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Microbes in human welfare: NEET MCQs with answers

120 questions on this topic of Biology and Human Welfare (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. Match the microbial biocontrol agent in Column-I with its target organism or application in Column-II: Column-I (A) Bacillus thuringiensis (B) Trichoderma (C) Ladybird (D) Dragonfly Column-II (i) Mosquitoes (ii) Aphids (iii) Butterfly caterpillars (iv) Plant root pathogens

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

Answer: (A) (A)-(iii), (B)-(iv), (C)-(ii), (D)-(i)

Bacillus thuringiensis is effective against butterfly caterpillars; Trichoderma species are free-living fungi that control several plant root pathogens; Ladybird beetles control aphids; and Dragonflies are useful in controlling mosquitoes.

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2. In the production of alcoholic beverages, which of the following pairs of drinks are produced without distillation of the fermented broth?

  1. Wine and Beer
  2. Whisky and Brandy
  3. Rum and Gin
  4. Brandy and Beer
Show answer and explanation

Answer: (A) Wine and Beer

Depending on the type of raw material used for fermentation and the processing type, wine and beer are produced without distillation, whereas whisky, brandy, and rum are produced by distillation of the fermented broth.

hard

3. Assertion (A): Sewage water with a high BOD is highly polluting. Reason (R): BOD measures the organic matter that microbes would oxidise, so higher BOD means more organic waste. Choose the correct option.

  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is not the correct explanation of A
  3. A is true but R is false
  4. A is false but R is true
Show answer and explanation

Answer: (A) Both A and R are true and R is the correct explanation of A

BOD reflects the organic matter in water; the greater the BOD, the greater the polluting potential.

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4. The bacteria in anaerobic sludge digesters and in the rumen of cattle that produce methane-rich biogas are:

  1. Methanobacterium
  2. Rhizobium
  3. Azotobacter
  4. Lactobacillus
Show answer and explanation

Answer: (A) Methanobacterium

Methanobacterium grows anaerobically on cellulosic material, producing CH4 along with CO2 and H2. These bacteria are present in anaerobic sludge and in the rumen of cattle.

NCERT Class 12

easy

5. In a biological sewage treatment plant, sequential physical removal of floating debris and grit occurs in which specific stage?

  1. Primary treatment
  2. Primary settling tank
  3. Aeration tank
  4. Secondary clarifier
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Answer: (A) Primary treatment

Primary treatment involves physical removal of particles through filtration (for floating debris) and sedimentation (for grit like soil and small pebbles). The aeration tank and secondary clarifier are parts of biological (secondary) treatment.

hard

6. A municipal sewage sample has an initial BOD of 600 mg/L. After passing through the aeration tank in secondary treatment, its BOD is reduced by 85%. What is the final BOD of the effluent before it is discharged into the secondary settling tank?

  1. 90 mg/L
  2. 510 mg/L
  3. 15 mg/L
  4. 120 mg/L
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Answer: (A) 90 mg/L

Initial BOD = 600 mg/L. A reduction of 85% means that 85% of 600 = 0.85 × 600 = 510 mg/L has been removed. The remaining BOD is 600 - 510 = 90 mg/L (or 15% of 600 mg/L = 90 mg/L).

medium

7. Ladybirds and dragonflies are useful in biocontrol to get rid of:

  1. Fungal pathogens
  2. Butterfly caterpillars
  3. Aphids and mosquitoes respectively
  4. Weeds
Show answer and explanation

Answer: (C) Aphids and mosquitoes respectively

Ladybirds control aphids and dragonflies control mosquitoes.

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8. Match Column-I (Industrial Product / Enzyme) with Column-II (Source Microorganism) and choose the correct combination: Column-I (a) Citric acid (b) Butyric acid (c) Lipases (d) Statins Column-II (i) Candida lipolytica (ii) Monascus purpureus (iii) Aspergillus niger (iv) Clostridium butylicum

  1. (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
  2. (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
  3. (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
  4. (a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
Show answer and explanation

Answer: (A) (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)

Aspergillus niger (a fungus) produces citric acid; Clostridium butylicum (a bacterium) produces butyric acid; lipases are obtained from microbes such as yeasts like Candida; and statins are derived from the yeast Monascus purpureus.

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9. Lipases used in detergent formulations help in:

  1. Clarifying bottled juices
  2. Removing oily stains from laundry
  3. Dissolving blood clots
  4. Lowering cholesterol
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Answer: (B) Removing oily stains from laundry

Lipases are used in detergents to remove oily stains; pectinases and proteases are used to clarify bottled juices.

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10. Bacillus thuringiensis is used for pest control by:

  1. Injecting it into soil to fix nitrogen
  2. Using it as a fungal biofertiliser
  3. Spraying its dried spores on plants; the toxin released in the gut of insect larvae kills them
  4. Releasing it into ponds to eat mosquito larvae
Show answer and explanation

Answer: (C) Spraying its dried spores on plants; the toxin released in the gut of insect larvae kills them

Dried Bt spores are mixed with water and sprayed on vulnerable plants such as brassicas and fruit trees. When insect larvae eat them, the toxin released in the gut kills the larvae.

NCERT Class 12

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11. Bacteria that grow anaerobically on cellulosic material and produce large amounts of methane along with CO2 and H2 are collectively called:

  1. Cyanobacteria
  2. Nitrogen fixers
  3. Lactic acid bacteria
  4. Methanogens, e.g. Methanobacterium
Show answer and explanation

Answer: (D) Methanogens, e.g. Methanobacterium

Methanogens such as Methanobacterium produce methane; they are found in anaerobic sludge and in the rumen of cattle.

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12. In a biogas plant, the spent slurry removed from the outlet can be used as:

  1. Fertiliser
  2. Drinking water
  3. Fuel directly
  4. Cement
Show answer and explanation

Answer: (A) Fertiliser

A biogas plant has a concrete tank in which a slurry of cattle dung is fed. Gas collects under a floating cover, and spent slurry is removed through another outlet and may be used as fertiliser.

NCERT Class 12

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