Biology MCQs for Class 12 with Answers Chapter 16 Environmental Issues

Free PDF Download of CBSE Biology Multiple Choice Questions for Class 12 with Answers Chapter 16 Environmental Issues. Biology MCQs for Class 12 Chapter Wise with Answers PDF Download was Prepared Based on Latest Exam Pattern. Students can solve NCERT Class 12 Biology Environmental Issues MCQs Pdf with Answers to know their preparation level.

Environmental Issues Class 12 Biology MCQs Pdf

1. The thickness of ozone is measured as
(a) parts per billion
(b) Dobson units
(c) parts per million
(d) decibel.

Answer

Answer: b


2. Polyblend was first developed by
(a) Ramesh Chandra Dagar
(b) Ahmed Khan
(c) KhadiandVillagelndustriesCommission
(d) Indian Institute of Science.

Answer

Answer: b


3. Good ozone is found in the
(a) stratosphere
(b) troposphere
(c) mesosphere
(d) ionosphere.

Answer

Answer: a


4. Eutrophication causes a/an
(a) decrease in organic matter
(b) increase in inorganic nutrients
(c) decrease in dissolved oxygen
(d) increase in dissolved oxygen.

Answer

Answer: c


5. Increase in cases of skin cancer and high mutation rate are the result of
(a) ozone depletion
(b) acid rain ,
(c) CO2 pollution
(d) CO pollution

Answer

Answer: a


6. Increase in the concentration of pollutants/chemicals in higher trophic levels, is known as
(a) biodegradation
(b) eutrophication
(c) greenhouse effect
(d) biomagnification

Answer

Answer: d


7. Ozone hole is the largest over
(a) Africa
(b) Antarctica
(c) America
(d) Europe

Answer

Answer: b


8. Phosphate pollution in a waterbody is brought about by
(a) phosphate rock weathering
(b) fertilizers
(c) phosphate rocks and sewage
(d) fertilizers and sewage.

Answer

Answer: d


9. Which of the following causes biomagnifi¬cation?
(a) SO2
(b) Mercury
(c) DDT
(d) Both (b) and (c)

Answer

Answer: d


10. Catalytic converters are fitted into automobiles to reduce emission of harmful gases. Catalytic converters change unbumt hydrocarbons into [NCERT Exemplar]
(a) carbon dioxide and water
(b) carbon mono oxide
(c) methane
(d) carbon dioxide and methane.

Answer

Answer: a


11. Nuisance growth of aquatic plants and bloom-forming algae in natural waters is generally due to high concentrations of [NCERT Exemplar]
(a) carbon
(b) sulphur
(c) calcium
(d) phosphorus

Answer

Answer: d


12. Which one of the following impurities is easiest to remove from wastewater? [NCERT Exemplar]
(a) Bacteria
(b) Colloids
(c) Dissolved solids
(d) Suspended solids

Answer

Answer: d


13. According to Central Pollution Control Board (CPCB), particulates of size ______ or more in diameter are responsible for causing harm to human health.

Answer/Explanation

Answer:
Explaination: 2.5 micrometres


14. The discharge of domestic sewage into a river will decrease the ______ of the waterbody.

Answer/Explanation

Answer:
Explaination: Dissolved oxygen.


15. A mere ______ per cent impurities makes the domestic sewage unfit for human use.

Answer/Explanation

Answer:
Explaination: 0.1


16. Inflammation of cornea, called ______ is caused by UV-B radiation.

Answer/Explanation

Answer:
Explaination: Snow blindness.


17. ______ gas is continuously produced by the action of UV rays on molecular oxygen.

Answer/Explanation

Answer:
Explaination: SOzone.


18. ______ per cent of the forests have been lost in the tropics.

Answer/Explanation

Answer:
Explaination: 40.


19. ______ cultivation in the north-eastern states of India has also contributes to deforestation.

Answer/Explanation

Answer:
Explaination: Jhum.


20. Faecal matter, paper fibres, bacteria and cloth fibres are the ______ material present in sewage water.

Answer/Explanation

Answer:
Explaination: Colloidal.


21. Excess growth of ______ algae causes algal bloom in eutrophied waterbodies.

Answer/Explanation

Answer:
Explaination: Planktonic.


22. Euro II norms stipulate that sulphur be controlled at ______ in diesel.

Answer/Explanation

Answer:
Explaination: 350 ppm.


23. Match the Government initiatives to reduce pollution in Column I with the year in which they into effect in Column II.

Column I Column II
A. Air  (Prevention and Control of Pollution) Act 1. 1974
B. Joint Forest Management water 2. 1986
C. Water (Prevention and Control Pollution) Act 3. 1980
D. Environment (Protection) Act 4.1981
Answer/Explanation

Answer:
Explaination: A – 4, B – 3, C – 1, D – 2


24. Match the DDT concentration in Column I with the organisms in an aquatic food chain in Column II.

Column I Column II
A. 0.04 ppm 1. Large fish
B. 2.0 ppm 2. Zooplanktons
C. 0.5 ppm 3. Fish-eating birds
D. 25 ppm 4. Small fish
Answer/Explanation

Answer:
Explaination: A – 2, B – 1, C – 4, D – 3


25. The Montreal Protocol is associated with the control of emission of ozone-depleting substances. [True/False]

Answer/Explanation

Answer:
Explaination: True.


26. Dobson units are used to measure oxygen content in waterbodies. [True/False]

Answer/Explanation

Answer:
Explaination: False.


27. A brief exposure to high level sound, 150 dB or more can damage the ear drum.[True/False]

Answer/Explanation

Answer:
Explaination: True.


28. There is a substantial fall in NO2 and CO2 levels in the air in Delhi between 1997 and 2005. [True/False]

Answer/Explanation

Answer:
Explaination: False.


29. CNG can be easily siphoned off compared to petrol or diesel. [True/False]

Answer/Explanation

Answer:
Explaination: False.


Directions (Q30 to Q32): Mark the odd one in each of the following groups.
30. Jaundice, Hepatitis B, Typhoid, Dysentery

Answer/Explanation

Answer:
Explaination: Hepatitis-B.


31. Sand, Silt, Clay, Nitrate

Answer/Explanation

Answer:
Explaination: Nitrate.


32. Oxygen, Carbon monoxide, Sulphur dioxide, Nitrogen oxides.

Answer/Explanation

Answer:
Explaination: Oxygen


33. What are pollutants?

Answer/Explanation

Answer:
Explaination: Pollutants are those substances/agents which bring about undesirable changes in the properties of air, water and soil, which adversely affect the living organisms.


34. Name the two harmless gases released by thermal power plants/smelters.

Answer/Explanation

Answer:
Explaination: Nitrogen and oxygen.


35. Name the device used to remove
(a) particulate air pollutants
(b) pollutant gases like SO2 from the exhaust.

Answer/Explanation

Answer:
Explaination:
(a) Electrostatic precipitator.
(b) Scrubber.


36. An electrostatic precipitator in a thermal power plant is not able to generate high voltage of several thousands. Write the ecological implication because of it. [AI 2017]

Answer/Explanation

Answer:
Explaination: Electrostatic precipitator removes 99 per cent of the particulate matter from the exhaust from thermal plant; in its absence, the particulate matter will get into the atmosphere and cause respiratory disorders.


37. What is the size of the particulate matter that causes the greatest harm to human health?

Answer/Explanation

Answer:
Explaination: 2.5 micrometres or less.


38. Why is the use of unleaded petrol recommended for motor vehicles equipped with catalytic convectors? [AI 2013, 2010]
Or
Why is it desirable to use unleaded petrol in vehicles fitted with catalytic converters? [AI 2012, Foreign 2010]
Or
Why should motor vehicles equipped with catalytic converter use unleaded petrol? [Delhi 2011C]

Answer/Explanation

Answer:
Explaination: Otherwise lead will inactivate the catalyst.


39. What is the goal of auto fuel policy of the Indian government, regarding sulphur in auto fuels?

Answer/Explanation

Answer:
Explaination: The goal is to reduce sulphur to 50 ppm in petrol and diesel and bring down the level to 35 ppm.


40. List two advantages of the use of unleaded petrol in automobiles as fuel. [AI2015]

Answer/Explanation

Answer:
Explaination:
(i) The catalysts will not be inactivated.
(ii) There will be no lead in the exhaust from the vehicle.


41. Why is it necessary to remove sulphur from petroleum products?

Answer/Explanation

Answer:
Explaination: There will be no oxides of sulphur in the automobile exhause; oxides of sulphur in the atmosphere cause acid rains.


42. List two gaseous products that are produced when exhaust of an automobile passes through a catalytic converter. [Delhi 2012C]

Answer/Explanation

Answer:
Explaination: Carbon dioxide and nitrogen.


43. When did the Air (Prevention and Control of Pollution) Act, (a) come into force and (b) when was it amended to include noise as an air pollutant?

Answer/Explanation

Answer:
Explaination:
(a) It came into force in the year 1981.
(b) It was amended in 1987 to include noise.


44. What is noise?

Answer/Explanation

Answer:
Explaination: Noise is defined as undesirable high level of sound.


45. What per cent of sewage water has impurities that make it unfit for human use?

Answer/Explanation

Answer:
Explaination: 0.1 percent.


46. Given below are a few impurities in urban waste water. Select two colloidal impurities: ammonia, faecal matter, silt, bacteria, calcium.

Answer/Explanation

Answer:
Explaination: Faecal matter and bacteria.


47. Which component in the domestic sewage is difficult to remove?

Answer/Explanation

Answer:
Explaination: The dissolved salts like nitrates and phosphates.


48. How do algal blooms affect the life in water bodies? [AI 2011]

Answer/Explanation

Answer:
Explaination:
– Algal blooms reduce the dissolved oxygen content of the water and cause mortality (death) of aquatic animals like fish.
– They also secrete chemicals toxic to aquatic animals.


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

Answer/Explanation

Answer:
Explaination:
– Eichhornia crassipes (water hyacinth)
– Eutrophic water bodies.


50. Why is Eichhomia crassipes nicknamed as ‘Terror of Bengal’? [Delhi 2012]
Or
Eichhomia crassipes is an alien hydrophyte . introduced in India. Mention the problems posed by this plant. [AI 2010C]

Answer/Explanation

Answer:
Explaination:
– They grow faster than our ability to remove them and cause blocks in our waterways.
– Their abundant growth leads to an imbalance in the ecosystem dynamics of the waterbody.


51. Name flie pollutants, the industrial waste water contains.

Answer/Explanation

Answer:
Explaination: The industrial waste water contains toxic substances like heavy metals and some organic compounds.


52. Excessive nutrients in a fresh water body cause fish mortality. Give two reasons. [Delhi 2016]

Answer/Explanation

Answer:
Explaination:
(i) Excessive nutrients in a freshwater body stimulate the excess growth of planktonic algae, which ultimately reduce the dissolved oxygen content of the water body and cause fish mortality.
(ii) Some of these algae also secrete toxins, which lead to fish mortality.


53. Eutrophication is the natural ageing of a lake. Mention any other feature which defines the term. [CBSE Sample Paper 2013,2014]

Answer/Explanation

Answer:
Explaination: Nutrient enrichment of water.


54. State the cause of accelerated eutrophication. [Delhi 2014]

Answer/Explanation

Answer:
Explaination: Effluents from industries and homes.


55. What is cultural/accelerated eutrophication?

Answer/Explanation

Answer:
Explaination: Cultural/accelerated eutrophication is a phenomenon of man-induced nutrient enrichment and accelerated ageing of the water bodies.


56. What is the raw material for polyblend?

Answer/Explanation

Answer:
Explaination: Plastic wastes.


57. The use of incinerators is crucial for the disposal of hospital waste. Justify [HOTS]

Answer/Explanation

Answer:
Explaination: Hospitals generate hazarduous wastes that contain harmful chemicals, disinfectants and pathogenic microbes; such wastes require disposal using incinerators.


58. Inspite of being non-polluting, why are there great apprehensions in using nuclear energy for generating electricity? [Foreign 2014]

Answer/Explanation

Answer:
Explaination:
Because using nuclear energy has two problems.
(i) The safe disposal of nuclear wastes.
(ii) Any accidental leakage can prove to be extremely damaging to living organisms.


59. Write in full form, the name of the organisation that makes an assessment of die greenhouse gases in the atmosphere.

Answer/Explanation

Answer:
Explaination: Intergovernmental Panel on Climate Change (IPCC).


60. Why is the climate change expected to increase the spread of human diseases?

Answer/Explanation

Answer:
Explaination: It would increase the size of population of pathogens and their vectors.


61. What is meant by greenhouse effect?

Answer/Explanation

Answer:
Explaination: Greenhouse effect is a naturally occurring phenomenon, in which the shortwave radiations of solar energy are absorbed and longwave radiations are reflected by the earth and is responsible for heating of earth’s surface and atmosphere.


62. What is global warming?

Answer/Explanation

Answer:
Explaination: Global warming refers to the increase in the global mean temperature.


63. What is the expected rise in the global temperature by die year 2100?

Answer/Explanation

Answer:
Explaination: It may rise by 1.4-5.8 °C.


64. Name the greenhouse gases that contribute to total global wanning. [Delhi 2014]

Answer/Explanation

Answer:
Explaination: Carbon dioxide, methane, nitrous oxide and chlonofluoro carbons.


65. Name the greenhouse gases contributing maximum to the greenhouse effect. [AI2014C]

Answer/Explanation

Answer:
Explaination: Carbon dioxide and methane.


66. Name the layer of atmosphere that is associated with ‘good ozone’.

Answer/Explanation

Answer:
Explaination: Strastosphere.


67. Where is good ozone present? Why is it called so? [Delhi 2014C]

Answer/Explanation

Answer:
Explaination:
– It is found in the stratosphere of the atmosphere.
– Since it acts as a shield to absorb the ultraviolet radiation from the sun, it is called good ozone.


68 Write the unit used for measuring ozone thickness. [Delhi 2011]

Answer/Explanation

Answer:
Explaination: Dobson units (DU).


69. Mention the causes of thinning of ozone layer. [Delhi 2010C]

Answer/Explanation

Answer:
Explaination: Chlorofluorocarbons (CFCs) release Cl atoms when UV rays act on them; Cl degrades the ozone into molecular oxygen.


70. What is ozone shield?

Answer/Explanation

Answer:
Explaination: The thin layer of ozone in the upper part or the stratosphere of the atmosphere that prevents entry of UV rays, is called ozone shield.


71. What is meant by ozone hole?

Answer/Explanation

Answer:
Explaination: The decline in the thickness of spring time ozone layer over Antarctica, is called ozone hole.


72. When does the ozone hole develop over Antarctica every year?

Answer/Explanation

Answer:
Explaination: It develops each year between late August and early October.


73. State the effect of UV-B on human eyes. [Foreign 2013]
Or
Mention two harmful effects ofUV-B exposure on human eyes. [AI 2012C]

Answer/Explanation

Answer:
Explaination:
– High dose of UV-B causes inflammation of cornea, called snow-blindness and also cataract.
– It may permanently damage the cornea.


74. Mention the effect of UV rays on DNA and proteins in living organisms. [Foreign 2013]

Answer/Explanation

Answer:
Explaination: UV rays are preferentially absorbed by DNA and proteins of living beings; the high energy of UV rays break the chemical bonds within these molecules and causes damage to them.


75. How is snow-blindness caused in humans? [AI 2010]

Answer/Explanation

Answer:
Explaination: Snow-blindness is caused by a high dose of UV-B radiation.


76. State the purpose of signing the Montreal Protocol. [Foreign 2014]

Answer/Explanation

Answer:
Explaination: The purpose is to control the emission of CFCs and other ozone-depleting substances.


77. Mention two problems (that degrade soil fertility) that have come in the wake of Green Revolution.

Answer/Explanation

Answer:
Explaination:
– Soil erosion and desertification.
– Water logging and soil salinity.


78. What is meant by deforestation?

Answer/Explanation

Answer:
Explaination: Deforestation is the conversion of forested areas into non-forested ones.


79. How does Jhum cultivation promote desertification? [AI 2011C]

Answer/Explanation

Answer:
Explaination: In Jhum cultivation, after cultivation, the land/area is left free for several years to allow its recovery; but with increasing demand for food, and repeated cultivation, the recovery phase is often ignored leading to deforestation.


80. How/Why does deforestation lead to global warming?

Answer/Explanation

Answer:
Explaination: The plants which can hold a lot of carbon in their biomass are lost due to deforestation; the increased concentration of carbon dioxide in the atmosphere causes global warming.


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