2nd PUC Biology Question Bank Chapter 16 Environmental Issues

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Karnataka 2nd PUC Biology Question Bank Chapter 16 Environmental Issues

2nd PUC Biology Environmental Issues NCERT Text Book Questions and Answers

Question 1.
What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
Domestic waste – Waste that is produced from our homes and passed down into sewer system matter that floats . Effects of sewage on river.

Quality of water is decreased . So it becomes unsuitable for bathing, domestic uses etc.
2nd PUC Biology Question Bank Chapter 16 Environmental Issues 1

B.O.D- [Biological oxygen demand] – More waste in water, more decomposers come into action, much larger amount of O2 utilized so, B.O.D. increases and dissolved oxygen becomes less.
2nd PUC Biology Question Bank Chapter 16 Environmental Issues 2

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Question 2.
List all the wastes that you generate, at home, school or during your trips to other places, which you could easily reduce? Which would be difficult or rather impossible to reduce?
Plastic containers, paper, electronic goods, leftover food, food package, disposable glasses, cup plates, polythenes, excreta, soap and detergent waste are the wastes that one can generate at home, school or during trips to other places. Yes, we can easily reduce waste through judicious use of material by changing our habits & lifestyles.
Out of these, polythene and plastic material are hard to dispose of off as they are non-biodegradable and can be recycled back.

Question 3.
Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
The greenhouse effect is the progressive, gradual warming of the earth’s atmosphere caused by the insulating effect of carbon dioxide and other greenhouse gases that have proportionately increased in the atmosphere. The greenhouse effect disturbs the way the earth’s climate maintains the balance between incoming and outgoing energy by allowing short-wave radiation from the sun to penetrate through to warm the earth but preventing the resulting long-wave infrared radiation from escaping back into the atmosphere. There is concern that increasing the concentration of greenhouse gases, including carbon dioxide, methane, and man-made chlorofluorocarbons, may enhance the greenhouse effect and cause global warming.
Effects of global warming are :

(i) Warming of the atmosphere will significantly increase its moisture carrying capacity. While the troposphere warms up, the stratosphere will cool down. This would cause extensive changes in precipitation patterns due to changing patterns of air-mass movements. Besides, the frequency of droughts, floods, etc., is estimated to increase substantially. Climate change will increase threats to human health, predominantly in tropical and subtropical countries, due to changes in ranges of disease vectors, water-borne pathogens, etc.

(ii) global warming may contribute to sea-level rise due to the thermal expansion of oceans as it warms, and the melting of glaciers and Greenland ice sheets. A rise of even half a meter in sea level would profoundly affect the human population, one-third of which lives within 60 km of a coastline. Numerous low-lying islands may be submerged. The inundation of coastal salt marshes and estuaries may deprive many important birds and fishes, their breeding grounds, forcing their extinction.
Strategies to deal with global warming:

  • Complete replacement of chlorofluorocarbon with substitutes that have little effect on ozone and global warming.
  • Increasing vegetation cover of forests for photosynthetic utilisation of CO2.
  • Reduction in use of nitrogen fertilisers and instead relying more on nitrogen fixation.
  • Limiting use of fossil fuels by developing alternate sources of energy, e.g., solar energy, wind energy.
  • Increasing use of alternative, renewable, nonpolluting sources of energy like solar energy, wind energy, hydropower etc.

Question 4.
Match the items given in column A and B:

Column A – Column B
(a) Catalytic converter – (i) Particulate matter
(b) Electrostatic – (ii) Carbon precipitator monoxide and nitrogen oxides
(c) Earmuffs – (iii) High noise level
(d) Landfills – (iv) Solid wastes
(a) Catalytic converter – (i) Co & NO
(b) Electrostatic – precipitator (ii) Particulate matter
(c) Earmuffs – (iii) High noise level
(d) Landfills – (iv) Solid wastes

Question 5.
Write critical notes on the following:
(a) Eutrophication
(b) Biological magnification
(c) Groundwater depletion and ways for its replenishment.
(a) Eutrophication: Eutrophication is the phenomenon of nutrient enrichment of a water body that initially supports a dense growth of plant and animal life. It is caused by run-off from fertilised fields, suburban lawns, feedlots, and detergent-rich sewage. Organic loading or occurrence of excess organic matter occurs inside water. The rapid growth of water plants especially the algae is called bloom. They cut off light from submerged plants and later die. This decreased oxygen putrefaction further decreases dissolved oxygen replenishment inside water. Blue-green algae present in the bloom also release toxins. Both toxicity and decreased oxygen level kill aquatic animals.
2nd PUC Biology Question Bank Chapter 16 Environmental Issues 3
(b) Biological magnification: Biomagnification is due to the introduction of toxic substances from industrial and household waste into the aquatic food chain. The concentration of toxic substance accumulated by organism increases at each trophic level – Biomagnification, eg: Toxic substances like mercury, DDT, etc.
They later lead to eutrophication.

Birds (25 ppm)

large fish (2ppm)

small fish (0.5 ppm)

zooplankton (0.04 ppm)

water (0.003 ppm)
(DDT concentration showing biomagnification)

(c) Groundwater depletion and ways for its replenishment
Groundwater depletion – due to high demand of water in urban, hilly, arid areas where surface water is not available or polluted, groundwater is the major source of water drawn using tube wells, pumps etc., [in Punjab, T.N, Rajasthan]


  • Reduced consumption or stop using groundwater for irrigation and cleaning etc.
  • Rainwater harvesting – Collection of rainwater and diverting them into the ground using pipes or into rivers or rainwater tanks. [As an alternate source of water also].

Question 6.
Why ozone hole form over Antarctica? How will enhanced ultraviolet radiation affect us?
A large amount of ODS (Ozone Depleting Substances) like CFCs, N2O, halons, SO2, CH4, Cl-are released by advanced countries like the USA, Japan, European countries. These are released in the stratosphere, drift towards poles, and reach there before the coming of winter. During winter (temp. 85°C) ice clouds are formed over Antarctica and no sunrise is received in polar areas. It catalyses the release of Cl from CFCs. With the coming of the spring season, Cl reacts with ozone in the presence of sunlight and converts 03 into 02 causing ozone depletion/thining of ozone shield in stratosphere called ozone hole. This hole disappears in summer due to the free mixing of air of Antarctica with there to the global air.

Effect of Enhanced UV Radiation:

  • Snow blindness or inflammation of the cornea
  • Damage of skin cells and development of skin cancer
  • Damage to nucleic acids and proteins
  • Reduced immunity
  • A higher number of cataracts in humans.

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Question 7.
Discuss the role of women and communities in the protection and conservation of forests.
In 1731, a Bishnoi woman Amrita Devi showed exemplary courage by hugging a tree to prevent its cutting. Her three daughters and hundreds of other Bishnois followed her. They were killed by the soldiers of king of Jodhpur. This movement forced the king to abandon the cutting trees. Later ‘Chipko Movement’ was started by Sundar Lai Bahuguna and others to prevent the cutting of trees.

Question 8.
What measures, as an individual, you would take to reduce environmental pollution?
The following initiatives can be taken to prevent environmental pollution:
Measures for preventing air pollution:

  • Planting more trees.
  • Use of clean and renewable energy sources such as CNG and biofuels.
  • Reducing the use of fossil fuels.
  • Use of catalytic converters in automobiles.

Measures for preventing water pollution:

  • Optimizing the use of water.
  • Using kitchen wastewater in gardening and other household purposes measures for controlling noise pollution:
    • Avoid burning crackers on Diwali,
    • Plantation of more trees.

Measures for decreasing solid waste generation:

  • Segregation of waste.
  • Recycling and reuse of plastic and paper.
  • Composting of biodegradable kitchen waste.
  • Reducing the use of plastics.

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Question 9.
Discuss briefly the following:
(a) Radioactive wastes
(b) Defunct ships and e-wastes
(c) Municipal solid wastes
(a) Radioactive Waste. They are nonusable discards which possess radioactivity. Radioactive wastes are of three types:

  • Wastes with low-level radioactivity: Coolant water of atomic reactors and pond water used for cooling spent fuel contains a very small amount of radioactivity. This, however, undergoes biomagnification.
    Irradiation centres, radiotherapy units and laboratories also produce wastes with low-level radioactivity,
  • Wastes with intermediate level radioactivity: They are radioactive wastes of many ores which are separated during refinement of minerals,
  • Wastes with high-level radioactivity: Spent fuel of atomic reactors and leakage from reactors have very high level of radioactivity. All wastes with radioactivity have to be handled carefully and dumped 500 m deep in earth or inside sea after placing them inside very thick protective containers.
    Radioactive wastes are highly dangerous to human beings, animals, microbes and vegetation. They kill all of them. Loss of hair, nails appearance of deformities, cancers and genetic defects appear due to mutations.

(b) Defunct ships and e-wastes – Defunct ships also contribute to solid wastes. Such ships are broken down for scrap metal in developing countries like India. These defunct ships are the source of toxicants like asbestos, polychlorinated biphenyls, tributyltin, lead, mercury, etc. The workers get exposed to these chemicals and the coastal area in the vicinity of ship breaking yard gets polluted. Irreparable computers and other electronic goods are responsible for electronic wastes or e-wastes. Such wastes can only be buried in landfills or incinerated. Developed countries export the e-wastes to developing countries where metals like copper, iron, silicon, nickel and gold are recovered from e-waste by the recycling process. In the process, workers get exposed to these harmful toxic substances.

(c) Municipal solid wastes – Municipal solid wastes include domestic/kitchen wastes, market wastes, sweepings, wastes, from commercial complexes, rubbish, hospitals, slaughterhouses, livestock/poultry wastes, and trash like waste metals e.g., cans, plastic, pet bottles, polyethylene carry bags etc. Hospital wastes include vials, plastic and glass bottles, syringes, needles, organic wastes, chemicals and a lot of pathogen carriers. Hospital and domestic wastes are thus a source of a variety of pathogens. Municipal wastes are partly degradable and partly nondegradable. Burning reduces the volume of wastes although it is generally not burnt to completion and open dumps often serve as a breeding ground for rats and flies.

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Question 10.
What initiatives were Jtaken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
Delhi has been categorized as the fourth most polluted city in the world in a list of 41 cities. The burning of fossil fuels has added to the pollution of air in Delhi. Various steps have been taken to improve the quality of air in Delhi:

  • Introduction of CNG (Compressed Natural Gas): By the order of the supreme court of India, CNG-powered vehicles were introduced at the end of the year 2006 to reduce the levels of pollution in Delhi. CNG is a clean fuel that produces very few unburnt particles.
  • Phasing out of old vehicles.
  • Use of unleaded petrol.
  • Use of low-sulphur petrol and diesel.
  • Use of catalytic converters.
  • Application of stringent pollution-level norms for vehicles.
  • Implementation of Bharat stage I, which is equivalent to euro II norms in vehicles of major Indian cities.
  • The introduction of CNG-powered vehicles has improved Delhi’s air quality, which has lead to a substantial fall in the level of CO2 and SO2. However, the problem of Suspended Particulate Matter (SPM) and Respiratory.
  • Suspended Particulate Matter (RSPM) still persists.

Question 11.
Discuss briefly the following :
(a) Greenhouse gases
(b) Catalytic converter
(c) Ultraviolet B
Greenhouse gases – are those gases which allow short wave radiations to pass through but absorb longwave heat radiations: eg: CO2, CH2, N2O, CFCs.
They cause the greenhouse effect and increase surface temperature making the earth. Sustainable or life

Question Downward flux of long waves by greenhouse gases is called greenhouse reflux. It keeps the earth warm at 15°C, without it earth’s temperature would dropto-18°C.
2nd PUC Biology Question Bank Chapter 16 Environmental Issues 4
But enhanced greenhouse effect causes global warming that is leading to deleterious changes in the environment and resulting in odd climate changes.
2nd PUC Biology Question Bank Chapter 16 Environmental Issues 5
(b) Catalytic Converter : It is a method to reduce emissions from automobiles. The device has platinum-palladium, and Rhodium as catalyst. Exhaust emissions passes through it; nitric oxide splits into nitrogen and oxygen, Carbon monoxide into carbon dioxide, unburned hydrocarbons get burned to form CO2 and H2O. It is useful only is unleaded petrol because lead inactivates catalyst of the convertor.

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(c) Ultraviolet B (UVB) – They normally do not reach earth’s surface as ozone layer reflects it back. But due to the ozone hole, UVB reaches earth surface these days.
They cause:

  • Skin cancer
  • Blinding – Corneal damage.
  • Immune system is partially suppressed
  • Larval stages die
  • Photosynthesis – is impaired so crop yield falls.
  • Nucleic acids – Mutations
  • Phytoplankton – their function is disturbed so productivity falls.
  • Global warning.

2nd PUC Biology Environmental Issues Additional Questions and Answers

2nd PUC Biology Environmental Issues One Mark Questions

Question 1.
Name two important methods to control air pollution from industries.
Electrostatic precipitators and scrubbers.

Question 2.
What are the causes of air pollution?
The causes of air pollution: The main causes of air pollutions are fossil fuels industries, factories, and particulate matter are produced due to the combustion of petrol, diesel, kerosene, etc. in vehicles, houses, and factories which pollute air.

In thermal power plants, steel and glass industries, paper and sugar mills etc. combustion of coal and furnace oil produce carbon monoxide, carbon dioxide, sulphur dioxide, ash, dust particles and some heavy metals which are released into atmosphere. Similarly, various types of chemicals released from cloth mills, cement industries, asbestos industries, pesticides, industries etc. also causes air pollution.

Question 3.
Two very serious inherent problems related to nuclear energy.

  1. Accidental leakage
  2. Safe disposal of radioactive wastes.

Question 4.
What is an ozone shield or ozone layer?
The region in the stratosphere where ozone is present in high concentration is called the ozonosphere or ozone layer or ozone shield.

Question 5.
What is ozone hole?
The thinning of ozonal layer over the Antarctic region is called the ozone hole.

Question 6.
What is acid rain.
It is the deposition of acidic chemicals of the atmosphere over the earth by combining them with rain droplets.

Question 7.
What constitutes smog.
It is an opaque dark fog that is formed by smoke, dust, oxides of sulphur, nitrogen, H2S, water vapour, etc.

Question 8.
Expand the term PAN and BOD, PPN. (CBSE 2005, 2007, 2008)

  • PAN – Peroxy acyl nitrate
  • BOD – Biological oxygen demand
  • PPN – Peroxy – propional nitrate.

Question 9.
High DDT pollution in water bodies causes a decline in the bird population. Evaluate.
The high concentration of DDT disturbs calcium metabolism in birds, which causes thinning of eggshells and their premature breaking eventually causing a decline in bird populations.

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Question 10.
What is Sonic Boom?
It is a series of shock waves left behind by a supersonic Jet flying at a speed. It produced sudden rattling of windows and doors. Building many develop cracks.

Question 11.
Define biomagnification.
It is the increase in the concentration of certain toxic chemicals like DDT at successive trophic levels through the food chain is called biomagnification.

Question 12.
What do you mean by eutrophication?
It is defined as the nutrient enrichment in the water bodies leading to the depletion of oxygen and deadening of the life-supporting environment, due to slow ageing of water bodies.

Question 13.
How can you measure the amount of biodegradable organic matter in sewage water?
It is possible to estimate the amount of biodegradable organic matter by Biochemical Oxygen Demand.

Question 14.
Name the world’s most problematic aquatic weed? What is the nature of water body in which this weed grows? (CBSE 2008)
Eichhornia crassipes is the problematic aquatic weed grow in an eutrophied water body.

Question 15.
Expand CPCB..
Central Pollution Control Board.

Question 16.
Define Pollutants.
Those agents which bring undesirable change in the physical-chemical and biological characteristics of air, water and soil are called pollutants.

Question 17.
Write the main aim of the Environment Act in 1986 (pollution).
“Protect and improve the quality of our environment i.e. air, water and soil”.

Question 18.
What is meant by the greenhouse effect?
The greenhouse effect is a naturally occurring phenomenon, in which the short wave radiations of solar energy are absorbed and longwave radiations are reflected by the earth, but reabsorbed by certain gases and increases the temperature of the earth’s surface and atmosphere.

Question 19.
Between amphibians and birds, which will be able to cope with global warming? Give reason.
Birds. Because they are warm-blooded animals can adjust the body temperatures as per the changes in the environment.

Question 20.
What gases cause stratospheric ozone depletion? What is the result of this depletion? (CBSE 2004)
N2O, CH4, CO2, chlorine are some of the gases that lead to ozone depletion. The depletion leads to the ozone hole which allows the entry of UV-B radiation to the earth’s surface. This radiation causes skin cancer, blindness, global warming etc.

Question 21.
What will be the consequences if the electrostatic precipitator of a thermal power plant fails to function?
In the absence of an electrostatic precipitator, the particulate pollutants and gaseous pollutants of the exhaust will get into the atmosphere.

Question 22.
What is Snow blindness?
Snow blindness is the inflammation of the cornea caused by a high dose of UV-B radiation.

Question 23.
Where did the Chipko movement start?
In Garhwal Himalayas.

Question 24.
What is the Chipko movement?
The movement led by Gaura Devi along with Sunder Lai Bahuguna of Tehri region of Uttara Khand to prevent the felling of trees by hugging the trees.

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Question 25.
What JFM. What are its main objectives?

  • Joint Forest Management.
  • Protection of Sal forest by local communities.

Question 26.
What ITS the main objective of the Montreal Protocol?
Limiting production and consumption of chloroform carbon to half the level.

2nd PUC Biology Environmental Issues Two Marks Questions

Question 1.
What are major causes of soil erosion?

  • Over Cultivation
  • Poor irrigation practices
  • Deforestation
  • Unrestricted grazing.

Question 2.
What is Montreal Protocol? What is its aim?
Montreal Protocol is an international treaty, that was signed in Montreal (Canada) in 1987 and become effective in 1989. The main .aim is to control the emission of ozone-depleting substances.

Question 3.
Waterlogging can increase soil salinity. Discuss.
Waterlogging draws salt to the surface of the soil. This salt is then deposited as a thin crust on the land surface and starts collecting roots of the plant.

Question 4.
Mention the harms caused by fine particulates in humans.

  • They may be inhaled deep into the – lungs and cause breathing and respiratory problems.
  • Irritation of lungs.
  • Inflammation of lungs.
  • Premature death.

Question 5.
How is letting of sewage into water bodies cause fish mortality?

  • As the sewage is discharged into water bodies, there is an increase in biodegradable organic matter.
  • The microorganisms multiply fast with the increase in organic matter, which Is used as its substrate for them.
  • These microbes consume a lot of oxygen and there is a sharp decline in the dissolved oxygen content of the water body, this leads to fish mortality.

Question 6.
Differentiate between biodegradable and nonbiodegradable waste.

  • Biodegradable: These are the waste which can be broken down into simpler harmless substances by the activity of decomposers. These substances are used as manures.
  • Non-biodegradable: The substances which cannot be broken down into simpler substances by microbes and start accumulating in the biosphere.
  • This causes pollution and can lead to biomagnification.

Question 7.
Write an account on Ecosan -Ecological sanitation.

  • Ecological sanitation is a sustainable system for handling human excreta, using dry composition toilets.
  • This is a practical, hygienic, efficient, and cost-effective solution to human waste disposal.
  • In this method, human excreta can be recycled into manures that reduce the need for chemical fertilizers.
  • There are working eco sans in Kerala and Srilanka.

Question 8.
How is organic farming advantageous?

  • This allows maximum utilization of resources.
  • It increases the efficiency of production.
  • There is no need for chemical fertilizers for crops, as cattle excreta, can be used as manures.
  • Crop wastes are also decomposed and used as manures.
  • Cattle dung and crop wastes are used to generate biogas, which is used for cooking and lighting.

Question 9.
How is the greenhouse effect caused?

  • The atmospheric gases absorb half of the incoming solar radiation and heat the earth’s surface.
  • Earth surface re-emits the heat in the form of infrared radiation.
    A large part of this is absorbed by greenhouse gases (CO2, CH4, N2O, CFCs etc).
  • The molecule of these gases radiate heat energy back into the atmosphere and the earth’s surface is heated up once again.
  • This cycle is repeated a number of times and there is an increase in the global temperature.

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Question 10.
Differentiate between “Good ozone” and “Bad ozone”.

Good ozone Good ozone
Good ozone refers to the ozone found in the stratosphers. Bad ozone refers to the ozone found in the troposphere.
It absorbs UV radiations and protects the living organisms of the earth. This is harmful to plants and animals.

Question 11.
Mention any 3 reasons for deforestation.
Deforestation is caused due to human activation for the following purposes.

  • Forests are cleared for making homes and industries due to overpopulation.
  • Forests are converted into agricultural land to produce food for increasing population.
  • Trees are fell for timber, firewood and other uses.

Question 12.
Write preventive measures to control air pollution.
Measures for the control of air pollution :

  • Industrial smokes must be filtered before releasing them into the atmosphere.
  • Tree plantation should be increased and deforestation prevented.
  • The use of automobiles should be minimized which reduce the nitrogen contents in the atmosphere.
  • The use of crude fuels should be avoided and use of high-quality fuels should be recommended.
  • Nuclear explosions should be avoided.
  • Legal control of air pollution.
  • Plantation of air-purifying plants.
  • Development of parks and gardens in cities.

Question 13.
Define pollution. Compare the biodegradable and non-biodegradable pollutants.
Pollution is an undesirable change in the physical, chemical or biological characteristics of air, water and land that may harmfully affect human, animal and plant life and may destroy our valuable resources. Pollutants are broadly classified into biodegradable and non-biodegradable. Pollutants, which decompose rapidly by natural processes are called biodegradable pollutants (e.g. market garbage, livestock wastes, municipal sewage etc). Non-biodegradable pollutants are the materials that either do not degrade or degrade only very slowly in nature (e.g. DDT, BHC, waste plastic bottles, polyethylene bags, used soft drink cans etc).

Question 14.
What does BOD indicate? What is its relationship with the dissolved oxygen content of the water body?
BOD is Biological oxygen demand which is a measure of the oxygen required by aerobic decomposers for the degradation of biodegradable organic matters in the water bodies.
If BOD is higher, it indicates the high level of organic matter and vice versa.

2nd PUC Biology Environmental Issues Three Marks Questions

Question 1.
Mention the harmful effects of noise on human health.

  • Sleeplessness and headache
  • Noise level of 150 dB or more than these can cause permanent hearing impairment
  • Increased heart beating and blood pressure
  • Difficulty in breathing
  • Stress and strain

Question 2.
Describe the particular type of agriculture practiced in northeastern states of India which has also contributed to deforestation. What is it commonly called?
Slash and Burn agriculture is practiced in the north-eastern states of India.
In this method, the farmers cut down the trees of the forest and burn them and clear a certain area for farming.

The ash is used as manure and the land is used for the cultivation of crops or grasses for cattle grazing. ‘After cultivation for a period of time, the land is left free for several years to allow its recovery The farmers move to a different area in the forest and this process is repeated. This practice is commonly called Jhum Cultivation.

Question 3.
It has been recorded that the temperature of the earth’s atmosphere has increased by 0.6°C.
a. What has caused this increase?
b, Explain its consequences.
a. Increase in the level of greenhouse gases has led to considerable heating of earth leading to global warming. The temperature of the earth has increased by 6°C, most of it during the last three decades.

b. The rise in temperature is leading to deleterious changes in the environment and results in odd climatic changes, thus leading to increased melting of polar ice caps as well as of other places like the Himalayan snowcaps. This will result in a rise in sea level that can submerge many coastal areas

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Question 4.
The figure given aside shows the relative contributions of various greenhouse gases to total global warming.
2nd PUC Biology Question Bank Chapter 16 Environmental Issues 6
(i) Name the gases a and b.
(ii) Explain how an increase in greenhouse gases in the earth’s atmosphere leads to the melting of the caps.
(i) (a) N2O
(b) CH4
(ii) Increase in greenhouse gases (GHGs) results in increased greenhouse flux or trapping long wave radiations and sending them back to earth. It increases atmospheric temperature called global warming. High atmospheric temperature results in the melting of ice caps and glaciers.

Question 5.
2nd PUC Biology Question Bank Chapter 16 Environmental Issues 7
The above diagram shows a simplified biogeochemical cycle.
(a) Name the compound whose cycle is deposited
(b) In what way do vehicles add this compound to the atmosphere?
(c) What adverse effect does excess have on the environment?
(d) Cite an event that depicts this effect in modern times.
(e) Suggest 2 ways of reducing this effect.
(a) CO2 cycle
(b) By burning fossil fuel
(c) Global Warming
(d) Melting of glaciers and a slow rise in sea level, submerging of low-lying islands.

  • Limiting the use of fossil fuels
  • Increase the vegetation cover

Question 6.
2nd PUC Biology Question Bank Chapter 16 Environmental Issues 8
Study the graph and answer the following questions
(1) What is the relationship between dissolved oxygen and biochemical oxygen demand (BOD)
(2) Mention their effect on the aquatic life of the river.

  1. The dissolved oxygen content is inversely proportional to BOD i.e. when BOD rises, the content of dissolved oxygen decreases and vice versa.
  2. When BOD is high, the aerobic aquatic organism will die due to decreased availability of dissolved oxygen.
  3. When BOD is low, the content of dissolved oxygen becomes high. In clear water, aerobic aquatic organisms reappear.

2nd PUC Biology Environmental Issues Five Marks Questions

Question 1.
Differentiate between Biological magnification and eutrophication. (CBSE2007)

Biological Magnification Eutrophication
(a) It is increasing the concentration of a persistent pollutant With the rise in trophic level. It is the nutrient enrichment of a water body.
(b) It occurs both in terrestrial and aquatic ecosystem Occurs only in the aquatic ecosystem
(c) There is no excessive growth There is excessive growth of algae
(d) Organic loading is absent Organic loading occurs in the water body.
(e) The higher-order consumers are harmed most. The whole aquatic ecosystem is damaged.

Question 2.
Given below are the sources of pollution and their effects. Using this information, fill the spaces in the given box. Each pollutant may have more than one source and may show more than one effect. Pollutant source: Automobile exhaust, Burning of fossil fuels, refrigerant, the agricultural field, lire extinguisher, paint solvents, Deforestation, plastic foam.
Effect: Photochemical smog, Acid deposition, global warming, Depletion of ozone.

Name of pollutant Source Effect
  1. CFC
  2. Suspended particulate matter (SPM)
  3. Oxides of nitrogen
  4. Sulphur dioxide
  5. Methane (CH4)


  • CFC: Sources – Refrigerant, Fire extinguisher, paint solvents, plastic foam.
    Effects: Depletion of ozone, global warming
  • SPM: Sources – Automobile exhaust, Burning of fossil fuel
    Effect: Photochemical smog.
  • Oxides: Source-Automobile exhaust, Burning of nitrogen of fossil fuel, Agricultural field.
    Effect: Photochemical smog, Acid-deposition, global warming.
  • Sulphur dioxide: Source – Automobile exhaust, Burning of fossil fuel.
    Effect: Acid deposition.
  • Methane Sources: Agricultural field, Burning of fossil fuel.
    Effect: global warming.

KSEEB Solutions

Question 3.
Differentiate between
(a) BOD and COD
(b) Montreal and Kyoto protocols.
(a) BOD and COD

(i) It is biochemical oxygen demand It is chemical oxygen demand.
(ii) Its value is lower Its value is higher
(iii) It measures oxygen demand for the completion of degradation of organic matter. It measures oxygen demand for oxidizing all the red­uced substances, whether organic or inorganic.
(iv) It employs decompose microbes It employs potassium permanganate or potassium dichromate.

(b) Montreal and Kyoto protocols.

Montreal Protocol Kyoto protocols
(i) It is related to a reduction in the production and consumption of CFC and other ODS. It is related to the emission of CO2 and other greenhouse gases
(ii) The protocol was signed in 1987 (ii) This was signed in 1997
(iii) It was followed by Helsinki decla­ration to phase out CFCs and halons. The road map was prepared to help the actions to replace CFC and ODS. (iii) It has been followed by the Bati conference in 2007 Road map has been prepared to reduce the emission of greenhouse gases by 2012.

(a) What is meant by deforestation? Mention the cause of it.
(b) Why is CNG preferred to diesel/petrol
It is the conversion of forest areas to non-forest areas and ultimately to a desert.
(a) Causes of deforestation are

  • Conversions of forest land to agricultural land to produce food for the increasing population.
  • Cutting of trees for timber and wood
  • Jhumcultivation in the north-eastern states of India
  • Forest fires.


  • CNG burns most efficiently in automobiles and leaves very little of it unburnt.
  • CNG cannot be adulterated like petrol/diesel
  • It cannot be siphoned by thieves
  • It is cheaper than petrol/diesel.

Question 4.
Write the effects of noise pollution.
Effects of Noise pollution:

  • The more acute and immediate effect of noise pollution is impairing of hearing leading to auditory fatigue and may finally lead to deafness.
  • Interference with speech communication.
  • Noise pollution leads to neurosis, anxiety hypertension, cardiovascular disease, hepatic stress, giddiness.
  • Annoyance leading to ill-temper, bickering, mental disorientation, and violent behaviour.
  • The high intensity of noise pollution can cause blood vessels to contract, skin becomes pale, muscles to contract, and adrenaline to be short into the bloodstream with consequence rise in blood pressure. This ultimately results in tension and nervousness.
  • Affects different metabolic activities.
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