Question 1. How is our atmosphere different from the atmospheres on Venus and Mars?
Solution : Earth’s atmosphere is different from those of Venus and Mars. This difference lies essentially in their compositions. Earth’s atmosphere is a mixture of nitrogen (79%), oxygen (20%), and a small fraction of carbon dioxide, water vapours and other gases. This makes the existence of life possible on Earth. However, the atmospheres on Venus and Mars mainly consist of carbon dioxide. The amount of carbon dioxide on these planets can range from 95% to 97%.
Question 2. How does the atmosphere act as a blanket?
Solution :
The atmosphere acts as a blanket by performing the following functions :
(a) It keeps the average temperature of the Earth fairly constant during day time and even during the course of whole year.
(b) It prevents a sudden increase in the temperature during day time.
(c) It slows down the escape of heat from the surface of the Earth into outer space during night time.
Question 3. What causes winds?
Solution : An uneven heating of the Earth’s surface causes winds. On being heated, air becomes lighter and rises up. As a result, a region of low pressure is created. Then, air from a high pressure region moves to a low pressure region, causing wind.
Question 4. How are clouds formed?
Solution : During day time, on being heated, a large amount of water evaporates from various water bodies and goes into the air. A part of this water vapour also reaches the atmosphere through biological activities such as transpiration and respiration. This causes the air in the atmosphere to heat up. When this heated air rises, it expands and cools, which results in the condensation of water vapour forming water droplets. The presence of dust and other suspended particles in air also facilitates the process of condensation. The formation of water droplets leads to the formation of clouds.
Question 5. How many times did you fall ill in the last one year? What were the illnesses?
(a) Think of one change you could make in your habits in order to avoid any of/most of the above illnesses.
(b) Think of one change you would wish for in your surroundings in order to avoid any of/most of the above illnesses.
Solution :
I fall ill only once last year. I had suffered from typhoid.
(a) I will avoid street food specially those which are cooked at unhygienic places
and kept uncovered.
(b) I shall keep my surroundings cleaner than earlier.
Question 6. A doctor/nurse/health-worker is exposed to more sick people than others in the community. Find out how she/he avoids getting sick herself/himself.
Solution : A doctor/nurse/health-worker is exposed to more sick people than others in the community still they avoid getting sick themselves because they take care of the preventive measures like personal and community hygiene/cleanliness and immunisation to prevent infectious diseases.
Question 7. Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by your local authorities to bring down the incidence of these diseases.
Solution : Three most common diseases in my locality are diarrhoea, malaria and tuberculosis and following steps I would suggest to be taken by our local authorities to bring down the incidence of these diseases :
(i) Supply of safe drinking water and preventing incidences of open drains.
(ii) Improved and hygienic environment free of garbage and wastes thrown in the open.
(iii) Eradication of mosquitoes
(iv) mmunisation/vaccination camps
Question 8. A baby is not able to tell her/his caretakers that she/he is sick. What would help us to find out
(a) that the baby is sick?
(b) what is the sickness?
Solution :
(a) If the baby is crying and remains restless no matter whatever is done to ease him/her out then he/she is sick.
(b) We must observe symptoms and severity of the symptoms to diagnose the sickness.
Question 9. Under which of the following conditions is a person most likely to fall sick?
(a) when she is recovering from malaria.
(b) when she has recovered from malaria and is taking care of someone suffering from chicken-pox.
(c) when she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox. Why?
Solution : A person is most likely to fall sick when she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox because during her fast she was on a limited diet and didn’t get sufficient nourishment hence her health condition is poor such that she is very likely to fall sick.
Question 10. Under which of the following conditions are you most likely to fall sick?
(a) when you are taking examinations.
(b) when you have travelled by bus and train for two days.
(c) when your friend is suffering from measles. Why?
Solution : We are most likely to fall sick when a friend is suffering from measles since measles is an infectious/communicable disease that can spread easily from one person to the other.
Question 11. Why is the atmosphere essential for life?
Solution :
We need atmosphere for following reasons:
(i) It works like a blanket and traps the radiations reflected back from earth surface that keeps the average temperature of earth of quite steady and suitable for sustenance of life.
(ii) It provides carbon dioxide for photosynthesis and oxygen for respiration and combustion.
(iii) Prevents sudden change in temperature.
(iv) Enables us to hear sounds.
Question 12. Why is water essential for life?
Solution :
Water essential for life because:
(i) All organisms are made up of cells. All cellular processes take place in a water medium. All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.
(ii) Substances are also transported from one part of the body to the other in a dissolved form.
(iii) Essential for digestion.
(iv) Helpful in excretion and egestion.
(v) Regulates our body temperature by sweating and evaporation.
Question 13. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?
Solution : Plants need simple nutrients like certain elements for their proper growth and they get most of these elements from soil. With the help of these elements plants prepare their own food in the presence of sunlight. Since all other organisms are dependent upon plants for their nutrition hence we can say that organisms that live in water are not totally independent of soil as a resource. Another reason is that organic matter from soil dissolves into water and provides nutrients to the aquatic organisms.
Question 14. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Solution : The weather predictions are made based on information obtained about general patterns of changes in temperature, humidity, winds and clouds.
Question 15. We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?
Solution : Isolating many human activities lead to increasing levels of pollution of the air, water-bodies and soil would help in reducing water and soil pollution but it can hardly make any difference to air pollution severity the reason is gases will spread from isolated places and reach everywhere. Instead of isolating we must stress on sustainable management of our resources and cut down or replace their use like using cleaner fuels like CNG in place of fossil fuels.
Question 16. Write a note on how forests influence the quality of our air, soil and water resources.
Solution : Quality of air: Forests have trees and plants that absorb carbon dioxide and liberate oxygen thus maintaining their levels in the biosphere.
Quality of soil: Roots of trees hold the soil particles and prevent soil erosion from taking place. Dead trees and plants or their parts add humus and organic matter to soil thus making it fertile.
Quality of water: Forest allows easy going of the water cycle in nature with cloud formation and condensation in the form of rain.