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Biology
Environmental Issues
94 questions from 32 papers, each with its answer.
- 94 questions
- 32 papers
- 2.67% of Biology
Ozone Depletion in the Stratosphere
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The thickness of ozone in a column of air in the atmosphere is measured in terms of:
Ozone column thickness is measured in Dobson units.
The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU). -
Dobson units are used to measure thickness of:
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Montreal protocol was signed in 1987 for control of:The Montreal Protocol was signed at Montreal (Canada) in 1987 (effective from 1989) to control the emission of ozone depleting substances.
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Which of the following protocols did aim for reducing emission of chloroflurocarbons into the atmosphere?
Air Pollution and Its Control – Electrostatic Precipitator
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Given below are two statements: Statement I: Electrostatic precipitator is most widely used in thermal power plant. Statement II: Electrostatic precipitator in thermal power plant removes ionising radiations In the light of the above statements, choose the most appropriate answer from the options given below:
An electrostatic precipitator removes particulate matter, not ionising radiation.
There are several ways of removing particulate matter; the most widely used of which is the electrostatic precipitator, which can remove over 99 per cent particulate matter present in the exhaust from a thermal power plant.
Air Pollution and Its Control
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The device which can remove particulate matter present in the exhaust from a thermal power plant is:
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In a coal fired power plant electrostatic precipitators are installed to control emission ofThermal power plants that burn coal release particulate and gaseous air pollutants.
The electrostatic precipitator is the most widely used device for removing particulate matter; it can remove over 99 percent of the particulate matter present in the exhaust of a thermal power plant.
It has electrode wires maintained at several thousand volts, which produce a corona that releases electrons.
These electrons attach to the dust particles and give them a net negative charge; the charged particles are then attracted to and collected on earthed plates.
So electrostatic precipitators control the emission of SPM (suspended particulate matter).
Gases such as $SO_2$ are removed by a scrubber, and CO and $NO_x$ from vehicles are controlled by catalytic converters.
Air Pollution – Case Study of Delhi
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The entire fleet of buses in Delhi were converted to CNG from diesel. In reference to this, which one of the following statements is false?
Ozone Depletion in the Stratosphere – Effects of UV-B
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Snow-blindness in Antarctic region is due to:In the human eye, the cornea absorbs UV-B radiation. A high dose of UV-B causes inflammation of the cornea, called snow-blindness.
Solid Waste Management – Radioactive Wastes
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Which of these following methods is the most suitable for disposal of nuclear waste?
Greenhouse Effect and Global Warming
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Which of the following pairs of gases is mainly responsible for green house effect?
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Which one of the following pairs of gases are the major cause of \"Greenhouse Effect\""?"Greenhouse gases absorb the long-wave (infra-red) radiation emitted by the earth and so warm the atmosphere.
The relative contributions of the greenhouse gases to total global warming are: $CO_2$ 60%, $CH_4$ 20%, CFCs 14% and $N_2O$ 6%.
So $CO_2$ and $N_2O$ are both recognised greenhouse gases.
CO and $SO_2$ are air pollutants but are not listed among the greenhouse gases, and ozone is not one of the four major contributors.
Among the given pairs, the one in which both gases are major greenhouse gases is $CO_2$ and $N_2O$. -
The two gases making highest relative contribution to the greenhouse gases areRelative contribution of the greenhouse gases to total global warming: $CO_2$ 60%, $CH_4$ 20%, CFCs 14% and $N_2O$ 6%.
The two largest contributors are carbon dioxide (60%) and methane (20%).
Hence the two gases are $CO_2$ and $CH_4$. -
Which one of the following is the correct percentage of the two (out of the total of 4) greenhouse gases that contribute to the total global warming ?The four main greenhouse gases and their relative contributions to total global warming (as given in NCERT) are:
Carbon dioxide ($CO_2$) - 60 percent
Methane ($CH_4$) - 20 percent
Chlorofluorocarbons (CFCs) - 14 percent
Nitrous oxide ($N_2O$) - 6 percent
Checking the pairs: $CO_2$ is 60 percent (not 86 or 40), $N_2O$ is 6 percent (not 18) and CFCs are 14 percent (not 30).
The only pair in which both values are correct is CFCs 14% and Methane 20%. -
Maximum green house gas released by which country : -Greenhouse gases such as $CO_2$, methane and nitrous oxide are released mainly by burning fossil fuels in industry, power plants and transport.
At the time of this paper, the U.S.A., being the most industrialised country with very high per capita energy use, released the largest amount of greenhouse gases in the world.
(In later years China's total emissions became the largest, though the U.S.A. still has much higher emissions per person.)
So, at the time of this question, the maximum greenhouse gas was released by the U.S.A.
Solid Waste Management – Plastics
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Polyblend, a fine powder of recycled modified plastic, has proved to be a good material for:
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Which of the following is an innovative remedy for plastic waste?
Air pollution control - CNG
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Why CNG is considered better fuel than diesel? (a) It can not be adulterated. (b) It takes less time to fill the fuel tank. (c) It burns more efficiently. (d) It is cheaper. (e) It is less inflammable. Choose the most appropriate answer from the options given below:CNG burns most efficiently, is cheaper than petrol or diesel, and cannot be siphoned off by thieves or adulterated. So (a), (c) and (d) are correct.
Ozone depletion
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Which of the following statements about ozone is correct?
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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?Greater UV radiation from ozone depletion causes mutations, skin cancer, eye damage and reduced immunity.
Liver cancer is not one of its health risks. -
\"Good ozone\"" is found in the"Ozone is called 'good' or 'bad' depending on where it is found.
Good ozone is found in the upper part of the atmosphere called the stratosphere, where it acts as a shield absorbing the harmful ultraviolet radiation from the sun.
Bad ozone is formed in the lower atmosphere (troposphere), where it is a pollutant that harms plants and animals.
The thickness of the ozone layer is measured in Dobson units.
Hence good ozone is found in the stratosphere. -
Montreal protocol aims atThe Montreal Protocol is an international treaty signed at Montreal, Canada, in 1987 (effective from 1989).
Its aim is to control the emission of ozone-depleting substances such as CFCs, in order to protect the ozone layer of the stratosphere.
Control of $CO_2$ and other greenhouse gases is the aim of the Kyoto Protocol.
Biodiversity conservation was the subject of the Earth Summit at Rio de Janeiro (1992).
Hence the Montreal Protocol aims at the reduction of ozone depleting substances. -
Global agreement in specific control strategies to reduce the release of ozone depleting substances was adopted byThe Montreal Protocol was signed at Montreal (Canada) in 1987 and became effective in 1989.
It laid down definite control strategies and time-bound road maps, separately for developed and developing countries, for reducing the emission of CFCs and other ozone-depleting chemicals.
The Vienna Convention (1985) only provided a general framework for protecting the ozone layer, without specific control measures.
The Rio de Janeiro conference (1992) dealt with biodiversity and sustainable development, and the Kyoto Protocol (1997) with greenhouse gases.
Hence the specific control strategies were adopted by the Montreal Protocol. -
Montreal Protocol which calls for appropriate action to protect the ozone layer from human activities was passed in the year -Ozone in the stratosphere absorbs the harmful ultraviolet radiation of the sun.
Chlorofluorocarbons (CFCs) and other ozone depleting substances release chlorine atoms in the stratosphere, which break down ozone and have caused the ozone hole over Antarctica.
Recognising this, an international treaty known as the Montreal Protocol was signed at Montreal (Canada) in 1987 to control the emission of ozone depleting substances.
It became effective in 1989.
Subsequently many more efforts were made, and protocols have laid down definite roadmaps, separately for developed and developing countries, for reducing the emission of CFCs and other ozone depleting chemicals.
So the Montreal Protocol was passed in the year 1987.
Soil salinity due to irrigation
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If an agricultural field is liberally irrigated for a prolonged period of time, it is likely to face problem of:
Ozone depletion – World Ozone Day
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World Ozone Day is celebrated on
Ozone Day (16 Sept) marks the Montreal Protocol.
World Ozone Day is celebrated on 16th September. 5th June – World Environment Day; 22nd April – Earth Day; 21st April – National Yellow Bat Day.
Air pollution – primary and secondary pollutants
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Which of the following is a secondary pollutant?
Ground-level ozone forms from reactions of primary pollutants.
$O_3$ (ozone) is a secondary pollutant. Secondary pollutants are formed by the reaction of primary pollutants. CO – quantitative pollutant; $CO_2$ – primary pollutant; $SO_2$ – primary pollutant.
Ozone depletion by CFCs
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In stratosphere, which of the following elements acts as a catalyst in degradation of ozone and release of molecular oxygen?
Cl atoms from CFCs catalytically destroy ozone.
UV rays act on CFCs, releasing Cl atoms; chlorine reacts with ozone in a sequential (catalytic) manner, converting it into oxygen. Carbon, oxygen and Fe are not related to ozone layer depletion.
Pollution, ozone depletion and deforestation
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Match the items given in Column I with those in Column II and select the correct option given below:
Pick the matching item from Column II for each row.
Column I
- a. Eutrophication
- b. Sanitary landfill
- c. Snow blindness
- d. Jhum cultivation
Column II
- i. UV-B radiation
- ii. Deforestation
- iii. Nutrient enrichment
- iv. Waste disposal
Correct answer: a → iii, b → iv, c → i, d → ii
Eutrophication, landfill, snow blindness and jhum map to nutrients, waste, UV-B and deforestation.
Eutrophication – nutrient enrichment Sanitary landfill – waste disposal Snow blindness – UV-B radiation Jhum cultivation – deforestation Correct match: a-iii, b-iv, c-i, d-ii.
Ozone depletion – UV and skin cancer
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Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancers
Loss of stratospheric ozone increases UV-B exposure.
The ozone layer in the stratosphere prevents UV radiation from reaching the earth. Release of CFCs depletes ozone, forming holes that allow UV radiation to reach the earth and cause skin cancer.
Deforestation – Joint Forest Management
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Joint Forest Management Concept was introduced in India during'Out of Syllabus'
Water pollution – BOD
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A river with an inflow of domestic sewage rich in organic waste may result in
High BOD depletes dissolved oxygen.
Organic waste in sewage is decomposed by microbes that use up dissolved oxygen, increasing the biological oxygen demand (BOD). This causes death of fish due to lack of oxygen.
Soil conservation – ley farming
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A system of rotating crops with legume or grass pasture to improve soil structure and fertility is called
Rotation with grass/legume pasture = ley farming.
Ley farming involves rotation of crops with legume plants and grass pasture to improve the fertility and health of the soil; it also helps prevent pests by disrupting their life cycles.
Water pollution – organic waste and BOD
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A lake which is rich in organic waste may result in:
Biomagnification
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The highest DDT concentration in aquatic food chain shall occur in:
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Increase in concentration of the toxicant at successive trophic levels is known as:
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In an area where DDT had been used extensively, the population of birds declined significantly becauseDDT accumulates along the food chain (biomagnification) and reaches high concentrations in fish-eating birds.
It disturbs calcium metabolism in birds, which causes thinning of the egg shell and premature breaking of eggs.
So many of the eggs laid did not hatch and the bird population declined. -
DDT residues are rapidly passed through food chain causing biomagnification because DDT isBiomagnification is the increase in concentration of a toxicant at successive trophic levels.
It happens because the toxic substance accumulated by an organism cannot be metabolised or excreted, and is passed on to the next higher trophic level.
DDT is insoluble in water but soluble in fats (lipo-soluble); it is stored in the body fat of organisms and is not broken down.
So its concentration rises at each step: for example, from 0.003 ppb in water to 25 ppm in fish-eating birds.
Hence DDT is biomagnified because it is lipo soluble.
Climate change conferences
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The UN conference of Parties on climate change in the year 2011 was held inThe 2011 UN Conference of Parties on Climate Change was held in Durban, South Africa, where it was agreed to work towards a new treaty to limit carbon emissions.
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The UN conference of Parties on climate change in the year 2012 was held at:
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Kyoto Protocol was endorsed at:The Kyoto Protocol was adopted at the third Conference of Parties (CoP-3) of the UNFCCC, held in Kyoto, Japan in 1997.
Pesticides and biomagnification
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Rachel Carson's famous book 'Silent Spring' is related toSilent Spring describes the entry of DDT into food chains and its effects on animals at different trophic levels, i.e. pesticide pollution.
Water pollution
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Eutrophication of water bodies leading to killing of fishes is mainly due to non-availability of:
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Eutrophication is often seen inEutrophication is the natural ageing of a lake by nutrient enrichment of its water.
Streams draining into a lake bring nutrients such as nitrates and phosphates, which encourage the growth of aquatic organisms and algal blooms.
Organic remains accumulate at the bottom, the lake becomes shallower and warmer, and it is gradually converted into land.
Pollutants from sewage and agricultural and industrial wastes greatly speed up this process (cultural or accelerated eutrophication).
It is a phenomenon of standing fresh water bodies and is not seen on mountains or deserts; the open ocean is too large and well mixed.
Hence eutrophication is often seen in fresh water lakes. -
When domestic sewage mixes with river waterDomestic sewage contains a large amount of biodegradable organic matter.
Micro-organisms in the receiving water body decompose this organic matter, and in doing so they consume a lot of oxygen.
As a result there is a sharp decline in dissolved oxygen downstream from the point of sewage discharge (high BOD), which causes mortality of fish and other aquatic creatures.
Although the impurities are only about 0.1%, they include pathogens and make the water unfit for drinking.
Hence the increased microbial activity uses up dissolved oxygen. -
Biochemical Oxygen Demand (BOD) in a river waterBOD is the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria.
It is therefore an indirect measure of the organic matter present in the water: the greater the BOD, the greater the polluting potential.
Sewage contains a large amount of biodegradable organic matter, so when it mixes with river water the BOD increases, and the dissolved oxygen falls sharply.
An algal bloom also adds organic matter when the algae die, so BOD does not remain unchanged.
BOD is not a count of any particular bacterium such as $Salmonella$.
Hence BOD increases when sewage gets mixed with river water.
Air pollution
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Acid rain is caused by increase in the atmospheric concentration of:
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Which of the following are most suitable indicator of $SO_2$ pollution in the environment?
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A location with luxuriant growth of lichens on the trees indicates that the:Lichens are very sensitive to air pollution, especially $SO_2$, and do not grow in polluted areas. Their luxuriant growth shows the location is not polluted.
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The Air Prevention and Control of Pollution Act came into force in:The Air (Prevention and Control of Pollution) Act came into force in 1981 and was amended in 1987 to include noise.
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Which one of the following statements is wrong in case of Bhopal tragedy?The Bhopal gas tragedy took place on the night of 2–3 December 1984 at the Union Carbide pesticide plant in Bhopal.
About 40 tonnes of the highly toxic gas methyl isocyanate (MIC) leaked from a storage tank.
Thousands of people died and many more suffered lasting damage to their lungs and eyes.
It was a chemical (industrial gas leak) disaster; no radioactive material was involved, so there was no radioactive fall out.
Hence the wrong statement is that radioactive fall out engulfed Bhopal. -
According to Central Pollution Control Board (CPCB), which particulate size in diameter (in micrometers) of the air pollutants is responsible for greatest harm to human health?Particulate matter is one of the major air pollutants released from thermal power plants, smelters, industries and vehicles.
According to the Central Pollution Control Board (CPCB), particulate size 2.5 micrometers or less in diameter (PM 2.5) is responsible for causing the greatest harm to human health.
These fine particulates can be inhaled deep into the lungs, as they are not filtered out by the nose and upper respiratory tract.
They can cause breathing and respiratory symptoms, irritation, inflammation and damage to the lungs, and premature deaths.
Larger particles are trapped in the upper respiratory passages and are removed more easily.
So the particulate size responsible for the greatest harm is 2.5 micrometers or less.
Ozone layer
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The zone of atmosphere in which the ozone layer is present is called:Good ozone forms a layer in the stratosphere, where it absorbs harmful ultraviolet radiation.
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Which one of the following is a wrong statement?Ozone in the upper atmosphere (stratosphere) is good ozone: it absorbs ultraviolet radiation from the sun and protects living organisms.
It is ozone in the lower atmosphere (troposphere) that is harmful.
So the statement that ozone in the upper part of the atmosphere is harmful to animals is wrong.
Air pollution control
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A scrubber in the exhaust of a chemical industrial plant removes:A scrubber removes gases like sulphur dioxide: the exhaust is passed through a spray of water or lime.
Particulate matter is removed by electrostatic precipitators.
Global warming
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Global warming can be controlled by:Global warming can be controlled by cutting down the use of fossil fuel, improving the efficiency of energy usage, reducing deforestation and planting trees.
Natural resources
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A renewable exhaustible natural resource isA renewable resource is one that can be replenished by natural processes or regeneration within a reasonable time.
A forest can regenerate, so it is renewable; but if it is exploited faster than it regrows, it can be used up, so it is also exhaustible.
Coal, petroleum and minerals take millions of years to form; they are non-renewable exhaustible resources.
Hence a renewable exhaustible natural resource is the forest.
Noise pollution
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dB is a standard abbreviation used for the quantitative expression ofdB stands for decibel, the unit in which the intensity (loudness) of sound is expressed.
Noise is undesired high level of sound and is recognised as an air pollutant; noise pollution is therefore measured in decibels.
A sound level of 150 dB or more, such as that of a jet plane or rocket taking off, may damage the ear drums and permanently impair hearing.
Hence dB is used for the quantitative expression of a particular pollutant (noise). -
What is the intensity of sound in normal conversation : -Sound intensity is measured in decibels (dB).
Normal conversation is about 30–60 dB (often quoted as about 60 dB).
A whisper is about 20 dB, heavy traffic about 80–90 dB, and a jet plane at take-off about 150 dB. Sound above 80 dB is harmful, and above 120 dB causes pain and can damage hearing.
So the intensity of sound in normal conversation is 30–60 decibel.
Deforestation and people's participation
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Chipko movement was launched for the protection ofThe Chipko movement started in 1974 in the Garhwal Himalayas.
Local women showed enormous bravery in protecting trees from the axes of contractors by hugging them ('chipko' means to hug or cling).
It is a well-known example of people's participation in the conservation of forests.
Hence the Chipko movement was launched for the protection of forests.
Biofuels
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Which one of the following is being tried in India as a biofuel substitute for fossil fuels?Biofuels are fuels obtained from biological sources and are renewable substitutes for fossil fuels.
Jatropha curcas (family Euphorbiaceae) is a hardy shrub that grows on wastelands and in dry areas.
Its seeds contain about 30 to 40 percent of non-edible oil, which is converted into biodiesel by transesterification.
For this reason Jatropha is being cultivated and tried in India as a biofuel (biodiesel) substitute for fossil fuels.
Musa is banana, Aegilops is a wild grass related to wheat, and Azadirachta is neem, known for the biopesticide azadirachtin; none of these is the biodiesel crop.
So the answer is Jatropha. -
Which one of the following is being utilized as a source of biodiesel in the Indian countryside?Biodiesel is a renewable fuel obtained from vegetable oils by transesterification.
Pongamia pinnata (pongam or karanja) is a leguminous, nitrogen-fixing tree whose seeds contain 30-40 percent oil.
It is commonly planted as an ornamental and shade tree, and in the Indian countryside its seed oil is being used as a source of biodiesel.
Jatropha is another important biodiesel plant.
Sugarcane and beetroot are sources of sugar, which is fermented to give ethanol (bioethanol), not biodiesel.
Euphorbia species are petrocrops that yield latex rich in hydrocarbons, but they are not the source being utilised for biodiesel in the countryside.
So the answer is Pongamia.
Eutrophication
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Which one of the following statements is correct?Chemical fertilisers, mainly nitrates and phosphates, that are used in excess are washed from the fields into nearby ponds, lakes and rivers.
This nutrient enrichment causes heavy growth of algae (algal bloom) and, later, depletion of oxygen in the water. The process is called eutrophication. So this statement is correct.
Rhizobium fixes nitrogen in the root nodules of legumes, but Azotobacter is a free-living nitrogen-fixing bacterium of the soil; it does not live in root nodules.
Anabaena and Nostoc are nitrogen-fixing cyanobacteria. Phosphates are mobilised mainly by mycorrhizal fungi.
Maize, like other crops, can be grown without chemical fertilisers, using organic manures and biofertilisers (organic farming).
So the correct statement is that extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies.
Energy Sources and Pollution
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Which one of the following pairs is mismatched -Nuclear power plants produce radioactive wastes, which are very harmful and must be stored safely; correctly matched.
Burning of fossil fuels (coal, petroleum) releases large amounts of $CO_2$; correctly matched.
Burning of biomass (wood, crop residues, dung) also releases $CO_2$; correctly matched.
Solar energy is a clean, non-polluting, renewable source of energy. Using it does not release greenhouse gases, so it does not cause the greenhouse effect.
(The greenhouse effect is caused by gases such as $CO_2$, $CH_4$, CFCs and $N_2O$ trapping the heat radiated by the earth.)
So the mismatched pair is solar energy - greenhouse effect.
Water Treatment
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Which of the following is not used for disinfection of drinking water -Disinfection is the destruction of disease-causing micro-organisms in water.
Chlorine is the most commonly used disinfectant for drinking water; it kills bacteria and other pathogens.
Chloramines (formed from chlorine and ammonia) are used because they give a longer lasting disinfection.
Ozone is a powerful oxidising agent and is also used to disinfect drinking water.
Phenyl (phenol-based disinfectant) is used for cleaning floors and toilets. It is toxic and gives an unpleasant taste and smell, so it is never used for disinfecting drinking water.
So the one not used is phenyl.
International Environmental Agreements
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Identify the correctly matched pair -The Kyoto Protocol (1997) is an international agreement under the UN Framework Convention on Climate Change; it commits industrialised countries to reduce their emissions of greenhouse gases. So Kyoto Protocol - climatic change is correct.
The Montreal Protocol (1987) deals with the protection of the ozone layer by controlling ozone depleting substances, not with global warming.
The Basel Convention (1989) deals with the control of the movement and disposal of hazardous wastes across borders, not with biodiversity conservation.
The Ramsar Convention (1971) deals with the conservation of wetlands, not with ground water pollution.
So the correctly matched pair is Kyoto protocol - climatic change.
Soil Degradation
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Prolonged liberal irrigation of agricultural fields is likely to create the problem of -Irrigation water always contains dissolved salts.
When fields are irrigated heavily for a long time without proper drainage, the water table rises (waterlogging), and the water evaporates from the soil surface, leaving the salts behind.
The salts are also drawn up to the surface by capillary action.
Over the years the salts accumulate in the upper layers of the soil, forming a white crust; the soil becomes saline and its fertility falls, and crop growth is badly affected.
This problem of salinity is seen in many irrigated areas, for example parts of Punjab and Haryana.
So prolonged liberal irrigation is likely to create the problem of salinity.
Air Pollution: Industrial Accidents
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In 1984, the Bhopal gas tragedy took place because methyl isocyanate :-In December 1984, a large amount of methyl isocyanate (MIC, $CH_3NCO$) gas leaked from the Union Carbide pesticide factory in Bhopal.
Water entered a storage tank of MIC. MIC reacts with water in a strongly exothermic reaction:
$CH_3NCO + H_2O \rightarrow CH_3NH_2 + CO_2$ (with release of a large amount of heat)
The heat raised the temperature and pressure in the tank, and the safety systems failed, so a cloud of toxic MIC gas escaped into the city. Thousands of people died and many more suffered lung and eye damage.
So the tragedy took place because methyl isocyanate reacted with water.
Alternative Fuels: Ethanol Blending
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Recently Govt. of India has allowed mixing of alcohol in petrol. What is the amount of alcohol permitted for mixing in petrol :-To reduce dependence on imported petrol and to reduce pollution, the Government of India started the ethanol blended petrol programme in 2003.
Under this programme, petrol was allowed to be blended with up to 5 percent ethanol (alcohol made from sugarcane molasses), initially in nine states.
(The blending target was raised in later years, but at the time of this paper it was 5 percent.)
So the amount of alcohol permitted for mixing in petrol was 5%.
Water Pollution: Indicators
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Common indicator organism of water pollution is :-Escherichia coli (a coliform bacterium) lives normally in the intestine of humans and other warm-blooded animals and is passed out in faeces in huge numbers.
Its presence in water shows that the water is contaminated with sewage (faecal matter) and may contain disease-causing organisms. So the coliform count (E. coli count) is the standard test of the quality of drinking water.
Eichhornia (water hyacinth) and Lemna grow abundantly in nutrient-rich (eutrophic) water but are not the standard indicator. Entamoeba is a pathogen, not a routine indicator.
So the common indicator organism of water pollution is Escherichia coli. -
Escherichia coli is used as an indicator organism to determine pollution of water with :-Escherichia coli is a normal inhabitant of the human (and animal) large intestine and is passed out in faeces in very large numbers.
So its presence in a water sample shows contamination with sewage (faecal matter), and therefore the possible presence of intestinal pathogens (e.g. those causing cholera, typhoid and dysentery).
The coliform (E. coli) count is the standard test of drinking water quality. It does not indicate heavy metals, industrial effluents or pollen.
So E. coli is used as an indicator of pollution of water with faecal matter.
Water Pollution: Fluoride
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Fluoride pollution mainly affects : -Fluoride is present naturally in the groundwater of some regions (in India, parts of Rajasthan, Andhra Pradesh, Gujarat and others).
In small amounts (about 1 ppm) it protects teeth from decay, but excess fluoride (above about 1.5 ppm) causes fluorosis.
The first and most common effect is dental fluorosis: mottling, brown staining and pitting of the tooth enamel. Higher levels also cause skeletal fluorosis (stiff joints, bone deformities).
So fluoride pollution mainly affects the teeth (and bones).
Water Pollution: Biochemical Oxygen Demand
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What is B.O.D. : -BOD (biochemical oxygen demand) is the amount of oxygen consumed by microorganisms (bacteria) in decomposing (oxidising) the organic matter present in a litre of water, usually measured over 5 days at 20 °C.
It is a measure of the amount of biodegradable organic pollution: the more organic waste (e.g. sewage), the higher the BOD.
So BOD is the amount of $O_2$ utilised by micro-organisms for decomposition.
That is every question in Environmental Issues for this filter.
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