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Chapter 1

Earth as a Planet

Class 9 - Total Geography Morning Star


Fill in the blanks

Question 1

When seen from a seashore, mast of a ship appears first.

Question 2

If the earth were flat, the Pole Star would have the same height for all latitudes.

Question 3

The Pole Star can be seen at an angle of 90 degrees at the North Pole.

Question 4

The earth rotates from west to east.

Question 5

The shape of the earth is an Oblate spheroid.

Question 6

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

Question 7

The earth has an average temperature of 17 degrees Celsius.

Question 8

Ocean is the major reservoir of carbon on the earth.

Question 9

Biosphere is the life zone of the earth.

Question 10

Life-giving cycles are the nature's mechanism to maintain balance in the ecosystem.

Short Answer Questions

Question 1

How can you prove that the earth is a sphere by looking at the horizon?

Answer

The view of the earth's surface as seen from a height is circular. We can prove that the earth is a sphere by looking at the horizon as with increase in altitude, the circular horizon also widens. Had the earth's surface been flat, the horizon would have been the same irrespective of the altitude.

Question 2

Briefly describe the shape of the earth.

Answer

The earth is said to be spherical, but it is not a perfect sphere. The diameter at the equator is greater than the diameter at the poles. The bulge at the equator and compression at the poles gives earth the shape of an oblate spheroid or 'Geoid'.

Question 3

What is the earth's mean temperature? State its one advantage.

Answer

The mean temperature of the earth is 17 degrees Celsius. This temperature is ideal for life to exist.

Question 4

Why is the earth called a watery planet?

Answer

Earth is called a watery planet because 70% of the earth's surface is covered by water.

Question 5

What is 'biosphere'?

Answer

Biosphere is the life zone of the earth. It is that part of the earth's terrestrial system - including air, land and water - in which life develops and where life processes in turn get transformed.

Question 6

Name the conditions necessary for life on earth.

Answer

The conditions necessary for life on earth are as follows:

  1. Optimum distance from the sun
  2. Ideal temperature of 17 degrees Celsius
  3. Presence of Atmosphere
  4. Presence of water
  5. Presence of lithosphere and biosphere
  6. Life-giving cycles operate in nature

Question 7

Give any two features of the earth that make it a 'Unique Planet'.

Answer

Two features of the earth that make it a 'Unique Planet' are as follows:

  1. Presence of Atmosphere
  2. Presence of water

Structured Questions

Question 1(a)

How does the sighting of a ship from the seashore prove about that the earth is round in shape?

Answer

While standing at the seashore, watching an approaching ship, we first see only its mast. Then, as it comes closer, we can see the deck in the middle, then its funnel, and finally the hull comes into full view. This can only happen when the earth's surface is curved. Thus, it is proved that the earth is round in shape.

Question 1(b)

State briefly the Bedford Level Experiment.

Answer

An experiment was carried out in the Bedford Level canal area in England.

Procedure- Three poles of equal length were fixed at intervals of 5 km. It was ensured that the poles had the same height above the water in the canal.

Observation- When the poles were viewed from one end of the canal, the middle pole looked slightly higher.

Result- This experiment demonstrated that the surface of the earth is curved.

Question 1(c)

Give a geographical reason for each of the following:
(i) The sunrise and sunset occur at different times at different places.
(ii) The earth is not a perfect sphere.
(iii) Venus is hotter than mercury.

Answer

(i) The sunrise and sunset occur at different times at different places because the earth rotates from west to east and therefore, people in the east can see the sun earlier than those in the west.

(ii) The earth is not a perfect sphere because the diameter of th earth varies at the equator and at the poles. This difference is due to the centrifugal force of the earth's rotation at a great speed which forms a bulge at the equator and a compression at the poles.

(iii) Venus is hotter than mercury because Venus is mainly composed of carbon dioxide which produces Greenhouse effect on the surface of Venus. Thus, the temperature on its surface remains very high.

Question 1(d)

Draw a well labelled diagram to show that the horizon of the earth is circular in shape.

Answer

Draw a well labelled diagram to show that the horizon of the earth is circular in shape. Total Geography ICSE Class 9

Question 2(a)

Describe the role of atmosphere in making earth a habitable planet.

Answer

The atmosphere of the earth is composed of gases like nitrogen (78%), oxygen (21%), carbon dioxide, helium and argon (less than 1%). Atmosphere plays a major role in making earth a habitable planet as-

  1. The atmosphere receives heat from the sun by solar radiation and loses heat by earth's radiation. In this way, a balance is maintained.

  2. The earth's atmos[here is made up of life-supporting gases like nitrogen, oxygen and carbon dioxide.

  3. Ozone present in the earth's atmosphere absorbs harmful ultraviolet rays of the sun.

  4. The atmosphere also prevents loss of heat from the earth's surface and helps to keep earth warm.

Question 2(b)

Describe the role of water in making earth a habitable planet.

Answer

Earth is a watery planet with 70% of the earth's surface being covered by water. Water plays a major role in making earth a habitable planet as-

  1. Distribution of water is responsible for moderating the climate and surface condition of the earth.

  2. Water bodies like lakes, ponds, rivers etc. are important parts of the ecosystems and biosphere.

  3. Water moves in a continuous hydrological cycle. There is a proper balance between evaporation, condensation and precipitation without which life would not be possible.

  4. Water bodies help to maintain the temperature of the earth's surface. They rapidly absorb enormous amount of heat during the day, and keep the earth fairly cool. At night, they release the heat absorbed during the day, which along with other atmospheric effects, keep most of the surface from freezing at night.

Question 2(c)

Describe the role of temperature in making earth a habitable planet.

Answer

Temperature plays a major role in making earth a habitable planet as the earth is the third planet from the sun. It has an average temperature of 17 degrees Celsius which is suitable for life to exist. Other planets of the solar system are either too hot or too cold to support life.

Question 2(d)

Describe the role of distance from the sun in making earth a habitable planet.

Answer

Distance from the sun plays a major role in making earth a habitable planet as-

  1. The earth is at an optimum distance from the sun. Hence, it is neither too hot nor too cold.

  2. The distance between the earth and the sun makes life possible on earth. It it was closer to the sun, any life present would get burnt from too much heat of the sun. If it was farther from the sun, life would freeze because of lack of heat.

Question 3(a)

How does each of the following prove the circular shape of the earth:
(i) Lunar Eclipse
(ii) Pole Star

Answer

(i) Lunar Eclipse

The shadow of the earth on the surface of the moon is clearly visible from earth during lunar eclipse. It appears as an arc of a circle. Since the earth is bigger than the moon, it is rarely oriented in the same position as the moon but the shadow is always circular. This proves the circular shape of the earth.

(ii) Pole Star

The Pole Star can be seen at an angle of 90 degrees at the North Pole. It lies in line with the axis of the earth, and its angle decreases towards the equator. At the equator, the angle is 0 degrees. This can happen only in an arc of a circle. This proves the circular shape of the earth.

Question 3(b)

What is an ecosystem? Give an example.

Answer

The self-regulating and self-sustaining structural and functional unit of the biosphere is called an ecosystem. This system depends upon the sun for its energy.

For example, Ecosystem of a forest include plants and trees which are eaten by herbivores (deer, rabbit). These animals are eaten by carnivores (lion, tiger). When these animals perish, they are decomposed by decomposers and return to the environment. Again they are consumed by producers and so on.

Question 3(c)

Give a geographical reason for each of the following:
(i) Earth is a habitable planet.
(ii) From space Earth looks blue.
(iii) Water bodies reduce the day-night temperature variations.

Answer

(i) Earth is a habitable planet as it is covered with green vegetation, enormous blue-green oceans containing over a million islands, a large number of streams and rivers, huge land masses called continents with mountains, ice caps and deserts. It also has ideal temperature for the existence of life.

(ii) From space Earth looks blue because 70% of the earth's surface is covered by water.

(iii) Water bodies reduce the day-night temperature variations as water can absorb enormous amounts of heat without causing much change in its temperature. Water bodies rapidly absorb enormous amount of heat during the day, and keep the earth fairly cool. At night, they release the heat absorbed during the day, which along with other atmospheric effects, keep most of the surface from freezing at night.

Question 3(d)

Draw a well labelled diagram to show the cyclic circulation of water between the three realms of the earth.

Answer

Draw a well labelled diagram to show the cyclic circulation of water between the three realms of the earth. Total Geography ICSE Class 9
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