rain stops. Anexample is given below:

Glossary

Fig. 5.1: Water Cycle

Condensation

Precipitation

Run off

Evaporation

5 Water

When you think of water, what images come to yourmind? You think of rivers, the waterfalls, the pitter patterof raindrops, water in your taps... Children love to floatpaper boats in rain puddles. By noon the puddles vanish.Where does the water go?

The sun’s heat causes evaporation of water vapour.When the water vapour cools down, it condenses andforms clouds. From there it may fall on the land or seain the form of rain, snow or sleet.

The process by which water continually changes itsform and circulates between oceans,atmosphere and land is knownas the water cycle (Fig 5.1).

Our earth is like aterrarium. The same waterthat existed centuries agostill exists today. Thewater used to irrigate afield in Haryana mayhave flowed down theAmazon River ahundred years ago.

The major sourcesof fresh water are therivers, ponds,springs andglaciers. Theocean bodies andthe seas containsalty water. Thewater of theoceans is salty orsaline as itcontains large

Terrarium: It is anartificial enclosure forkeeping small houseplants.

Activity

Fill one-fourth of a bigjar with soil andpress it well. Put athin layer of humuson top of it. Plant thelargest plants firstand then arrange thesmaller area aroundthem. Spray thearrangement withwater and close thejar. The water thatevaporates from theleaves and soilcondenses and fallsback as forms ofwater drops.

A Terrarium

Make your ownTerrarium

Fig

. 5

.2:

Wor

ld –

Ma

jor

Sea

s, L

ak

es a

nd

Riv

ers

WATER 31

amount of dissolved salts. Most of the salt is sodiumchloride or the common table salt that you eat.

32 OUR ENVIRONMENT

Do you know?

Activity

Distribution of fresh water

1 Drop = rivers

9 Spoons =icecaps

2 Spoons =ground water

½ Spoons =fresh water lakes

Take 2 litres of water. Let it represent the totalwater on the surface of the earth. Measure out12 spoons of water from this vessel into anotherbowl. The water that is left behind in the vesselrepresents the salty water found in oceans andseas. This water is obviously not fit forconsuming. It is saline (contains salts).

The 12 spoons of water that was taken in abowl is the total amount of fresh water on earth.The figure shows us the distribution of this freshwater. See for yourself how much water canactually be used by you.

Do you know?

Dead sea in Israel hassalinity of 45 partsper thousand.Swimmers can floatin it because theincreased salt contentmake it dense.

Oceans : 97.3

Ice-caps : 02.0

Ground water : 0.68Fresh Water

Fresh water lakes : 0.009Inland seas &

Salt lakes : 0.009

Atmosphere : 0.0019

Rivers : 0.0001

100.00

Saline Water

Fresh Water

Salinity is theamount of salt ingrams present in1000 grams of water.The average salinityof the oceans is 35parts per thousand.

DISTRIBUTION OF WATER BODIES

We all know that three-fourth of the earth surface iscovered by water. If there is more water than land onthis earth, why do so many countries face water scarcity?

Is all the water on earth available to us? The followingtable gives the distribution of water in percentage.

Water distribution can be demonstrated by a simpleactivity (see activity box).

Water is absolutely essential for survival. Water alonecan quench our thirst when we are thirsty. Now don’tyou think we are wasting a precious resource when weuse water carelessly?

WATER 33

OCEAN CIRCULATION

There is something magical about walking bare feeton the seashore. The wet sand on the beach, the coolbreeze, the seabirds, the smell of the salt in the airand music of the waves; everything is so fascinating.Unlike the calm waters of ponds and lakes, ocean waterkeeps moving continuously. It is never still. Themovements that occur in oceans can be broadlycategorised as: waves, tides and currents.

Do you know?

March 22 iscelebrated as WorldWater Day when theneed to conservewater is reinforced indifferent ways.

• Why water is important for us?• Suggest some ways in which water can be conserved in your home

and in your school

Fig. 5.3: Pacific Ocean

34 OUR ENVIRONMENT

WavesWhen you are playing throw ball on the beach and theball falls into the water, what happens? It is fun to watchhow the ball gets washedback to the shore by thewaves. When the water on thesurface of the ocean rises andfalls alternately, they arecalled waves.

Do you know?

Tsunami is aJapanese word thatmeans “Harbourwaves” as theharbours getdestroyed wheneverthere is tsunami.

TSUNAMI – THE EARTH’S PANDEMONIUM

Tsunami or the harbour wave struck havoc in the Indian Ocean on the26 December 2004. The wave was the result of the earthquake that hadits epicenter close to the western boundary of Sumatra. The magnitudeof the earthquake was 9.0 on the Richter scale. As the Indian platewent under the Burma plate, there was a sudden movement of the seafloor, causing the earthquake. The ocean floor was displaced by about10 – 20m and tilted in a downwardly direction. A huge mass of oceanwater flowed to fill in the gap that was being created by the displacement.This marked the withdrawal of the water mass from the coastlines ofthe landmasses in the south and southeast Asia. After thrusting of theIndian plate below the Burma plate, the water mass rushed back towardsthe coastline. Tsunami travelled at a speed of about 800km. per hour,comparable to speed of commercial aircraft and completely washed away

Do you know?

Waves are formedwhen gentle windsscrape across theocean surface. Thestronger the windblows, the bigger thewave becomes.

Fig. 5.4: Waves

During a storm, the winds blowing at very high speedform huge waves. These may cause tremendousdestruction. An earthquake, a volcanic eruption orunderwater landslides can shift large amounts of oceanwater. As a result a huge tidal wave called tsunami, thatmay be as high as 15m., is formed. The largest tsunamiever measured was 150m. high. These waves travel at aspeed of more than 700 km. per hour. The tsunami of2004 caused wide spread damage in the coastal areas ofIndia. The Indira point in the Andaman and Nicobarislands got submerged after the tsunami.

WATER 35

some of the islands in the Indian ocean. The Indira point in the Andamanand Nicobar islands that marked the southernmost point of India gotcompletely submerged. As the wave moved from earthquake epicenterfrom Sumatra towards the Andaman islands and Sri Lanka the wavelength decreased with decreasing depth of water. The travel speed alsodeclined from 700-900km. per hour to less than 70km. per hour. Tsunamiwaves travelled upto a depth of 3 km. from the coast killing more than10,000 people and affected more than lakh of houses. In India, theworst affected were the coastal areas of Andhra Pradesh, Tamil Nadu,Kerala, Pondicherry and the Andaman and Nicobar Islands.

While the earthquake cannot be predicted in advance, it is possibleto give a three-hour notice of a potential tsunami. Such early warningsystems are in place across the Pacific ocean, but not in the IndianOcean. Tsunamis are rare in the Indian Ocean as the seismic activityis less as compared to the Pacific.

Destruction caused by tsunami on Tamil Nadu Coast

The tsunami that ravaged the South and South east Asian coasts inDecember 2004, is the most devastating tsunami in the last severalhundred years. The large damage caused to life and property wasprimarily a result of lack of monitoring, the early warning systems andknowledge among the coast dwellers of Indian ocean.

The first indication that tsunami is approaching is the rapidwithdrawal of water from the coastal region, followed by destructivewave. When this happened on the coast, instead of people going to highground, they started assembling at the coast to view the miracle. As aconsequence there was a large casualty of curious onlookers when thegigantic wave (tsunami) struck.

TidesThe rhythmic rise and fall of ocean water twice in aday is called a tide. It is high tide when water coversmuch of the shore by rising to its highest level. It islow tide when water falls to its lowest level and recedesfrom the shore.

36 OUR ENVIRONMENT

The strong gravitational pullexerted by the sun and the moonon the earth’s surface causes thetides. The water of the earth closerto the moon gets pulled underthe influence of the moon’sgravitational force and causes hightide. During the full moon and newmoon days, the sun, the moon andthe earth are in the same line andthe tides are highest. These tidesare called spring tides. But whenthe moon is in its first and lastquarter, the ocean waters get drawnin diagonally opposite directions bythe gravitational pull of sun andearth resulting in low tides. Thesetides are called neap tides (Fig. 5.5).

High tides help in navigation.They raise the water level close tothe shores. This helps the ships toarrive at the harbour more easily.The high tides also help in fishing.Many more fish come closer to the

shore during the high tide. This enables fishermento get a plentiful catch. The rise and fall of water dueto tides is being used to generate electricity insome places.

OCEAN CURRENTS

Ocean currents are streams of water flowing constantlyon the ocean surface in definite directions. The oceancurrents may be warm or cold (Fig. 5.6). Generally,the warm ocean currents originate near the equatorand move towards the poles. The cold currents carrywater from polar or higher latitudes to tropical or lowerlatitudes. The Labrador Ocean current is cold currentwhile the Gulf Stream is a warm current. The oceancurrent influence the temperature conditions of thearea. Warm currents bring about warm temperatureover land surface. The areas where the warm and coldcurrents meet provide the best fishing grounds of the

Activity

Fill three-fourths of abucket with tapwater. Heat the waterby putting animmersion road onone side of thebucket. On the otherside introduce an icetray just removedfrom the freezer. Adda drop of red ink toobserve the path ofcurrent by theprocess of convection.

Fig. 5.5: Spring Tides and Neap Tide

Spring Tide

SunSun EarthEarth

MoonMoon

SunSun EarthEarth

MoonMoon

SunSun EarthEarth

MoonMoon

Neap Tide

WATER 37

Exercises

Fig. 5.6: Ocean Currents

world. Seas around Japan and the eastern coast ofNorth America are such examples. The areas where awarm and cold current meet also experience foggyweather making it difficult for navigation.


(i) What is precipitation?(ii) What is water cycle?(iii) What are the factors affecting the height of the waves?(iv) Which factors affect the movement of ocean water?(v) What are tides and how are they caused?(vi) What are ocean currents?

2. Give reasons.(i) Ocean water is salty.(ii) The quality of water is deterioting.

38 OUR ENVIRONMENT


(i) The process by which water continually changes its form and circulatesbetween oceans, atmosphere and land(a) Water cycle (b) Tides (c) Ocean currents

(ii) Generally the warm ocean currents originate near(a) Poles (b) Equator (c) None of these

(iii) The rythmic rise and fall of ocean water twice in a day is called(a) Tide (b) Ocean current (c) Wave


(i) Caspian Sea Largest lake(ii) Tide Periodic rise and fall of water(iii) Tsunami Strong seismic waves.(iv) Ocean currents Streams of water moving in definite paths.

5. For fun.

Be a Detective

(i) The name of one river is hidden in each of the sentences below. Spot it.

Example: Mandra, Vijayalakshmi and Surinder are my best friends

Answer: Ravi

(a) The snake charmer’s bustee, stables where horses are housed, andthe piles of wood, all caught fire accidentally. (Hint: Another name forRiver Brahmputra)

(b) The conference manager put pad, material for reading and a pencil foreach participant. (Hint: A distributary on the Ganga-Brahmputra delta)

(c) Either jealousy or anger cause a person’s fall (Hint: Name of a juicy fruit!)

(d) Bhavani germinated the seeds in a pot (Hint: Look for her in West Africa)

(e) “I am a zonal champion now” declared the excited atheletic. (Hint: Theriver that has he biggest basin in the world)

(f) The tiffin box rolled down and all the food fell in dusty potholes. (Hint:Rises in India and journeys through Pakistan)

(g) Malini leaned against the pole when she felt that she was going to faint.(Hint: Her delta in Egypt is famous)

(h) Samantha mesmerised everybody with her magic tricks. (Hint: Londonis situated on her estuary)

(i) “In this neighbourhood, please don’t yell! Owners of these houses liketo have peace”. Warned my father when we moved into our new flat”.(Hint: colour!)

(j) ‘Write the following words, Marc!’ “On”, “go”, “in”…….. said the teacherto the little boy in KG Class. (Hint: Rhymes with ‘bongo’)

Now make some more on your own and ask your classmates to spot thehidden name. You can do this with any name: that of a lake, mountains,trees, fruits, school items etc.

Carry on Detective

(ii) With the help of an atlas, draw each river which you discoverd inFor fun (i), on an outline map of the world.

6 Natural Vegetationand Wild Life

Salima was excited about the summer camp she wasattending. She had gone to visit Manali in HimachalPradesh along with her class mates. She recalled howsurprised she was to see the changes in the landformand natural vegetation as the bus climbed higher andhigher. The deep jungles of the foothills comprising saland teak slowly disappeared. She could see tall treeswith thin pointed leaves and cone shaped canopies onthe mountain slopes. She learnt that those were coniferoustrees. She noticed blooms of bright flowers on tall trees.These were the rhododendrons. From Manali as she wastravelling up to Rohtang pass she saw that the land wascovered with short grass and snow in some places.

From Salima’sobservations, we surmisethat there is a closerelationship betweenheight of land and thecharacter of vegetations.With the change in height,the climate changes andthat changes naturalvegetation. The growth ofvegetation depends on

temperature and moisture. It also depends on factorslike slope and thickness of soil.

The type and thickness of natural vegetation variesfrom place to place because of the variation in these factors.

Natural vegetation is generally classified in to threebroad categories as follows:

(a) Forests: Which grow where temperature and rainfallare plentiful to support a tree cover. Depending uponthese factors, dense and open forests grown.

Let’s do

Now can you tell whySalima saw changesin the naturalvegetation as sheclimbed higher andhigher? What type ofvegetations did shesee in the Himalayasstarting with thefoothills and going tothe higher altitudes?

Let’s do

• Like Salima, whenyou go to visit anynew place, noticethe type of naturalvegetation occurringthere and try tothink of factorsresponsible for thegrowth of suchvegetation in thathabitat.

• Note down if anyhuman interferencehas taken place inthat area in termsof deforestation,grazing, cultivationof cash crops,constructionalactivities etc.

Fig. 6.1: Rhododendron

40 OUR ENVIRONMENT

(b) Grasslands: Which grow in the region of moderate rain.

(c) Shrubs: Thorny shrurbs and scrubs grow in the dryregion (Fig. 6.2).

Salima was sharing her experience of Himalayan tripwith her father. Her father visited various places in theworld. He told Salima about his observations of the varietyof vegetation in different parts of different continents.Hementioned about coniferous forests in the sub polarregions, thorny bushes in the deserts, thick tropicalhardwood forest in the humid regions and many more.Salima realised the Himalayas have almost all variety ofvegetation which one can see while moving from theequator to the polar region.

The changes in the type of natural vegetation occurmainly because of the changes of climatic condition. Letus get to know the different types of natural vegetationof the world with their characteristic features and wildlifeinhabiting there.

FORESTS

Tropical Evergreen ForestsThese forests are also called tropical rainforests(Fig. 6.3). These thick forests occur in the regions nearthe equator and close to the tropics. These regions arehot and receive heavy rainfall throughout the year. Asthere is no particular dry season, the trees do not shedtheir leaves altogether. This is the reason they arecalled evergreen. The thick canopies of the closelyspaced trees do not allow the sunlight to penetrateinside the forest even in the day time. Hardwood treeslike rosewood, ebony, mahogany are common here.

Do you know?

The tropical evergreenforest in Brazil is soenormous that it islike the lungs of theearth: Can you tellwhy?

Do you know?

Anaconda, one of theworld’s largest snakesis found in thetropical rainforest. Itcan kill and eat alarge animal such asa crocodile. Fig. 6.3: Tropical Evergreen Forests

Fig. 6.2: Thorny shrubs

NATURAL VEGETATION AND WILD LIFE 41

Tropical Deciduous ForestsTropical deciduous are the monsoon forests found inthe large part of India,northern Australia and in centralAmerica (Fig. 6.4).These regions experience seasonalchanges. Trees shed their leaves in the dry season toconserve water. The hardwood trees found in theseforests are sal, teak, neem and shisham. Hardwood treesare extremely useful for making furniture, transportand constructional materials. Tigers, lions, elephants,langoors and monkeys are the common animals of theseregions (Fig. 6.5, 6.6 and 6.8).

Fig. 6.4: Tropical Deciduous Forests

Fig. 6.5: Tiger

Fig. 6.6: Golden Langoor

Let’s do

• Where in India dotropical evergreenand tropicaldeciduous forestsoccur? Name thestates.

• Which type of forestdominates mostpart of India?

Fig. 6.7: Temperate Evergreen Forest

Temperate Evergreen ForestsThe temperate evergreen forests are located in the mid-latitudinal coastal region (Fig. 6.7). They are commonlyfound along the eastern margin of the continents, e.g., Insouth east USA, South China and in South East Brazil.They comprise both hard and soft wood trees like oak,pine, eucalyptus, etc.

Fig. 6.8: Elephants

42 OUR ENVIRONMENT

Temperate Deciduous ForestsAs we go towards higher latitudes, there are moretemperate deciduous forests (Fig. 6.11). These are foundin the north eastern part of USA, China, New Zealand,Chile and also found in the coastal regions of WesternEurope. They shed their leaves in the dry season. Thecommon trees are oak, ash, beech, etc. Deer, foxes, wolvesare the animals commonly found. Birds like pheasants,monals are also found here (Fig. 6.9 and 6.10).

Do you know?

• Mediterranean treesadapt themselves todry summers withthe help of theirthick barks and waxcoated leaves whichhelp them reducetranspiration.

• Mediterraneanregions are knownas ‘Orchards of theworld’ for their fruitcultivation.

Fig. 6.12: A vineyard in the Mediterranean Region

Fig. 6.9: Pheasant

Fig. 6.10: Monal

Fig. 6.11: Temperate Deciduous Forest

Mediterranean VegetationYou have learnt that most of the east and north eastmargins of the continents are covered by temperateevergreen and deciduous trees. The west and south westmargins of the continents are different. They haveMediterranean vegetation (Fig. 6.12). It is mostly foundin the areas around the Mediterranean sea in Europe,Africa and Asia, hence the name. This kind of vegetationis also found outside the actual Mediterranean region inCalifornia in the USA, south west Africa, south western


Let’s doSouth America and South west Australia. These regionsare marked for hot dry summers and mild rainy winters.Citrus fruits such as oranges, figs, olives and grapes arecommonly cultivated here because people have removedthe natural vegetation in order to cultivate what theywant to. There isn’t much wildlife here.

Coniferous ForestsIn the higher latitudes (50° – 70°) of Northernhemisphere the spectacular Coniferous forests are found(Fig. 6.13 a and b). These are also called as Taiga. Theseforests are also seen in the higher altitudes. These arethe trees which Salima found in the Himalayas inabundance. They are tall, softwood evergreen trees.These woods are very useful for making pulp, which isused for manufacturing paper and newsprint. Matchboxes and packing boxes are also made from softwood.Chir, pine, cedar are the important variety of trees inthese forests. Silver fox, mink, polar bear are thecommon animals found here.

• Look around in yoursurroundings andfind out the articlesmade of hard woodand soft wood.

• Find out and learnfew names of treesof your locality.

Fig. 6.13 (b): Snow covered Coniferous ForestFig. 6.13 (a): Coniferous Forest

GRASSLANDS

Tropical grasslands: These grow on eitherside of the equator and extend till the tropics(Fig. 6.14). This vegetation grows in theareas of moderate to low amount of rainfall.They can grow very tall, about 3 to 4 metresin height. Savannah grasslands of Africaare of this type. Elephants, zebras, giraffes,deer, leopards are common in tropicalgrasslands (Fig. 6.15).

Do you know?

Taiga means pure oruntouched in theRussian language

Fig. 6.14: Tropical Grassland

44 OUR ENVIRONMENT

Do you know?

Temperate grasslands: These are found in the mid-latitudinal zones and in the interior part of thecontinents. Usually, grass here is short andnutritious.Wild buffaloes, bisons, antilopes are commonin the temperate region.

Thorny bushes: These are found in the dry desert likeregions.Tropical deserts are located in the westernmargins of the continents. The vegetation cover is scarcehere because of scanty rain and scorching heat. Identifythe desert regions in the world map given. Can you namethe great desert of India? Name some of the commonanimals of the desert which you have learnt earlier.

If you reach the polar region you will find the placeextremely cold. The growth of natural vegetation is verylimited here. Only mosses, lichens and very small shrubsare found here. It grows during the very short summer.This is called Tundra type of vegetation. This vegetationis found in the polar areas of Europe, Asia and NorthAmerica. The animals have thick fur and thick skin toprotect themselves from the cold climatic conditions, seal,walruses, musk-oxen, Arctic owl, Polar bear and snowfoxes are some of the animals found here (Fig. 6.16).

Salima’s father showed her some photographs of thickforests. In some of the photographs, Salima observedthat people were cutting trees and clearing the forests.

Her father explained that the localpeople wanted their land foragriculture and settlements, sothey cleared up the forests.Salima started wondering forestsare cleared, then where will thewild lives go? Will the forest takeits original shape again? If peoplego on cutting the trees like these,will there be enough oxygen,water vapour, timbers, fruits, nutsavailable in future?

Do you agree with Salima?Hold a discussion with yourfriends about the depletion of ourdiversified flora and fauna.Suggest some measures toconserve them.

Grasslands areknown by differentnames in differentregions.

Tropical GrasslandsEast Africa- SavannaBrazil- CamposVenezuela- Llanos

Temperate GrasslandsArgentina- PampasN. America- PrairieS. Africa- VeldC. Asia- SteppeAustralia- Down

Fig. 6.15: Giraffes

Fig. 6.16

Walrus Polar Bear

Seal


Exercises


(i) Which are the two factors on which the growth of vegetation mostly depends?

(ii) Which are the three broad categories of natural vegetation?

(iii) Name the two hardwood trees commonly found in tropical evergreen forest.

(iv) In which part of the world and tropical deciduous forest is found?

(v) In which climatic conditions, citrus fruits cultivated?

(vi) Mention the uses of coniferous forest.

(vii) In which part of the world is seasonal grassland is found?


(i) Mosses and Lichens are found in:(a) Desertic Vegetation(b) Tropical evergreen forest(c) Tundra vegetation

(ii) Thorny bushes are found in:(a) Hot and humid tropical climate(b) Hot and dry desertic climate(c) Cold polar climate

(iii) In tropical evergreen forest, one of the common animals is:(a) Monkey (b) Girraffe (c) Camel

(iv) One important variety of coniferous forest is:(a) Rosewood (b) Pine (c) Teak

(v) Steppe grassland is found in(a) S. Africa (b) Australia (c) Russia


(i) Walrus (a) Soft wood tree

(ii) Cedar (b) An animal of tropical deciduous forest

(iii) Olives (c) A polar animal

(iv) Elephants (d) Temperate grassland in Antarctica

(v) Campos (e) A citrus fruit

(vi) Downs (f) Tropical grassland of Brazil

4. Give reasons.

(i) The animals in polar region have thick fur and thick skin.

(ii) Tropical deciduous trees shed their leaves in the dry season.

(iii) The type and thickness of vegetation changes from place to place.

5. Activity.

(i) Collect pictures and photographs of forests and grasslands of different partsof world. Write one sentence below each picture.

(ii) Make a collage of rainforest, grassland and coniferous forests.

46 OUR ENVIRONMENT

6. For fun.

In the crossword table given below, some words are hidden. They are all aboutvegetation and wildllife and are to be found horizontally and vertically. Twohave been worked out for you. Work in pairs with a friend.

M T N L P L M E H R T B A M B O O P

B E A R A I X S E E R C M W H A L E

T L P F L O R A N L E O P A R D C E

A E I A M N L I C H E N S L F O A P

N P G U D O G R T Z X E D R H X M A

A H T N H N D P I N E S C U I V E L

C A C A M P O S G V N N A S E A L M

O N A C F O W L E E E A C D E O D A

N T C H I R N G R V E K T M O S S E

D O T E A K S R S E M E U S A P C G

A X U R M A A N G R A S S W K A R Q

P S S B H F T A I G A T U L S I U Y

G H F I R P R A I R I E S A B E B O

B R B R G O A T D E C I D U O U S W

T U N D R A X Z E B R A H O R S E L

C B E E A X L L A N O S A T P A M P

N A

D C

E M

E S

R J

D K

Q U

R M

S O

A N

V K

A E

N Y

N A

A K

A S

In Chapter 1 you have learnt that early human beingsdepended entirely on nature for food, clothing andshelter; but with time they learnt new skills to grow food,build homes and develop better means of transport andcommunication. In this way they modified theenvironment where they lived.

Settlements are places where people build theirhomes. Early human beings lived on trees and in caves.When they started to grow crops it became necessary tohave a permanent home. The settlements grew near theriver valleys as water was available and land was fertile.With the development of trade, commerce andmanufacturing, human settlements became larger.Settlement flourished and civilizations developed nearriver valleys. Do you recall the names of civilization thatgrew along the banks of rivers Indus, Tigris, Nile andHwang-He.

Settlements can bepermanent or temporary.Settlements which areoccupied for a short timeare called temporarysettlements. The peopleliving in deep forests, hot andcold deserts and mountainsoften dwell in such temporarysettlements. They practicehunting, gathering, shiftingcultivation and transhumance.However more and moresettlements today arepermanent settlements. Inthese settlements, peoplebuild homes to live in. Fig. 7.1: Human Settlement

Do you know?

The place where abuilding or asettlement develops iscalled its site.

The naturalconditions forselection of an idealsite are-1. favourable climate2. availability of

water3. suitable land4. fertile soil

48 OUR ENVIRONMENT

Glossary

Fig. 7.2: Compact Settlement

It was Mary’s birthday party. She and her friendswere waiting for Gurpreet to arrive so that Mary couldcut the cake. At last Gurpreet arrived- tired, coughingand wheezing. She explained that the traffic jam wasterrible. Mary’s mother Mrs.Thomas patted Gurpreet’sback and sighed, “Oof! The pollution in our city!” Prasadhad recently come from his village. He asked, “Why dowe have such traffic jams and such pollution in thecities?” “The number of vehicles is increasing day byday due to the growing population in the cities”, Mary’sfather, Mr. Thomas replied. Mary asked, “Then whyare people coming to the cities?” Her mother replied,“They come looking for jobs, better education andmedical facilities.” Mary further enquired, “If so manypeople keep coming to cities, where will all the peoplelive?” Mr. Thomas said, “That is why you see so manyslums and squatter settlements where people stay incongested and unhygienic conditions. Shortage ofpower and water supply are common problems in thecities”. Prasad said, “Our villages may not have bigcinema halls, well-equipped schools and good hospitals,but we have lot of open spaces and fresh air to breathe

in. When my grandfather was sick wehad to rush him to the city hospital.”

From the above conversation wecan identify two different pictures ofsettlements – the rural and the urbansettlements. The villages are ruralsettlement where people are engagedin activities like agriculture, fishing,forestry, crafts work and trading etc.Rural settlements can be compact orscattered. A compact settlement is aclosely built area of dwell ings,wherever f lat land is available(Fig. 7.2). In a scattered settlementdwellings are spaced over anextensive area. This type of settlementis mostly found in hilly tracts, thickforests, and regions of extremeclimate (Fig. 7.3).

In rural areas, people build housesto suit their environment. In regions

Transhumance: It isa seasonal movementof people. People whorear animals move insearch of newpastures according tochanges in seasons.

Fig. 7.3: Scattered Settlement

HUMAN ENVIRONMENT – SETTLEMENT, TRANSPORT AND COMMUNICATION 49

Let’s do

of heavy rainfall, they have slantingroofs. Places where wateraccumulates in the rainy season thehouses are constructed on a raisedplatform or stilts (Fig. 7.4).

Thick mud walled houses withthatched roofs are very common inareas of hot climate. Local materialslike stones, mud, clay, straw etc areused to construct houses.

The towns are small and the citiesare larger urban settlements. Inurban areas the people are engaged in manufacturing,trading, and services. Name some of the villages, townsand cities of your state.

TRANSPORT

Transport is the means by which people and goodsmove. In the early days it took a great deal of time, totravel long distances. People had to walk and usedanimals to carry their goods. Invention of the wheelmade transport easier. With the passage of timedifferent means of transport developed but even todaypeople use animals for transport (Fig. 7.5).

Where do you finddwellings made of ice?Who makes them andwhat are they called?

Fig. 7.5: Horse cart as a mode of transportationList the differentmodes of transportused by the studentsof your class whilecoming to school.

Fig. 7.4: House on Stilts

In our country donkeys, mules, bullocks and camelsare common. In the Andes Mountains of SouthAmerica, llamas are used, as are yaks in Tibet. Theearly traders from other countries used to take severalmonths to reach India. They took either the sea routeor the land route. Airplanes have made travel faster.Now it takes only 6-8 hours to travel from India toEurope. Modern means of transport thus saves timeand energy.

50 OUR ENVIRONMENT

The four major means of transport are roadways,railways, waterways and airways.

ROADWAYS

The most commonly used means of transport especiallyfor short distances are roads. They can be metalled(pucca) and unmetalled (kutcha) (Fig. 7.6 and 7.7). Theplains have a dense network of roads. Roads have alsobeen build in terrains like deserts, forests and even highmountains. Manali-Leh highway in the HimlayanMountains is one of the highest roadways in the world.Roads built underground are called subways/underpaths. Flyovers are built over raised structures.

Fig. 7.6: Metalled Road Fig. 7.7: Unmetalled Road

RAILWAYS

The railways carry heavy goods andpeople over long distances quickly andcheaply. The invention of the steamengine and the Industrial Revolutionhelped in speedy development of railtransport. Diesel and electric engineshave largely replaced the steamengines. In places super fast trainshave been introduced to make thejourney faster. The railway networkis well developed over the plain areas.Advanced technological skills haveenabled laying of railway lines indifficult mountain terrains also. But

these are much fewer in number. Indian railway networkis well developed. It is the largest in Asia.

Do you know?

There are severalNational and Statehighways in India. Thelatest development inIndia is the constructionof Express Ways. TheGolden Quadrilateralconnects Delhi,Mumbai, Chennai andKolkata.

Do you know?

The train from Xining to Lhasa runs atan altitude of 4,000m above sea leveland the highest point is 5,072 m


Do you know?

WATERWAYS

You have already learnt that since early days waterwayswere used for transportation. Waterways are thecheapest for carrying heavy and bulky goods over longdistances. They are mainly of two types – inlandwaterways and sea routes.

Navigable rivers and lakes are used as inlandwaterways. Some of the important inland waterways arethe Ganga-Brahmaputra river system, the Great Lakesin North America and the river Nile in Africa.

Sea routes and oceanic routes are mostlyused for transporting merchandise andgoods from one country to another. Theseroutes are connected with the ports. Someof the important ports of the world areSingapore and Mumbai in Asia, New York,Los Angeles in North America, Rio deJanerio in South America, Durban andCape Town in Africa, Sydney in Australia,London and Rotterdam in Europe (Fig. 7.11).Can you name some more ports of the world?

The Trans-Siberian Railway is the longest railway systemconnecting St. Petersburg in Western Russia to Vladivostok on thePacific coast.

Trans – Siberian Railway

Fig. 7.8: Inland Waterways

52 OUR ENVIRONMENT

Let’s do

AIRWAYS

This is the fastest way of transport developed in the earlytwentieth century. It is also the most expensive due tohigh cost of fuels. Air traffic is adversely affected by badweather like fog and storms. It is the only mode oftransport to reach the most remote and distant areasespecially where there are no roads and railways.Helicopters are extremely useful in most inaccessibleareas and in time of calamities for rescuing people anddistributing food, water, clothes and medicines (Fig. 7.9).Some of the important airports are Delhi, Mumbai, NewYork, London, Paris, Frankfurt and Cairo (Fig. 7.11).

COMMUNICATION

Communication is the process of conveying messages toothers. With the development of technology humans havedevised new and fast modes of communication. The Fig.7.10 explains the evolution of the communication system.

The advancement in the field of communication hasbrought about an information revolution in the world.Different modes of communication are used to provideinformation, to educate as well as to entertain. Throughnewspapers, radio and television we can communicatewith a large number of people. They are therefore calledmass media. The satellites have made communicationeven faster. Satellites have helped in oil exploration,survey of forest, underground water, mineral wealth,weather forecast and disaster warning. Now we can sendelectronic mails or e-mails through Internet. Wirelesstelephonic communications through cellular phones

have become very popular today. Internet notonly provides us with worldwide informationand interaction but has also made our lives

more comfortable. Now wecan reserve tickets for railways,

airways and even cinemas andhotels sitting at home.

With this kind

Fig. 7.9: A Helicopter

Fig. 7.10: Progress in the meansof communication

Find out the names ofsome newspapers andTV news channels inEnglish, Hindi and aregional language.

52 OUR ENVIRONMENT


of inter connectivity of people, services and institutions –across the world, we are a large global society.

Fig

. 7

.11

: W

orld

– M

ajo

r S

ea P

orts

an

d A

irp

orts

54 OUR ENVIRONMENT

Exercises


(i) What are the four means of transport?

(ii) What do you understand by the term ‘settlement’?

(iii) Which are the activities practised by the rural people?

(iv) Mention any two merits of railways.

(v) What do you understand by communication?

(vi) What is mass media?


(i) Which is NOT a means of communication?(a) telephone (b) books (c) table

(ii) Which type of road is constructed under the ground?(a) fly over (b) expressways (c) subways

(iii) Which mode of transport is most suitable to reach an island?(a) ship (b) train (c) car

(iv) Which vehicle does not pollute the environment(c) cycle (b) bus (c) airplane


(i) Internet (a) areas where people are engaged in

manufacturing, trade and services

(ii) Canal route (b) closely built area of houses

(iii) Urban areas (c) inland waterway

(iv) Compact settlement (d) a means of communication

4. Give reasons.

(i) Today’s world is shrinking.

5. For fun.

(i) Conduct a survey in your locality and find out how people commute to theirrespective workplaces using –(a) more than two modes of transport(b) more than three modes of transport(c) stay within walking distance.

(ii) Mention which mode of communication you will prefer most in the followingsituations –(a) Your grandfather has suddenly fallen ill. How will you inform the doctor?(b) Your mother wants to sell the old house. How will she spread this news?(c) You are going to attend the marriage of your cousin for which you will

be absent from the school for the next two days. How will you inform theteacher?

(d) Your friend has moved out with his/her family to New York. How willyou keep in touch on a daily basis?

Renuka was excited. Shrikant Uncle was home after agap of nearly four months. He was a wildlife photographerand travelled widely. Renuka’s interest in wildlife andforests began at an early age, when her uncle introducedher to books on nature. Pictures of distant lands andpeople, who lived there, always fascinated her.

Fig. 8.1: People from various parts of the world

“In these pictures Renuka, you can see people fromdifferent parts of the world – some from dry deserts, somefrom frozen lands and some from hot wet rainforests.”“They look so different from me”, observed Renuka. “Theymay look different, but they share the same basic needsof life – food, clothing and shelter”, explained Shrikant Uncle.“Their children do the same things as you probably do,play games, quarrel sometimes and then make-up, sing,dance and help the families with various things that needto be done. They live closer to nature and very early intheir lives have learnt to care for nature. They learn howto catch fish and how to collect material from the forests.”

56 OUR ENVIRONMENT

Glossary

In Chapters 8, 9 and 10, you will learn about the lifeof people in the different natural regions of the world.

LIFE IN THE AMAZON BASIN

Before learning about the Amazon basin, let us look at themap (Fig. 8.2). Notice that the tropical region lies veryclose to the equator; between 10°N and 10°S. So, it is referredto as the equatorial region. The river Amazon flows throughthis region. Notice how it flows from the mountains to thewest and reaches the Atlantic Ocean to the east.

The place where a river flows into another body ofwater is called the river’s mouth. Numerous tributariesjoin the Amazon River to form the Amazon basin. Theriver basin drains portions of Brazil, parts of Peru, Bolivia,Ecuador, Columbia and a small part of Venezuela.

Name the countries of the basin through which theequator passes.

Tributaries: Theseare small rivers thatjoin the main river.The main river alongwith all its tributariesthat drain an areaform a river basin orthe catchment area.The Amazon Basin isthe largest river basinin the world.

Fig. 8.2: Amazon Basin in South America

Do you know?

When Spanishexplorers discoveredAmazon river, theywere attacked by agroup of local tribeswearing headgearsand grass skirts.These peoplereminded them of thefierce tribes of womenwarriors known inancient RomanEmpire as theAmazons. Hence thename Amazon.

HUMAN ENVIRONMENT INTERACTIONS: THE TROPICAL AND THE SUBTROPICAL REGION 57

CLIMATE

As you now know, the Amazon Basin stretches directlyon the equator and is characterized by hot and wet climatethroughout the year. Both day and nights are almostequally hot and humid. The skin feels sticky. It rainsalmost everyday, that too without much warning. Theday temperatures are high with very high humidity. Atnight the temperature goes down but the humidityremains high.

RAINFORESTS

As it rains heavily in this region, thick forestsgrow (Fig. 8.3). The forests are in fact so thickthat the dense “roof” created by leaves andbranches does not allow the sunlight to reachthe ground. The ground remains dark and damp.Only shade tolerant vegetation may grow here.Orchids, bromeliads grow as plant parasites.

The rainforest is rich infauna. Birds such as toucans (Fig. 8.4),humming birds, bird of paradise withtheir brilliantly coloured plumage,oversized bills for eating make themdifferent from birds we commonly seein India. These birds also make loudsounds in the forests. Animals likemonkeys, sloth and ant-eating tapirs

are found here (Fig. 8.5). Various species of reptiles andsnakes also thrive in these jungles. Crocodiles, snakes,pythons abound. Anaconda and boa constrictor aresome of the species. Besides, the basin is home tothousands of species ofinsects. Several species offishes including the flesh-eating Piranha fish is alsofound in the river. This basinis thus extraordinarily rich inthe variety of life found there.

PEOPLE OF THE RAINFORESTS

People grow most of their food in small areas after clearingsome trees in the forest. While men hunt and fish alongthe rivers, women take care of the crops. They mainly grow

Do you know?

Bromeliads arespecial plants thatstore water in theirleaves. Animals likefrogs use thesepockets of water forlaying their eggs.

Let’s do

Some TV channelsbroadcastdocumentaries on thewildlife of the world.Try to watch some ofthe films and shareyour experience withthe class.

Fig. 8.3 Amazon Forest

Fig. 8.4 Toucans

Fig. 8.5 Tapir

58 OUR ENVIRONMENT

Fig. 8.6: Gradual Destruction of Forests

Do you know?

Slash and Burn is away of cultivating landwhere farmers clear apiece of land byslashing or cuttingdown trees and bushes.These are then burnt,which releases thenutrients into the soil.Now crops are grown inthis cleared field for afew years.

After repeatedlyusing the patch ofland, the soil loosesits nutrients. So it isabandoned. Then theyclear another plot ofland to plant. In themean time youngtrees grow in the oldfield. In this way soilfertility is restored.People can thenreturn to it and startcultivating it again.

tapioca, pineapple and sweet potato. As hunting and fishingare uncertain it is the women who keep their families aliveby feeding them the vegetables they grow. They practice“slash and burn agriculture”. The staple food is manioc,also known as cassava that grows under the ground likethe potato. They also eat queen ants and egg sacs. Cashcrops like coffee, maize and cocoa are also grown.

The rainforests provide a lot of wood for the houses.Some families live in thatched houses shaped likebeehives. There are other large apartment-like housescalled “Maloca” with a steeply slanting roof.

Life of the people of the Amazon basin is slowlychanging. In the older days the heart of the forest, couldbe reached only by navigating the river. In 1970 the TransAmazon highway made all parts of the rainforestaccessible. Aircrafts and helicopters are also used forreaching various places. The indigenous population waspushed out from the area and forced to settle in newareas where they continued to practice their distinctiveway of farming.

The developmental activities are leading to the gradualdestruction of the biologically diverse rainforests. It isestimated that a large area of therainforest has been disappearingannually in the Amazon basin.You can see that thisdestruction of forests hasa much wider implication(Fig. 8.6). The topsoil iswashed away as therains fall and thelush forestturns intoa barrenlandscape.


LIFE IN THE GANGA-BRAHMAPUTRA BASIN

The tributaries of rivers Ganga andBrahmaputra together form theGanga-Brahmaputra basin in theIndian subcontinent (Fig. 8.8). Thebasin lies in the sub-tropical regionthat is situated between 10°N to 30°Nlatitudes. The tributaries of the RiverGanga like the Ghaghra, the Son, theChambal, the Gandak, the Kosi andthe tributaries of Brahmaputra drainit. Look at the atlas and find namesof some tributaries of the RiverBrahmaputra.

The plains of the Ganga and theBrahmaputra, the mountains and the foothills of the

Fig. 8.8: Ganga-Brahmputra Basin

Fig. 8.7 Brahmaputra river

INDIA

60 OUR ENVIRONMENT

Glossary

Himalayas and the Sundarbans delta are the mainfeatures of this basin. Ox-bow lakes dot the plain area.The area is dominated by monsoon climate. Themonsoon brings rains from mid-June to mid-September.The summers are hot and the winters cool.

Look at the map of India (Fig. 8.8). Find out the statesin which the Ganga-Brahmputra basin lies.

The basin area has varied topography. Theenvironment plays a dominant role in the distributionof the population. The mountain areas with steep slopeshave inhospitable terrain. Therefore less number ofpeople live in the mountain area of the Ganga-Brahmaputra basin. The plain area provides the mostsuitable land for human habitation. The soil is fertile.Agriculture is the main occupation of the people whereflat land is available to grow crops. The density ofpopulation of the plains is very high. The main crop ispaddy (Fig. 8.9). Since cultivation of paddy requiressufficient water, it is grown in the areas where the amountof rainfall is high.

Wheat, maize, sorghum, gram and millets are theother crops that are grown. Cash crops like sugarcaneand jute are also grown. Banana plantations are seen insome areas of the plain. In West Bengal and Assam tea isgrown in plantations (Fig. 8.10). Silk is produced throughthe cultivation of silk worms in parts of Bihar and Assam.In the mountains and hills, where the slopes are gentle,crops are grown on terraces.

The vegetation cover of the area varies according tothe type of landforms. In the Ganga and Brahmaputraplain tropical deciduous trees grow, along with teak, saland peepal. Thick bamboo groves are common in theBrahmaputra plain. The delta area is covered with the

Fig. 8.9 Paddy Cultivation Fig. 8.10 Tea Garden in Assam

Let’s do

River Brahmaputra isknown by differentnames in differenceplaces. Find the othernames of the river.

Activity

Collect somehandicrafts madefrom jute, bamboo andsilk. Display them inthe class. Find out inwhich area they weremade in?

Population density:It means the numberof persons that live inone sq. km. of areae.g. the populationdensity of Uttaranchalis 159 while thedensity of WestBengal is 904 andthat of Bihar is 880.


Fig. 8.12 CrocodilesFig. 8.11 One horned rhinoceros

Lake: A source of livelihood(A case study)

Binod is a fishermanliving in the MatwaliMaun village of Bihar.He is a happy mantoday. With the effortsof the fellowfishermen – Ravindar,Kishore, Rajiv andothers, he cleaned themaun or the ox-bowlake to cultivate

different varieties of fish. The local weed (vallineria,hydrilla) that grows in the lake is the food of the fish.The land around the lake is fertile. He sows cropssuch as paddy, maize and pulses in these fields.The buffalo is used to plough the land. Thecommunity is satisfied. There is enough fish catchfrom the river – enough fish to eat and enough fish

Do you know?

In the fresh waters ofRiver Ganga and RiverBrahmaputra, avariety of dolphinlocally called Susu(also called blinddolphin) is found. Thepresence of Susu is anindication of thehealth of the river. Theuntreated industrialand urban wastes withhigh amount ofchemicals are killingthis species.

A clean lake

mangrove forests. In parts of Uttaranchal, Sikkim andArunachal Pradesh, coniferous trees like pine, deodarand fir can be seen because the climate is cool and theslopes are steep.

There is a variety of wildlife in the basin. Elephants,tigers, deer and monkeys are common. The one-hornedrhinoceros is found in the Brahmaputra plain. In thedelta area, Bengal tiger, crocodiles and alligator are found.Aquatic life abounds in the fresh river waters, the lakesand the Bay of Bengal Sea. The most popular varieties ofthe fish are the rohu, catla and hilsa. Fish and rice isthe staple diet of the people living in the area.

Blind Dolphin

Do you know?

Terraces are built onsteep slopes to createflat surfaces on whichcrop are grown. Theslope is removed sothat water does notrun off rapidly.

Terrace Farming

62 OUR ENVIRONMENT

Fig. 8.13: Varanasi along the River Ganga

The Ganga-Brahmaputraplain has several big townsand cities. The cities ofAllahabad, Kanpur, Varanasi,Lucknow, Patna and Kolkataall with the population ofmore than ten lakhs arelocated along the RiverGanga (Fig. 8.13). Thewastewater from these towns

and industries is discharged into the rivers. This leadsto the pollution of the rivers.

All the four ways of transport are well developed inthe Ganga-Brahmaputra basin. In the plain areas theroadways and railways transport the people from oneplace to another. The waterways, is an effective means oftransport particularly along the rivers. Kolkata is animportant port on the River Hooghly. The plain area alsohas a large number of airports.

Tourism is another important activityof the basin. Taj Mahal on the banks ofRiver Yamuna in Agra, Allahabad on theconfluence of the Rivers Ganga andYamuna, Buddhists stupas in UttarPradesh and Bihar, Lucknow with itsImambara, Assam with Kaziranga andManas with wild life sanctuaries andArunachal Pradesh with a distincttribal culture are some of the placesworth a visit (Fig. 8.14).

to sell in the market. They have even begun supplyto the neighbouringtown. The communityis living in harmonywith nature. As longas the pollutants fromnearby towns do notfind their way into thelake waters, the fishcultivation will notface any threat. A Polluted Lake

Fig. 8.14: Tiger in Manas Wildlife sanctuary



(i) Name the continent in which the Amazon Basin is located.

(ii) What are the crops grown by the people of the Amazon Basin.

(iii) Name the birds that you are likely to find in the rainforests of the Amazon.

(iv) What are the major cities located on the River Ganga.

(v) Where is the one-horned rhinoceros found?


(i) Toucans are a type of(a) birds (b) animals (c) crops

(ii) Manioc is the staple food of(a) Ganga Basin (b) Africa (c) Amazon

(iii) Kolkata is located on the river(a) Orange (b) Hooghly (c) Bhagirathi

(iv) Deodars and firs are a type of(a) Coniferous trees (b) Deciduous trees (c) shrubs

(v) Bengal tiger is found in(a) mountains (b) delta area (c) Amazon


(i) Cotton textile (a) Assam

(ii) Maloca (b) Sericulture

(iii) Piranha (c) Slanting roof

(iv) Silk worm (d) Ganga plain

(v) Kaziranga (e) Fish

4. Give reasons.

(i) The rainforests are depleting.

(ii) Paddy is grown in the Ganga-Brahmaputra plains.

5. Map skills.

(i) On an outline map of Indian Sub-continent, draw the rivers Ganga andBrahmaputra from the source to the mouth. Also show the importanttributaries of both the rivers.

(ii) On the political map of the South America, draw the equator. Mark thecountries located on the equator.

6. For fun.

Make a collage to show places of attractions in India. You can divide the classin different groups to show attractions based on mountain landscapes, coastalbeaches, wildlife sanctuaries and places of historical importance.

Exercises

64 OUR ENVIRONMENT

7. Activity.

Collect under mentioned material and observe how destruction of trees effectthe soil cover.

Material

(i) Three small flowerpots or food cans (e.g., cold drinks tin cans),

(ii) one big can with holes punched in the bottom (this will act as asprinkling can),

(iii) twelve coins or bottle caps

(iv) soil.

Process

Take three small cans or pots. Fill them with soil till the top. Press the soil tomake it level with the top of the can. Now put four coins or bottle caps on thesoil of each can. Take the big can that has been punched with holes and fill itwith water. You can also take the sprinkling can from your garden. Now, sprinklewater on the three cans. On the first can sprinkle water very slowly so that nosoil splashes out. Let moderate amount of water be sprinkled on the secondcan. On the third can, sprinkle the water heavily. You will observe thatunprotected soil splashes out. Where the ‘rain’ is heavy the amount of soil thatsplashes out is the maximum and least in case of the first can. The coins orcaps represent the tree covers. It is clear that if the land is cleared completelyof the vegetation, the soil cover will quickly disappear.

Just as a forest can be defined as the place where treesare the main type of vegetation, grassland can bedefined as a region where grasses form the dominanttype of plant life. Grasslands make up almost a quarterof the total land surface. The types of plants thatgrow here greatly depend on what the climate and soilare like. As climate plays an important role in theformation of grasslands, it is generally used as a basisto divide the world’s grasslands into two broadcategories: those that occur in the temperate regionand those that occur in the tropical regions.

THE PRAIRIES

The temperate grasslands of North America are knownas the Prairies (Fig. 9.1). It is a region of flat, gentlysloping or hilly land. For the most part, prairies aretreeless but, near the low lying plains, flanking rivervalleys, woodlands can be found. Tall grass, upto twometres high, dominates, the landscape. It is actually a“sea of grass.”

The prairies are bound by theRocky Mountains in the West andthe Great Lakes in the East. Lookat the map of North America(Fig. 9.2). You can see that theprairies cover parts of United Statesof America and parts of Canada. Inthe USA, the area is drained by thetributaries of Mississippi and theCanadian prairies are drained bythe tributaries of SaskatchewanRivers.

Word Origin

The word Prairieoriginated from Latinword priata whichmeans meadow.

Fig. 9.1: The Prairies

66 OUR ENVIRONMENT

CLIMATE

Being located in the heart of a continent, the climate isof continental type with extreme temperatures.The summers are warm with temperatures of around20°C, while in winter -20°C has been recorded inWinnipeg, Canada. In winters a thick blanket of snowcovers this region.

The annual rainfall is moderate and is ideal for thegrowth of grass. Due to the absence of the north-southbarrier, a local wind “Chinook” blows here.

Do you know?

Chinook is a hot windthat blows in winterand therefore raisesthe temperature in ashort time. Thisincrease intemperature resultsin the melting ofsnow, making pastureland available forgrazing of animals.

Fig. 9.2: The Prairies in North America

Do you know?

The grasslands ofPrairies were thehome of AmericanIndians, morepopularly known as‘Blackfoot Indians’.The Prairies werehome of other tribesalso like the Apache,the Crow, the Creeand the Pawnee.

67LIFE IN THE TEMPERATE GRASSLANDS

Glossary

FLORA AND FAUNA

Prairies are practically tree-less. Where wateris available, trees such as willows, alders andpoplars grow. Places that receive rainfall ofover 50 cm, are suitable for farming as thesoil is fertile. Though the major crop of thisarea is maize, other crops including potatoes,soybean, cotton and alfa-alfa is also grown.Areas where rainfall is very little or unreliable,grasses are short and sparse. These areasare suitable for cattle rearing. Large cattlefarms called ranches are looked after by

sturdy men calledcowboys (Fig. 9.3). Bison or theAmerican buffalo is the mostimportant animal of this region(Fig. 9.4). It nearly got extinctdue to its indiscriminate huntingand is now a protected species.The other animals found in thisregion are rabbits, coyotes,gophers and Prairie dog.

PEOPLE

The people of this region are very hardworking. Theyhave successfully harnessed technology to utilise theirrich natural resources. Two of the most developedcountries in the world - the USA and Canada are locatedin this region. Scientific methods of cultivation and useof tractors, harvesters and combines has made NorthAmerica a surplus food producer. The Prairies are alsoknown as the “Granaries of the world,” due to the hugesurplus of wheat production.

Dairy farming is another major industry. The dairybelt extends from the Great Lakes to the Atlantic Coastin the east. Dairy farming and extensive agriculture bothpromote setting up of food processing industries.

Large mineral deposits particularly coal and ironand a good network of roads, railways and canals inthis region have made it the most industrialised regionin the world.

Fig. 9.3: Cowboy

Combine: A machinewhich can sow,plough and work asthresher all by itself.

Do you know?

Important cities inthe USA are Chicago,Minneapolis,Indianapolis Kansasand Denver. InCanadian prairies theimportant cities areEdmonton,Saskatoon, Calgaryand Winnipeg.

Fig. 9.4: Bison

68 OUR ENVIRONMENT

Let’s do

THE VELDS

The temperate grasslands of South Africa are called thevelds (Fig. 9.5). Velds are rolling plateaus with varyingheights ranging from 600 m to 1100 m. It is bound bythe Drakensburg Mountains on the east. To its west liesthe Kalahari desert. On the northeastern part, “high velds”are located that attain a height of more than 1600 m, insome places. Look at the map of Africa. Name thecountries that are covered by the Velds. The tributariesof rivers Orange and Limpopo drain the region.

Velds lie in theSouthern hemisphere.When it is summersin velds, what seasonwould it be in theprairies?

Do you know?

The Veld name wasgiven by the Dutchsettlers before SouthAfrica was colonisedby the British.

Fig. 9.5: Veld in Africa

CLIMATE

The velds have a mild climate due to the influence of theIndian Ocean. Winters are cold and dry. Temperaturesvary between 5°C and 10°C and July is the coldestmonth. Summers are short and warm. Johannesburgrecords about 20°C temperature in the summer.

Let’s do

Some type of grassgrows on almost everysurface of the earth.List names of placeswhere you haveobserved grassgrowing, e.g., lawns,cricket field, betweencracks of a side walketc.

69LIFE IN THE TEMPERATE GRASSLANDS

The velds receive rainfall mainly in the summer monthsfrom November to February. This is mainly because ofthe warm ocean currents that wash the shores of thevelds. If the rainfall is scanty in the winter months fromJune till August, drought may occur.

FLORA AND FAUNA

The vegetation cover is sparse. Grassesdominate the landscape. Red grass growsin bush velds. In the high velds acacia andmaroola are seen to be growing. The animalsof the velds are primarily lions, leopards,cheetah and kudu (Fig. 9.6).

PEOPLE

Velds are known for cattle rearing and mining. The soilsare not very fertile in the velds due to the presence ofdiscontinuous grasses exposing barren surface. Howeverwhere the land is fertile crops are grown. The main cropsare maize, wheat, barley, oats and potato. Cash cropslike tobacco, sugarcane and cotton are also grown.

Sheep rearing is the most importantoccupation of the people. Sheep is bredmainly for wool and has given rise to thewool industry in the velds. Merino sheep isa popular species and their wool is verywarm. Dairy farming is the next importantoccupation. Cattle are reared in the warmerand wetter regions and the dairy productslike butter, cheese are produced for bothdomestic supply and also for export.

The velds have rich reserve of minerals.Iron and steel industry has developed wherecoal and iron are present. Gold and diamondmining are major occupations of people ofthis region. Johannesburg is known for beingthe gold capital of the world. Kimberley isfamous for its diamond mines (Fig. 9.7).Mining of diamond and gold in South Africaled to the establishment of trade ties withBritain and gradually South Africa becamea British Colony. This mineral rich area hasa well-developed network of transport. Fig. 9.7: Diamond Mine, Kimberley

Fig. 9.6: Leopard

70 OUR ENVIRONMENT


(i) What are the Temperate Grasslands of North America called?

(ii) What are the cattle farms in the North American Grasslands known as?

(iii) Name the rivers that drain the Velds.

(iv) When is the rainy season in the Velds?

(v) What is the major occupation of the people of the South African grasslands?


(i) River Mississippi drains(a) Canada (b) Africa (c) USA

(ii) Drakensberg Mountains bound the(a) Prairies (b) Velds (c) Pampas

(iii) Merino is a species of(a) fish (b) elephant (c) sheep

(iv) Kimberley is famous for(a) diamonds (b) silver (c) platinum


(i) Cowboys (a) Iron and Steel

(ii) Gold (b) Prairies

(iii) Kudu (c) Hot wind

(iv) Chinook (d) Johannesberg

(v) Coal (e) Animal

4. Give reasons.

(i) The Prairies are known as the ‘Granaries of the World’.

(ii) Rise of wool industry in the Velds.

5. Map skills.

On an outline map of North America, mark the Rocky mountains, the GreatLakes, river Mississippi, river Saskatchewan, the cities – Chicago and Winnipeg.

6. For fun.

Make a grass whistle

You will require a blade of grass about 5 cm in length. Be sure to choose thegrass blade longer than your thumbs. The thickness of the grass should beabout 0.5 to 0.7 cm. Choose the grass that is broad and wide. Narrow blade isdifficult to hold. Put your thumbs together as your nails are facing you. Stretchthe blade of grass lengthwise between the thumbs and the base of the hand.Your hands should be cupped to create a hollow or a narrow opening betweenyour palms. You should just be able to see the edge of the grass only throughthe narrow opening. Place your lips over the opening and blow gently into thepalm. You may even feel the grass blade vibrating as you blow. As you graduallyblow you will hear sound of whistle created by grass.

Exercises

10 Life in the Deserts

In Chapter 5, you have seen that water means life toplants, animals and people. It is difficult for anyone tolive in places where there is no water to drink, wherethere is no grass for their cattle to feed on and wherethere is no water to help the crops to grow.

We will now learn about the places in the world wherepeople have learned to cope with extreme harshtemperatures; in some places as hot as fire and some ascold as ice. These are the desert areas of the world. Theseare characterised by low rainfall, scanty vegetation andextreme temperatures. Depending on the temperaturesthere can be hot deserts or cold deserts. The peopleinhabit these lands wherever little water is available topractise agriculture.

THE HOT DESERT – SAHARA

Look at the map of the world and thecontinent of Africa. Locate the Saharadesert covering a large part of NorthAfrica. It is the world’s largest desert. Ithas an area of around 8.54 millionsq. km. Do you recall that India has anarea of 3.2 million sq. km? The Saharadesert touches eleven countries. Theseare Algeria, Chad, Egypt, Libya, Mali,Mauritania, Morocco, Niger, Sudan,Tunisia and Western Sahara.

When you think of a desert the picturethat immediately comes to your mind is that of sand. Butbesides the vast stretches of sands, that Sahara desert iscovered with, there are also gravel plains and elevatedplateaus with bare rocky surface. These rocky surfacesmay be more than 2500m high at some places.

Fig. 10.1: The Sahara Desert

Glossary

Desert: It is an aridregion characteriesedby extremely high orlow temperatures andhas scarce vegetation.

72 OUR ENVIRONMENT

Do you know?

Fig. 10.2: Sahara in Africa

Al Azizia in Saharadesert, south of Tripoli,Libya recorded thehighest temperature of57.7°C in 1922.

ClimateThe climate of the Sahara desert is scorching hot andparch dry. It has a short rainy season. The sky iscloudless and clear. Here, the moisture evaporatesfaster than it accumulates. Days are unbelievably hot.The temperatures during the day may soar as high as50°C, heating up the sand and the bare rocks, whichin turn radiates heat making everything around hot.The nights may be freezing cold with temperaturesnearing zero degrees.

Flora and FaunaVegetation in the Sahara desert includes cactus, datepalms and acacia. In some places there are oasis – greenislands with date palms surrounding them. Camels,hyenas, jackals, foxes, scorpions, many varieties of

Do you know?

You will be surprisedto know that presentday Sahara once usedto be a lush greenplain. Cave paintingsin Sahara desertshow that there usedto be rivers withcrocodiles. Elephants,lions, giraffes,ostriches, sheep,cattle and goats werecommon animals. Butthe climate haschanged it to a veryhot and dry region.

Morocco

Morocco

Morocco

Morocco

Morocco

LIFE IN THE DESERTS 73

Do you know?

Depressions are formedwhen the wind blowsaway the sands. In thedepressions whereunderground waterreaches the surface,an oasis is formed.These areas are fertile.People may settlearound these waterbodies and grow datepalms and othercrops. Sometimes theoasis may beabnormally large.Tafilalet Oasis inMorocco is a largeoasis with an area ofabout 13,000 sq.km.

Fig. 10.3: Oasis in the Sahara Desert

PeopleThe Sahara desert despite its harsh climate has beeninhabited by various groups of people, who pursuedifferent activities. Among them are the Bedouins andTuaregs. These groups are nomadic tribes rearinglivestock such as goats, sheep, camels and horses.These animals provide them with milk, hides fromwhich they make leather for belts, slippers, waterbottles; hair is used for mats, carpets, clothes andblankets. They wear heavy robes as protection againstdust storms and hot winds.

The oasis in the Sahara and the Nile Valley in Egyptsupports settled population. Since water is available, thepeople grow date palms. Crops such as rice, wheat, barleyand beans are also grown. Egyptian cotton, famousworldwide is grown in Egypt.

The discovery of oil – a product in great demandthroughout the world, in Algeria, Libya and Egypt isconstantly transforming the Sahara desert. Otherminerals of importance that are found in the area includeiron, phosphorus, manganese and uranium.

The cultural landscape of the Sahara is undergoingchange. Gleaming glass cased office buildings tower overmosques and superhighways crisscross the ancient camelpaths. Trucks are replacing camels in the salt trade.Tuaregs are seen acting as guides to foreign tourists.More and more nomadic herdsmen are taking to city lifefinding jobs in oil and gas operations.

snakes and lizards are the prominent animal speciesliving there.

Do you know?

Scientists haveactually foundskeletons of fish inthis desert. Whatcould have happened?

74 OUR ENVIRONMENT

THE COLD DESERT - LADAKH

Ladakh is a cold desert lying in the Great Himalayas,on the eastern side of Jammu and Kashmir (Fig. 10.4).The Karakoram Range in the north and the Zanskarmountains in the south enclose it. Several rivers flowthrough Ladakh, Indus being the most importantamong them. The rivers form deep valleys and gorges.Several glaciers are found in Ladakh, for example theGangri glacier.

The altitude in Ladakh varies from about 3000min Kargil to more than 8,000m in the Karakoram.Due to its high altitude, the climate is extremely coldand dry. The air at this altitude is so thin that theheat of the sun can be felt intensely. The daytemperatures in summer are just above zero degreeand the night temperatures well below 30°C. It isfreezing cold in the winters when the temperaturesmay remain below 40°C for most of the time. As it lies

Word Origin

Ladakh is made up oftwo words – Lameaning mountainpass and Dakmeaning country

Do you know?

Drass, one of thecoldest inhabitedplaces on earth islocated in Ladakh.

Fig. 10.4: Ladakh


in the rain shadow of the Himalayas, there is littlerainfall, as low as 10 cm every year. The areaexperiences freezing winds and burning hot sunlight.You will be surprised to know that if you sit in thesun will your feet in the shade, you may suffer fromboth sunstroke and frost bite at the same time.

Flora and FaunaDue to high aridity, the vegetation is sparse. There arescanty patches of grasses and shrubs for animals tograze. Groves of willows and poplars are seen in thevalleys. During the summers, fruit trees such as apples,apricots and walnuts bloom. Several species of birds aresighted in Ladakh. Robins, redstarts, Tibetan snowcock,raven and hoopoe are common. Some of these aremigratory birds. The animals of Ladakh are wild goats,wild sheep, yak and special kinds of dogs. The animalsare reared to provide for the milk, meat and hides. Yak’smilk is used to make cheese and butter. The hair of thesheep and goat is used to make woollens.

PeopleDo you find any resemblance between the people ofLadakh and the inhabitants of Tibet and Central Asia?The people here are either Muslims or Buddhists. Infact several Buddhists monasteries dot the Ladakhilandscape with their traditional ‘gompas’. Somefamous monasteries are Hemis, Thiksey, Shey andLamayuru (Fig. 10.5).

In the summer season the people are busy cultivatingbarley, potatoes, peas, beans and turnip. The climate inwinter months is so harsh thatpeople keep themselves engaged infestivities and ceremonies. Thewomen are very hard working. Theywork not only in the house andfields, but also manage smallbusiness and shops. Leh, the capitalof Ladakh is well connected both byroad and air. The National Highway1A connects Leh to KashmirValley through the Zoji la Pass. Canyou name some more passes inthe Himalayas?

Do you know?

The finest cricket batsare made from thewood of the willowtrees.

Do you know?

The Chiru or theTibetan antelope is anendangered species. Itis hunted for its woolknown as shahtoosh,which is light inweight and extremelywarm.

Fig. 10.5 Thiksey Monastery

Do you know?

Ladakh is also knownas Khapa-chan whichmeans snow land.

76 OUR ENVIRONMENT

Tourism is a majoractivity with severaltourists streaming in fromwithin India and abroad.Visits to the gompas,treks to see the meadowsand glaciers, witnessingceremonies and festivitiesare important activities.

Life of people isundergoing change dueto modernisation. Butthe people of Ladakhhave over the centuries learned to live in balance andharmony with nature. Due to scarcity of resources likewater and fuel, they are used with reverence and care.Nothing is discarded or wasted.

Exercises

Do you know?

Manali - Leh highwaycrosses four passes,Rohtang la,Baralacha laLungalacha la andTanglang la. Thehighway opens onlybetween July andSeptember when snowis cleared from the road.

Baralacha la


(a) What are the two types of deserts found in the world?

(b) In which continent is the Sahara desert located?

(c) What are the climatic conditions of the Ladakh desert?

(d) What mainly attracts tourists to Ladakh?

(e) What type of clothes the people of the Sahara desert wear?

(f) Name the trees that grow in Ladakh.


(i) Sahara is located in which part of Africa(a) eastern (b) northern (c) western

(ii) Sahara is what type of desert(a) cold (b) hot (c) mild

(iii) The Ladakh desert is mainly inhabited by(a) Christians and Muslims(b) Buddhists and Muslims(c) Christians and Buddhists

(iv) Deserts are characterised by(a) scanty vegetation(b) heavy precipitation(c) low evaporation

Fig. 10.6. Ladakhi Women inTraditional Dress


(v) Hemis in the Ladakh is a famous(a) temple (b) church (c) monastery

(vi) Egypt is famous for growing(a) wheat (b) maize (c) cotton


(i) Oasis (a) Libya

(ii) Bedouins (b) monastery

(iii) Oil (c) glacier

(iv) Gangri (d) depressions with water

(v) Lamayuru (d) Sahara

4. Give reasons.

(i) There is scanty vegetation in the deserts.

(ii) People of the Sahara desert wear heavy robes.

5. Map skills.

(i) On the outline map of Africa, mark the Sahara desert.

(ii) On the outline map of India, mark the Karakoram Range, Zanskar Range,Ladakh and Zoji La pass.

Desert Game

This is a class room activity involving all the students. The teacher will create alist of desert creatures. The number of the creatures should be same as the numberof students in the class. The creatures can be picked up from the categories ofmammals, birds and reptiles. Mammals can include – camel, yak, fox, sheep, goat,antelope…Birds – raven, eagle, vulture, turkey…Reptiles – snakes …

Assign one desert creature to each student. Ask the student to write threecharacteristics of the creature on plain sheet of paper. (students can use indexcards of size 10 cm × 15 cm). Questions such as - in what type of deserts it isfound? Major adaptation? Use to man?

These characteristics will be used as clues in the guessing game. On the boardmake three columns – mammals, birs and reptiles. Paste a sheet of paper in thecolumn under the particular category. The class can be divided in three to fourgroups. They will compete against each other in the ‘desert game’. Each group nowtakes turn in guessing the correct answer. Explain to the class that they have toguess what animal matches the characteristics listed on the paper.For example:

• Animal of hot desert• Has double set of eyelashes to keep away the sand• The hide is used for making water bottles

The correct answer is ‘camel’. Within the group there will be a student who hasprepared the card. That student should not answer. Ten points are awarded forthe correct answer.

This game will enable students to understand the desert. You can play thesame game by taking different types of fruits, flora and the clothes the people wear.

6. For fun.

http://school.discovery.com/

http://nationalgeographic.com/

http://www.incredibleindia.org/

http://www.wikipedia.org/

http://www.greenpeace.org/

http://www.britannica.com/

http;//www.animalplanet.co.uk/

Some Internet Sources for More Information

APPENDIX

http://school.discovery.com/

http://nationalgeographic.com/

http://www.incredibleindia.org/

http://www.wikipedia.org/

http://www.greenpeace.org/

http://www.britannica.com/

http;//www.animalplanet.co.uk/

Some Internet Sources for More Information

AAAAAPPENDIXPPENDIXPPENDIXPPENDIXPPENDIX

14147666 NCERT Book Social Science Our Environment Class VII

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Transcript of 14147666 NCERT Book Social Science Our Environment Class VII