CBSE ADDA

CBSE NCERT Questions with solutions Q. State the role of the atmosphere in climate control? Ans: Atmosphere prevents sudden increase in temperature during the day light hours. It slows down the escape of heat into outer space during the night. Q. How is acid rain caused ? Ans: The fossil fuels like coal and petroleum/contain small amounts of nitrogen and sulphur/When the fossil fuels are burnt,/nitrogen and sulphur are burnt/and produces different oxides of nitrogen and sulphur/When these oxides dissolve in rain it gives rise to acid rain. Q. What are the different ways in which water gets polluted ? How does it affect the life forms ? Ans: (a) The addition of undesirable substances like fertilizers and pesticides, mercury salts in water/can cause cholera produced by the bacteria. (b) The removable of desired substances like oxygen from the water/adversely affect the aquatic organisms. (c) A sudden change in temperature in water bodies/would be dangerous and effect the

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Question: Why plants do not utilize nitrogen directly from atmosphere? Ans. Most of the plants cannot utilise nitrogen directly from the atmosphere. They use nitrogen only when it is converted into nitrates and nitrites by the process nitrogen fixation. Question: Name the substance that reduces the amount of dissolved oxygen in water. Ans. Excessive growth of phytoplanktons reduces dissolved oxygen level in water Question: Name the organisms found to be very sensitive to the levels of contaminants like sulphur dioxide in the air. Ans. Lichens Question: What do you understand by the term ‘Natural resources’? Ans. Natural resources are the variety of substances that human beings get from the nature to meet their basic needs. Question: What is strip-cropping? Ans. Strip-cropping is the planting of crops in rows or strips to check flow of water. It is practiced in the sloping areas of hills to check soil erosion Question: What is greenhouse effect? How is it caused? Ans. Greenho