Class Notes NCERT Solutions for CBSE Students
Question: Mention the three main components of the environment.
Answer: The three main components of the environment are the lithosphere, the atmosphere and the hydrosphere. The lithosphere is the solid portion of the earth. The gaseous layers that surround the earth is the atmosphere. The atmosphere is made up of oxygen, nitrogen, carbondioxide and other gases. The hydrosphere refers to the big area of water that covers the earth’s surface. This water is in the forms of ice, water and water vapour.
Question: Write a short note on the ‘hydrosphere’.
Answer: The hydrosphere refers to the water bodies that are found on the earth’s surface. More than 71% of the earth is covered with water. This water is found in all its forms—ice, water and water vapour. Running water in oceans and rivers and in lakes, ice in glaciers, underground water and the water vapour in atmosphere. More than 97% of the earth’s water is found in oceans. The ocean water is very salty, hence not of human utility. A large proportion of the rest of water is in the form of the icesheets and glaciers or under the ground. A very small percentage (0.03%) is available as fresh water. It is this water that we use.
Question: Explain biosphere – the domain of life.
Answer: The biosphere is a narrow zone of the earth where land, water and air interact with each other to support life. It is in this zone that life exists. There are several species of organisms that vary in size from microbes and bacteria to large mammals. All living organisms including humans are linked to each other and to the biosphere for survival.
Question: Give an account of the composition of atmosphere. Also discuss
the importance of the components.
Answer: The atmosphere is composed mainly of nitrogen, and oxygen. Together they make up about 99% of clean, dry air. Nitrogen 78% and oxygen 21%. Apart from these two major gases, there are other gases too in the atmosphere. These gases include carbon dioxide, argon and others comprise 1% by volume. ‘Oxygen is the breath of life while nitrogen helps in the growth of living organisms. Carbon dioxide absorbs heat radiated by the earth. In this way, it keeps the planet warm. It is also essential for the growth of plants.
Question:What is atmosphere? Write about its different layers.
Answer: The atmosphere is a thin blanket of air that surrounds the earth. It provides us with the air we breathe and protects us from the harmful effects of sun’s rays. The atmosphere extends upto a height of about 1,600 km. The atmosphere is divided into five layers based on composition, temperature and other properties. These layers are—the troposphere, the stratosphere, the mesosphere, the themosphere and the exosphere.
