MAJOR DOMAINS OF THE EARTH

TERM 2-PT-1 

1. What is atmosphere?  Draw and label different layers of atmosphere? (1 Mark) (30 words)

2. Write a note on the different domains of the earth. (2 Marks) (80 words)

3. Why Biosphere is important for living organism? (1 Mark)    (30 words)

Four domains of the earth

The surface of the earth is a complex zone. It can be divided into three main portions, viz. lithosphere, atmosphere and hydrosphere.

Lithosphere

• The solid portion of the earth is called lithosphere.

• It is composed of rocks of the earth’s crust.

• There is a thin layer of soil on top that contains mineral nutrients which sustain various organisms.

• The earth’s surface can be divided into two main parts, viz. the continents and the ocean basins.
→ Continents: The huge landmasses on the earth are called continents.
→ Ocean Basins: The huge water bodies on the earth are called ocean basins.

Continents
• There are seven continents and all of them are separated by large water bodies. The seven continents of the world are; Asia, Europe, Africa, North America, South America, Australia and Antarctica.
• Asia: This is the largest continent. Asia covers about one-third of the total land area of the earth. This continent lies in the eastern hemisphere.

• Europe: Europe lies to the west of Asia and is much smaller than Asia. It is bound by water bodies from three sides.

• Africa: Africa is the second largest continent. The major portion of Africa lies in the northern hemisphere. 

• North America: It is the third largest continent. North America and South America are connected to each other by the Isthmus of Panama.

• Isthmus: A narrow strip of land which joins two landmasses is called isthmus. North America lies in the northern hemisphere and western hemisphere.

• South America: A major portion of South America is in southern hemisphere. This continent is surrounded by two oceans, viz. the Atlantic and Pacific oceans.

• Australia: This is the smallest continent. It lies entirely in the southern hemisphere. Since Australia is surrounded on all sides by ocean hence it is called the island continent.

• Antarctica: This is a huge continent and is present on the South Polar Region. In fact, the South Pole lies at the centre of this continent.

Atmosphere

• Atmosphere plays an important role in the environment on earth.

• Atmosphere is made of air which is composed of many gases, water vapour and dust particles.

Composition of Air: Air is mainly composed of nitrogen and oxygen. 78% of the air is composed of nitrogen, 21% is composed of oxygen and rest 1% is composed of carbon dioxide, argon, neon, helium and many other gases.

Layers of Atmosphere

1. Troposphere:

The closest layer to Earth where we live.

Weather changes like rain, snow, and storms happen here.

Contains most of the atmosphere's air and oxygen.

2. Stratosphere:

Contains the ozone layer, which protects Earth from harmful UV rays.

Airplanes often fly in this layer because it is stable.

The temperature increases with height in this layer.

3. Mesosphere:

Meteors burn up in this layer, creating shooting stars.

It is the coldest layer of the atmosphere.

4. Thermosphere:

Very hot because the Sun's rays hit this layer first.

The auroras (northern and southern lights) occur in this layer.

Space shuttles and the International Space Station orbit here.

5. Exosphere:

The outermost layer of the atmosphere, merging into space.

Satellites orbit in this layer.

Very thin air, almost like outer space.

Hydrosphere

More than 71% of the earth’s surface is covered with water. But 97% of the total water on earth is available as saline water in oceans and seas.

Oceans

• All the oceans of the world are connected to each other. Due to this, the level of sea water is same everywhere. Elevation of land is measured from the sea level and the sea level is taken as zero.

• Waves, tides and ocean currents are the three main movements of ocean water. There are five major oceans, viz. Pacific, Atlantic, Indian, Arctic and Southern oceans.

• Pacific Ocean: This is the largest ocean. It is almost circular in shape. The Pacific Ocean is surrounded by Asia, Australia, North America and South America.

• Atlantic Ocean: This is the second largest ocean. It is S-shaped. North America and South America are to the west of this ocean. Europe and Africa are on the east of this ocean. As it is irregular in shapes. This creates natural harbours and ports, which are ideal for ships to dock.

• Indian Ocean: Indian Ocean is the only ocean to be named after a country. This ocean is almost triangular in shape. Asia is towards north, Africa is towards west and Australia is towards east of this ocean.

• Southern Ocean: This Ocean encircles Antarctica. It extends northwards up to 60°S latitude.

• Arctic Ocean: This Ocean is within the Arctic Circle. It surrounds the North Pole. It is bound by the northern coasts of North America and Eurasia.

Biosphere

• The narrow zone of contact between the lithosphere, hydrosphere and atmosphere is called biosphere.

Why Biosphere is considered the domain of life?

The biosphere is the narrow zone of contact between the lithosphere, hydrosphere, and atmosphere.

The earth is the only planet where human beings find three life-sustaining elements—land, water, and air.

Life exists in this zone. A variety of organisms exist on earth. All the living organisms including humans, are linked to each other and to the biosphere for survival.

The organisms in the biosphere may broadly be divided into the plant kingdom and the animal kingdom.

Increase in the amount of C02 leads to an increase in global temperature. This is termed as global warming.

1. What is the Lithosphere? Give examples.

Answer:
The lithosphere is the solid part of the Earth where we live. It includes land, mountains, and the ocean floor. Some important parts of the lithosphere are:

• Continents – Large land areas like Asia, Africa, and Europe.
• Mountains and Plateaus – Examples: Himalayas, Andes, and the Tibetan Plateau.
• Plains and Deserts – Examples: Indo-Gangetic Plain, Sahara Desert.
• Ocean Floors – The land under the sea.

The lithosphere is important because it gives us land to live on, soil for farming, and minerals like coal and gold. Earthquakes and volcanoes happen because of movements in the lithosphere.

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2. What is the Hydrosphere? Why is it important?

Answer:
The hydrosphere includes all the water on Earth. It covers about 71% of our planet. It includes:

• Oceans – Pacific, Atlantic, Indian, Southern, and Arctic Oceans.
• Rivers and Lakes – Amazon River, Nile River, and Lake Victoria.
• Glaciers and Ice Caps – Huge blocks of ice in Antarctica and Greenland.
• Groundwater – Water found under the ground in wells.

The hydrosphere is important because it gives us water to drink, helps in farming, and provides food. Oceans also control the climate. Pollution of water bodies is a big problem, so we must protect them.

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3. What is the Atmosphere? What are its layers?

Answer:
The atmosphere is the layer of air around the Earth. It is made up of gases like oxygen (which we breathe) and carbon dioxide (which plants need). The atmosphere has different layers:

• Troposphere – Closest to Earth; where weather happens.
• Stratosphere – Contains the ozone layer, which protects us from the Sun’s harmful rays.
• Mesosphere – Destroys meteors before they reach Earth.
• Thermosphere – Where satellites and the space station orbit.
• Exosphere – The outermost layer that slowly merges into space.

The atmosphere helps us breathe, keeps Earth warm, and protects us from harmful space radiation.

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4. What is the Biosphere? How is it connected to other domains?

Answer:
The biosphere is the part of Earth where living things exist. It includes plants, animals, and people. It is connected to other domains:

• Lithosphere – Plants grow in soil, and animals live on land.
• Hydrosphere – Fish and sea creatures live in water.
• Atmosphere – Humans and animals breathe oxygen from the air.

The biosphere is important because it has all living things. If we cut too many trees or pollute water and air, life on Earth will be in danger. We must take care of nature to keep the balance.