CBSE Class 9 Science Natural Resources VBQs

Question. How does the atmosphere act as a blanket?
Answer : The presence of ozone in the upper layer of atmosphere protects life from harmful ultraviolet radiations. Atmosphere maintains the temperature on the surface of the earth during day and night time. In this way, atmosphere acts as a blanket.

Question. What is soil erosion?
Answer : The removal of top fertile layer of soil by the action of air, wind, water etc. is called soil erosion.

Question. How are clouds formed?
Answer : During day time water from different sources like river, sea etc. rises in the form of water vapours and goes into the air. At a particular height the air cools and the water vapours condense to form minute droplets and form clouds.

Question. What are the different states in which water is found during the water cycle ?
Answer : Solid (snow, ice), liquid (water) and gas (water vapours).

Question. Why do organisms need water?
Answer : (i) Plants require water for photosynthesis.
(ii) All cellular processes occur in a water medium.
(iii) Transportation of substances in our body takes place in dissolved form.
(iv) It helps to maintain body temperature.

Question. How is our atmosphere different from the atmospheres on Venus and Mars?
Answer : Atmosphere on Venus and Mars have high percentage (approx. 95%) of CO₂ which does not support life, while atmosphere of our earth consists of various gases like nitrogen (78%), oxygen (21%), carbon dioxide (0.03%), argon (0.91%), water vapour etc. that help life to exist on earth.

Question. List any three human activities which would lead to an increase in the carbon dioxide content of air?
Answer : (i) Burning of fuels like coal, petrol, diesel etc.
(ii) Deforestation.
(iii) Human induced forest fires.

Question. What causes winds ?
Answer : The uneven heating of the earth’s surface is the main cause for the winds. On being heated more the air raises up and hence low pressure is created. Hence the air in high pressure occupies the low-pressure region causing the wind.

Question. Do you know of any activity which may be polluting this water source?
Answer : Discharge of sewage, industrial wastes, hospital wastes, chemical fertilizers etc. into the rivers and streams pollutes these fresh water sources.

Question. What is the greenhouse effect ?
Answer : Gases like CO2 and methane trap Sun’s radiation reflected from earth’s surface. This causes warming of atmosphere. This effect is called greenhouse effect.

Question. What are the methods of preventing or reducing soil erosion ?
Answer : Methods of preventing or reducing soil erosion-
• Intensive cropping;
• planting grasses and other trees;
• Terrace farming;
• Proper drainage canals around the fields.

Question. Name two biologically important compounds that contain both oxygen and nitrogen ?
Answer : Proteins and nucleic acids (DNA and RNA).

Question. List any three human activities that you think would lead to air pollution.
Answer : (i) Harmful gases released from various industries.
(ii) Burning of fossil fuels like coal and petroleum.
(iii) Burning of diesel and petrol in vehicles.

Question. How is soil formed?
Answer : Soil is formed by breaking down of rocks at or near the surface of earth through various physical, chemical and biological processes by various factors such as sun, water, wind and living organisms.
(iv) Respiration.

Question. What is the major source of fresh water in the city/town/village where you live?
Answer : Major Sources of fresh water in the city/town/village are ground water, rivers, streams, lakes, etc.

Question. What are the two forms of oxygen found in the atmosphere ?
Answer : Oxygen gas (O₂) and Ozone gas (O₃).

Exercise Question-Answers

Question. We know that many human activities lead to increasing levels of pollution of the air, waterbodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?
Answer : Limiting activities to certain place will definitely help the air pollution to be controlled to some extent.

Question. Why is water essential for life?
Answer : (i) Plants require water for photosynthesis.
(ii) All cellular processes occur in a water medium.
(iii) Transportation of substances in our body takes place in dissolved form.
(iv) It helps to maintain body temperature.

Question. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Answer : Weather is studied as the collection of various elements like high and low temperatures, humidity, rainfall, wind speed and more using various figures and facts with relevant instruments.

Question. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?
Answer : All living organisms are directly or indirectly dependent on soil. Plants obtain water, minerals from the soil and prepare food for themselves and for other animals.
Organisms that live in water are not totally independent of soil because the microbes growing on the soil in water are the primary producers which start the food chain and even other microbes that live in soil help in the decomposition of dead plants and animals in water to return the nutrients back to the water.

Question. Write a note on how forests influence the quality of our air, soil and water resources?
Answer : Role of forest in influencing the quality of: (1) Air:
• It helps in purifying the air.
• It takes carbon dioxide gas during photosynthesis thus greenhouse effect is controlled.
• Transpiration helps in the formation of clouds and thus helps in raining.
(2) Soil:
• Plants in forest prevent soil erosion.
• It helps in increasing the underground water level.
• Forest increases the fertility of soil.
(3) Water:
• Forest helps in bringing rain and increasing the level of water in the underground and water bodies.

Question. Why is the atmosphere essential for life ?
Answer : Atmosphere is very important for sustaining life because:
• It contains various gases like O₂ CO₂, N₂ which are required for various life processes by plants and animals.
• CO₂ gas is used by plants to prepare food . by the process called photosynthesis.
• Oxygen is required for combustion and respiration.
• Ozone layer acts as a protective layer which prevents harmful U.V. rays to enter the earth’s atmosphere.
• Atmosphere acts as a temperature buffer.