A. Tick the correct option.
1. Which one of the following is an old mountain?
Answer: The Aravalli Range
2. How much surface of the earth is covered by oceans?
Answer: 71%
3. The largest ocean of the world is-
Answer: Pacific Ocean
4. Which continent is the most advanced and economically developed continent?
Answer: Europe
5. Which one of the following gases has the largest volume in the atmosphere?
Answer: Nitrogen
B. Fill in the blanks.
1. ___________ is a narrow belt or zone of the earth where all forms of life exist.
2. An envelope of the air surrounding the earth is called ___________.
3. ___________ is the upper surface of the earth consisting of rocks.
4. A highly elevated land from the surroundings with very steep slopes is known as ___________.
5. An upland with rugged surface is called ___________.
Answer: (1) Biosphere (2) atmosphere (3) Lithosphere (4) mountains (5) plateau
C. Match the following:
Answer: (1) e, (2) c, (3) a, (4) b, (5) d.
D. Answer the following questions in brief.
1. Name the four realms of the earth.
Answer: Lithosphere, hydrosphere, atmosphere and biosphere are the four realms of the earth.
2. Which four gases constitute only one per cent of the total volume of the atmosphere?
Answer: Carbon dioxide, argon, hydrogen and helium are the four gases which constitute only one percent of the total volume of the atmosphere.
3. Which continent is not inhabited by the people and why?
Answer: Antarctica is the continent that is not inhabited by the people. It is due to very cold conditions.
4. Why is earth known as a unique planet?
Answer: Earth is a unique planet because it is the only planet where life exists.
5. Name three major landforms on the land surface.
Answer: Plateaus, mountains and plains are the three major landforms on the land surface.
E. Answer the following questions.
1. What are plains? Explain briefly the formation of plains.
Answer: A plain is a relatively low-lying flat land. Most of the plains in the world have been formed by rivers. The rivers carry away large volume of silt and sediments from the mountains and deposit them in low-lying areas to form plains.
2. Give a brief account of the plateaus of the world.
Answer: A plateau is an upland with rugged surface. The average height of a plateau is 600 metres above the sea level. Nearly 40% of total land surface of the earth is plateau. The Plateau of Tibet is also called Roof of the World, is the highest plateau in the world. The Deccan Plateau in India, the Arabian Plateau and the Brazil Plateau are some of the large plateaus of the world.
3. Name the two main gases of the atmosphere. Write the significance of each.
Answer: The two main gases of the atmosphere are Nitrogen and Oxygen. It is nitrogen that dilutes oxygen and prevents rapid burning at the earth’s surface. Oxygen is essential for respiration and burning.
4. What is meant by hydrosphere? Briefly explain the importance of hydrosphere.
Answer: Hydrosphere refers to the layer of water on the surface of the earth, below the surface of the earth and also in the air. It covers 71% of the total surface of the earth. It occurs on land in the form of lakes and rivers.
5. How are human activities responsible for causing ecological imbalance?
Answer: Human population is increasing rapidly, more space is required for different human activities such as agriculture, industry and urbanization. Man is destroying the forests carelessly and exploiting the resources. As a result of these activities, several problems have emerged before human beings, for example soil erosion, floods, etc. In this way, human activities responsible for causing ecological imbalance.
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