NCERT Solutions for Class 12 Biology Chapter 16 Environmental Issues

• filter
• lime
• spray of water
• both 2 and 3

• Forest fire
• Pneumonia
• Increased incidence of skin cancer
• None of these

• Bacterial oxygen demand
• Biological optimum density
• Biochemical oxygen demand
• Bioorganisation decay

• CO
• Hydrocarbon
• Fly-ash
• NO

• myopia
• snow blindness
• biomagnification
• None of the above

• Aluminium ions
• Methane and ozone
• smoke and fog
• water and smoke

• 105 dB
• 75 dB
• 135 dB
• 165 dB

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere

• Biomagnification
• Eutrophication
• BOD
• COD

• CO₂ and CO
• SO₂ and NO2
• SO₃ and CO
• Ozone and dust

• Smog
• Photochemical Oxidants
• Chlorofluorocarbons
• Sulphur Dioxide

• Jaundice
• Minamata
• Fluorosis
• Black food disease

• Methane
• Carbon Dioxide
• Hydrogen 
• Nitrous Oxide

• NO₂
• CO₂
• CFCs
• Sulfur dioxide

1. Increase in concentration of soluble salts in the soil is called.........

2. Aforestation can check the advancement of......... .

3. DDT is a serious pollutant as it is a.........pollutant and undergoes......... .

4 .........plant has become a troublesome weed in agricultural fields.

5 .........are major aerosol pollutant present in jet aircraft emission.

A.

B.

C.

D.

E.

Discarded computer parts like monitors, key boards, mouse etc.

Make a chart illustrating the kinds of water pollutants.

Discuss the causes and effects of global warming. What measures need to be taken to control global warming?

2. What is the norm set by Euro II for petrol and diesel vehicles ?

(a) How was the algal bloom caused ?

(b) What would be the consequences ?

(c) Give the term for the cause of it.

Write critical notes on the following:
(a) Eutrophication
(b) Biological magnification
(c) Groundwater depletion and ways for its replenishment

(a) Radioactive wastes.

(b) Defunct ships and e-wastes.

(c) Municipal solid wastes.

(a) Greenhouse gases.

(b) Catalytic converter

(c) Ultraviolet B

List all the wastes that you generate, at home, school or during your trips to other places. Could you very easily reduce the generation of these wastes? Which would be difficult or rather impossible to reduce?

Why does ozone hole form over Antarctica? How will enhanced ultraviolet radiations affect us?

Write the name of the organism that is referred to as the 'Terror of Bengal'.

State the cause of accelerated eutrophication.

'Determination of Biological Oxygen Demand (BOD) can help in suggesting the quality of a water body.' Explain.

Since October 02, 2014 'Swachh Bharat Abhiyan' has been launched in our country.

(a) Write your views on this initiative giving justification.

(b) As a biologist name two problems that you may face while implementing the programme in your locality.

(c) Suggest two remedial methods to overcome these problems.

Name any two sources of e-Wastes and write two different ways for their disposal.

How have human activities caused desertification? Explain. 

How does algal bloom destroy the quality of a fresh water body? Explain.

Why is Eichhornia crassipes nicknamed as Terror of Bengal? 

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.

Why is it desirable to use unleaded petrol in vehicles fitted with catalytic converters?

Mention two advantages for preferring CNG over diesel as an automobile fuel.

Explain the relationship between CFCs and Ozone in the stratosphere.

Excessive nutrients in a fresh water body cause fish mortality. Give two reasons

(a) Name any two places where it is essential to install electrostatic percipitators. Why is it required to do so?

(b) Mention one limitation of the electrostatic precipitator.

How do algal blooms affect the life in water bodies? 

Give reasons why:
a. Most zygotes in angiosperms divide only after certain amount of endosperm is formed.

b. Groundnut seeds are exalbuminous and castor seeds are albuminous.

c. Micropyle remains as a small pore in the seed coat of a seed.

d. Integuments of an ovule harden and the water content is highly reduced, as the seed matures.

e. Apple and cashew are not called true fruits.

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.

(a) List the three states the annuals and biennial angiosperms have to pass through during their life cycle.
(b) List and describe any two vegetative propagules in flowering plants.

Describe how do ‘flocs’ and ‘activated sludge’ help in sewage treatment.

Explain the role(s) of the following in biotechnology.
(a) Restriction endonuclease
(b) Gel-electrophoresis
(c) Selectable markers in pBR322

Public all over India is very much concerned about the deteriorating air quality in large parts of North India. Alarmed by this situation the Resident’s Welfare Association of your locality organised an awareness programme entitled ‘Bury not burn’. They invited you, being a biology student to participate.
(a) How would you justify your arguments that promote burying and discourage burning?
(Give two reasons)
(b) With the help of flow charts, one for each practice, depict the chain of events that follow.

List four benefits to human life by eliminating the use of CFCs .

Secondary treatment of the sewage is also called Biological treatment. Justify this statement and explain the process

How did a citizen group called Friends of Arcata Marsh, Arcata, California, USA, help to improve water quality of the marshland using Integrated Waste Water Treatment ? Explain in four steps.

Looking at the deteriorating air quality because of air pollution in many cities of the country, the citizens are very much worried and concerned about their health. The doctors have declared a health emergency in the cities where the air quality is very severely poor.

(a) Mention any two major causes of air pollution.

(b) Write the two harmful effects of air pollution on plants and humans.

(c) As a captain of your school Eco-club, suggest any two programmes you would plan to organise in the school so as to bring awareness among the students on how to check air pollution in and around the school

Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancers

• ozone

• ammonia

• methane

• nitrous oxide

Joint Forest management Concept was introduced in India during

• 1970s

• 1980s

• 1990s

• 1960s

A river with an inflow of domestic sewage-rich in organic waste may result in

• increased population of aquatic food web organism

• an increased production of fish due to biodegradable nutrients

• death of fish due to lack of oxygen

• drying of the river very soon due to algal bloom

Kyoto Protocol was endorsed at 

• CoP-3

• CoP-5

• Cop-6

• CoP-4

Global warming can be controlled by

• Reducing deforestation, cutting down use of fossil fuel

• Reducing reforestation, increasing the use of fossil fuel

• Increasing deforestation, slowing down the growth of human population

• Increasing deforestation reducing efficiency of energy usage

The air prevention and control of pollution Act came into force in

• 1975

• 1981

• 1985

• 1990

The UN conference of Parties on climate change in the year 2012 was held at

• Durban

• Doha

• Lima

• Warsaw

Increase in concentration of the toxicant at successive tropic levels is known as 

• biomagnification

• biodeterioration

• biotransformation

• biogeochemical cycling

Acid rain is caused by increase in the atmospheric concentration of

Eutrophication of water bodies leading to killing of fishes is mainly due to non-availability of 

• food

• light

• essential minerals

• oxygen

In an area where DDT had been used extensively, the population of birds declined significantly because

• birds stopped laying eggs

• earthworms in the area got eradicated

• cobras were feeding exclusively on birds

• many of the birds eggs laid, did not hatch

Which one of the following is a wrong statement

• Most of the forests have been lost in tropical areas

• Ozone in upper part of atmosphere is harmful to animals

• Greenhouse effect is a natural Phenomenon

• Eutrophication is a natural phenomenon in freshwater bodies

Measuring Biochemical Oxygen Demand (BOD) is a method used for

• Estimating the amount of organic matter in sewage water

• Working out the efficiency of oil driven automobile engines

• Measuring the activity of Saccharomyces cerevisae in producing curd on a commercial scale

• Working out the efficiency of oil driven automobile engines

The zone of atmosphere in which the ozone layer is present is called 

• ionosphere

• mesophere

• stratosphere

• troposphere

The organisation which publishes the Red List of species is

• ICFRE

• IUCN

• UNEP

• WWF

A scrubber in the exhaust of a chemical industrial plant removes

• Gases like sulphur dioxide

• Particulate matter of the size 5 micrometre or above

• Gases like ozone and methane

• Particulate matter of the size 2.5 micrometre or less

The domestic sewage in large cities

• has a high BOD as it contains both aerobic and anaerobic bacteria

• is processed by aerobic and then anaerobic bacteria in the secondary treatment is Sewage Treatment Plants (STPs)

• When treated in STPs does not really require the aeration step as the sewage contains adequate adequate oxygen

• has very high amounts of suspended solids and dissolved salts

The UN Conference of Parties on climate change in the year 2011 was held in

• Poland

• South Africa

• Peru

• Qatar

High value of BOD (Biochemical Oxygen Demand) indicates that

• water is pure

• water is highly polluted

• water is less polluted

• consumer of organic matter in the water is higher by the microbes

Rachel Carson's famous book 'Silent Spring' is related to

• pesticide pollution

• noise pollution

• population explosion

• ecosystem management

Which of the following is not one of the prime health risks associated with greater UV radiation through the atmosphere due to depletion of stratospheric ozone?

• Increased skin cancer

• Reduced Immune System

• Damage to eyes

• Increased liver cancer

Which one of the following pairs of gases are the major cause of 'Greenhouse Effect'?

• CO₂ and CO

• CFCs and SO₂

• CO₂ and N₂O

• CO₂ and O₃

Which one of the following expanded forms of the followings acronyms is correct?

• UNEP = United Nations Environmental Policy

• EPA = Environmental Pollution Agency

• IUCN = International Union for Conservation of Nature and Natural Resources

• IPCC = International Panel for Climate Change

Which one of the following statements in wrong in case Bhopal gas tragedy?

• Thousands of human beings died

• Radioactive fallout engulfed Bhopal

• It took place on the night of December 2/3, 1984

• Methyl isocyanate gas leakage took place

Eutrophication is often seen in 

• fresh water lakes

• Ocean

• Mountains

• deserts

Good ozone is found in the 

• mesosphere

• troposphere

• stratosphere

• ionosphere

Select the correct statement from the following

• Bio-gas is produced by the activity of aerobic bacteria on animal waste

• Methanobacterium is an aerobic bacterium found in rumen of cattle

• Biogas, commonly called gobar gas, is pure methane

• Activated sludge-sediment in settlement tanks of sewage treatment plant is a right source of aerobic bacteria

Which two of the following changes (1-4) usually tend to occur in the plain dwellers when they move to high altitudes (3500 m or more)?

1) Increase in red blood cell size
2) Increase in red blood cell production
3) Increase in breathing rate
4) Increase in thrombocytes count

Changes occurring are

• (2) and (3)

• (3) and (4)

• (1) and (4)

• (1) and (2)

A renewable exhaustible natural resource is

• coal

• petroleum

• minerals

• forest

dB is a standard abbreviation used for the quantitative expression of 

• the density of bacteria in a medium

• a particular pollutant

• the dominant Bacillus in a culture

• a certain pesticide

The two gases making highest relative contribution to the green house gases are

• CO₂ and CH₄

• CH₄ and NO₂

• CFCs and N₂O

• CO₂ and N₂O

Which one of the following is not used in organic farming?

• Glomus

• Earthworm

• Oscillatoria

• Snail

Chipko movement was launched for the protection of 

• grasslands

• forests

• livestock

• Wet lands

Montreal protocol aims at

• reduction of ozone depleting substances

• biodiversity conservation

• control of water pollution

• control of CO₂ emission

Steps taken by the Government of India to control air pollution include

• compulsory mixing of 20% ethyl alcohol with petrol and 20% biodiesel with diesel

• Compulsory PUC (pollution Under control) certification of petrol driven vehicles, which tests for carbon monoxide and hydrocarbons

• permission to use only pure diesel with a maximum of 500 ppm sulphur as fuel for vehicles

• Use of non-polluting Compressed natural Gas (CNG) only as fuel by all buses and trucks

Global agreement on specific control strategies to reduce the release of ozone depleting substance was adopted by

• Rio de Janerio Conference

• The Montreal protocol

• The koyoto protocol

• The Vienna convention

A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this

(1) lost of urea and phosphate fertiliser were used in the crops in the vicinity.

(2) The area was sprayed with DDT by an aircraft.

(3) The lake water turned green and stinky/

(4) Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis.

Which were two of above the main causes of fish mortality in the lake?

• 2, 3

• 3, 4

• 1,3

• 1,2

About 70% of total global carbon is found in 

• grasslands

• agro -ecosystem

• Oceans

• forests

Modern detergents contain enzyme preparations of 

• acidophiles 

• alkaliphiles

• thermoacidophiles 

• thermophiles

According to central pollution control Board (CPCB), which particulate size in diameter (n micrometres) of the air pollutants is responsible for greatest harm to human health?

• 2.5 or less

• 1.5 or less

• 1.0 or less 

• 5.2 or 2.5 

Which one of the flowing is the correct percentage of the two (out of the total of 4 ) green-house gases that contribute to the total global warming? 

• CFC 14%, CH₄ 20%

• CO₂ 40% CFCs 30%

• N₂O 6%, CO₂ 86%

• CH₄ 20% N₂O 18%

World summit on sustainable development (2002) was held in 

• Brazil

• Sweden

• Argentina

• South Africa

Quercus species are the dominant component in 

• temperature deciduous forests

• alpine forests

• scrub forests

• tropical rain forests

Which one of the following statements is correct?

• Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies

• Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants.

• Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and for plant nutrition in soil.

• At present it is not possible to grow maize without chemical fertilizers.

Which one of the following is being utilised as a source of biodiesel in the Indian countryside?

• betroot

• sugarcane

• pongamia

• euphorbia

In which one of the following the BOD (Biochemical Oxygen Demand ) of sewage (s), distillery effluent (DE), paper mill effluent (PE) and sugar mill effluent (SE) have been arranged in ascending order?

• SE < S < PE < DE

• SE < PE < S < DE

• PE < S < SE < DE

• S < DE < PE < SE

In a coal-fired power plant, electrostatic precipitators are installed to control emission of

• SO₂

• NO_X

• SPM

• CO

Which one of the following is not a bioindicator of water pollution?

• Sludge-worms

• Blood-worms

• Stone files

• Sewage fungus

Montreal Protocol which calls for appropriate action to protect the ozone layer from human activities was passed in the year

• 1986

• 1987

• 1988

• 1985

Photochemical smog pollution does not contain

• ozone

• nitrogen dioxide

• carbon dioxide

• PAN (Peroxy Acyl Nitrate)

Limit of BOD prescribed by Central Pollution Control Board for the discharge of industrial and municipal waste water into natural surface water, is:

• < 3.0 ppm

• < 10 ppm

• < 100 ppm

• < 30 ppm

Which one of the following statements is not valid for aerosols?

• They are harmful to human health

• They alter rainfall and monsoon patterns

• They cause increased agricultural productivity

• They have negative impact on agricultural land

Which of the following in sewage treatment remove suspended solids?

• Tertiary treatment

• Secondary treatment

• Primary treatment

• Sludge treatment

IUCN stands for 

• Indian Union for Conservation of Nature

• International Union for Conservation of Nature

• Indian Union of Chemical Nomenclature

• International Union for the conservation of Nutrients

Which one of the following combination is incorrect?

• Rio convention → Air pollution

• Kyoto protocol  → Climate change

• Montreal Protocol → Ozone depletion

• Ramsar Convention → Wetland conservation

Soil salinity is measured by

• Porometer

• Calorimeter

• Conductivity meter

• Potometer

Which of the following species are restricted to an area?

• Sympatric species

• Sibling species

• Allopatric species

• Endemic species

Factor govering the earth surface is

• Topographic

• Edaphic

• Temperature

• Biotic

Biological treatment of water pollution is done with the help of

• Fungi

• Lichen

• Phytoplanktons

• None of the above

Which insecticide is more hazardous to human health?

• Rotenone

• Pyrethrum

• DDT

• Humulin

In a cola fired power plant, electrostatic precipitators are installed to control emission of

• SO₂

• NO_x

• SPM

• CO

A lake with an inflow of domestic sewage rich in organic waste may result in

• Drying of the lake very soon due to algal bloom

• An increased production of fish due to lot of nutrients

• Death of fish due to lack of oxygen

• Increased population of the aquatic food web organisms

Besides dung, the weed that can be used in biogas production is

• Hydrilla

• Solanum- nigrum

• Eichhornia Crassipes

• Parthenium hysterophorus

Amount of Co, in expired air is about

• 0.04%

• 0.03%

• 4.5%

• 21%

Minamata disease is caused due to the presence of in water.

• Cadmium

• Lead

• Arsenic

• Mercury

The Montreal Protocol refers to

• Persistent organic pollutants

• Global warming and climate change

• Substances that deplete the ozone layer

• Biosafety of genetically modified organisms

Ozone depletion in staratosphere would result in 

• forest fires

• global warming

• skin cancer incidence

• None of the above

Which is always present in photochemical smog?

• O₃

• CO₂

• SO₂

• CH₄

The soil which is transported by wind is known as

• colluvial

• eolian

• aluvial

• glacial soil

In the treatment of waste water discharge, which treatment stage involves biological treatment?

• Primary treatment

• Secondary treatment

• Tertiary treatment

• Reverse osmosis stage

Ozone depletion in stratosphere would result in 

• forest fires

• global warming

• skin cancer incidence

• None of the above

A lake with nutrients is called

• trophic

• euphotic

• oligotrophic

• eutrophic

According to Kyoto protocol the major nations abide to reduce concentration of green house gases by

• 2008

• 2010

• 2012

• 2018

Bio- indicators are used for

• oxygen demand

• air pollution

• mineral present

• All of the above