STD 7 Social Science: Chapter 07 Earth and Biosphere - Questions and Answers | Teaching Manual


Textbooks Solution for Class 7 Social Science (English Medium) ഭൂമിയും ജീവലോകവും | Text Books Solution Social Science (English Medium) Chapter 07 Earth and Biosphere | ഈ അധ്യായത്തിന്റെ Teachers Handbook, Teaching Manual എന്നിവ ഡൗൺലോഡ് ചെയ്യാനുള്ള ലിങ്ക് ചോദ്യോത്തരങ്ങളുടെ അവസാനം നൽകിയിട്ടുണ്ട്.


Chapter 07: Earth and Biosphere - Questions and Answers
1.  What is called lithosphere?
Answer: The solid portion of the earth which contains all the landforms, rocks and soil is called the lithosphere.

2. What are mountains?
Answer: Landforms having an altitude of more than 900 metres above the mean sea level and with Steep slopes.

3. What are called plateaus?
Answer: Landforms with an almost flat top and which stands at a comparatively higher elevation than the surroundings.

4. What are plains?
Answer: Comparatively low lying and expansive landforms

5. How is soil formed?
Answer: 
• Rocks exposed to sunlight, rain and snow for many years begin to disintegrate. Sometimes chemical changes also occur in them.
• When the dead remains of plants and animals decay, it adds humus content to the soil. Soil is formed through such processes that take place constantly over thousands of years.

6. Can you name a few activities that adversely affect soil fertility?
Answer: 
• Excessive use of fertilizers.
• Excessive use of pesticides.
• Continuous farming etc.

7. How did man's indiscrete actions decrease the number of paddy fields?
Answer:  Vast paddy fields were once Kerala's unique feature. But now our paddy field and other wetlands undergo reclamation by being filled up with soil for human purposes. By doing this we are causing permanent damage to these natural sites of rainwater percolation. In some places, the clay in the paddy fields is mined and baked in the kilns for making bricks. Clay stores water in paddy fields. If there is no clay there will be no paddy field. In some places, the sand below the clay is mined after removing the clay from the paddy field.

8. What are the problems caused by excessive sand mining from rivers?
Answer:  The water level of many of our rivers, which were once rich, drops drastically after the rainy season. This is because of the increase in the depth of river bed due to sand mining from rivers. It also leads to lowering the water level in the nearby wells and ultimately to water scarcity. Many rivers, due to the increase in depth, have almost reached the bedrock level. This leads to bank shelving. Shelving of fertile banks results in loss of life and property.

9. How will hill mining affect water availability?
Answer:  Most of the mining areas are filled up with groundwater and rainwater. This water will then be mixed up with impurities in the mining field. This will cause water pollution. It will reduce the availability of freshwater.

10. What are the activities that destroy soil?
Answer: 
• Deforestation
• Unscientific agricultural practices
• Construction and development, etc.

11. Suggest an alternative to bricks made from the topsoil of paddy fields?
Answer:  The technology of making bricks out of waste from clay factories and plastics is available now. It could be used as an alternative to bricks made from the topsoil of paddy fields.

12. Suggest an alternative to sand as a construction material?
Answer: The use of rock debris for construction purposes instead of river sand is noteworthy. It is proven that rock debris is as strong and as durable as river sand.

13. What is called a hydrosphere?
Answer: Water, in a liquid state, is found in oceans, rivers, lakes and streams, on the earth's surface and below it as well. While water is found in solid States in polar regions and atop high mountains, it exists as water vapour and water droplets in the atmosphere. Water found on the earth in the said forms is called the hydrosphere.

14. ‘Even though two-thirds of the surface of the earth is water, we feel water scarcity Why?
Answer:  Even though two-third of the surface of the earth is water, only three per cent of it is freshwater. From this freshwater, only less than one per cent of it is available for human consumption. This scarce quantity of water is obtained from rivers, ponds, lakes, wells etc. The rest of the water is found in solid-state in polar regions and atop mountains. There are many limitations to using underground water. So, we feel water scarcity.

15. Suggest any three scientific modes of Water Management?
Answer: 
• Promote terraced farming
• Cultivate fruit-bearing trees, instead of crops like Coconut and areca nut that have fibrous roots, along the rocky hill slopes with shallow soil.
• Instead of concrete, use locally available rocks and wood to create a check dam along hill slopes.

16. What is the atmosphere?
Answer: Atmosphere is a layer of air that protects the Earth like a blanket.

17. "In different ways atmosphere is useful to us’. Which are they?
Answer: 
• Atmosphere provides carbon dioxide required for plants.
• It also provides oxygen required for various Organisms on earth
• It protects us from harmful ultraviolet and gamma rays.
• Atmosphere is the reason for climatic phenomena like rain and snow.

18. Name some activities of man that lead to air pollution?
Answer: 
• Gases used in refrigerators.
• Carbon dioxide emission from vehicles.
• Burning fossil fuels etc.

19. Delhi city has huge machines which pump fresh air into the atmosphere. Why does the urban administration take such measures?
Answer:  The city suffers from air pollution caused by road dust and industry, etc. Thus the city lacks sufficient fresh air. Delhi is the latest city to try to come up with ways to tackle increasingly dangerous pollutants in the air. So, Delhi city has huge machines which pump fresh air into the atmosphere.

20. Collect information regarding various methods to reduce atmospherically pollution.
Answer: 
• Reduce or eliminate fireplace and wood stove use.
• Avoid burning leaves, trash, and other materials.
• Use public transportation for travel.
• Reduce the use of fossil fuels
• Use CNG vehicles instead of vehicles that run on petrol.

21. What is Biosphere?
Answer: Biosphere includes all living things on the Earth. The biosphere exists because of the interaction of the lithosphere, hydrosphere and atmosphere.

22. What are natural disasters?
Answer:  Natural disasters are phenomena that occur naturally and result in heavy loss to the life and property of man.

23. Write some examples of Government Departments and systems for the prevention and risk reduction of natural disasters.
Answer: 
• Kerala Revenue - Disaster Management Department
• State Disaster Management Authority
• Hazard Vulnerability and Risk Assessment cell.
• Land and Disaster Management Institute.

24. What is Landslide?
Answer: Landslide is the fast down-slope movement of rocks, soil and mud along the steep slopes

25. Write some safety measures to be taken during a landslide?
Answer: 
• move to safer places as early as possible
• give priority to small children, aged people and persons with physical disabilities during the rescue operations.
• give first aid to injured people.
• be cautious of the possibility of recurrence of landslides.
• contact police, ambulance services etc.
• take precautions to avoid electric shock.

26. What is Flood
Answer: Surplus water during the monsoons causes overflowing of rivers leading to floods.

27. Suggest some ways to tackle floods?
Answer: 
• Do not construct houses very close to rivers
• Do not venture into rivers during the rainy season.
• Paddy fields are places for the percolation of rainwater. Avoid reclamation.
• People residing in coastal areas should be more careful during the rainy
season. Valuables should be shifted to elevated places.
• Cut off the electric connections if the water level rises.

Let us assess

1. Man's unscientific interventions adversely affect the lithosphere. Explain with suitable examples.
Answer:  Man's unscientific interventions mostly destroy the precious lithosphere on which we live. Uncontrolled exploitation of natural resources can lead to imbalances in nature. Vast paddy fields were once Kerala's unique feature. But now our paddy field and other wetlands undergo reclamation by being filled up with soil for human purposes. By doing this we are causing permanent damage to these natural sites of rainwater percolation. This makes it prone to flooding even in light rains.
The water level of many of our rivers, which were once rich, drops drastically after the rainy season. This is because of the increase in the depth of river bed due to sand mining from rivers.

2. Scientific interventions are essential for the existence of a healthy biosphere. Identify and write down three activities needed for this.
Answer: 
• Restore damaged ecosystems by planting trees on land where forests have been cut down.
• Establish parks to protect rainforests and wildlife.
• Encourage people to live in a way that doesn't hurt the environment.

3. How are the freshwater sources of your place getting polluted?
Answer: 
• Groundwater gets polluted when contaminants from pesticides and fertilizers to waste leaching from landfills and septic systems make their way into an aquifer, rendering it unsafe for human use.
• In most of the places factory wastes are drained into rivers. It makes the river water unsafe for drinking etc.

4. Hydrosphere exists in three forms. Identify where and in what forms do they exist.
Answer:  Water, in the liquid state, is found in oceans, rivers, lakes and streams, on the earth's surface and below it as well. While water is found in solid-state in polar regions and atop high mountains, it exists as water vapour and water droplets in the atmosphere.

5. What are the things that you can do to reduce air pollution? Prepare a note.
Answer:  Most of the places on the earth are suffering from air pollution. Thus, there is a necessity to reduce air pollution. By reducing the use of vehicles that run on fossil fuels, we can reduce air pollution. Reduce or eliminate fireplace and wood stove use, avoid burning leaves, use public transports instead of private vehicles, use fans instead of Air Conditioner are some other ways to reduce air pollution.




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