Earth as a Planet

Answer the following questions

Question 1

Why is the earth a unique planet?

Answer

Earth is known as a unique planet because it is the only planet to support life. No other planet till date is known to have life on it.

Question 2

Why the earth is called the blue planet?
OR
Why earth is called the watery planet?

Answer

The earth is called the blue planet or watery planet because abundance of water on the earth gives it a vivid blue colour when viewed from space.

Question 3

What is the surface of the earth made up of?

Answer

The surface of earth is made up of solid crust of rocks. The main part of the crust consists of igneous rocks, the rest consists of sedimentary and metamorphic rocks.

Question 4

Name a planet that cannot support life. Give reasons for your answer.

Answer

Venus is one of the planets that cannot support life because it is the hottest planet of the solar system. Venus is the second nearest planet to the Sun. Its atmosphere contains large amount of carbon dioxide due to which it is the hottest planet. Due to its high temperature it cannot support life.

Question 5

State three factors that have made life possible on the planet earth.
OR
State the conditions favourable for life to exist on earth.

Answer

The three factors that have made life possible on the planet earth are:

1. Its distance from the Sun is neither too near nor too far, hence ideal temperature conditions.
2. It has atmosphere containing oxygen and nitrogen necessary to support life.
3. It has water cycle. Presence of water has made existence of life possible on earth. It is essential for all kinds of life.

Question 6

Name the various realms of the earth.

Answer

The various realms of the earth are — lithosphere, hydrosphere and atmosphere. Biosphere consists of all these realms along with the life.

Question 7

Why is the shape of the earth described as an oblate spheroid?

Answer

The shape of the earth is described as an oblate spheroid because the measurements of earth at the equator and poles show that it has a slight bulge at the equator while it is slightly flattened at the poles. This shape is also known as a Geoid, meaning earth shaped.

Question 8

Give two proofs about the shape of the earth.

Answer

Two proofs about the shape of the earth are:

1. All celestial bodies are spherical — Spheres are the only geometrical shapes that are circular in outline. Sun, Moon amd all other celestial bodies appear to have circular outline. Since Earth too belongs to the same system, there is no reason why Earth should be an exception.
2. Circumnavigation of the earth — Time and again people travelling round the world in different directions came back to the starting point.

Question 9

What is the significance of the atmosphere on earth as compared to other planets?

Answer

The significance of the atmosphere on earth as compared to other planets are:

1. The earths atmosphere contains 21% oxygen, 78% nitrogen with traces of carbon dioxide, water vapour and other gases. This allows the existence of life on earth.
2. It extends up to 1600 km.
3. Atmosphere acts as a blanket of air protecting us from the harmful ultraviolet rays of the sun.
4. It retains the heat radiated from the earth's surface.

Question 10

List the conditions favourable to life on earth.

Answer

The conditions favourable to life on earth are:

1. The position of earth in solar system is such that it is neither too far nor too near to the sun. Hence, it receives just the right amount of heat necessary for life.
2. The atmosphere of other planets is either too thin or too dense, full of poisonous gases, making it impossible for life to exist. On the other hand, earth's atmosphere extends up to 1600 km and contains adequate amount of nitrogen (78%), oxygen (21%) and other gases like helium, carbon dioxide and water vapour.
3. It acts as a blanket, protecting us from harmful ultraviolet rays of the sun, and retains the heat radiated from the earth's surface.
4. Earth's water cycle is the most unique feature. Water is essential for the existence of life.

Explain the following terms

Question 1

Terrestrial planets

Answer

The planets that are made up of hard silicate rocks or metals are called Terrestrial planets. The other planets lack a solid surface. The four inner planets of the solar system- Mercury, venus, earth and Mars are terrestrial planets.

Question 2

Oxygen cycle

Answer

Oxygen cycle refers to the biochemical cycle which is involved in maintaining the level of oxygen in the atmosphere. Men, animals inhale oxygen and exhale carbon dioxide which is taken by plants. Plants use this carbon dioxide in photosynthesis and release oxygen, which is again used in respiration.

Question 3

Unique planet

Answer

Earth is known as a unique planet because it is the only planet to support life. No other planet till date is known to have life on it. The presence of oxygen, water and habitable temperature enables earth to sustain life.

Question 4

Water Cycle

Answer

Water cycle refers to circulation of water from earth's surface by evaporation and transpiration to cloud formation by condensation and again falling back on earth's surface in the form of precipitation.

Question 5

Biosphere

Answer

Biosphere refers to three realms of earth i.e. lithosphere, atmosphere and hydrosphere; along with life present on it. It is the sphere of living organisms or biological processes lying at the interfaces between atmosphere, lithosphere and hydrosphere.

Question 6

Environment

Answer

The surroundings or conditions in which a person, animal or plant lives or operates is called environment. It consists of all the biotic and abiotic factors and their effects on the organism.

Question 7

Atmosphere

Answer

The envelop of air surrounding the earth is called atmosphere. The atmosphere consists of oxygen, nitrogen, carbon dioxide, argon, water vapour etc. It forms a 1600 km thick covering around the earth.

Give reasons for the following

Question 1

The earth is the only habitable planet.

Answer

The earth is only habitable planet because of the following reasons:

1. It has habitable temperature condition.
2. It has atmosphere containing oxygen and nitrogen necessary to support life.
3. It has water in all three states.

Question 2

The earth's shape is Geoid.

Answer

The Earth is shaped like an orange, slightly flattened at the poles and with a bulge at the Equator. Hence, the earth's shape is Geoid. The word 'Geoid' means earth-shaped.

Question 3

The earth is the home of humankind.

Answer

The earth is the home of humankind because it is the only planet which can support human life. The life exists on earth because it has the right temperature, gases like oxygen and nitrogen; and water.

Tick mark the correct answer

Question 1

Earth's orbit lies between

1. Venus and Mars
2. Mercury and Venus
3. Mars and Jupiter
4. Jupiter and Saturn

Answer

Venus and Mars

Question 2

The amount of oxygen in earth's atmosphere is

1. 60%
2. 21%
3. 78%
4. 10%

Answer

21%

Question 3

Earth's biosphere is also called

1. ecosystem
2. environment
3. atmosphere
4. hydrosphere

Answer

ecosystem

Question 4

The average distance of earth from the sun is

1. 150 million km
2. 108 million km
3. 1433 million km
4. 228 million km

Answer

150 million km

Question 5

Earth completes its one revolution around the sun in

1. 360 days
2. 365 1⁄4 days
3. 366 days
4. 300 days

Answer

365 1⁄4 days

Question 6

Earth's shape is described as

1. Circular
2. Spherical
3. Oblate spheroid
4. Oval

Answer

Oblate spheroid

Question 7

Which of the following process is not involved in water cycle process?

1. Infiltration
2. Evaporation
3. Precipitation
4. Lithification

Answer

Lithification

Question 8

Lithosphere consists of

1. Soil & minerals
2. Different gases
3. Water
4. All the above

Answer

Soil & minerals

Question 9

The earth is the ............... planet from the Sun.

1. Fourth
2. Sixth
3. Eighth
4. Third

Answer

Third

Question 10

Our solar system is the part of which of the following galaxy?

1. Andromeda Galaxy
2. Elliptical Galaxy
3. Milky Way Galaxy
4. Large Magellanic cloud

Answer

Milky Way Galaxy

Question 11

Which of the following force is responsible for the oblate spheroid shape of earth?

1. Coriolis force
2. Centrifugal force
3. Compression force
4. Tidal force

Answer

Centrifugal force

Question 12

Geoid means

1. Apple shaped
2. Orange shaped
3. Earth shaped
4. Elliptical shape

Answer

Earth shaped

Diagrams

Question 1

Draw a neat diagram to show the realms of the Earth.

Answer

Below diagram shows the realms of the earth:

Question 2

Draw a neat diagram to show the water cycle on the earth.

Answer

Below diagram shows the water cycle on the earth: