CBSE Class 12 Biology Environmental Issues Assignment Set B

Read and download free pdf of CBSE Class 12 Biology Environmental Issues Assignment Set B. Get printable school Assignments for Class 12 Biology. Standard 12 students should practise questions and answers given here for Biology in Grade 12 which will help them to strengthen their understanding of all important topics. Students should also download free pdf of Printable Worksheets for Class 12 Biology prepared as per the latest books and syllabus issued by NCERT, CBSE, KVS and do problems daily to score better marks in tests and examinations

Environmental Issues Class 12 Biology Assignment Pdf

Class 12 Biology students should refer to the following printable assignment in Pdf for Environmental Issues in standard 12. This test paper with questions and answers for Grade 12 Biology will be very useful for exams and help you to score good marks

Class 12 Biology Assignment for Environmental Issues



Pollution : Undesirable physical/chemical/biological characteristics of air/water/ land which cause damage to the animals/plants/humans and architectural structures.

Pollutants : Agents which cause pollution.

Slash and Burn Agriculture (Jhum Cultivation) : Farmers cut down trees and burn the plant remains. Ash is used as a fertiliser and the land is then used for farming or cattle grazing.

Reforestation : Process of restoring a forest that was removed at some point of time in the past.

Effluents : Something flowing over a large body of water (may be sewage or industrial effluents).

CPCB : Central Pollution Control Board

BOD : Biological Oxygen Demand

CNG : Compressed Natural Gas

FOAM : Friends of Arcata Marsh

JFM : Joint Forest Management.

Biochemical Oxygen Demand (BOD)

❑ BOD refer to the amount of oxygen that would be consumed if all the organic matter is one litre of water were oxidized by bacteria. The BOD test measures the rateof uptake of oxygen by micro-organisms in a sample of water.

❑ Indirectly BOD is a measure of the organic matter present in the water. The greater the BOD of waste water, more is its polluting potential.

❑ In the given figure the effect of sewage on some imporant characteristic of a river is shown:


Important Questions for NCERT Class 12 Biology Environmental Issues

Question. Which of the following devices is best for reducing emission of poisonous gases -
(a) Scrubber
(b) Catalytic convertors
(c) Electrostatic precipitators
(d) Filters

Answer : B

Question. The goal of Euro-IV norms, according to roadmap is to reduce sulphur to -
(a) 50 ppm in petrol and diesel
(b) 150 ppm in petrol and diesel
(c) 350 ppm in petrol and diesel
(d) 250 ppm in petrol and diesel

Answer : A

Question. Slash and Burn agriculture are associated with -
(a) Deforestration
(b) Jhum cultivation
(c) Shifting cultivation
(d) All the above

Answer : D

Question. Regarding to composition of waste water which among the following is not true -
(a) Suspended solid - sand, silt & clay
(b) Colloidal matter - faecal matter, bacteria & cloth
(c) Dissolved material - nitrate, ammonia & phosphate
(d) Dissolved material - faecal matter, bacteria & nutrients

Answer : D

Question. Pollutants from man's activities like effluents from industries and homes can radically accelerate the aging of lake, that is known as -
(a) Cultural Eutrophication
(b) Accelerated Eutrophication
(c) Rising Eutrophication
(d) Both (a) & (b)

Answer : D

Question. Integrated waste water treatment plant of town of Arcata is supported by biologists of Humboldt state university, involves -
(a) Conventional sedimentation
(b) Filteration
(c) Series of six marshes
(d) All the above

Answer : D

Question. What is the main problem with switching over to CNG from petrol and diesel ?
(a) High cost
(b) Difficulty of lying down pipelines to deliver CNG for uninterrupted supply
(c) Lack of suitable engines
(d) All the above

Answer : B

Question. Beside use of CNG, simultaneously parallel steps taken in Delhi for reducing vehicular pollution,except-
(a) Use of unleaded petrol
(b) Use of low sulphur petrol and diesel
(c) Use of catalytic convertors
(d) Use of Electrostatic precipitators

Answer : D

Question. Series of six connected marshes over 60 hectares of marshland, with appropriate plants, algae, fungi and bacteria is responsible for -
(a) Neutrilisation of pollutants
(b) Absorbtion of pollutants
(c) Assimillation of pollutants
(d) All the above

Answer : D

Question. Practical ,hygienic efficient and cost effective solution to human waste disposal is -
(a) Eco - San toilets
(b) Natural toilets
(c) Ecofriendly toilets
(d) Ecological sanitation

Answer : D

Question. Open dumps often serve as breeding ground for rats and flies and not burnt to completion. Which among the following were adopted as the substitute for open burning dumps -
(a) Eco san
(b) Electronic Burners
(c) Sanitary Landfills
(d) Solar Burners

Answer : C

Question. Which among the following was developed by company of Ahmed Khan by a fine powder of recycled modified plastic -
(a) Polysterene
(b) Polyblend
(c) Polyethylene
(d) Polyplastic

 Answer : B

Question. Which among the following is a cyclical, zero waste procedure, where waste products from one process are cycled in as nutrients for other processes-
(a) Integrated organic farming
(b) Integrated remedy for plastic waste
(c) Integrated waste water treatment
(d) Sustainable waste treatment

Answer : A

Ques. Which of the following is a secondary pollutant?
(a) CO
(b) CO2
(c) SO2
(d) O3 

Answer: D

Ques. A renewable exhaustible natural resource is
(a) coal
(b) petroleum
(c) minerals
(d) forest. 

Answer: D

Ques. Which is the cause of damage to relative biological effectiveness?
(a) High temperature
(b) Pollution
(c) Radiation
(d) Low temperature

Answer: B

Ques. Which of the following is a secondary pollutant?
(a) PAN
(b) Aerosol
(c) CO
(d) CO2 

Answer: A

Ques. Petroleum is a
(a) synthetic product
(b) renewable resource
(c) nonrenewable resource
(d) inconvenient resource. 

Answer: C

Ques. Minerals and metals are
(a) biodegradable resources
(b) renewable
(c) non-renewable
(d) renewable and non-renewable resources.

Answer: D

Ques. Domestic waste constitutes
(a) non-biodegradable pollution
(b) biodegradable pollution
(c) effluents
(d) air pollution.

Answer: B

Ques. Which one of the following statements is not valid for aerosols?
(a) They alter rainfall and monsoon patterns.
(b) They cause increased agricultural productivity.
(c) They have negative impact on agricultural land.
(d) They are harmful to human health.

Answer: B

Ques. Acid rain is caused by increase in the atmospheric concentration of
(a) CO2 and CO
(b) O3 and dust
(c) SO2 and NO2
(d) SO3 and CO. 

Answer: C

Ques. Which of the following are most suitable indicators of SO2 pollution in the environment?
(a) Algae
(b) Fungi
(c) Lichens
(d) Conifers 

Answer: C

Ques. A location with luxuriant growth of lichens on the trees indicates that the
(a) trees are very healthy
(b) trees are heavily infested
(c) location is highly polluted
(d) location is not polluted. 

Answer: D

Ques. A scrubber in the exhaust of a chemical industrial plant removes
(a) gases like sulphur dioxide
(b) particulate matter of the size 5 micrometer or above
(c) gases like ozone and methane
(d) particulate matter of the size 2.5 micrometer or less. 

Answer: A

Ques. The Air Prevention and Control of Pollution Act came into force in
(a) 1985
(b) 1990
(c) 1975
(d) 1981 

Answer: D

Ques. Which one of the following is not correct with regard to the harmful effects of particulate matter of the size 2.5 micrometer or less?
(a) It can cause respiratory problems.
(b) It can directly enter into our circulatory system.
(c) It can cause inflammation and damage to the lungs.
(d) It can be inhaled into the lungs.

Answer: B

Ques. dB is a standard abbreviation used for the quantitative expression of
(a) the density of bacteria in a medium
(b) a particular pollutant
(c) the dominant Bacillus in a culture
(d) a certain pesticide. 

Answer: B

Ques. Steps taken by the Government of India to control air pollution include
(a) compulsory PUC (Pollution under control) certification of petrol driven vehicles which tests for carbon monoxide and hydrocarbons
(b) permission to use only pure diesel with a maximum of 500 ppm sulphur as fuel for vehicles
(c) use of non-polluting compressed natural gas (CNG) only as fuel by all buses and trucks
(d) compulsory mixing of 20% ethyl alcohol with petrol and 20% biodiesel with diesel. 

Answer: A

Ques. According to Central Pollution Control Board (CPCB), which particulate size in diameter (in micrometers) of the air pollutants is responsible for greatest harm to human health?
(a) 1.0 or less
(b) 5.2 - 2.5
(c) 2.5 or less
(d) 1.5 or less 

Answer: C

Ques. In a coal fired power plant electrostatic precipitators are installed to control emission of
(a) NOX
(b) SPM
(c) CO
(d) SO2

Answer: B

Ques. Photochemical smog pollution does not contain
(a) PAN (peroxyacyl nitrate)
(b) ozone
(c) nitrogen dioxide
(d) carbon dioxide. 

Answer: D

Ques. Lead concentration in blood is considered alarming if it is
(a) 20 mg / 100 mL
(b) 30 mg / 100 mL
(c) 4 - 6 mg / 100 mL
(d) 10 mg / 100 mL.

Answer: B

Ques. Fluoride pollution mainly affects
(a) brain
(b) heart
(c) teeth
(d) kidney. 

Answer: C

Ques. What is the intensity of sound in normal conversation?
(a) 10-20 dB
(b) 30-60 dB
(c) 70-90 dB
(d) 120-150 dB 

Answer: B

Very Short Answer Type Questions

Question. Use of lead-free petrol or diesel is recommended to reduce the pollutants emitted by automobiles. What role does lead play?
Answer : Catalytic converters, having expensive metals namely platinum, palladium and rhodium as the catalysts are fitted into automobiles for reducing emission of poisonous gases and to convert unburnt hydrocarbons into CO2 and H.

Question. Name an industry which can cause both air and thermal pollution and as well as eutrophication.
Answer : Chemical fertiliser unit, thermal power plant, refineries, smelting and metallurgical processing units steel mills, and the industries using steam or water as coolant causes both air and thermal pollution. The chemical release form these Industries (if rich in nitrogen and phosphorus) may result in eutrophication.

Question. What is an algal bloom?
Answer : The extensive growth of planktonic (free-floating) algae in water bodies due to the presence of organic matter in water (cnitrogen and phosphores) that acts as a food source is called an algal bloom. This imparts a distinct colour to the water bodies.

Question. It is a common practice to undertake desilting of the overhead water tanks. What is the possible source of silt that gets deposited in the water tanks?
Answer : The source of silt that get deposited in overhead water tank are soil particles, which are carried out with water from the source of supply like deep borewell, rivers, etc.

Question. What is cultural eutrophication?
Answer : The phenomenon wherein effluents from the industries and homes accelerate the natural and cultural ageing process of lakes and other water bodies that normally may take thousands of years is called accelerated eutrophication.

Question. What is reforestation?
Answer : Reforestation is the process of restoring a forest that had once existed but was removed at some point of time in the past. Though, it can occur naturally in a deforested area but we can expedite it by planting trees with due consideration to biodiversity that earlier existed in that area.

Question. What is the best solution for the treatment of electronic wastes?
Answer : The best solution for the treatment of electronic wastes is to recycle it. Electronic waste recycling facilities have advanced considerably and now they can be recycled 95-98% by weight. Recycling has two fold benefits
(i) It prevents the toxic components of computers from entering the delicate environment and ground water via landfill.
(ii) It also slows the use and mining of primary raw materials.

Question. List any two adverse effects of particulate matter on human health.
Answer : The fine particulate (PM of size 2.5 μm or less) can problems cause
(i) Breathing and respiratory
(ii) Irritation
(iii) Inflammations
(iv) Damage to the lungs and premature death

Short Answer Type Questions

Question. Is it true that if the dissolved oxygen level drops to zero, the water will become septic. Give an example which could lower the dissolved oxygen content of an aquatic body.
Answer : Yes, it is true, in case of zero level of dissolved oxygen (DO), the water becomes septic. Organic pollution like fertiliser in aquatic bodies is responsible for lowering (upto zero) the level of dissolved oxygen.

Question. Name any one green house gas and its possible source of production on a large scale. What are the harmful effects of it?
Answer : The common green house gases areCO2,CH4, CFC, oxide of nitrogen (N O 2 ), water vapour and O3. The level of CO2 (green house gas) is increasing due to large scale deforestation, change in land use and unlimited buring of fossils fuel and is leading to global warming. The source of methane and other main green house gases are garbage dump, incomplete decomposition by anaerobic methanogens, flooded paddy field and marshy land. About 90-95% of CH4 is produced/generated by rice fields of Asia.

Question. Observe the figure A and B given below and answer the following questions
(i) The power generation by the above two methods is non-polluting, True/False.
(ii) List any two applications of solar energy
(iii) What is a photovoltaic cell?
Answer : (i) Figure A is solar energy panel and figure B is wind mill device. Both devices produce power without polluting the environment.
(ii) Solar lamp (lantern) (made up of a LED lamp, a photo-voltaic solar panel and rechargeable battery) and solar hot water system (geyser) are the two application of solar energy.
(iii) A solar cell is also called as photovoltaic cell. It is a form of photoelectric cell which converts the light energy into electrical energy by photovoltaic cell.

Question. It is a common practice to plant trees and shrubs near the boundary walls of buildings. What purpose do they serve?
Answer : A common practice to grow and maintain trees and shrub near the boundary wall of residential, official building acts as a barrier for sound and check noise pollution. This green belt of tree and shrub also acts as an effective measure to check primary air pollutants like dust, flyash, etc.

Question. Why has the National Forest Commission of India recommended a relatively larger forest cover for hills than for plains?
Answer : It is our moral duty to protect, restore and conserve/preserve forest as they are highly beneficial for mankind In India, around 30% of land was covered by forest in early 20th century, which has been reduced to 18-19% by the year 2000. National Forest Commission of India (1988) recommended a relatively large forest cover (67%) for the hills and 33% for the plains. Recommendation a large forest area for hills is due to its properties like checking soil erosion, percolation and recharging ground water, checking landslide and other natural calamities and to maintain the original flora and fauna of hills.

Long Answer Type Questions

Question. Observe figure and answer the following questions. (Image 288)
(i) What ecological term is used to describe the DDT accumulation at different trophic levels?
(ii) List any one effect of DDT accumulation on birds.
(iii) Will DDT accumulation lead to eutrophication?
(iv) Does it affect the BOD?
(v) Name disease caused by accumulation of any heavy metal.
Answer : (i) The ecological term used to describe the DDT accumulation at different trophic levels is called biomagnification.
(ii) High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of egg shell and their premature breaking, eventually causing decline in bird populations.
(iii) Yes, DDT accumulation can lead to eutrophication.
(iv) It increases the BOD, resulting in a decrease in dissolved oxygen in the water body.
(v) Eating fish that has accumulated mercury, a heavy metal, causes a disease called Minamata. It is characterised by diarrhoea, haemolysis, numbness, deafness, mental derangement, meningitis and death.

Question. Water logging and soil salinity are some of the problems that have come in the wake of the Green Revolution. Discuss their causes and adverse effects to the environment.
Answer : Water logging and soil salinity is caused by extensive irrigation without proper drainage of water. Continuous presence of water draws salt to the surface of the soil, which gets deposited as a thin crust on the land surface or start collecting at the roots of the plants.
Adverse effects
(i) Increased salt content stunts the growth of crop plants.
(ii) Root cells saturated with saline water gets damaged.
(iii) Plants die.
(iv) Crop yield gets affected.
(v) Financial loss to the farmers. Although properly managing the soil-water system can correct the salination and water logging, but the economic costs of this are very high.

Question. What are multipurpose trees? Give the botanical and local names of any two multipurpose trees known to you and list their uses.
Answer : Multipurpose trees are those tree which on plantation fulfills a number of purpose, like shade, providing, soil improvement, provide wood, fruit and food etc. In other words, multipurpose trees serve a wide variety of function and services for human needs. Neem ( Azardicta, indica) is known for its medicinal properties. Its fruit, leaves, wood and oil extracted from wood is used in most of the ayurvedic medicines. Its wood is pest resistant due to chemical azardiction. Another most important tree is coconut palm. Its botanical name is Coccos nucifera and belongs to the family-Palmae, it serves a variety of function. As we get oil, wood and food fibre, from this plant. This plant has fibre, medicinal and commercial importance. Some other multipurpose trees are Moringa oleifera and Gliricidia sepium, which is widely used for fences in central America and provide fire wood fooder and fix atmospheric N2. While M.oleifera is commonly used for animal forage and shade, its leaves are edible.


1. Why should the velocity of air between the plates of an electrostatic precipitator be low?

2. PM2.5 is responsible for causing greatest harm to human health. What is  it? How is it harmful?

3. What is the noise level that can cause permanent impairment of hearing ability of human beings?

4. Why was the Montreal Protocol signed?

5. Jhum cultivation has been in practice from earlier days, but its considered more problematic these days. Why?

6. A radiation causes ageing of skin, skin cancer, and inflamation of cornea called snow blindness. It also damages DNA. Name the radiation.

7. Landfills are not much a solution for getting rid of solid wastes. Why?

8. Electrostatic precipitator can remove over 99% particulate matter present in exhaust from a thermal power plant. How?

9. Why is a scrubber used? Which spray is used on exhaust gases passing through a scrubber?

10. There is a sharp decline in dissolved oxygen downstream from the point of sewage discharge. Why? What are its adverse effects?

11. Catalytic converters use expensive metals as catalysts.

(a) Name the metals generally used.

(b) What precaution should be observed while using catalytic converter.

12. What are e-wastes? Why are they creating more problem in developing countries in comparision to developed countries?

13. Water logging and salinity are some of the problems that have come in the wake of Green revolution. How does water logging create problems ofsalinity?

14. What is the relationship between BOD, mcro-organisms and amount of biodegradable matter?

Please refer to the link below for CBSE Class 12 Biology Environmental Issues Assignment Set B

Chapter 2 Sexual Reproduction In Flowering Plants
CBSE Class 12 Biology Sexual Reproduction in Flowering Plants Set A

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