CBSE 12th Standard Biology Subject Environmental Issues Case Study Questions 2021
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CBSE 12th Standard Biology Subject Environmental Issues Case Study Questions 2021
12th Standard CBSE
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Reg.No. :
Biology
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Looking at the deteriorating air quality because of air pollution in many cities of our country, the citizens are very much worried and concerned about their health. The doctors have declared health emergency in the cities, where the air quality is very poor/hazarduous.
(a) Mention any two major causes of air pollution.
(b) Write any two harmful effects of air pollution on plants.
(c) Mention any two factors on which the harmful effects of air pollution on organisms depend.(a) -
In 1990s, due to the enormous vehicular traffic, Delhi ranked fourth among the most polluted cities of the world. The remedial measures taken by the Delhi Government brought marked improvement in the air quality by 2005
(a) Mention any four measures taken by the Delhi Government that reduced vehicular air pollution in Delhi.
(b) What is the norm set by Euro II for petrol and diesel vehicles?.(a) -
Greenhouse effect is a naturally occurring phenomenon that is responsible for heating earth's surface and atmosphere. Earth's surface emits heat in the form of infrared radiation, but most of it is absorbed by certain gases, called greenhouse gases, leading to global warming.
(a) Name two gases that contribute the most to global warming and mention their relative contribution towards this.
(b) What would have been the temperature of earth without greenhouse effect?
(c) What is the mean temperature ofthe earth now?(a) -
Ozone gas is continuously formed by the action of UV rays on molecular oxygen and· also degraded into molecular oxygen. There should be a balance between the formation and degradation of ozone in the stratosphere.
(a) What is meant by ozone hole?
(b) Mention the unit to measure the thickness of ozone.
(c) When is the ozone hole formed each year?(a) -
The degradation of natural resources can occur not only by the effects of pollutants but also by improper practices of resource utilisation. For example, the formation of fertile top soil takes centuries, but it is removed very easily (soil erosion) due to certain human activities.
(a) Write any four such human activities that lead to soil erosion.
(b) Mention two such problems that have come in the wake of Green Revolution.(a)
Case Study Questions
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CBSE 12th Standard Biology Subject Environmental Issues Case Study Questions 2021 Answer Keys
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(a) Major causes of air pollution
(i) Automobiles
(ii) Smokestacks of industries/thermal power plants.
(b) Effects of air pollution on plants
(i) Reduced growth and yield of crops.
(ii) Premature death of plants.
(c) The factors include
(i) concentration of pollutants.
(ii) duration of exposure to the pollutant. -
(a) Measures taken by Delhi Government.
(i) All buses were converted to run on CNG.
(ii) Phasing out of old vehicles.
(iii) Use of catalytic converters in the vehicle.
(iv) Application of stringent pollution level norms for vehicles.
(b) It stipulated that sulphur be controlled at 350 ppm in diesel and 150 ppm for petrol and aromatic hydrocarbons at 42 per cent of diesel and petrol. -
(a) Carbon dioxide - 60%
Methane - 20%
(b) -18°C
(c) 15°C -
(a) Ozone hole refers to the large area ofthinned ozone formed over Antarctica.
(b) Dobson unit.
(c) Ozone hole is formed over Antarctica each year between late August and early October. -
(a) Causes of soil erosion
(i) Over cultivation
(ii) Unrestricted grazing
(iii) Deforestation
(iv) Poor irrigation practices.
(b) (i) Waterlogging and
(ii) soil salinity are the problems that have come up due to Green Revolution.
Case Study Questions
