CBSE Class 12 Biology HOTs Environmental Issues

Please refer to CBSE Class 12 Biology HOTs Environmental Issues. Download HOTS questions and answers for Class 12 Biology. Read CBSE Class 12 Biology HOTs for Chapter 16 Environmental Issues below and download in pdf. High Order Thinking Skills questions come in exams for Biology in Class 12 and if prepared properly can help you to score more marks. You can refer to more chapter wise Class 12 Biology HOTS Questions with solutions and also get latest topic wise important study material as per NCERT book for Class 12 Biology and all other subjects for free on Studiestoday designed as per latest CBSE, NCERT and KVS syllabus and pattern for Class 12

Chapter 16 Environmental Issues Class 12 Biology HOTS

Class 12 Biology students should refer to the following high order thinking skills questions with answers for Chapter 16 Environmental Issues in Class 12. These HOTS questions with answers for Class 12 Biology will come in exams and help you to score good marks

HOTS Questions Chapter 16 Environmental Issues Class 12 Biology with Answers

Very Short Answer Type Questions

Question. What is the raw material for polyblend?
Answer : Polyblends are natural man made fibres, made by the mixture of two or more polymers especially plastic waste products

Question. Motor vehicles equipped with catalytic to converter need to use unleaded petrol because lead in the petrol, inactivates the catalyst and increases the hydrocarbon emission, there by harming the environment.In which year was the Air (Prevention and Control of Pollution) Act amended to include noise as air pollution.
Answer : In 1987, the Air (Prevention and Control of Pollution) Act was amended to include noise as a source of air pollution.

Question. Name the city in our country where the entire public road transport runs on CNG.
Answer : In Delhi, the entire public surface transport especially road transport runs on compressed Natural Gas (CNG)

Question. Blends of polyblend and bitumen, when used, help to increase road life by a factor of three. What is the reason?
Answer : Polyblend is a fine powder of recycled modified plastic. The binding property of plastic makes the road last longer besides giving added strength to withstand more loads. This is because (i) Plastic increases the melting point of the bitumen which would prevent it from melting in India’s hot and extremely humid climate, where temperature frequently cross 50°C. (ii) Rainwater will not seep through because of the plastic in the tar.

Question. Mention any two examples of plants used as wind breakers in the agricultural fields.
Answer : Wind breakers or shelter belts provide shelter from wind and protect soil from erosion. Jamun and imli and some other trees like babul, Lawsonia, Thevetia and Calotropis acts as wind breakers in the agricultural field.

Question. What do you understand by biomagnification?
Answer : Biomagnification refers to the increase in the concentration of the toxic substances at successive trophic level ls in the food chain. This happens because a toxic substance accumulated by an organism cannot be metabolised or excreted and when this organism is eaten up by another animal of higher trophic level, it is passed on to this and then to the next higher trophic level and so on.

Question. What are the three major kinds or impurities in domestic wastewater?
Answer : The three major kinds of impurities in domestic waste water are
(i) Dissolved salts such as nitrates, phosphates, other nutrients, toxic, metal ions and organic compounds.
(ii) Biodegradable organic matter.
(iii) Pathogenic microorganisms.

 

Short Answer Type Questions

Question. How can slash and burn agriculture become environment friendly?
Answer : Slash and burn agriculture can be environment friendly if
(i) small widely scattered plots are used for cultivation as the forest ecosystem will not suffer damage.
(ii) crop rotation is used so that soil does not loose fertility entirely.
(iii) keeping cropping period small and fallow (unplanted) period longer.

Question. What is the main idea behind “Joint Forest Management Concept” introduced by the Government of India?
Answer : The main idea behind joint forest management concept introduced by the Government of India was involving the local communities in the forest conservation. This concept was adopted considering the extraordinary courage and dedication the local people showed in protecting the wildlife through the movements like Bishnoi’s is movement in Jodhpur and Chipko Movement in Garhwal Himalayas.

Question. Is it true that carpets and curtains/drapes placed on the floor or wall surfaces can reduce noise level. Explain briefly?
Answer : Yes, it is true, that the placing/using carpets on floor and curtains on wall surface, windows, reduces noise level. This is because the curtains and carpets on wall surface and carpet acts as muffling device and absorb sounds of moderate level.

Question. What is hybrid vehicle technology? Explain its advantages with a suitable example?
Answer : The technology used to run vehicles on dual mode like petrol or compressed natural gas is said to be hybrid vehicle technology. These vehicles runs on either petrol or CNG. As CNG is a clean and green fuel so it is helpful to reduce environmental pollution and also to conserve petrol, fossil fuel.

Question. What do you understand by Snow-blindness?
Answer : The inflammation of cornea caused due to the excessive absorption of ultravioet-B radiations is called snow-blindness cataract.

Question. How has DDT caused decline in bird population?
Answer : 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.

 

Long Answer Type Questions

Question. What are the basic characteristics of a modern landfill site. List any three and also mention the reasons for their use.
Answer : Characteristics of a modern landfill includes
(i) Methods to contain leachate such as lining clay or plastic liners.
(ii) Compaction and covering of the waste to prevent it from being blown by wind.
(iii) Installation of a landfill gas extraction system to extract the gas for use in generation of power. The use of modern landfill sites must be promoted due to the following reasons
(i) They stimulate the waste prevention via recycling and recovery of waste.
(ii) They create a uniform cost for the disposal of waste which consequntly will prevent the unecessary transport of waste.
(iii) They prevent or reduce the negative eftects on the envirionment, as well as the risks to human health arising from the landfilling of the waste.

Question. Write a short note on electronic waste. List the various sources of e-wastes and the problems associated with its disposal.
Answer : Solid waste can be biodegradable recyclable non-biodegradable, and can be categoriesed as municipal wastes (se-wage), industrial waste, hospitals and nursing wastes and electronic waste. Irrepairable computers, mobiles and other electronic goods are often known as ‘e’ waste or electronic waste. Source of e-waste Majority of the developing countries like China, Pakistan and India import irrepairable electronic goods for their valuable metals like copper, nickel and gold. Disposal of e-waste Such waste should be burried in landfills or incinerated. In developing countries, metal from e-waste is extracted manually. So, during working with e-waste, one can expose with toxic substances present in it, and may get affected by skin diseases in future. However, recycling is the only solution for the treatment of electronic waste.

Question. What is organic farming? Discuss the benefits of organic farming as a viable practise in the context of developing nations like India.
Answer : Organic farming system primarily aims at sustainable production in an eco-friendly and pollution free environment. The land is cultivated by using techniques such as crop rotation, green manure, composting and biological pesticides alongwith beneficial microbes (biofertilisers) instead of chemical fertilisers and pesticides, etc.
Benefits of organic farming are
(i) Maintains long-term soil fertility.
(ii) Controls pests and diseases without harming the environment.
(iii) Ensures that water stays clean and safe.
(iv) Makes use of resources which the farmer already has, to make it economic.
(v) Helps produce nutritious food and high quality crops. Organic farming in India Using organic farming techniques makes much more sense for developing nations like India. As we know that modern, intensive agriculture makes the use of expensive chemical fertilisers and herbicides, which leach out from the soil and pollute rivers, lakes and water bodies and also damage the soil fertility in the long run.

Question. How does an electrostatic precipitator work?
Answer : Electrostatic precipitator can remove over 99% particulate matter present in the exhaust from a thermal power plant by the following mechanism
(i) It has electrode wires that are maintained at several thousand volts, which produce a corona that releases electrons.
(ii) These electrons attach to dust particles giving them a net negative charge.
(iii) The collecting plates are grounded and attract the charged dust particles.
(iv) The velocity of air between the plates is kept low enough to allow the dust to fall.

Question.. During the past century, lakes and ponds in many parts of the earth have been gradually converted into land.
(a) What is the phenomenon called?
(b) How does human activity accelerate this phenomenon?
(c) What measures can we take to control this? 
Answer : a) Accelerated eutrophication
         b) Sewage from homes, agricultural waste and Industrial wastes containing nutrients like nitrogen , phosphorus etc.
         c ) Domestic sewage and agricultural wastes should be treated before releasing into river / avoid to release in river.
        d) Mandatory for all industries to install treatment plants.
 
Question. During last few decades, most products are being sold in secure ‘consumer friendly’packages .
a) Should this be encouraged?
b) How are modern packaging techniques turning into a major environmental threat?
c) Give some examples where such packaging can be easily avoided. 
Answer : a) No
b) (i) Polythene causes leakage in sewer system
    (ii) If burnt, produces toxic gases and causes air pollution
c) (i) Use of cotton / jute bags , paper bags encouraged
   (ii) Polythene packets can be used to make polyblend which can be used in making roads
 
Question. Why are grains and vegetables produced in organic farms supposed to be better for human consumption than those produced in farms where chemical fertilizers, pesticides etc. has been used? 
Answer : Chemical fertilizers / pesticides --non -biodegradable , enter into food chain through vegetables / grains , causes biomagnification in humans . In organic farms manure is used , whose produce causes no harm to human health .
 
Question. Why is organic farming considered more eco –friendly than agro-chemical farming? 
Answer : Organic farming ---in which no use of chemicals like fertilizers and pesticides . It is a Zerowaste procedure where waste products of one process are cycled as nutrients for other processes .
 
Question. There are reports that the size of Arctic ice cap is decreasing every year.
(a) What are its possible reasons?
(b) How we the human beings are responsible to a greater extent for this?
(c) How we can contribute to check this trend? 
Answer : a) Global warming due to increase of green- house gases like CO2 , methane etc.
         b) Excess use of fossil fuel, and deforestation
         c ) Reforestation , encouraging use of non-conventional energy sources .
 
Question. You want to set up a chemical producing unit. What steps will you take that your project does not turn into a hazard to environment? 
Answer : Treatment of waste material, Use of high chimney, using electrostatic precipitator to remove particulate matter, use scrubber to remove harmful gases like SO2 .
 
Question. India in last two decades has seen a boom in automobile production and use.
(a) What has been its environmental impact?
(b) What steps are being taken so that the rapid increase in the number of automobiles does not become a curse? 
Answer : a) Enhance air pollution
        b) Proper maintenance of automobiles along with use of lead-free petrol or diesel .
 
Question. A farmer established a farmhouse where along with agriculture, he also kept cattle for dairy purpose, started bee-keeping and rainwater harvesting .Ultimately he observed that there was no waste material.
a) Name the type of farming.
b) How did he manage all this.
c) What are its benefits of the process adopted by him.. 
Answer : (a) Integrated organic farming
         (b) Waste products of one activity are cycled and used for other activity.
        ( c) (i) no waste material , no pollution
              (ii) Maximum utilization of resources and increased efficiency of production
              (iii) Economical and sustainable venture
 
Question. Observe the diagram (see page 271, NCERT Book—Electrostatic precipitator)
(a) What will happen if electrode wires are not maintained at several thousand volts?
(b) The velocity of air is high. 
Answer : (a) Corona will not be formed ,no release of electrons ,dust particles can not be negatively charged , so can not settle down in electrostatic precipitator .
         (b) Dust will not settle down
 
Question. Why do certain organisms that disappear at the point of sewage disposal reappear at a certain distance in a river? 
Answer : BOD increases , O2 utilized in decomposition , DO becomes zero . After complete decomposition, BOD lowers and DO increases as oxygen dissolves in water .
 
Question. In a survey it is observed that the population of fish-eating birds living on the bank of lake is continuously declining, where DDT is regularly sprayed to check mosquitoes.
i) What could be the reason behind this?
ii) Name the phenomenon involved. 
Answer : (i) Increase in the level of DDT with each trophic level.
          (ii) Biomagnification
 
Question. A study was conducted in Delhi on petrol driven cars and following data was collected.
Sample size 30 cars             I              II                III
                                      ppm           ppm             ppm
Sulphur                           150           140               350
No.of cars                         6               12                12
Answer the following questions
(i) How many cars are in the limited norm? Suggest any other fuel with reason which can bring down the pollution level.
(ii) Which other kind of pollution has been added in Air (Prevention & Control of Pollution) Act? 
Answer : (i) 18
(ii) CNG-It burns more efficiently, and very little of it is left un burnt.
(iii) Noise.
 
Question. Children of a school visited the river near a large farm. They were surprised to see that the colour of the water had changed and was having unpleasant odour .Also large green floating plants grew in abundance. When they visited the same place before rainy season, the water was clear.
(i) What could be the reason for this change?
(ii) What will be the effect of such type of change on the fishes?
(iii) Suppose the path of flowing water from the field is diverted elsewhere, Can we still find this type of change? 
Answer : (i) River eutrophicated due to run off water from field containing nonbiodegradable chemicals like fertilizers containing Nitrogen / Phosphorus .Water becomes nutrient- rich . A large algal bloom is formed..
          (ii) DO deplete ---fish will die.
          (iii) No
 
Question. what in your opinion is more polluted and why – Domestic sewage or ndustrial effluents/waste from a agricultural field containing fertilizes and pesticides? 
Answer : Wastes from agricultural field /& Industrial effluents, because they are non-Biodegradable and toxic.
 
Question. Why was Eichhornia introduced into India? What is the consequence of its introduction? 
Answer : Introduced for their lovely flowers - have caused havoc by their excessive growth and causing blocks in our waterways.
 
Question. List some of the waste which is generated at home. Which of them can you avoid or reduce easily? 
Answer : (a) polythene packets 
          (b) vegetable peels 
          (c ) Dry cells , blades
          (d) aluminium foils (e)Pieces of glass etc.
Polythene packets can be avoided by using cotton bags, jute bags etc.(or any other waste with reason )
 
Question. Suppose your father is planning to set up a factory. .
(i) What measures would you suggest to him to provide protection against noise pollution.
(ii) Mention two harmful effects of noise pollution. 
Answer : (i) a) Planting trees around the factory .
b) Walls should be equipped with sound absorbent material.
c) Workers should be equipped with ear-muffs.
(ii) a) impairing hearing ability
b) Sleeplessness, increased heart beat

 

ONE MARK QUESTIONS

 

Question. A factory drains its waste water into a nearby lake. What will be its effect on the lake after a few days?
Answer :
Eutrophication due to growth of algal bloom. 
 
Question. The names of organisms in an aquatic food chain is given below. Give the organism having the maximum concentration of DDT. 1 Large fish-Zooplankton-fish Eating birds- small fish-phytoplankton. 
Answer : Fish-eating birds 
 
Question. The central pollution control board observed that a thermal power plant is emitting 80% of its particulate matter in the exhaust due to poor maintenance? What could be the cause for this increase in % of particular matter?  
Answer : Poor maintenance of the electrostatic Precipitator.
 
Question. The birds egg shells become thinner in an area where there is an excess application of pesticides. Comment.
Answer : High concentration of DDT disturb calcium metabolism in birds which causes thinning of egg shell.
 
Question. Motor vehicles with catalytic converter should use unleaded petrol. Why?
Answer : Lead inactivates catalyst
 
Question. Why should we be thankful to micro-organism present in domestic sewage? 
Answer : Microorganism present in domestic sewage break down organic substances present in the sewage.
 
TWO MARKS QUESTIONS
 
Question. Vehicles are fitted with catalytic converters. Give reason  
Answer : Catalytic converter has platinum palladium and rhodium as catalyst to reduce emission of poisonous gases. As the exhaust passes through the converter unburnt hydrocarbon are converted into CO2 and water and carbon monoxide;
nitric oxide are changed in to CO2 and nitrogen gas.
 
Question. It was observed that some of the aquatic birds’ population has been declining. On analysis of the water in their habitat, high concentration of DDT was found 
a) What caused the decline is birds’ population? 
b) What is this phenomenon known as?  
Answer : a) DDT in the body interferes with the calcium metabolism, resulting in thinning of egg shell & their premature breaking ultimately leading to a decline is bird population 1+1
     b) Biomagnification
 
Question.  A man had a B. class Benz which has a very good catalytic converter. On his way the petrol was exhausted & he stopped at a petrol pump. The person at the petrol pump had only leaded petrol. Out of necessity the man had to fill leaded petrol in his car. 2
Answer :
a) What is its impact on the catalytic activity of the converter?
 
b) Explain the impact on the environment.
 
Ans.3) a) Lead in the petrol inactivates the catalyst 1+1
    b)Unburnt hydrocarbons are released which increases the air pollution.
 
Question. A person has inhaled air having particulate pollutants of size less than 2.5 micrometers in diameter. What could be the impact of their pollutants on his respiratory system? 2
 Answer :
Ans.4)Particulate pollutants inhaled deep into the lungs cause irritation, inflammation, damage to the lungs, & premature death.
 
Question. Mention the green house gases & their proportion in the pie diagram given below.2
CBSE_Class_12_Biology_Environmental_1
 
Answer : a = CO2 = 60%
b = methane = 20%
c = CFC'S = 14%
d-N2O = 06%
½x4=2
 
Question. A farmer saw water in a pond turned green & with dead fishes. 
a) What is the reason for the death of fishes? 
b) Name the phenomenon that leads to the death of
Answer : a) Algal bloom resulting in depletion of oxygen 
           b) Eutrophication.
 
Question. (Fig 16.3 pg No. 274-biology text book for class xii)
CBSE_Class_12_Biology_Environmental_2
In the above graph what does A & B depict? 2
Answer : 7) A-BOD 1+1 
           B-Dissolved oxygen
 
Question. The application of DDT for a long period resulted in the elimination of bird species from a locality. How does it happen? Explain.  
Answer : Bio magnification - (accumulation of DDT in the body of bird) disturbs the metabolism of calcium - thin egg shell.
      -Premature hatching - decline in population
 
Question. Identify the wrong pair/s and correct it. 
a) Chernobyl incident-Radio active waste
b) Snow blindness cataract- High dose of CFC
c) Chipko movement- Save trees
d) Polyblend-Solves air pollution.
Answer : b-snow blindness cataract-High dose of UV-B
    D-Polyblend-solve plastic pollution.
 
Question. Dumping waste in landfills is not a real solution for disposing wastes. Why? 
Answer : a) The amount of garbage generation specially in the metros has increased so much that these sites are getting filled too. 
     b) Also there is a damage of seepage of chemicals etc from these land fills polluting the underground water resources
 
Question. Ramesh collected water samples on his boat-trip downstream along a river. On analysis it was observed that the dissolved oxygen content reduced initially and later increased gradually. Can you help him plot a graph on concentration of DO & BOD downstream.
 
11) P.NO 274 fig 16.3
CBSE_Class_12_Biology_Environmental_3
THREE MARKS QUESTIONS
 
Question. Many coastal areas may get submerged due to the environmental changes taking place at the present rate. Give the cause, and state two measures to check it. 
Answer :  Global warming due to the increase in conc. of green house gases It can be checked by.  (Any 2)
i) Growing more trees (afforestation)
ii) Reduce the use of fossil Fuel iii) Prevent deforestation

Question. Integrated organic forming is a cyclical zero waste procedure. Justify. 
Answer : Integrated organic farming is a cyclical zero waste procedure_
a) Waste products from one process are cycled in as nutrients for the other process.
b) There is no need for chemical fertilizers as cattle excreta are used as manure.
c) Crop waste is used to create compost, which is used as manure to generate      electricity.

Question. Ecosan toilets are a hygienic, efficient and cost effective solution to the disposal of human wastes. Justify.
Answer : Human  excreta are  also  recycled  into  manure which  reduces the  use  of chemical fertilizers.

FIVE MARKS QUESTIONS

Question. Observe the following figure carefully and answer the questions that follow.   
a) Label the parts A, B, C & D
b) What are the steps involved in the removal of particulate matter?
c) How is it different from scrubber? 

Answer : a) a- collection plate                   
b- Dirty air 
c-discharge corona                   
d-Clean air                               

B)   i) The electrode wires are maintained in several thousand volts, which produces corona that releases electron.         1 

ii) Those electrons attach a dust giving negative charge.   ½ 

iii) The collecting plates attract the charged dust particles  ½ 

C) The electrostatic precipitator removes the particulate matter where as the scrubber removes the gases like SO2.

Question. Why does biomagnifications occur with certain substances ?name two such substances.
Answer : A Biomagnifications is the phenomenon in which harmful chemicals get accumulated in the tissues of organism in increasing concentrations at successive trophic levels.DDT and mercury.

Question. Study the given aquatic food chain and answer the question that follow:

CBSE_Class_12_Biology_Environmental_Set_B_1

i)Give reasons why there is a continuous increase in the DDT content in different trophic levels of the chain. 
ii) Name the phenomenon responsible for the increase in DDT content. 
Answer : i) the concentration of DDT increases at successive trophic levels because it is neither metabolized nor excreated;instead it accumulates in the tissues of the organisms. 
ii) biomagnification.
 
Question. Blends of polybend and bitumen , when used, help to increase the life of roads by a factor of of three what is the reason? 
Answer : i) enhanced bitumen's water repellant property, and helped to increase road life by a factor of three.
 
Question. Through auto fuel policy,Euro II norms,the government of india has laid out a road map to cut down the vehicular air pollution in many cities of india.what this norms stipulated? 
Answer : Euro II norms stipulates that sulphur be controlled at 350 ppm in diesel and 150 ppm in petrol.aromatic hydrocarbons are to be contained at 42 percent of the concerned fuel.according to the road map,is to reduce sulphur to 50ppm in petrol and diesel and bring down the level to 35 percent.
 
Question.  The figure shows the relative contribution of four greenhouse gases to global warming.
       i) Identify the gases A and C.
       ii) Why are these four gases called the greenhouse gases?
CBSE_Class_12_Biology_Environmental_Set_B_2
Answer : i) A-carbon dioxide ,C-CFCs
      ii) The molecules of these gases radiate heat energy, and a major part of which again comes to earth's surface, thus heating it up once again, results green house effect.
 
 

Very Short Answer Questions

Question. Mention two advantages for preferring CNG over diesel as an automobile fuel. 
Answer. Advantages of CNG are:
(i) burns efficiently and leaves behind less unburnt residues
(ii) cheaper than petrol or diesel
(iii) causes less pollution
(iv) cannot be adulterated
(v) cannot be siphoned by thieves. (any two)

Question. In which year was the Air Prevention and control of pollution Act amended to include noise as air pollution. 
Answer. 1987.

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 soil particles carried by water from the source of supply.

Question. Name the city in which the entire public road transport runs on CNG. 
Answer. Delhi.

Question. List two advantages of the use of unleaded petrol in automobiles as fuel.
Answer. (i) Allows the catalytic convertor to remain active.
(ii) Reduces air pollution.

Question. How is snow-blindness caused in humans? 
Answer. In human eye, cornea absorbs UV-B radiation, and a high dose of UV–B causes inflammation of cornea leading to snow-blindness.

Question. 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. 
Answer. As a result of this particulate matter or dust particles will be released in the air causing air pollution.

Question. What is an algal bloom? 
Answer. The excessive growth of algae (free-floating) that causes colouration of water bodies is called algal bloom.

Short Answer Questions

Question. Thermal power plants are inevitable in an industrial and densely populated country like ours.
What harm do they do to the environment? Also mention any precaution that could be taken to save our environment.
Answer. The particulate and gaseous pollutants are released from thermal power plants which lead to harmful effects. These pollutants can cause:
(i) breathing or respiratory symptoms when inhaled.
(ii) irritation, inflammations and damage to lungs and premature death.
Precautionary measures include use of electrostatic precipitators by which 99% of the particulate matters can be removed from the exhaust.

Question. What is hybrid vehicle technology? Explain the advantages with a suitable example.
Answer. Vehicle running on dual mode like petrol and CNG are hybrid vehicle. As CNG is a green fuel there is conservation of fossil fuel and reduction in the environmental pollution.

Question. A person has inhaled air having particulate pollutants of size less than 2.5 micrometers in diameter. What could be the impact of their pollutants on his respiratory system? 
Answer. Particulate pollutants inhaled deep into the lungs cause irritation, inflammation, damage to the lungs, and premature death.

Question. (a) Name any two places where it is essential to install electrostatic precipitators. Why it is required to do so?
(b) Mention one limitation of the electrostatic precipitator. 
Answer. (a) It is essential to install electrostatic precipitators in thermal power plants and smelters to remove particulate matter.
(b) Limitation of the electrostatic precipitator:
(i) particulate matter less than 2.5 micrometres are not removed.
(ii) velocity of air between plates must be low enough to allow the dust to fall.
(iii) it cannot work without electricity. (Any one)

Question. Discuss the role of women and communities in protection and conservation of forests.
Answer. Women and communities played an important role in protection and conservation of forests. In 1731, a Bishnoi woman, Amrita Devi showed exemplary courage by hugging a tree to prevent its cutting. Amrita Devi Bishnoi Wildlife protection Award is being awarded by the Government of India to individuals or communities from rural areas that show extraordinary courage and dedication in protecting wildlife. In Garhwal, local women hugged trees to prevent the contractor from cutting down trees.

Question. What is polyblend? Why did the plastic manufacturers think of producing it? Write its usefulness. 
Answer. Polyblend is a fine powder of recycled modified plastic. Polyblend was produced to recycle plastic waste. When blended with bitumen, polyblend can be used to lay roads that have increased road life.

Question. Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
Answer. (i) Cause
 Increase in the level of greenhouse gases (CO2, methane, etc.) in the atmosphere.
These gases allow the heat waves to reach earth but prevent their escape and thus the earth becomes warm.
(ii) Effects
 The temperature of the earth has increased by 0.6°C in the last three decades, which will lead to changes in precipitation patterns.
 Rise in temperature leads to deleterious changes in environment resulting in odd climatic changes called El Nino effect.

Question How do automobiles fitted with catalytic converters reduce air pollution? Suggest the best fuel for such vehicles.
Answer. Catalytic converters have expensive metals like platinum-palladium and rhodium as catalysts.
As exhaust emission passes through catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water, and carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas. Unleaded petrol is the best fuel for such vehicles.

Question. (a) Why are the colourful polystyrene and plastic packaging used for protecting the food,considered an environmental menace?
(b) Write about the remedy found for the efficient use of plastic waste by Ahmed Khan of Bangalore. 
Answer. (a) The colourful polystyrene and plastic packaging are non-biodegradable and non-ecofriendly.
(b) The remedy was found by developing polyblend, which is a fine powder of recycled modified plastic. Polyblend is mixed with bitumen to lay roads. This enhanced the water repellent
property of bitumen and enhanced the life of roads.

Question. Plenty of algal bloom is observed in a pond in your locality.
(a) Write what has caused this bloom and how does it affect the quality of water.
(b) Suggest a preventive measure.
Answer. (a) Presence of large amounts of nutrients (Nitrogen and Phosphorus) in water causes excessive growth of algae. This growth depletes dissolved oxygen in water and imparts distinct colour to the water bodies. The bloom forming algae are extremely toxic and deteriorates water quality resulting in fish mortality.
(b) Following preventive measures can be carried out:
(i) Treatment of waste water before it reaches the pond.
(ii) Integrated waste water treatment.
(iii) Avoid using NPK fertilisers.
(iv) Use of organic or biodegradable manure or resort to organic farming.

Long Answer Questions

Question. Explain any three remedial measures to overcome the acute air pollution in our cities.
Answer. (i) Electrostatic precipitators to remove paritculate matter present in the exhaust from thermal power plant.
(ii) Scrubber to remove SO2 from the exhaust of thermal power plant.
(iii) Alternative sources of energy in place of petrol.
(iv) Lead-free petrol or diesel.
(v) Catalytic convertors – to reduce lead pollution.
(vi) Use of CNG.
(vii) Use of low sulphur petrol and diesel.
(viii) Phasing out of old vehicles and stringent enforcement of pollution level norms.

Question. (i) State the consequence if the electrostatic precipitator of a thermal plant fails to function.
(ii) Mention any four methods by which the vehicular air pollution can be controlled.
Answer. (i) Particulate matter will pollute the air.
(ii) Vehicular pollution can be controlled by:
Control of air pollution in Delhi
 In 1990’s Delhi ranked 4th among 41 most polluted cities of the world. A Public Interest Litigation (PIL) was filed in the Supreme Court.
 All buses of Delhi were converted to run on CNG by the end of 2002 as per the directives of the Supreme Court.
 Advantages of CNG over diesel/petrol:
(a) CNG burns most efficiently without leaving any unburnt remnant behind.
(b) CNG is cheaper than petrol or diesel.
(c) CNG cannot be siphoned off by thieves and adulterated like petrol or diesel.

Question. How does an electrostatic precipitator work to remove particulate pollutants released from the thermal power plants? 
Answer. Electrostatic precipitator (ESP)
 It is an electrical device used to remove particulate matter present in the exhaust of thermal power plant.
 More than 99% particulate matter can be removed by this method.
 ESP has electrode wires and a stage of collecting plates.
 Electrode wires are provided with an electric current of several thousand volts, which produces a corona that releases electrons.
For diagram,

Question. Mention the major cause of air pollution in metro cities. Write any three ways by which it can be reduced. 
Answer. Major causes of air pollution are: Causes
(a) Smoke from forest fires, volcanic eruptions, etc.
(b) Decomposition of garbage resulting in release of unwanted gases into the atmosphere.
(c) Burning of fossil fuels in automobiles and industries release particulate and air pollutants.
(d) Use of leaded petrol.
(e) Gaseous wastes or particulate matter as by-products of various industries.
(f) Smoke stacks of thermal power plants, smelters and other industrial release, particulate and gaseous air pollutants with harmless gases like N2, O2, etc.
Control methods:
(i) Using electrostatic precipitators to remove particulate matter from exhaust of industries and thermal power plant.
(ii) Using scrubber to remove gases like SO2.
(iii) Use of catalytic converters in automobiles for reducing emission of poisonous gases.

Question. By the end of 2002 the public transport of Delhi switched over to a new fuel. Name the fuel.
Why is this fuel considered better? Explain.
Answer. The fuel was CNG or compressed natural gas. CNG is considered better because of the following reasons:
(i) CNG burns more efficiently unlike diesel or petrol.
(ii) Very little of it is left unburnt.
(iii) It cannot be adulterated.
(iv) It is cheaper than petrol or diesel.

Question. Discuss briefly the following:
(a) Radioactive wastes
(b) Defunct ships and e-wastes
(c) Municipal solid wastes
Answer. (a) Radioactive wastes: These are nuclear wastes which are most potent pollutants as they cause mutations. These cannot be reused or recycled and are disposed off carefully to prevent leakage.
(i) Accidents: There are accidental leakage as in Three Mile Island and Chernobyl incidents.
(ii) Radioactive waste disposal: Radiation given off by nuclear waste is extremely damaging to living organisms as it causes mutation at an extremely high rate, causing cancer.
Therefore, nuclear waste is an extremely potent pollutant.
(b) Defunct ships: Old defunct ships are dismantled to obtain scrap metals. Defunct ships contains toxicants like asbestos, mercury, lead, tributylin, etc. The workers engaged in ship are exposed to toxic chemicals. The coastal areas connected with ship breaking yard also become polluted.
e-wastes: These are the wastes (like irreparable computers and other electronic goods) generated in the developed countries and exported to developing countries including India, China and Pakistan where metals like gold, nickel, silicon, copper, iron, etc., are recovered during recycling process. Recycling is done manually by workers and hence they are exposed to some toxic substances.
(c) Municipal solid wastes: Wastes produced from homes, offices, schools, hospitals, etc., are collected and disposed off by the municipality. These generally consists of paper, leather,
textile, rubber, glass, etc. Sanitary landfills are used to dump these wastes.

Question. Write any three ways by which noise pollution affects the human body adversely. List any three steps that should be followed in order to reduce noise pollution. 
Answer. Effects of noise pollution are: sleeplessness, increased heart beat, altered breathing pattern,damaged hearing ability and damaged ear drum (Any three)
Steps to be followed to reduce noise pollution:
(i) Following of stringent laws laid down in relation to noise level.
(ii) Delimitation of horn free zones around hospitals and schools.
(iii) To adopt permissible sound level of crackers and loudspeakers.
(iv) Adhereing to time limit for loudspeakers beyond which it cannot be played.
(v) Use of sound absorbent material in industries.
(vi) Muffling of noise. (Any three)

ONE MARK QUESTIONS:

1. What is the role of catalytic convertor?
Hint: Conversion of poisonous gases
 
2. Identify the catalytic convertor from the following:
a. Platinum b. Palladium c. Lead d. Radium
 
3. Accidental leakage and safe disposal are the problems of which energy?
 
4. In Bangalore recycled plastic is modified as _________________
 
5. In Delhi, the current auto fuel policy is ____________
 
6. A cyclical zero waste procedure of cropping is __________
 
7. Which size of the particulate matter is harmful to human health?
 
TWO MARKS QUESTIONS:
 
1.Study the graph and answer the questions given below
CBSE_Class_12_Biology_Environmental_Issue_Set_C_1
a. What measures would you take to decrease BOD and increase DO?
b. What kind of sewage discharge will increase BOD?
 
2. To what type of wastes do irreparable computers and other electronic goods belong to ?
 
Ans: Defunct ships and e-waste.
 
3. Name four metals which are recovered during the recycling of e-waste?
 
Ans: Copper, Iron Silicon Nickel and Gold.
 
4. Complete the following:
             A                                                   B
1. ____________                Carbon monoxide & Nitrogen oxide
2. Electrostatic precipitator            ______________________
3. _____________                              High noise level
4. Land fills                                    _____________________
 
Ans: 1. Catalytic converter
2. Particulate matter
3. Earmuffs
4. Solid waste
 
5. Water  →  Zooplanktons      Small fish       Fish eating birds
DDT (0.003ppm) (0.04ppm)        (0.5ppm)              (5ppm)
Why is the concentration of DDT increasing from the producers to consumers in the above food chain?
 
THREE MARKS QUESTIONS:
 
1. Why is CNG preferred than petrol or diesel?
Hint: Fuel efficiency, no adulteration, no theft
 
2. What are the wastes generated during trips and tours? How can it be minimized?
 
3. How do foam and ecosan help in waste water treatment?
 
FIVE MARKS QUESTIONS:
 
1. What measures would you take to reduce environmental pollution?
Hint: no biomass burning, vehicle use, no tobacco, electric chimney, noise, tree plantation, disposable and recyclable material, minimize fossil fuels.
 
2. Observe the following diagram and answer the questions at the end 
cbse-class-12-biology-hots-environmental-issues
a. Name the gases.(2)
b. Comment on the consequences of increase in the level of each gas (any three)(3) 
Chapter 01 Reproduction in Organisms
CBSE Class 12 Biology HOTs Reproduction In Organisms
Chapter 02 Sexual Reproduction In Flowering Plants
CBSE Class 12 Biology HOTs Sexual Reproduction In Flowering Plants
Chapter 03 Human Reproduction
CBSE Class 12 Biology HOTs Human Reproduction
Chapter 04 Reproductive Health
CBSE Class 12 Biology HOTs Reproductive Health
Chapter 05 Principles of Inheritance and Variation
CBSE Class 12 Biology HOTs Principles Of Inheritance And Variation
Chapter 06 Molecular Basis of Inheritance
CBSE Class 12 Biology HOTs Molecular Basis of Inheritance
Chapter 08 Human Health and Disease
CBSE Class 12 Biology HOTs Human Health and Disease
Chapter 09 Strategies for Enhancement In Food Production
CBSE Class 12 Biology HOTs Strategies For Enhancement In food Production
Chapter 10 Microbes In Human Welfare
CBSE Class 12 Biology HOTs Microbes In Human Welfare
Chapter 11 Biotechnology Principles and Processes
CBSE Class 12 Biology HOTs Biotechnology Principles and Processes
Chapter 12 Biotechnology and Its Application
CBSE Class 12 Biology HOTs Biotechnology And Its Applications
Chapter 13 Organisms and Populations
CBSE Class 12 Biology HOTs Organism And Population
Chapter 15 Biodiversity and Conservation
CBSE Class 12 Biology HOTs Biodiversity And Conservation
Chapter 16 Environmental Issues
CBSE Class 12 Biology HOTs Environmental Issues

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CBSE Class 12 Biology Chapter 16 Environmental Issues HOTS

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HOTS for Biology CBSE Class 12 Chapter 16 Environmental Issues

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Chapter 16 Environmental Issues HOTS Biology CBSE Class 12

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Chapter 16 Environmental Issues CBSE Class 12 HOTS Biology

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CBSE HOTS Biology Class 12 Chapter 16 Environmental Issues

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