CBSE Class 12 Biology Environmental Issues Worksheet Set A

CBSE Class 12 Biology Environmental Issues (1). CBSE issues sample papers every year for students for class 12 board exams. Students should solve the CBSE issued sample papers to understand the pattern of the question paper which will come in class 12 board exams this year. The sample papers have been provided with marking scheme. It’s always recommended to practice as many CBSE sample papers as possible before the board examinations. Sample papers should be always practiced in examination condition at home or school and the student should show the answers to teachers for checking or compare with the answers provided. Students can download the sample papers in pdf format free and score better marks in examinations. Refer to other links too for latest sample papers. 


1 BOD of two samples of water A and B were 120mg/L and 400mg/L respectively. Which sample is more polluted?

2 Name the world’s most problematic aquatic weed. What is the nature of the water body in which the weeds grow abundantly?

3 Between amphibians and birds, which will be able to cope with global warming? Give reason.


6 It has been recorded that the temperature of the earth’s atmosphere has increased by 0.6oC.

a) What has caused this increase?

b) Explain its consequences.

7 DDT content in the water of a lake that supplies drinking water to the near by villages, is found to be 0.003ppm.The kingfishers of that area are reported to have 2ppm of DDT. Why has the concentration increased in these birds? What harm will this cause to the bird population? Name the phenomenon.

8 How do automobiles fitted with catalytic converters reduce air pollution? Suggest the best fuel for such vehicles.

9 Explain accelerated eutrophication. Mention any two consequences of this phenomenon.

10 A crane has DDT level as 5ppm in its body. What would happen to the population of such bird? Explain giving reasons. 

11 Explain the causes of algal bloom in a water body. How does it affect an ecosystem?


12 A factory drains its waste water into the nearby lake. It has caused algal bloom. a) How was the algal bloom caused? b) What would be the consequences? c) Name the phenomenon that caused it. 

14 Explain the causes of global warming. Why is it a warning to mankind?

15 Explain any three measures which will control vehicular air pollution in Indian cities.

16 Particulate and gaseous pollutants along with harmless gases are released from the thermal power plants.

i) Name any two harmless gases released.

ii) Name the most widely used device of removing particulate pollutants from the air. Explain how the device is used.

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