Selina Textbook Solutions: Earth as a Planet | Geography Class 9 ICSE PDF Download

 Page 1


Earth as a Planet 
Exercises 
I. Short Answer Questions 
Question 1. 
How can you prove that the earth is a sphere by looking at the Pole Star ? 
Answer: 
The Pole Star can be seen at an angle of 90° at the North Pole, as it lies directly at the 
line of axis of the earth, while its angle decreases towards the Equator i.e. it is 0° at the 
equator. It is only possible in an quarter arc of a circle. It proves that the earth is a 
sphere with circular surface. 
Question 2. 
Briefly describe the shape of the earth. 
Answer: 
The earth has got a spherical shape, slightly bulging at the equator and flattened at the 
poles. The spherical shape is confirmed by the arrival of a ship seen first by its mast 
and later on the ship. The satellite picture of the earth, shadow of the earth on the moon 
as circular, and the views of circular horizons from the height etc. all these prove the 
spherical shape of the earth. 
Question 3. 
What is the earth’s mean temperature ? State its one advantage. 
Answer: 
The earth’s mean temperature is 17° C, which is ideal to support the survival of the life-
system. 
Question 4. 
Why is the earth called a watery planet ? 
Answer: 
The earth is called a watery planet, as its major part i.e. 70% is covered by water or 
hydrosphere. The earth is seen blue in the satellite pictures due to the majority of water. 
Question 5. 
What is ‘biosphere’ ? 
Answer: 
Biosphere is the narrow zone of contact amidst lithosphere, hydrosphere and 
atmosphere. 
 
Page 2


Earth as a Planet 
Exercises 
I. Short Answer Questions 
Question 1. 
How can you prove that the earth is a sphere by looking at the Pole Star ? 
Answer: 
The Pole Star can be seen at an angle of 90° at the North Pole, as it lies directly at the 
line of axis of the earth, while its angle decreases towards the Equator i.e. it is 0° at the 
equator. It is only possible in an quarter arc of a circle. It proves that the earth is a 
sphere with circular surface. 
Question 2. 
Briefly describe the shape of the earth. 
Answer: 
The earth has got a spherical shape, slightly bulging at the equator and flattened at the 
poles. The spherical shape is confirmed by the arrival of a ship seen first by its mast 
and later on the ship. The satellite picture of the earth, shadow of the earth on the moon 
as circular, and the views of circular horizons from the height etc. all these prove the 
spherical shape of the earth. 
Question 3. 
What is the earth’s mean temperature ? State its one advantage. 
Answer: 
The earth’s mean temperature is 17° C, which is ideal to support the survival of the life-
system. 
Question 4. 
Why is the earth called a watery planet ? 
Answer: 
The earth is called a watery planet, as its major part i.e. 70% is covered by water or 
hydrosphere. The earth is seen blue in the satellite pictures due to the majority of water. 
Question 5. 
What is ‘biosphere’ ? 
Answer: 
Biosphere is the narrow zone of contact amidst lithosphere, hydrosphere and 
atmosphere. 
 
Question 6. 
Name the conditions necessary for life on earth. 
Answer: 
The conditions necessary for life on earth, are ideal temperature range with an average 
between 10°C and 35°C, solar radiation, humidity, wind, water, land etc. 
Question 7. 
Give any two features of the earth that make it a ‘Unique Planet’. 
Answer: 
The earth is so for the only planet which consists of life- system. It is due to its ideal 
average temperature of 17°C to support the life and provide with atmosphere and 
hydrosphere to impart air and water essential for life. 
Question 8. 
Why is the planet Venus hotter than the planet Mercury? 
Answer: 
Venus is hotter than Mercury because the atmosphere around Venus is mainly 
composed of carbon dioxide. The carbon dioxide produces Greenhouse effect on the 
surface of Venus. Thus, the tempreature on its surface remain very high. 
Question 9. 
Name the two sources of heat in the interior of the earth. 
Answer: 
Two sources of heat in the interior of the earth are the radioactive elements trapped 
inside and the immense temperature and pressure in the deep interior. 
Question 10. 
What is meant by Terrestrial Life ? 
Answer: 
On the surface of the earth, there are continents and oceans. The life on the continents 
or on land is called ‘Terrestrial Life’. 
Question 11. 
Name the members of the Solar System. 
Answer: 
Members of the solar system includes the Sun and everything that orbits it like planets 
(Mercury, Venus, Earth, Mars, Jupiter, Saturn,.Uranus and Neptune), their satellites, 
asteroids, comets, interplanetary gas and dust. 
Question 12. 
What is a planet ? 
Answer: 
A planet is a rocky or gaseous mass that revolves around a star. 
Page 3


Earth as a Planet 
Exercises 
I. Short Answer Questions 
Question 1. 
How can you prove that the earth is a sphere by looking at the Pole Star ? 
Answer: 
The Pole Star can be seen at an angle of 90° at the North Pole, as it lies directly at the 
line of axis of the earth, while its angle decreases towards the Equator i.e. it is 0° at the 
equator. It is only possible in an quarter arc of a circle. It proves that the earth is a 
sphere with circular surface. 
Question 2. 
Briefly describe the shape of the earth. 
Answer: 
The earth has got a spherical shape, slightly bulging at the equator and flattened at the 
poles. The spherical shape is confirmed by the arrival of a ship seen first by its mast 
and later on the ship. The satellite picture of the earth, shadow of the earth on the moon 
as circular, and the views of circular horizons from the height etc. all these prove the 
spherical shape of the earth. 
Question 3. 
What is the earth’s mean temperature ? State its one advantage. 
Answer: 
The earth’s mean temperature is 17° C, which is ideal to support the survival of the life-
system. 
Question 4. 
Why is the earth called a watery planet ? 
Answer: 
The earth is called a watery planet, as its major part i.e. 70% is covered by water or 
hydrosphere. The earth is seen blue in the satellite pictures due to the majority of water. 
Question 5. 
What is ‘biosphere’ ? 
Answer: 
Biosphere is the narrow zone of contact amidst lithosphere, hydrosphere and 
atmosphere. 
 
Question 6. 
Name the conditions necessary for life on earth. 
Answer: 
The conditions necessary for life on earth, are ideal temperature range with an average 
between 10°C and 35°C, solar radiation, humidity, wind, water, land etc. 
Question 7. 
Give any two features of the earth that make it a ‘Unique Planet’. 
Answer: 
The earth is so for the only planet which consists of life- system. It is due to its ideal 
average temperature of 17°C to support the life and provide with atmosphere and 
hydrosphere to impart air and water essential for life. 
Question 8. 
Why is the planet Venus hotter than the planet Mercury? 
Answer: 
Venus is hotter than Mercury because the atmosphere around Venus is mainly 
composed of carbon dioxide. The carbon dioxide produces Greenhouse effect on the 
surface of Venus. Thus, the tempreature on its surface remain very high. 
Question 9. 
Name the two sources of heat in the interior of the earth. 
Answer: 
Two sources of heat in the interior of the earth are the radioactive elements trapped 
inside and the immense temperature and pressure in the deep interior. 
Question 10. 
What is meant by Terrestrial Life ? 
Answer: 
On the surface of the earth, there are continents and oceans. The life on the continents 
or on land is called ‘Terrestrial Life’. 
Question 11. 
Name the members of the Solar System. 
Answer: 
Members of the solar system includes the Sun and everything that orbits it like planets 
(Mercury, Venus, Earth, Mars, Jupiter, Saturn,.Uranus and Neptune), their satellites, 
asteroids, comets, interplanetary gas and dust. 
Question 12. 
What is a planet ? 
Answer: 
A planet is a rocky or gaseous mass that revolves around a star. 
Question 13. 
What is meant by Inner Planets ? Name them. 
Answer: 
The planets that lie within the asteroid belt that is Mercury, Venus, Earth and Mars are 
called the inner planets. 
Question 14. 
Why are the inner planets called the terrestrial planets? 
Answer: 
The inner planets are called the terrestrial planets because their structure is similar to 
that of the earth. 
Question 15. 
What are Jovian planets ? Name them. 
Answer: 
The planets whose structure is similar to that of Jupiter are – called Jovian planets. 
They have ring systems around and have a large number of moons. They are of 
gaseous origin. Saturn, Uranus and Neptune are Jovian planets. 
Question 16. 
How big is the sun ? Describe its size with respect to the earth. 
Answer: 
The sun is a star or a ball of hot gases. Its diameter is 1,392,000 km. i.e. 110 times 
larger than that of earth and its volume is 1.3 million times larger than the earth. 
Question 17. 
Distinguish the earth from the other planets in one important aspect. 
Answer: 
Our earth is also called a Tonely-planet’ because of its one important aspect having 
extensive life system. 
Question 18. 
How did the earth get its atmospheric blanket ? 
Answer: 
In the beginning, at the time of evolution of the planets, the earth was also a body of 
burning clouds of gases and dust. After cooling process, the heavy elements subsided 
downwards and the gases floated upwards and formed the atmosphere around the 
earth as a blanket. 
II. Fill in the blanks 
1. The Pole Star can be seen at an angle of 90° at the North Pole. 
2. The earth rotates from west to east. 
Page 4


Earth as a Planet 
Exercises 
I. Short Answer Questions 
Question 1. 
How can you prove that the earth is a sphere by looking at the Pole Star ? 
Answer: 
The Pole Star can be seen at an angle of 90° at the North Pole, as it lies directly at the 
line of axis of the earth, while its angle decreases towards the Equator i.e. it is 0° at the 
equator. It is only possible in an quarter arc of a circle. It proves that the earth is a 
sphere with circular surface. 
Question 2. 
Briefly describe the shape of the earth. 
Answer: 
The earth has got a spherical shape, slightly bulging at the equator and flattened at the 
poles. The spherical shape is confirmed by the arrival of a ship seen first by its mast 
and later on the ship. The satellite picture of the earth, shadow of the earth on the moon 
as circular, and the views of circular horizons from the height etc. all these prove the 
spherical shape of the earth. 
Question 3. 
What is the earth’s mean temperature ? State its one advantage. 
Answer: 
The earth’s mean temperature is 17° C, which is ideal to support the survival of the life-
system. 
Question 4. 
Why is the earth called a watery planet ? 
Answer: 
The earth is called a watery planet, as its major part i.e. 70% is covered by water or 
hydrosphere. The earth is seen blue in the satellite pictures due to the majority of water. 
Question 5. 
What is ‘biosphere’ ? 
Answer: 
Biosphere is the narrow zone of contact amidst lithosphere, hydrosphere and 
atmosphere. 
 
Question 6. 
Name the conditions necessary for life on earth. 
Answer: 
The conditions necessary for life on earth, are ideal temperature range with an average 
between 10°C and 35°C, solar radiation, humidity, wind, water, land etc. 
Question 7. 
Give any two features of the earth that make it a ‘Unique Planet’. 
Answer: 
The earth is so for the only planet which consists of life- system. It is due to its ideal 
average temperature of 17°C to support the life and provide with atmosphere and 
hydrosphere to impart air and water essential for life. 
Question 8. 
Why is the planet Venus hotter than the planet Mercury? 
Answer: 
Venus is hotter than Mercury because the atmosphere around Venus is mainly 
composed of carbon dioxide. The carbon dioxide produces Greenhouse effect on the 
surface of Venus. Thus, the tempreature on its surface remain very high. 
Question 9. 
Name the two sources of heat in the interior of the earth. 
Answer: 
Two sources of heat in the interior of the earth are the radioactive elements trapped 
inside and the immense temperature and pressure in the deep interior. 
Question 10. 
What is meant by Terrestrial Life ? 
Answer: 
On the surface of the earth, there are continents and oceans. The life on the continents 
or on land is called ‘Terrestrial Life’. 
Question 11. 
Name the members of the Solar System. 
Answer: 
Members of the solar system includes the Sun and everything that orbits it like planets 
(Mercury, Venus, Earth, Mars, Jupiter, Saturn,.Uranus and Neptune), their satellites, 
asteroids, comets, interplanetary gas and dust. 
Question 12. 
What is a planet ? 
Answer: 
A planet is a rocky or gaseous mass that revolves around a star. 
Question 13. 
What is meant by Inner Planets ? Name them. 
Answer: 
The planets that lie within the asteroid belt that is Mercury, Venus, Earth and Mars are 
called the inner planets. 
Question 14. 
Why are the inner planets called the terrestrial planets? 
Answer: 
The inner planets are called the terrestrial planets because their structure is similar to 
that of the earth. 
Question 15. 
What are Jovian planets ? Name them. 
Answer: 
The planets whose structure is similar to that of Jupiter are – called Jovian planets. 
They have ring systems around and have a large number of moons. They are of 
gaseous origin. Saturn, Uranus and Neptune are Jovian planets. 
Question 16. 
How big is the sun ? Describe its size with respect to the earth. 
Answer: 
The sun is a star or a ball of hot gases. Its diameter is 1,392,000 km. i.e. 110 times 
larger than that of earth and its volume is 1.3 million times larger than the earth. 
Question 17. 
Distinguish the earth from the other planets in one important aspect. 
Answer: 
Our earth is also called a Tonely-planet’ because of its one important aspect having 
extensive life system. 
Question 18. 
How did the earth get its atmospheric blanket ? 
Answer: 
In the beginning, at the time of evolution of the planets, the earth was also a body of 
burning clouds of gases and dust. After cooling process, the heavy elements subsided 
downwards and the gases floated upwards and formed the atmosphere around the 
earth as a blanket. 
II. Fill in the blanks 
1. The Pole Star can be seen at an angle of 90° at the North Pole. 
2. The earth rotates from west to east. 
3. Biosphere is the narrow zone of contact between lithosphere, hydrosphere and 
atmosphere. 
4. The earth has an average temperature of 17° C. 
5. Atmosphere is the major reservoir of carbon on the earth. 
6. In terms of size, the earth is fifth planet in the Solar System. 
7. Eratosthenes worked out the circumference of the earth to be 46,250 km. 
8. A typical galaxy may contain large cluster of stars. 
III. Long Answer Questions 
Question 1. 
Study the picture and answer the questions that follow. 
 
(a) What does the picture show you about the earth ? 
(b) State briefly the Bedford Level Experiment. 
(c) The sun rises and sets at different times in different places. What does the 
statement show about the shape of the earth. 
(d) In what way is the earth’s atmosphere beneficial to mankind ? 
Answer: 
(a) The picture shows the spherical shape of the earth. 
(b) Three pillars of equal height were put along the Bedford Level canal area in England 
each at 5 kms. interval. After observation it came to know that the middle pole was 
higher than the sideward poles. This proved that the earth’s surface was curved and the 
earth is a spherical body. 
(c) The times of sunset and sunrise are different in the different part of the earth, 
because the earth moves from west to east and the places situated in the east get 
sunrise first. Japan is called the land of rising sun, as it is in the eastern-most part of the 
Eastern Hemisphere and the date starts from the Eastern Hemisphere. It proves that 
the earth is spherical. 
Page 5


Earth as a Planet 
Exercises 
I. Short Answer Questions 
Question 1. 
How can you prove that the earth is a sphere by looking at the Pole Star ? 
Answer: 
The Pole Star can be seen at an angle of 90° at the North Pole, as it lies directly at the 
line of axis of the earth, while its angle decreases towards the Equator i.e. it is 0° at the 
equator. It is only possible in an quarter arc of a circle. It proves that the earth is a 
sphere with circular surface. 
Question 2. 
Briefly describe the shape of the earth. 
Answer: 
The earth has got a spherical shape, slightly bulging at the equator and flattened at the 
poles. The spherical shape is confirmed by the arrival of a ship seen first by its mast 
and later on the ship. The satellite picture of the earth, shadow of the earth on the moon 
as circular, and the views of circular horizons from the height etc. all these prove the 
spherical shape of the earth. 
Question 3. 
What is the earth’s mean temperature ? State its one advantage. 
Answer: 
The earth’s mean temperature is 17° C, which is ideal to support the survival of the life-
system. 
Question 4. 
Why is the earth called a watery planet ? 
Answer: 
The earth is called a watery planet, as its major part i.e. 70% is covered by water or 
hydrosphere. The earth is seen blue in the satellite pictures due to the majority of water. 
Question 5. 
What is ‘biosphere’ ? 
Answer: 
Biosphere is the narrow zone of contact amidst lithosphere, hydrosphere and 
atmosphere. 
 
Question 6. 
Name the conditions necessary for life on earth. 
Answer: 
The conditions necessary for life on earth, are ideal temperature range with an average 
between 10°C and 35°C, solar radiation, humidity, wind, water, land etc. 
Question 7. 
Give any two features of the earth that make it a ‘Unique Planet’. 
Answer: 
The earth is so for the only planet which consists of life- system. It is due to its ideal 
average temperature of 17°C to support the life and provide with atmosphere and 
hydrosphere to impart air and water essential for life. 
Question 8. 
Why is the planet Venus hotter than the planet Mercury? 
Answer: 
Venus is hotter than Mercury because the atmosphere around Venus is mainly 
composed of carbon dioxide. The carbon dioxide produces Greenhouse effect on the 
surface of Venus. Thus, the tempreature on its surface remain very high. 
Question 9. 
Name the two sources of heat in the interior of the earth. 
Answer: 
Two sources of heat in the interior of the earth are the radioactive elements trapped 
inside and the immense temperature and pressure in the deep interior. 
Question 10. 
What is meant by Terrestrial Life ? 
Answer: 
On the surface of the earth, there are continents and oceans. The life on the continents 
or on land is called ‘Terrestrial Life’. 
Question 11. 
Name the members of the Solar System. 
Answer: 
Members of the solar system includes the Sun and everything that orbits it like planets 
(Mercury, Venus, Earth, Mars, Jupiter, Saturn,.Uranus and Neptune), their satellites, 
asteroids, comets, interplanetary gas and dust. 
Question 12. 
What is a planet ? 
Answer: 
A planet is a rocky or gaseous mass that revolves around a star. 
Question 13. 
What is meant by Inner Planets ? Name them. 
Answer: 
The planets that lie within the asteroid belt that is Mercury, Venus, Earth and Mars are 
called the inner planets. 
Question 14. 
Why are the inner planets called the terrestrial planets? 
Answer: 
The inner planets are called the terrestrial planets because their structure is similar to 
that of the earth. 
Question 15. 
What are Jovian planets ? Name them. 
Answer: 
The planets whose structure is similar to that of Jupiter are – called Jovian planets. 
They have ring systems around and have a large number of moons. They are of 
gaseous origin. Saturn, Uranus and Neptune are Jovian planets. 
Question 16. 
How big is the sun ? Describe its size with respect to the earth. 
Answer: 
The sun is a star or a ball of hot gases. Its diameter is 1,392,000 km. i.e. 110 times 
larger than that of earth and its volume is 1.3 million times larger than the earth. 
Question 17. 
Distinguish the earth from the other planets in one important aspect. 
Answer: 
Our earth is also called a Tonely-planet’ because of its one important aspect having 
extensive life system. 
Question 18. 
How did the earth get its atmospheric blanket ? 
Answer: 
In the beginning, at the time of evolution of the planets, the earth was also a body of 
burning clouds of gases and dust. After cooling process, the heavy elements subsided 
downwards and the gases floated upwards and formed the atmosphere around the 
earth as a blanket. 
II. Fill in the blanks 
1. The Pole Star can be seen at an angle of 90° at the North Pole. 
2. The earth rotates from west to east. 
3. Biosphere is the narrow zone of contact between lithosphere, hydrosphere and 
atmosphere. 
4. The earth has an average temperature of 17° C. 
5. Atmosphere is the major reservoir of carbon on the earth. 
6. In terms of size, the earth is fifth planet in the Solar System. 
7. Eratosthenes worked out the circumference of the earth to be 46,250 km. 
8. A typical galaxy may contain large cluster of stars. 
III. Long Answer Questions 
Question 1. 
Study the picture and answer the questions that follow. 
 
(a) What does the picture show you about the earth ? 
(b) State briefly the Bedford Level Experiment. 
(c) The sun rises and sets at different times in different places. What does the 
statement show about the shape of the earth. 
(d) In what way is the earth’s atmosphere beneficial to mankind ? 
Answer: 
(a) The picture shows the spherical shape of the earth. 
(b) Three pillars of equal height were put along the Bedford Level canal area in England 
each at 5 kms. interval. After observation it came to know that the middle pole was 
higher than the sideward poles. This proved that the earth’s surface was curved and the 
earth is a spherical body. 
(c) The times of sunset and sunrise are different in the different part of the earth, 
because the earth moves from west to east and the places situated in the east get 
sunrise first. Japan is called the land of rising sun, as it is in the eastern-most part of the 
Eastern Hemisphere and the date starts from the Eastern Hemisphere. It proves that 
the earth is spherical. 
(d) The atmosphere is indispensable for life on earth, as it provides air to inhale ; rainfall 
and fresh waterbodies after the hydro logical cycle. Moreover, it absorbs the extremely 
hot ultraviolet rays of the sun and makes the temperature ideal on earth. Other planets 
are either very hot or very cold due to the absence of atmosphere. 
Question 2. 
Provide reliable evidence to prove that the earth is spherical in shape. 
Answer: 
The earth can be clearly seen spherical in the photographs from the satellite. Other 
proofs are the sight of the mast of a ship first before the ship appears, varying heights of 
the poles fired at different places at an interval of 5 km, through the Bedford Level 
Experiment and the sight of Pole Star at 90° from North Pole and the view of the earth’s 
horizon as circular from higher attitudes. 
Question 3. 
Give the distinctive features of the earth as a unique planet. Also give three points of 
comparison with respect to other planets. 
Answer: 
The earth possesses all the essential features necessary for maintaining the life-
system. It is provided with atmosphere and hydrosphere along with the lithosphere. 
Moreover the average temperature of 17°C is ideal for survival. Three points of 
comparison with respect to other planets are as follows. 
1. Other planets are either too hot or too cold that are unfavourable for life. 
2. Other planets are devoid of atmosphere and hydrosphere and some are 
surrounded by poisonous gases. 
3. Other planets are devoid of fresh water bodies, like rivers and lakes. 
Question 4. 
Describe the role of each of the following in making earth a habitable planet. 
(a) Atmosphere 
(b) Water 
(c) Temperature 
Answer: 
(a) Atmosphere — Atmosphere play very important role in making earth a habitant 
planet. Atmosphere plays following role: 
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 atmosphere is made up of life supporting gases like nitrogen, oxygen 
and carbon dioxide. Other gases include Helium and Aigon.