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Jai Yadav
The Shri Ram School (TSRS), Aravali, DLF Phase IV, Gurgaon
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The Shri Ram School Aravali Subject (Handout): Biology Class: X Pollution (a) Explain the following terms: i) Eutrophication: Usually rapid increase in the nutrient status of a water body, both natural and occurring as a byproduct of human activity. It is due to run off of artificial fertilizers from agriculture land or by input of sewage /animal waste. It leads to excessive growth of aquatic plants and results in anaerobic condition for other forms of life. ii) Bio magnification: The increasing concentration of a compound in the tissues of organism as the compound passes up a food chain, usually as result of food intake. This results the accumulation of the compound at each level prior to its consumption by organisms at the next trophic level. (b) Mention the indirect consequences of depletion of the ozone hole. i) Most of the vegetables are very sensitive to the UV rays ii) Under greenhouse effect, plants exposed to UV radiations showed a 20-50% reduction in growth, reduction in chlorophyll content and increase in harmful mutations iii) Increased concentrations of UV rays disturb ecological balance in marine ecosystem. UV rays affect green algae, fish and other animals on continental shelves. Young cells and larvae of aquatic ecosystems get affected severely. iv) The UV rays can damage the physical and chemical properties of any complex chemical substance. Plastics become brittle when they come in contact with the UV rays. As most of the industries use plastic material in one form or the other they would become more affected. (c) Besides producing global warming, what harm do chlorofluorocarbons do? Chlorofluorocarbons are the major pollutants responsible for the depletion of ozone layer. CFCs are widely used as coolants, cleaning solvents etc. (d) How does acid rain reduce the rate of photosynthesis? Acid rain affects the growth of plants. It reduces the size of the leaves and causes them to become small and yellow which affects the rate of photosynthesis as efficiency of chlorophyll is reduced. (e) What is the advantage of having ozone layer? Ozone layer plays an important role in our life in the following waysi) Due to the presence of the ozone layer, Ultraviolet rays and Infrared rays from the sun cannot reach the earth directly. ii) It absorbs the harmful part of the sunlight and protects the life on the earth from harmful effects of these rays. (f) What do you understand by greenhouse effect? The increase in temperature due to the concentration of greenhouse gases (CO2, CH4, N20, CFCs) is known as greenhouse effect. The sun s radiation reaches the earth in the form of short wave radiation but is unable to escape due to long wave terrestrial radiation which leads to increase in the temperature in the earth. (g) Give any two consequences of greenhouse effect. i) The increase in the concentration of greenhouse gases leads to substantial rise in temperature which results in global warming. An increase of temperature impacts the distribution of trees and shifting of different climatic zones. ii) It also affects the agro ecosystem which may lead to insufficient soil water due to rapid evaporation, short sowing seasons and greater incidences of pests. Health threats to humans are also foreseen due to the influence of temperature. (h) Mention the different steps that should be followed to reduce the use of Greenhouse Gases. i) Reduce the combustion from fossil fuels by switching over to alternative fuels like solar energy, atomic energy and hydroelectricity ii) Checking deforestation and encourage tree planting programmes. iii) Reduction in the emission of nitrous oxide by regulating the application of fertilizers. Use of bio-fertilizers is preferred.

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