Construct an equilateral triangle of perimeter 18 cm
Answers
ANSWER:
The names of continents in increasing order of their size are as follows:
Australia
Europe
Antarctica
South America
North America
Africa
Asia
Page No 63:
Question I.2:
Name the oceans in increasing order of their size.
ANSWER:
The names of the oceans in order of their increasing size are as follows:
The Arctic Ocean
The Indian Ocean
The Atlantic Ocean
The Pacific Ocean
Page No 63:
Question I.3:
What is the composition of the atmosphere?
ANSWER:
The atmosphere is composed of several odourless, tasteless, colourless gases. The cover of the air that extends to a height of around 1,600 kilometres from the Earth's surface is known as the atmosphere. The composition of the air in the atmosphere is as follows:
Nitrogen - 78%
Oxygen - 21%
Argon - 0.93%
Carbon dioxide - 0.03%
Water vapour
Others gases like argon, helium and ozone
Page No 63:
Question I.4:
Name the different layers of the atmosphere.
ANSWER:
Following are the layers of the atmosphere:
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere
Ionosphere
Page No 63:
Question I.5:
What are the main elements of biosphere?
ANSWER:
The biosphere is a narrow zone where land, air and water interact with each other to support several forms of life. The biotic or living elements of the biosphere are plants, animals, human beings and microbes. They are dependent on one another for their existence. The abiotic or non-living components of the biosphere include rocks and minerals.
Page No 63:
Question J.1:
Write about at least one important physical feature from each continent.
ANSWER:
Important physical features of all continents are given below.
1. Africa: This continent has a lot of plateaus but no high mountains. A large part of the continent is covered with deserts, e.g. the Sahara Desert, the Kalahari Desert and the Namibian Desert. It also has thick forests in the equatorial region.
2. Asia: It is known as the continent of extremes because in this continent, the highest peak and the lowest point of Earth's surface are found, i.e. Mount Everest, which is the highest peak in the world, and the Mariana Trench, which is the lowest point of the Earth's surface. All kinds of topographic features are found in this continent.
3. Australia: It is a land of plateaus with few dispersed low mountain ranges. The Great Barrier Reef is an important feature of the continent, which is formed by the corals.
4. Europe: It is the only continent that is both populous and prosperous. It is a land of high mountains. Finland in Europe has more than 50,000 lakes; the continent is extremely beautiful.
5. North America: It is a land with extensive plains, mountain ranges and ancient plateaus. Grasslands are an important feature of this place. For example, the Prairies are important grasslands of this region.
6. South America: The Andes is the longest unbroken chain of mountains in the world. Apart from the mountains, almost half of the continent is covered with lowlands and river basins.
7. Antarctica: It has some mountain ranges and vast plateaus. It is completely covered with ice. Therefore, it is also known as the white continent.
Page No 63:
Question J.2:
What is the importance of oceans for human beings?
ANSWER:
The importance of oceans for human beings can be understood with the help of the following points:
They are a storehouse of a large number of minerals and energy resources.
They provide a large number of fish and other marine animals used as food in large quantities.
They play an important role in causing humidity in the atmosphere; this ultimately leads to rain.
They act as important trade routes.
They act as a link between several continents.
They are an important source of common salt.
They help in regulating climate by storing carbon; they also have a stabilising influence on the water cycle.
Tidal energy is of great potential in the present era of energy crisis.
Page No 63:
Question J.3:
What is the importance of the atmosphere?
ANSWER:
The importance of the atmosphere can be understood with the help of the below-mentioned points: