Top 50+ Microbes in Human Welfare - Biology Questions and Answers For NEET 2024 Exam Preparation

Q1. Match column I with column II and select the correct option using the codes given below.

1. A-(i), B-(iv), C-(ii), D-(iii)
2. A-(iii), B-(i), C-(ii), D-(iv)
3. A-(iii), B-(i), C-(iv), D-(ii)
4. A-(iii), B-(iv), C-(i), D-(ii

Answer: (c)

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Q2. Microbe used for biocontrol of pest butterfly caterpillars is

1. Streptococcus sp.
2. Saccharomyces cerevisiae
3. Bacillus thuringiensis
4. Trichoderma sp

Answer: (c)

Biopesticides are those biological agents that are used for control of weeds, insects and pathogens. The microorganisms used as biopesticides are viruses, bacteria, protozoa, fungi and mites. Some of the biopesticides are being used at a commercial scale.

Most important example is the soil bacterium, Bacillus thuringiensis (Bt). Spores of this bacterium produce the insecticidal cry protein. Therefore, spores of this bacterium kill larvae of insects which eat them.

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Q3. A nitrogen-fixing microbe associated with Azolla in rice fields is

1. Frankia
2. Spirulina
3. Anabaena
4. Tolypothrix.

Answer: (c)

Azolla plays a very important role in rice production. Azolla and its nitrogen-fixing partner, Anabaena, have been used as green manure to fertilise rice paddies and increase production.

With the help of Azolla, rice can be grown year after year, several crops a year, with little or no decline in productivity; hence no rotation of crops is necessary.

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Q4. The full potential as an effective antibiotic in the context of penicillin was studied by _________.

1. Chain and Florey
2. Sutton and Boveri
3. Watson and Crick
4. Edward Jenner

Answer: (a)

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Q5. Which one of the micro-organisms is used for production of citric acid in industries?

1. Penicillium citrinum
2. Lactobacillus bulgaricus
3. Aspergillus niger
4. Rhizopus nigricans

Answer: (c)

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Q6. Microbes are present in

1. soil
2. air
3. water
4. thermal springs

1. I, II, III, IV
2. I, III, IV
3. I, II
4. III, IV

Answer: (a)

Microbes are single-cell organisms and so tiny that millions can fit into the eye of a needle. Microbes include bacteria and archaebacteria, protists, some fungi and even some very tiny animals that are too small to be seen without the aid of a microscope. Microbes are present everywhere in soil, water, air, inside our bodies and that of the animals and plants.

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Q7. Statement 1 : Bioenergy is the energy available from biological sources.

Statement 2 : Fossil fuels are examples of bioenergy.

1. Statement -1 is True, Statement -2 is True ; Statement-2 is NOT a correct explanation for Statement - 1
2. Statement- 1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement -1
3. Statement - 1 is True, Statement- 2 is False
4. Both the Statements are False.

Answer: (c)

Bioenergy is the energy extracted from biological sources, both living and their immediate remains e.g.wood, gobar gas. It does not include fossil fuels (coal, petroleum, natural gas) etc.

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Q8. Which of the following statement is correct ?

1. Biogas (commonly called gobar gas) is pure methane.
2. Methanobacterium is an aerobic bacterium found in rumen of cattle.
3. Activated sludge sediment in settlement tanks of sewage treatment plants is rich source of aerobic bacteria.
4. Biogas is produced by the activity of aerobic bacteria on animal waste.

Answer: (c)

Activated sludge sediment in settlement tanks of sewage treatment plants is rich source of aerobic bacteria. Anaerobic bacteria digest the bacteria and fungi in the sludge by producing gases like methane, hydrogen sulphide and carbon dioxide. These gases form biogas.

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Q9. Big holes in Swiss cheese are made by

1. a bacterium that produces methane gas
2. a machine
3. a bacterium producing a large amount of carbon dioxide
4. a fungus that releases a lot of gases during its metabolic activities

Answer: (c)

The large holes in 'Swiss cheese' are due to the production of a large amount of $CO_2$ by a bacterium named, Propionibacterium shermanii.

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Q10. Penicillin was extensively used during which war?

1. World War II
2. World War I
3. Both (a) and (b)
4. Cold War

Answer: (a)

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Q11. Consider the following statements about organic farming. Which of the statements given below is correct?

1. Integrated pest, weed management and soil conservation systems are valuable tools of an organic farm
2. Organic farming promotes the use of crop rotations, and cover crops and encourages balanced host/predator relationships
3. Organic Farming protects the environment, minimise soil degradation and erosion and decrease pollution
4. All of the above

Answer: (d)

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Q12. Select the correct group of biocontrol agents.

1. Trichoderma, Baculovirus, Bacillus thuringiensis
2. Nostoc, Azospirillium, Nucleopolyhedrovirus
3. Bacillus thuringiensis, Tobacco mosaic virus, Aphids
4. Oscillatoria, Rhizobium, Trichoderma

Answer: (a)

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Q13. Assertion: Azospirillum and Azotobacter enriching the nitrogen content of soil.

Reason: They are free living nitrogen fixer in soil.

1. If both the assertion and reason are true but the reason is not a correct explanation of the assertion.
2. If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
3. If the assertion is true but the reason is false.
4. If both the assertion and reason are false.

Answer: (b)

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Q14. These bacteria grow anaerobically on cellulosic material, produce large amounts of methane along with $CO_2$ and $H_2$ , and are collectively called methanogens. Examples of such bacteria are

1. Methanobrevibacter
2. Methanobacterium
3. Methanococcus
4. All of these

Answer: (d)

Methanogens are microorganisms that produce methane as a metabolic byproduct in anoxic condition. They include Methanobcterium, Methanobrevibacter and Methanococcus.

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Q15. A nitrogen fixing bacterium that forms a loose association with the roots of crop plants is

1. Bacillus polymyxa
2. Azotobacter
3. Clostridium
4. Azospirillum

Answer: (d)

A bacteri um Azospillum lipoferum forms loose association with roots of maize and some Braziliangrasses which increase the crop yield up to a large extent.

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Q16. Gal ghotu' is a common name for which disease?

1. Diphtheria
2. Whooping cough
3. Plague
4. Leprosy

Answer: (a)

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Q17. What does 'P' indicate in the figure?

1. Water and dung
2. Dung and vegetable waste
3. Vegetable and human excreta
4. All of these

Answer: (a)

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Q18. What would happen if oxygen availability to the activated sludge flocs is reduced?

1. The centre of floes will become anoxic, which would cause the death of bacteria and eventually breakage of flocs.
2. It will slow down the rate of degradation of organic matter.
3. Flocs would increase in size as anaerobic bacteria would grow around flocs.
4. Protozoa would grow in large numbers.

Answer: (a)

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Q19. Mycorrhiza does not help the host plant in

1. increasing its tolerance to drought
2. enhancing its phosphorus uptake capacity
3. enhancing its resistance to root pathogens
4. increasing its resistance to insects

Answer: (d)

Mycorrhiza does not help the host plant in increasing its resistance to insects. Infact, plants having such associations show resistance only to root-borne plant pathogens, tolerance to salinity and drought and an overall increase in plant growth and development.

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Q20. In the primary treatment of sewage, the floating debris is removed by sequential ... by passing through wire mesh screens. The most appropriate word for filling the blank is

1. sedimentation
2. filtration
3. condensation
4. evaporation

Answer: (b)

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Q21. Which of the following statements is correct?

1. Wine is produced without distillation
2. Ethanol is produced by the fermentation of malted cereals and fruit juices
3. Saccharomyces is used for bread making
4. All of the above

Answer: (d)

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Q22. What does 'q' indicate in the figure (a)?

1. Collar
2. Head
3. Tail
4. Plate

Answer: (a)

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Q23. Which one of the following pair is wrongly matched?

1. Streptomycetes — Antibiotic
2. Methanogens — Gobar gas
3. Yeast — Ethanol
4. Coliforms — Vinegar

Answer: (d)

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Q24. The most common substrate used in distilleries for the production of ethanol is

1. ground gram
2. corn meal
3. soya meal
4. molasses.

Answer: (d)

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Q25. Glucose fermentation by yeast yields

1. ethanol + $H_{2}$O
2. ethanol + $CO_{2}$
3. methanol + $CO_{2}$
4. $H_{2}O + CO_{2}$

Answer: (b)

Fermentation is defined as an energy yielding process whereby organic molecules serve as both electron donors and electron acceptors. The molecule being metabolized does not have all its potential energy extracted from it.

Beer and wine are produced by fermenting glucose with yeast. Yeast contains enzymes that catalyse the breakdown of glucose to ethanol and carbon dioxide.

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Q26. When a natural predator (living being) is applied on the other pathogen organism to control them, this process is called

1. biological control
2. artificial control
3. confusion technique
4. genetic engineering.

Answer: (a)

The control of insect pests by the introduction, encouragement and artificial increase of biological agencies like predaceous and parasitic insects, other animals and diseases is termed as biological control. It is basically a natural control in which man plays significant role of making the biological agencies more effective.

Of these agencies, insect enemies play important role in nature for managing the phytophagous insect pests and keep a balance e.g., ladybugs or praying mantis, frog, toads, lizard and birds are employed by man to eat up the insect pests like aphids. It is a self perpetuating method.

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Q27. Which of the following is common to Azospirillum, Anabaena, Nostoc and Oscillatoria?

1. Prokaryotic organism
2. $N_2$ -fixer microbes
3. Both (a) and (b)
4. Eukaryotic organism

Answer: (c)

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Q28. Which one of the following helps in absorption of phosphorus from soil by plants?

1. Frankia
2. Glomus
3. Rhizobium
4. Anabaena

Answer: (b)

Some fungi form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza. The fungal symbiont in these associations absorbs phosphorus from soil and passes it to the plant.

Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.

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Q29. Which of the following is non-symbiotic biofertilizer?

1. VAM
2. Anabaena
3. Rhizobium
4. Azotobacter

Answer: (d)

Biofertilizers are organisms which bring about nutrient enrichment of the soil. Azotobacter is a free living, aerobic, nitrogen fixing bacteria. Anabena is a nitrogen fixing cyanobacteria that occurs in both free living and symbiotc associations with Azolla, Cycas roots, etc.

Rhizobium lives symbiotically in root nodules of legumes and non-legumes. Vesicular-arbuscular mycorrhiza (VAM) is an example of endomycorrhiza in which fungal hyphae penetrate the cortical cells of grasses to form vesicles.

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Q30. Which of the following is mainly produced by the activity of anaerobic bacteria on sewage?

1. Mustard gas
2. Laughing gas
3. Propane
4. Marsh gas

Answer: (d)

Marsh gas or methane gas is mainly produced by the activities of anaerobic bacteria on sewage. Sewage contains large amounts of organic matter and microbes, many of which are pathogenic. These microbes (bacteria and fungi) are digested during secondary treatment process of sewage by anaerobic bacteria.

During digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases are called biogas and can be easily used as a source of energy as it is inflammable.

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Q31. BOD _________ polluting potential of waste water.

1. Is directly proportional to
2. Is not proportional to
3. Is inversely proportional to
4. None of these

Answer: (a)

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Q32. Which gas is responsible for the puffed-up appearance of dough ?

1. $O_{2}$
2. $CO_{2}$
3. $SO_{2}$
4. $NO_{2}$

Answer: (b)

The dough, which is used for making bread, is fermented by using baker’s yeast (Saccharomyces cerevisiae). The puffed up appearance of dough is due to the production of $CO_{2}$ gas.

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Q33. After secondary treatment, the effluent is released into

1. Filtration unit
2. Digester tank
3. Water bodies
4. Chemical treatment unit

Answer: (c)

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Q34. The residue left after methane production from cattle dung is

1. Buried in landfills
2. Burnt
3. Used as manure
4. Used in civil construction

Answer: (c)

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Q35. Monascus purpureus is a yeast used commercially in the production of

1. citric acid
2. ethanol
3. streptokinase for removing clots from the blood vessels
4. blood cholesterol lowering statins

Answer: (d)

Statins are produced by the yeast Monascus purpureus which have been commercialised as bloodcholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

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Q36. IARI stands for

1. Indian Aerospace Research Institute
2. Indian Aviation Research Institute
3. Indian Atomic Research Institute
4. Indian Agricultural Research Institute

Answer: (d)

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Q37. Probiotics are

1. live microbial food supplement
2. cancer inducing microbes
3. new kind of food allergens
4. safe antibiotics

Answer: (a)

Probiotics are dietary supplements containing potentially beneficial bacteria or yeast, with lactic acid bacteria (LAB) as the most common microbes used. LAB have been used in the food industry for many years because they are able to convert sugars (including lactose) and other carbohydrates into lactic acid.

They not only provide the characteristic sour taste to fermented dairy foods such as yogurt, but also acts as a preservative, by lowering the pH and creating fewer opportunities for spoilage organisms to grow.

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Q38. Match the items in 'Column-A' and 'Column-B' and choose the correct answer.

The correct answer is

1. i-C, ii-D, iii-B, iv-A
2. i-B, ii-D, iii-C, iv-A
3. i-D, ii-A, iii-B, iv-C
4. i -C, ii-B, iii-A, iv-D

Answer: (a)

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Q39. Which one of the following micro-organisms is used for production of citric acid in industries?

1. Aspergillus niger
2. Penicillium citrinum
3. Rhizopus nigricans
4. Lactobacillus bulgaris

Answer: (a)

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Q40. The common nitrogen fixer in paddy fields is

1. Azospirillum
2. Rhizobium
3. Oscillatoria
4. Frankia

Answer: (a)

The common nitrogen fixer in paddy field is Azospirillum. It is an anaerobic bacteria that forms loose association with roots of paddy crops.

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Q41. What does figure (a) depict?

1. Rhinovirus
2. Adenovirus
3. Bacteriophage
4. Tobacco mosaic virus

Answer: (c)

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Q42. Bt' spores are mixed with _________ and sprayed on vulnerable plants.

1. Any organic solvent
2. Only alcohol
3. Only water
4. Any aqueous solvent

Answer: (c)

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Q43. Which of the following is the pair of biofertilizers?

1. Rhizobium and grasses
2. Azolla and BGA
3. Nostoc and legume
4. Salmonella and E.coli

Answer: (b)

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Q44. Which one of the following alcoholic drinks is produced without distillation?

1. Whisky
2. Wine
3. Rum
4. Brandy

Answer: (b)

Without distillation wine and beer are produced whereas whisky, brandy and rum are produced by distillation of the fermented broath.

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Q45. Which bacteria is utilized in gobar gas plant?

1. Ammonifying bacteria
2. Methanogens
3. Nitrifying bacteria
4. Denitrifying bacteria

Answer: (b)

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Q46. The primary treatment of waste water involves the removal of

1. Stable particles
2. Dissolved impurities
3. Toxic substances
4. Harmful bacteria

Answer: (a)

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Q47. Which of the following can be used as a biocontrol agent in the treatment of plant disease?

1. Chlorella
2. Lactobacillus
3. Trichoderma
4. Anabaena

Answer: (c)

Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens.

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Q48. The most common substrate used in distilleries for the production of ethanol is

1. Ground gram
2. Soya meal
3. Molasses
4. Corn meal

Answer: (c)

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Q49. The rotenone is

1. an insect hormone
2. a natural herbicide
3. a natural insecticide
4. a bioherbicide.

Answer: (c)

Natural insecticides are those which are obtained from microorganisms and plants. The first natural insecticide used by man is azadirachtin obtained from Azadirachta indica. Rotenone is another natural insecticide which is obtained from the roots of Derris and Lonchocarpers. It is harmless to warm blooded animals.

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Q50. Yeast is used in the production of

1. lipase and pectinase
2. citric acid and lactic acid
3. bread and beer
4. cheese and butter

Answer: (c)

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