Chapter 3 – The Earth and its Living World
EXERCISES
1. What’s the solution?
Dark patches appear on the skin after exposure to the sun.
Ans: The harmful radiation of the sun can cause a burning sensation in our skin. In order to avoid this, we should not roam in the harsh sunlight. If it is necessary to leave the house, we should use an umbrella or cap. Wear cotton clothes that cover the skin on your hands and legs. The use of sunscreen cream is advisable. Covering the face with a handkerchief can protect the delicate skin. After returning from outside. splash cold water on the face. This will help reduce the temperature of the skin.
2. Use your brain power !
(a) Why are micro-organisms important ?
Ans: In every envelope of the earth, there are microorganisms. These microorganisms perform an important function in degradation. They also occupy an important place in the food chain. The dead and decaying plant and animal matter is converted into soil and minerals by these microorganisms. If there were no microorganisms, huge piles of debris could have piled up everywhere on the earth. Therefore, microorganisms are very important organisms on earth.
(b) Think about all the foodstuffs obtained from the sea. Find more information and write ten lines about them.
Ans:
(1) Many marine organisms inhabit seas. Some of these are in our food.
(2) Many edible varieties of fish are caught from the seas.
(3) There are good-quality proteins and fatty acids in the fish. Therefore, it is a nutritious food.
(4) Shellfish varieties such as crabs, prawns, and lobsters are favourite food items worldwide. Prawns are abundantly available in the Indian waters; therefore, we get lots of foreign exchange through the export of prawns.
(5) Bivalves, squids, and oysters are also considered delicacies.
(6) Algae from the seas are also eaten in Asian countries, though not in India.
(7) Agar is a substance made from marine algae that is used in jellies and puddings.
(8) Salt is made from seawater.
(9) In some countries, potable water is made from seawater by special processes.
(10) Young prawns and fish are used for aquaculture.
3. Answer the following questions.
(a) What are clouds made of?
Ans: Clouds are made up of fine droplets of water. The sun’s heat evaporates the water to form vapours from the earth’s surface. This water vapour rises high in the atmosphere. At cool heights, it condenses, forming fine droplets of water, which in turn make the clouds.
(b) What is meant by ‘biosphere’?
Ans: Living things are seen in all the envelopes of the earth, such as the lithosphere, hydrosphere, and atmosphere. All the living things together in these three envelopes form a biosphere. Thus, the plants, animals, and microorganisms together make a biosphere.
(c) Make a list of the landforms you see in your surroundings and give a description of any two of them.
Ans: In my surroundings, there is a small hillock and a playground. I can see mountain ranges from afar. Between these mountain ranges are valleys and passes. Therefore, the list of landforms is: Hillocks, plains, mountains, valleys, and passes
(1) Hillock: A hillock is a small mountain. The land on the hillock is sloping. It is easy to climb a hill. We can plant trees on the slope of a hill to stop soil erosion.
(2) Plain: A playground is a plain. A plain is a flat part of the land. There is no slope or elevation on the plain. Since the entire surface is flat, we can use it for playing and other activities. We can plant trees around the plain.
4. In the following sentences, underline the words that refer to landforms.
(a) Anil lives at the foot of a hill.
Ans: hill
(b) Ria lives in the plateau region.
Ans: plateau
5. Write a note about the following.
(a) Evaporation
Ans: The heat changes water into vapour. This action is called evaporation. The sun’s heat converts the water present on the earth’s surface into water vapour. The water that has percolated into the soil also evaporates due to heat. All such vapour enters the atmosphere. This vapour condenses and comes back to the surface of the earth in the form of rain. Thus, evaporation is necessary for rainfall. The water cycle keeps on functioning due to evaporation.
(b) Condensation
Ans: Condensation is the process by which vapour is changed into water. In nature, due to condensation, there is rainfall. The water vapour that reaches the upper layers of the atmosphere gets condensed and forms fine droplets of water.
(c) The water cycle
Ans: The movement of water is continuously taking place from the earth’s surface to the earth’s atmosphere. The processes of evaporation, condensation, and rainfall are continuous. Due to the sun’s heat, the water on the earth’s surface continuously evaporates. Since water vapor is lighter than air, it rises high in the atmosphere. Due to the cool temperatures at the heights, the water vapour condenses, forming fine droplets of water. These droplets later form clouds. When small droplets of water become heavier and bigger, they descend on the earth in the form of rain. Rainwater mixes with different water bodies. The snowbound regions also show melting ice and glaciers. This water also eventually mixes with ocean water. In this way, water moves in a cyclic manner, which is known as the water cycle.
6. Give two examples of each.
(a) Weather-related events
Ans:
(i) Formation of clouds
(ii) Rainfall
(iii) Fog
(iv) Winds
(v) Storms
(b) Sources of water
Ans:
(i) Rills and brooks
(ii) Streams
(iii) Wells and rivers
(iv) Lakes and ponds
(v) Glaciers
7. Draw a labelled diagram showing the water cycle.
Ans:
