CBSE Class 12 Biology Environmental Issues Worksheet Set A

Read and download free pdf of CBSE Class 12 Biology Environmental Issues Worksheet Set A. Students and teachers of Class 12 Biology can get free printable Worksheets for Class 12 Biology in PDF format prepared as per the latest syllabus and examination pattern in your schools. Standard 12 students should practice questions and answers given here for Biology in Grade 12 which will help them to improve your knowledge of all important chapters and its topics. Students should also download free pdf of Practice Worksheets for Class 12 Biology prepared by school teachers as per the latest NCERT, CBSE, KVS books and syllabus issued this academic year and solve important problems provided here with solutions on daily basis to get more score in school exams and tests

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.

Important Questions for NCERT Class 12 Biology Environmental Issues

Ques. Global warming can be controlled by
(a) increasing deforestation, slowing down the growth of human population
(b) increasing deforestation, reducing efficiency of energy usage
(c) reducing deforestation, cutting down use of fossil fuel
(d) reducing reforestation, increasing the use of fossil fuel. 

Answer: C


Ques. Climate of the world is threatened by
(a) decreasing amount of atmospheric oxygen
(b) increasing amount of atmospheric carbon dioxide
(c) decreasing amount of atmospheric carbon dioxide
(d) increasing concentration of atmospheric oxygen. 

Answer: B


Ques. Which one of the following pairs of gases are the major cause of “greenhouse effect”?
(a) CO2 and O3 (b) CO2 and CO
(c) CFCs and SO2 (d) CO2 and N2

Answer: D


Ques. Which one of the following is correct expanded form of the acronym?
(a) IPCC = International Panel for Climate Change
(b) UNEP = United Nations Environmental Policy
(c) EPA = Environmental Pollution Agency
(d) IUCN = International Union for Conservation of Nature and Natural Resources 

Answer: D


Ques. The two gases making highest relative contribution to the greenhouse gases are
(a) CO2 and CH4 (b) CH4 and N2O
(c) CFCs and N2O (d) CO2 and N2O.

Answer: A


Ques. Which one of the following is the correct percentage of the two (out of the total of 4) greenhouse gases that contribute to the total global warming?
(a) N2O 6%, CO2 86%
(b) Methane 20%, N2O 18%
(c) CFCs 14%, methane 20%
(d) CO2 40%, CFCs 30% 

Answer: C


Ques. Which one of the following pairs is mismatched?
(a) Fossil fuel burning – release of CO2
(b) Nuclear power – radioactive wastes
(c) Solar energy – greenhouse effect
(d) Biomass burning – release of CO2

Answer: C


Ques. Maximum greenhouse gas released by which of the following country?
(a) India (b) France
(c) USA (d) Britain 

Answer: C


Ques. If there was no CO2 in the earth’s atmosphere, the temperature of earth’s surface would be
(a) higher than the present
(b) dependent on the amount of oxygen in the atmosphere
(c) same as present
(d) less than the present. 

Answer: D


Ques. The CO2 content by volume, in the atmospheric air is about
(a) 3.34% (b) 4%
(c) 0.0314% (d) 0.34%. 

Answer: C


Ques. The true statement about ‘greenhouse effect’ is that it is
(a) caused by combination of many gases
(b) caused only by CO2
(c) caused by CO2, CFC, CH4 and NO2 gases
(d) none of these. 

Answer: C


Ques. Which one of the following gases contributes maximum to the ‘greenhouse effect’ on the earth?
(a) Carbon dioxide
(b) Chlorofluorocarbon
(c) Freon
(d) Methane 

Answer: A


Ques. Greenhouse effect is warming due to
(a) infra-red rays reaching earth
(b) moisture layer in atmosphere
(c) increase in temperature due to increase in carbon dioxide concentration of atmosphere
(d) ozone layer of atmosphere. 

Answer: C


Ques. Montreal protocol was signed in 1987 for control of
(a) transport of genetically modified organisms from one country to another
(b) emission of ozone depleting substances
(c) release of greenhouse gases
(d) disposal of e-wastes.

Answer: B


Ques. Snow-blindness in Antarctic region is due to
(a) freezing of fluids in the eye by low temperature
(b) inflammation of cornea due to high dose of UV-B radiation
(c) high reflection of light from snow
(d) damage to retina caused by infra-red rays.

Answer: B


Ques. Which of the following protocols did aim reducing emission of chlorofluorocarbons into atmosphere?
(a) Geneva Protocol (b) Montreal Protocol
(c) Kyoto Protocol (d) Gothenburg Protocol

Answer: B


Ques. Which of the following statements about ozone is correct?
(a) Tropospheric ozone protects us from UV radiations.
(b) Stratospheric ozone is ‘bad’.
(c) Tropospheric ozone is ‘good’.
(d) Stratospheric ozone protects us from UV radiations.

Answer: D


Ques. In stratosphere, which of the following elements acts as a catalyst in degradation of ozone and release of molecular oxygen?
(a) Carbon (b) Cl
(c) Fe (d) Oxygen 

Answer: B


Ques. World Ozone Day is celebrated on
(a) 5th June (b) 21st April
(c) 16th September (d) 22nd April.

Answer: C


Ques. Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancers?
(a) Ammonia (b) Methane
(c) Nitrous oxide (d) Ozone

Answer: D


Ques. Which of the following is not one of the prime health risks associated with greater UV radiations through the atmosphere due to depletion of stratospheric ozone?
(a) Damage to eyes (b) Increased liver cancer
(c) Increased skin cancer
(d) Reduced immune system

Answer: B

Domestic sewage and industrial effluents Questions and Answers


Ques. Fill the gap in the above given diagram.

Domestic sewage and industrial effluents_1


 Domestic sewage and industrial effluents_3


Ques. Introduction of which nutrient in water bodies result eutrophication? Choose the correct answer.
1. Nitrogen and phosphorus
2. Calcium and phosphorus
3. Calcium and nitrogen
4. Iron and calcium

Ans. Nitrogen and phosphorus


Ques. Give reasons why there is a continuous increase in the DDT content in different trophic levels of the chain?

Domestic sewage and industrial effluents_2

Ans. This happens because a toxic substance accumulated by an organism cannot be metabolized or excreted,and is thus passed on to the next higher trophical level.


Ques. What percentage of global warming is contributed by each of the following?
i)Carbon di oxide
iii)nitrous oxide and
iv) methane

Ans. i)60%, ii) 14%, iii)6%, iv) 20%


Ques. Ornithologists observed a decline in the bird population I the area near a lake after the setting of an industrial unit in the same area. explain the cause responsible for the decline observed?

Ans. High concentration of DDT interferes with calcium metabolism in birds and cause thinning of egg shells and their premature breaking,this eventually leads to a decline in bird population.


Environmental Issue Questions and Answers


Ques. Match correctly the following and choose the correct option
i. Environment Protection Act A. 1974
ii. Air Prevention & Control of Pollution Act B. 1987
iii. W ater Act C. 1986
iv. Amendment of Air Act to include noise D. 1981
The correct matches is;
a. i-C, ii-D, iii-A, iv-B b. i-A, ii-C, iii-B, iv-D
c. i-D, ii-A, iii-B, iv-C d. I-C, ii-D, iii-B, iv-A

Ans. A


Ques. In the textbook you came across Three Mile Island and Chernobyl disasters associated with accidental leakage of radioactive wastes. In India we had Bhopal gas tragedy. It is associated with which of the following?
a. CO2 b. Methyl Iso-Cyanate
c. CFC’s d. Methyl Cyanate

Ans. B


Ques. Blends of polyblend and bitumen, when used, help to increase road life by a three times. What is the reason?

Ans. Water resistant; non biodegradable; long lasting


Ques. Why has the National Forest Commission of India recommended a relatively larger forest cover for hills than for plains?

Ans. Control soil erosion and land sliding


Ques. Name the Industry which causes air, soil and water pollution.

Ans. Fertilizer Industry.

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