Question

 Which of the following is put into anaerobic sludge digester for further sewage treatment? [NEET (Sep.) 2020]

(a) Floating debris

(b) Effluents of primary treatment

(c) Activated sludge

(d) Primary sludge

Answer/Explanation

Ans. (c)

Activated sludge is put into anaerobic sludge digester for further sewage treatment. It contains biological flocs that contain bacteria and protozoan for further digestion of organic wastes under aerobic conditions.

Question

 Which one of the following equipments is essentially required for growing microbes on a large scale, for industrial production of enzymes? [NEET (National) 2019]

(a) Sludge digester

(b) Industrial oven

(c) Bioreactor

(d) 800 incubator

Answer/Explanation

Ans. (c)

Bioreactors are required for growing microbes on large scale for the industrial production of enzymes. These large vessels provide biologically active environment. On the other hand, sludge digesters are used to decompose organic solid waste under aerobic conditions. $\mathrm{BOD}$ incubators are used to maintain the temperature for tissue culture growth, bacterial cultures, etc.

Question

 Match the items given in Column I with those in Column Il and select the correct option given below. [NEET 2018]

         1    2     3    4
(a) (iii) (iv) (i) (ii)
(b) (i) (iii) (iv) (ii)
(c) (ii) (i) (ii) (iv)
(d) (i) (ii) (iv) (iii)

Answer/Explanation

Ans. (a)

Eutrophication is the nutrient enrichment of water bodies containing excessive papulation of phytaplanktons. Saritary landfill is a method of solid waste disposal in which the waste material is
burried in the pits dug on the ground and later they get covered by sail. Snaw blindness is caused due to UV-B radiations exposure. These radiations can reach the earth surface due to the depletion of azane layer. In Jhum cultivation, land is cultivated tempararily and then abandoned so that, it can revert to its natural vegetation. It is a long term process and usually leads to defarestation.

Question

 A river with an inflow of domestic sewage rich in organic waste may result in [NEET 2016, Phase I]

(a) increased population ot aquatic food web arganisms

(b) an increased productian of fish due to biodegradable natrients

(c) death of fish due to lack of oxygen

(d) drying of the fiver very soon due to algal bloom

Answer/Explanation

Ans. (c)

A river with an inflow of domestic sewage rich in arganic waste will reduce the dissohed oxygen(DD). The organic waste will increase bialogical oxygen semand of the river thus depleting the $\mathrm{O}_2$ content and may result in death of fish due to lack of oxygen.

Question

 The highest DDT concentration in aquatic food chain shall occur in [NEET 2016, Phase II]

(a) phytoplankton

(b) seagull

(c) crab

(d) eel

Answer/Explanation

Ans. (b)

DDT is a taxic substance which gets concentrated subsequently in a tood. chain of an aquatic ecosystem in the follawing manner Phytoplanttons $\rightarrow$ Eel $\rightarrow$ Crab $\rightarrow$ Seagull $(0.04 \mathrm{ppm}\} \quad\{0.5 \mathrm{ppm} \quad(2 \mathrm{ppm}) \quad$ (25 pem
Thus, the animal or organism acquiring the highest position in a food chain would have the highest DDT cancentration(here seagull). This process is known as biological magnification of biomagnification.

Question

 A lake which is rich in orgaric waste may result in [NEET 2016, Phase II]

(a) increased population of aquatic organisms due to minerals

(b) drying of the lake due to algai bloom

(c) increased population of tish due to lots of nutrients

(d) mortality of fish due to lack of axygen

Answer/Explanation

Ans. (d)

When much of organic matter is present in lake, lots of microbial activity takes place in its decomposition process. So, demand for axygen increases. This increased $\mathrm{D}_2$ demand depletes the dissolved axygen in water at faster rates. This adversely affects the living canditions for ather organisms like fishes, etc. ultimately causing their death.

Question

Increase in concentration of the toxicant at successive tropic levels is known as [CBSE AIPMT 2015]

(a) biomagnification

(b) bladeterioration

(c) biotransformation

(d) biogeochemical cycling

Answer/Explanation

Ans. (a)

Biamagnification is the sequence of processes in an ecosystem by which higher concentrations of a particular toxicant, such as the pesticide or heavy metal are reached in higher organisms of the food chain, generally through a series of prey-predator relationships.

Question

 Eutrophication of water bodies leading to killing of fishes is mainly due to non-availability of [CBSE AIPMT 2015]

(a) food

(b) light

(c) essential minerals

(d) oxygen

Answer/Explanation

Ans. (c)

Eutrophication is a process where water badies receive excess nutrients that stimulate excessive plant growth. This can lead to overerowding and competition for sunlight, space and oxygen. This candition creates the lacking of essential nutrients for fishes due to which they die.

Question

 in an area where DDT had been used extensively, the population of birds declined significantly because [CBSE AIPMT 2012]

(a) birds stopped laying eggs

(b) earthworms in the area gat eradicated

(c) cabras were feeding exclusively on birds

(d) many of the birds laid eggs, that did nat hatch

Answer/Explanation

Ans. (d)

DDT, its breakdown products and other chlorinated hydrocarbon pesticides pase serious threat to birds. These persistant poisons enter the food chain and they accumulate in the fatty tissues of organisms at lower trophic level and then tend to concentrate in considerably toxic amount as they mave up through the food chain. This is called biomagnification or biocancentration. It weakens the calcarious egg shell at birds as it becomes very thin.

Question

Measuring Biochemical Dxygen Demand (BOD) is a method used for [CBSE AIPMT 2012]

(a) estimating the amount at organic matter in sewage water

(b) working out the efficiency ot oil driven automobile engines

(c) measuring the activity of Soccharomyces cerevisae in producing curd on a commercial scale

(d) warking out the efficiency of RBCs about their capacity to carry oxygen

Answer/Explanation

Ans. (a)

Decomposition of arganic matter by micrabial activity depends an axygen availability in water.
The degree of impurity of water due to the organic matter is measured in terms of BOD (Biochemical Dxygen Demand of BOD is the oxygen in miligrams required for five days in one litre of water at $20^{\circ} \mathrm{C}$ for the microorganisms to metabolise ofganic waste.

Question

 The domestic sewage in large cities [CBSE AIPMT 2012]

(a) has a high $\operatorname{BDD}$ as it contains both aerobic and anserobic bacteria

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

(c) when treated in STPs does not really require the aeration step as the sewage cantains adequate axygen

(d) has very high amounts of suspended solids and dissolved salts

Answer/Explanation

Ans. (b)
Sewage is waste water having food residue, animal and human excreta, detergents, discharges from commercial and industrial establishments. The damestic sewage is processed first by aerobic and then by anaerobic bacteria in secondary treatment in Sewage Treatment Plant [STPs) and then recycled for further use.

Question

 DDT residues are rapidly passed through food chain causing biomagnification because DDT is [CBSE AIPMT 2009]

(a) lipo soluble

(b) moderately toxic

(c) non-toxic to aquatic animals

(d) water soluble

Answer/Explanation

Ans. (a)

Many of the pesticides, such as DDT, aldrin and dieldrin are accurmulated in the environment. They are fat soluble and generally nan-biodegradable. Theyget incorparated into the food chain and ultimately deposited in the fatty tissues of animals and humans. In the food chain, because of their build up, they get magnified in the higher trophic levels cailed biological magnification. The phenomenon of bialogical magnification is also reported for certain ather pollutants such as. heavy metals, e-g-mercury, copper and radioactive substances as strontium-90.

Question

 Biochemical Oxygen Demand (BOD) in a river water [CBse AIPMT 2009]

(a) remains unchanged when algal bloom accurs

(b) has no relationship with concentration of axygen in the water

(c) gives a measure af Salmonella in the water

(d) increases when sewage gets mixed with river water

Answer/Explanation

Ans. (d)

When sewage gets mixed with river water, BDD will increase. 日iochemical Dxygen Demand(BDD) is the amount of oxygen used for biochemical axidation at organic mater by microarganisms in a unit volume of water. Polluted water has high BOD.

Question

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

1. 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? [CBSE AIPMT 2008]

(a) II, III

(b) $\mathrm{il}, \mathrm{IV}$

(c) I, IIII

(d) I, II

Answer/Explanation

Ans. (d)

A lake near a village suffered heavy mortality of fishes within a few days, because lots of urea and phosphate fertiliser were used in the crops in the vicinity and the area was sprayed with DOT by an aircraft. Inorganic phospharus and nitrogen are responsible for the growth of algae.
In polluted water, these increase due to which algae increase greatly at the surface of water forming water bloom. Due to the death of these algae their organic matter gets decomposed due to which oxygen gets depleted and aquatic. animals die.

Question

 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 fertiliser 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? [CBSE AIPMT 2008]

(a) II and 111

(b) IIl and IV

(c) and III

(d) I and II

Answer/Explanation

Ans. (d)
A lake near a vililage suffered heavy martality of fishes within a few days, because lots of urea and phosphate fertiliser were used in the crops in the vicinity and the area was sprayed with DDT by an aircraft.
Inorganic phaspharus and nitrogen are responsible far the growth of algae. In polluted water these increase due to which algae increase greatly at the surface of water forming water bloom. Due to death of these algae their organic. matter gets decamposed due to which axygengets depleted and aquatic animal dies.

Question

 Which one of the following is not a bioindicator of water pollution? [CBSE AIPMT 2007]

(a) Sludge worms

(b) Blood worms

(c) Stone flies

(d)Sewage fungus

Answer/Explanation

Ans. (c)

Amang the following stone flies are not bioindicators of pollution. Stone flies (e.g Peria sp.) belong to ofder-Plecoptera of class-insecta, which has the terrestrial mandibulates.

Question

 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? [CBSE AIPMT 2007]

(a) $\mathrm{SE}<S<P E<D E$

(b) $S E<P E<S<D E$

(c) $P E<S<S E<D E$

(d)$ S<D E<P E<S E$

Answer/Explanation

Ans. (d)

The ascending order of BOD is Sewage $(S)<$ Distillary Effuent $(D E)<$ Paper Mill Effluent (PE) < Sugar Mill Effluent (SE).

Question

 Photochemical smog pollution does not contain [CBSE AIPMT 2006]

(a) azone

(b) nitrogen dioxide

(c) carbon dioxide

(d) PAN (Peroxy Acyl Nitrate)

Answer/Explanation

Ans. (c)

Phatochemical smag is highly axidising pollutant comprising largely of ozone $10_5 \lambda$ oxides of nitrogen $\left(\mathrm{NO}_2\right)$, hydrogen perovide $\left(\mathrm{H}_2 \mathrm{O}_2\right)$, arganic perosides, Peroxy Acetyl Nitrate (PAN) and Peroxy Benzyl Nitrate [PBN] but not carbon dioxide ( $\left.\mathrm{CO}_2\right)$.

Question

 Limit of BOD prescribed by Central Pollution Control Board for the discharge of industrial and municipal waste water into natural surface water, is [CBSE AIPMT 2006]

(a) $<3.0 \mathrm{ppm}$

(b) $<10$ ppon

(c) $<100 \mathrm{ppm}$

(d) $<30 \mathrm{ppm}$

Answer/Explanation

Ans. (b)

The Central Pollution Control Board prescribed the BDD limit for the discharge of industrial and municipal waste water as $<10 \mathrm{ppm}$.

Question

Which of the following is not used for disinfection of drinking water? [CBSE AIPMT 2005]

(a) Phenyl

(b) Chloramine

(c) Chiorine

(d) Ozone

Answer/Explanation

Ans. (a)

Pherryl is not used for disinfection of Grinking water as it is a poisonous substance. Water is chlorinated for getting disinfected.

Question

 Fluoride pollution mainly affects [CBSE AIPMT 2004]

(a) teeth

(b) kidney

(c) brain

(d) heart

Answer/Explanation

Ans. (a)

Prolonged intake af fluaride polluted water causes stiffning of bone and joints particularly spinal cord. Due to the affinity with calcium, fluoride stores in banes which causes mattinng of teeth, bone pains and outward bending of legs from the knees. This is known as knock. knee syndrome.

Question

 Which of the following is absent in polluted water? [CBSE AIPMT 2002]
(a) Hydrillo

(b) Water hyacinth 

(c) Larva of stone fly

(d) Blue-green algee

Answer/Explanation

Ans. (c)

Stone flies are ewapterygate insects with aquatic nymphs; long antennae, biting mouth parts and weak flight. Adults have the tendency to feed an lichens and unicellular algae. These are good pollution indicators.

Question

 What is BOD? [CBSE AIPMT 2001]

(a) The amount of $D_2$ utilised by organisms in water

(b) The amount ofO, utilised by microorganisms for decomposition

(c) The total amount of $\mathrm{O}_2$ present in water

(d) All at the above

Answer/Explanation

Ans. (b)
Biological Dxygen Demand (BDD) is the amount of $D_2$ required tor biological coidation of arganic matter present in polluted water by microorganisms in any unit volume of water.

Question

 DDT is [CBse AIPMT 1999]

(a) a non-degradable pollutant.

(b) an antibiotic

(c) a biodegradable pollutant.

(d) not a pollutant

Answer/Explanation

Ans. (a)

DDT is non-degradable pollulant which accumulates in the tissues. Its concentration is estimated to be 13-31 ppm in body tat of indians, which has been accumulated in them through biomagnification of DDT through food chain.

Question

 A sewage treatment process in which a portion of the decomposer bacteria present in the waste is recycled into the beginning of the process, is called [CBSE AIPMT 1998]

(a) cyclic treatment.

(b) primary treatment

(c) activated sludge treatment

(d) tertiary treatment

Answer/Explanation

Ans. (c)

The word activated sludge system is derived from the practice of adding aerobic heterotrophic bacteria to the incoming sewage, from a previous batch. This sludge inoculum contains large numbers of metabolising bacteria, together with yeasts, malds and Protozas. An especially important. ingredient of the sludge are species of Zoogloee bacteria, which form flocculant. masses (floc) in the aeration tanik. The activity of these aerabic micro-organisms axidises much of the effluent’s arganic matter into carban diaxide and water. When the aefation phase is completed, the floc(secondary sludgel is allawed to settle to the battom, just as the primary sludge settles in primary treatment.

Question

 Which one the following organism is used as indicator of water quality? [CBSE AIPMT 1998]

(a) Beggiatoa

(b) Chiorelio

(c) Azospinillum

(d) Escherichia

Answer/Explanation

Ans. (d)

A variety of the enteric group of bacteria (facultative, aerabic) reside in the human large intestine (e-q. Ecoli]. Therefore, their presence in water supply indicates that water supply has been contaminated by sewage.

Question

Phosphate pollution is mainly caused by [CBSE AIPMT 1997]

(a) phosphate rock anly

(b) agricultural fertilisers only

(c) sewage and phosphate rocks

(d) sewage and agricultural fertilisers

Answer/Explanation

Ans. (d)

Man has been releasing large quantities of phospharus into the biosphere in the form of agricultural fertilisers (superphosphates) and synthetic detergents.

Question

Sewage drained into water bodies kill fishes because [CBSE AIPMT 1996]

(a) excessive carbon dioxide is added to water

(b) it gives off a bad smell

(c) it removes the food eaten by fish

(d) it increases competition with fishes for dissolved axygen

Answer/Explanation

Ans. (d)

Sewage provides foud for decamposers. Phosphorus and nitrogen compounds present in sewage result into excessive growth of algae on water surface, which is also called algal bloom, this all results in decrease in oxygen, which is dangerous for aquatic life.

Question

In Minamata Bay of Japan, the animals which remained free from Minamata disease, are [CBSE AIPMT 1995]
(a)pigs

(b) rabbits

(c) dogs

(d) cats

Answer/Explanation

Ans. (b)

Rabbits remained free from Minamata disease as they are herbivores and this disease is caused due to mercury pollution in water.

Question

 When huge amount of sewage is dumped into a river, its $B O D$ will [CBSE AIPMT 1995]

(a) increase

(b)decrease

(c)sharply decrease

(d) remain unchanged

Answer/Explanation

Ans. (d)
Taj Mahal of Agra is affected by gases discharged from oil refinery in Mathura which cansists of $\mathrm{SO}_2, \mathrm{H}_2$ Sand nitrogen oxide. $\mathrm{SO}_2$ corrodes metals, equipment and damages buildings marble.

Question

Highest DDT deposition shall accur in [CBSE AIPMT 1994]

(a) phytoplankton

(b) sea gull/birds

(c) crab

(d) eel

Answer/Explanation

Ans. (b)

DOT concentration increases in amount. with fise in trophic level because they accumulate in fat, this is biamagnitication. In the given options sea gull’birds are the top consumers so DDT concentration will be highest in them.

Question

 Disease caused by eating fish found in water contaminated with industrial waste having mercury is [CBSE AIPMT 1994]

(a) Minamata disease

(b) Bright’s disease

(c) Hashimoto’s disease

(d) Osteosclerosis

Answer/Explanation

Ans. (a)

Consumption of fishes poisoned with mercury causes defarmity called Minamata disease, which is characterised by diarrhoea, impairment of senses, haemalysis, meningitis and death.

Question

 Domestic waste constitutes [CeSE AIPMT 1991]

(a) non-biadegradable pollution

(b) biadegradable pollution

(c) effluents

(d) air pollution

Answer/Explanation

Ans. (b)

Domestic waste constitutes biadegradable pallutants, such pollutants are naturally present arganic compounds which can be braken down by microorganisms and can be recycled, e.g. sewage.

Question

 The maximum biomagnification would be in which of the following in case of aquatic ecosystem? [CBSE AIPMT 1999]

(a) Fishes

(b) Phytoplanktons

(c) Birds

(d) Zooplaniktons

Answer/Explanation

Ans. (a)

Non-degradable chemicals enter the food chain and their concentration goes up as they move up in the food chain. This phenamenon is called biomagnification. Naturally in a food chain, Prytoplankton $\rightarrow$ Zooplanktan $\rightarrow$ Fishes $\rightarrow$ Birds, it wauld be highest in fishes.

Question

 Animals/organisms floating on the surface of water are [CBSE AIPMT 1988]

(a)plankton

(b) pelagic

(c)benthos

(d) neritic

Answer/Explanation

Ans. (a)

Drganisms floating an the surface of water are planktons, these are of two types
(a) Zooplankton if the floating organisms are animals.

(b) Phytoplankton if the floating organism are plants.

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