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Biology
Environmental Issues
94 questions from 32 papers, each with its answer.
- 94 questions
- 32 papers
- 2.67% of Biology
Water Pollution and Its Control – Eutrophication and Algal Bloom
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Which of the following answers are NOT correct?
Algal blooms deteriorate water quality and cause fish mortality.
Presence of large amounts of nutrients in waters causes excessive growth of planktonic algae called an algal bloom which imparts a distinct colour to the water bodies. Algal blooms cause deterioration of the water quality and fish mortality. Some bloom forming algae are extremely toxic to human beings and animals.
Water Pollution and Its Control – Biomagnification
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Which of the following statements is correct?
Biomagnification is the increase in toxicant concentration at successive trophic levels.
Algal blooms cause deterioration of the water quality and fish mortality. Eutrophication is the natural aging of a lake by nutrient enrichment of its water. Presence of large amounts of nutrients in waters also causes excessive growth of planktonic (free-floating) algae, called an algal bloom.
Air Pollution and Its Control
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Given below are two statements: Statement I: In a scrubber the exhaust from the thermal plant is passed through the electric wires to charge the dust particles. Statement II: Particulate matter (PM 2.5) can not be removed by scrubber but can be removed by an electrostatic precipitator In the light of the above statements, choose the most appropriate answer from the options given below.
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Steps taken by the Government of India to control air pollution includeEvery petrol-driven vehicle must have a valid PUC (Pollution Under Control) certificate; the test measures the carbon monoxide and hydrocarbons in the exhaust. This is a compulsory step taken by the government.
CNG was made compulsory only for public transport buses in Delhi (by the end of 2002), not for all buses and trucks in the country.
There is no compulsory mixing of 20% alcohol with petrol or 20% biodiesel with diesel.
The norms prescribe much lower sulphur levels (350 ppm and then 50 ppm in diesel under the Euro norms), not simply a 500 ppm limit.
Hence the correct step is compulsory PUC certification of petrol-driven vehicles.
Air (Prevention and Control of Pollution) Act
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Air (Prevention and Control of Pollution) Act was amended in 1987 to include among pollutantsThe Air (Prevention and Control of Pollution) Act was amended in 1987 to include noise as an air pollutant.
Particulate matter and air pollution
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According to Central Pollution Control Board [CPCB] what size (in diameter) of particulate is responsible for causing greater harm to human health?According to the CPCB, particulate matter of size 2.5 micrometers or below (PM2.5) is considered responsible for causing greater harm to human health, as it can penetrate deep into the respiratory system.
Biochemical Oxygen Demand (BOD) and water pollution
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What will happen if fresh water lake gets contaminated by addition of polluted water with high BOD?Water with high BOD contains large amounts of organic matter that consume dissolved oxygen during microbial decomposition, so contamination of a lake with such water decreases the amount of dissolved oxygen in the lake, harming aquatic life.
Deforestation, reforestation, greenhouse effect and eutrophication
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Match List-I with List-II.
Pick the matching item from Column II for each row.
Column I
- A. Deforestation
- B. Reforestation
- C. Green-house effect
- D. Eutrophication
Column II
- I. Responsible for heating of Earth's surface and atmosphere
- II. Conversion of forested areas to non-forested areas
- III. Natural ageing of lake by nutrient enrichment of its water
- IV. Process of restoring a forest that once existed but was removed
Correct answer: A → II, B → IV, C → I, D → III
Deforestation is the conversion of forested areas to non-forested areas (A-II); Reforestation is the process of restoring a forest that once existed but was removed (B-IV); the Green-house effect is responsible for heating of Earth's surface and atmosphere (C-I); Eutrophication is the natural ageing of a lake by nutrient enrichment of its water (D-III).
Biochemical Oxygen Demand and water quality
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Select the correct statements regarding dissolved Oxygen and Biochemical Oxygen Demand. (A) BOD is inversely related to dissolved oxygen. (B) Low dissolved oxygen and high BOD lead to loss of aquatic life. (C) High BOD leads to high dissolved oxygen. (D) Both BOD and dissolved oxygen are indicator of health of a water body. (E) Both BOD and dissolved oxygen are affected by amount of organic matter in the water body. Choose the most appropriate answer from the options given below:BOD is inversely related to dissolved oxygen (A is correct); low dissolved oxygen combined with high BOD leads to loss of aquatic life (B is correct); both BOD and dissolved oxygen are indicators of water body health (D is correct) and are both affected by the amount of organic matter present (E is correct). High BOD actually leads to LOW dissolved oxygen, not high (C is incorrect). So A, B, D, E only.
Air pollution – aerosols
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Which one of the following statements is not valid for aerosols?
Aerosols harm, not help, agricultural productivity.
Aerosols cause various problems to agriculture through their direct or indirect effects on plants; they do not increase agricultural productivity. Continually increasing air pollution may represent a persistent and largely irreversible threat to agriculture in the future.
Water pollution
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The 'blue baby' syndrome results from -Excessive use of nitrogenous fertilisers leads to a high concentration of nitrates in ground water and drinking water.
In the intestine of infants, nitrates are reduced to nitrites by bacteria.
Nitrites enter the blood and oxidise the iron of haemoglobin from the ferrous ($Fe^{2+}$) to the ferric ($Fe^{3+}$) state, forming methaemoglobin.
Methaemoglobin cannot carry oxygen, so the oxygen supply to the tissues falls.
The skin of the baby turns bluish (cyanosis); the condition is called methaemoglobinaemia or 'blue baby' syndrome.
It is not caused by chlorides, dissolved oxygen or total dissolved solids.
So the 'blue baby' syndrome results from methemoglobin.
Eutrophication
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A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this?
(i) Lots of urea and phosphate fertilizer were used in the crops in the vicinity
(ii) The area was sprayed with DDT by an aircraft
(iii) The lake water turned green and stinky
(iv) Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis
Which two of the above were the main causes of fish mortality in the lake?(i) Urea and phosphate fertilisers used in the nearby crop fields are washed into the lake with run-off water. They enrich the water with nitrates and phosphates.
This nutrient enrichment causes an excessive growth of planktonic algae, called an algal bloom, which is the process of accelerated (cultural) eutrophication.
(iii) The algal bloom turns the water green and gives it a foul smell. When the algae die, decomposer microbes break them down and consume the dissolved oxygen of the water; the biochemical oxygen demand rises sharply.
The fall in dissolved oxygen, together with toxins released by some bloom-forming algae, causes heavy mortality of fishes within a few days.
(ii) DDT undergoes biomagnification over a long period and mainly harms the top consumers such as fish-eating birds; it does not cause such sudden mass death of fishes.
(iv) is opposite to what happens: the phytoplankton population increases greatly instead of declining.
So the two main causes are (i) and (iii).
Water Pollution and BOD
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Limit of BOD prescribed by Central Pollution Control Board for the discharge of industrial and municipal waste waters into natural surface waters, is -BOD (biochemical oxygen demand) is the amount of oxygen required by micro-organisms to oxidise the organic matter present in one litre of water; it is a measure of organic pollution.
Effluents with a high BOD use up the dissolved oxygen of the receiving water and kill the aquatic life.
So waste water must be treated to bring down its BOD before it is released into rivers and lakes.
The Central Pollution Control Board (CPCB) has prescribed that the BOD of industrial and municipal waste water discharged into natural surface waters should be less than 30 ppm (30 mg/L).
Clean water has a BOD of less than about 5 ppm, while untreated sewage has a BOD of a few hundred ppm.
So the prescribed limit is less than 30 ppm.
Water Pollution and Bioindicators
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Which one of the following is not a bioindicator of water pollution?Bioindicators of water pollution are organisms whose presence shows that the water is polluted with organic matter and is poor in dissolved oxygen.
Blood-worms (larvae of Chironomus) contain haemoglobin and can live in water with very little oxygen, so they indicate pollution.
Sludge-worms (Tubifex) live in the organic sludge at the bottom of heavily polluted water.
Sewage fungus (a slimy growth of bacteria such as Sphaerotilus and associated organisms) grows in water receiving sewage.
Stone flies (Plecoptera), on the other hand, have nymphs that need clean water rich in dissolved oxygen; they disappear when the water becomes polluted.
Their presence therefore indicates clean, unpolluted water, so they are not indicators of water pollution.
So the answer is stone flies.
Air Pollution: Photochemical Smog
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Photochemical smog pollution does not contain -Photochemical smog is formed in warm, dry and sunny conditions in cities with heavy traffic.
The primary pollutants, oxides of nitrogen ($NO$, $NO_2$) and unburnt hydrocarbons from vehicle exhausts, react in the presence of sunlight.
$NO_2$ is split by sunlight to give nascent oxygen, which combines with $O_2$ to form ozone ($O_3$).
Ozone and the oxides of nitrogen react with the hydrocarbons to form secondary pollutants such as peroxyacyl nitrate (PAN), formaldehyde and acrolein.
So the main components of photochemical smog are ozone, nitrogen dioxide (and other nitrogen oxides) and PAN, which make it oxidising and irritating to the eyes and lungs.
Carbon dioxide is not a component of photochemical smog.
So photochemical smog pollution does not contain carbon dioxide.
Heavy Metal Pollution: Lead
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Lead concentration in blood is considered alarming if it is -Lead is a toxic heavy metal that enters the body from leaded petrol exhaust, lead paints, batteries and contaminated water.
It damages the nervous system (especially in children), kidneys and blood formation, since it inhibits enzymes of haem synthesis.
Normal blood lead levels are only a few micrograms per 100 ml.
A blood lead level of 10 $\mu g$/100 ml (10 $\mu g$/dL) has been taken as the level of concern; at or above this value harmful effects, especially on the mental development of children, begin, so it is considered alarming.
So lead concentration in blood is considered alarming if it is 10 $\mu g$/100 ml.
Types of Soil
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In which of the following pairs is the specific characteristic of a soil not correctly matched :-Terra rossa (Italian for 'red earth') is a red clayey soil formed on limestone in Mediterranean regions. Its name refers to its red colour (due to iron oxides), not to roses, and it has no special suitability for growing roses. So this pair is not correctly matched.
Chernozems (black earth) of the grasslands of Russia and Ukraine are very rich in humus and are considered among the most fertile soils in the world; correctly matched.
Black soil (regur) of the Deccan is clayey and rich in calcium carbonate, magnesium and iron; correctly matched.
Laterite soil, formed by intense leaching in hot, wet regions, is rich in hydrated oxides of aluminium and iron; correctly matched.
So the pair not correctly matched is Terra rossa – most suitable for roses.
Water Pollution: Biological Indicators
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Which of the following is absent in polluted water : -Some organisms can live only in clean, well oxygenated water, so their presence or absence indicates the quality of water.
Stonefly larvae (and mayfly nymphs) need high dissolved oxygen and are very sensitive to pollution. They disappear from polluted water, so they are indicators of clean water.
Water hyacinth (Eichhornia) and blue green algae grow abundantly in polluted, nutrient-rich (eutrophic) water, and Hydrilla also tolerates such water.
So the larva of the stone fly is absent in polluted water.
That is every question in Environmental Issues for this filter.
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