MCQ Microbes in Human Welfare for ISC Class 12 Biology

(a) Biological process

(b) Chemical process

(c) Mechanical process

(d) Physical process

Answer: (a) Biological process

Question 2: The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is

(a) vitamin B₁₂

(b) vitamin E.

(c) vitamin D

(d) vitamin C

Answer: (a) vitamin B₁₂

Question 3: Waste water treatment generates a large quantity of sludge, which can be treated by:

(a) digesters
(b) activated sludge
(c) chemicals
(d) oxidation pond.

Answer: (d) oxidation pond.

Question 4: Methanogenic bacteria are not found in:

(a) rumen of cattle
(b) gobar gas plant
(c) bottom of water logged paddy fields
(d) activated sludge.

Answer: (d) activated sludge.

Question 5 : A nitrogen fixing microbe associated with the fern Azolla in rice fields is

(a) Frankia
(b) Rhizobium
(c) Spirulina
(d) Anabaena

Answer: (d) Anabaena

Question 6: Azolla pinnata has been found to be an important biofertiliser for paddy crops. This quality is due to the presence of

(a) N₂ fixing bacteria
(b) N₂ fixing cyanobacteria
(c) mycorrhizae
(d) all of these

Answer: (b) N₂ fixing cyanobacteria

Question 7: High biological oxygen demand in a water body means ________

(a) Water is not polluted

(b) Water is polluted

(c) Waterbody contains lots of lifeforms

(d) None of the above

Answer: (b) Water is polluted

Question 8: The guts of various ruminants contain _________

(a) Acidophiles

(b) Halophiles

(c) Methanogens

(d) All of the above

Answer: (c) Methanogens

Question 9: The primary treatment of waste water involves the removal of 

(a) dissolved impurities
(b) stable particles
(c) toxic substances
(d) harmful bacteria.

Answer: (b) stable particles

Question 10:  Which one of the following is not a nitrogenfixing organism?

(a) Anabaena
(b) Nostoc
(c) Azotobacter
(d) Pseudomonas

Answer: (d) Pseudomonas

Question 11:  Which of the following is widely used as a successful biofertiliser in Indian rice field ?

(a) Rhizobium
(b) Acacia arabica
(c) Acalypha indica
(d) Azolla pinnata

Answer: (d) Azolla pinnata

Question 12: Which of the following options incldes biofertilscrs ?

(a) cowdung manure and farmyard waste
(b) A quick growing crop ploughed back into the field
(c) Nostoc, Oscillatoria
(d) All of these

Answer: (c) Nostoc, Oscillatoria

Question 13: Streptomycin is produced by:

(a) By Streptomyces Scoleus
(b) By Streptomyces fradiae
(c) By Streptomyces venezueleae
(d) By Streptomyces griseus

Answer: (d) By Streptomyces griseus

Question 14: Antibiotics are:

(a) Medicines
(b) Toxin
(c) Plants
(d) Syrups

Answer: (a) Medicines

Question 15: Which of the following microbes are used for the commercial production of citric acid?

(a) Xanthomonas citri

(b) Asparagine

(c) Asparagus

(d) Aspergillus

Answer: (d) Aspergillus

Question 16:  Saccharomyces cerevisiae is used primarily for

(a) Baking

(b) Bleaching

(c) Biofuel

(d) None of the above

Answer: (a) Baking

Question 17:  BOD of waste water is estimated by measuring the amount of 

(a) total organic matter
(b) biodegradable organic matter
(c) oxygen evolution
(d) oxygen consumption.

Answer: (d) oxygen consumption.

Question 18:  Which of the following is a non-symbiotic biofertiliser ?

(a) VAM
(b) Azotobacter
(c) Anabaena
(d) Rhizobium

Answer: (b) Azotobacter

Question 19: Nitrogen fixation in root nodules of Alnus is brought about by

(a) Frankia
(b) Azorhizobium
(c) Bradyrhizobium
(d) Clostridium

Answer: (a) Frankia

Question 20: Wastewater treatment generates a large quantity of sludge, which can be treated by

(a) anaerobic digesters
(b) floe
(c) chemicals
(d) oxidation pond

Answer: (a) anaerobic digesters

Question 21: Methanogenic bacteria are not found in

(a) rumen of cattle
(b) gobar gas plant
(c) bottom of water-logged paddy field
(d) activated sludge

Answer: (d) activated sludge

Question 22: Example of a natural insect repellant

(a) Citronella oil

(b) Coconut oil

(c) Linseed oil

(d) None of the above

Answer: (a) Citronella oil

Question 23: Why is wine distilled?

(a) To reduce toxicity

(b) To enable fermentation

(c) To prevent spoilage

(d) To increase the alcohol percentage

Answer: (c) To prevent spoilage

Question 24: Which of the following is used as a substrate for alcohol fermentation?

(a) Maize

(b) Barley

(c) Sucrose

(d) None of the above

Answer: (c) Sucrose

Question 25: The primary treatment of wastewater involves the removal of

(a) dissolved impurities
(b) stable particles
(c) toxic substances
(d) harmful bacteria

Answer: (b) stable particles

Question 26: Which one of the following alcoholic drinks is produced without distillation ?

(a) Wine
(b) Whisky
(c) Rum
(d) Brandy

Answer: (a) Wine

Question 27: The free-living fungus Trichoderma can be used for

(a) killing insects
(b) biological control of plant diseases
(c) controlling butterfly caterpillars
(d) producing antibiotics

Answer: (b) biological control of plant diseases

Question 28: Mycorrhiza does not help the host plant in

(a) enhancing its phosphorus uptake capacity
(b) increasing its tolerance to drought
(c) enhancing its resistance to root pathogens
(d) increasing its resistance to insects

Answer: (d) increasing its resistance to insects

Question 29: A free-living aerobic and non-photosynthetic nitrogen fixing bacterium is:

(a) Anabaena
(b) Clostridium
(c) Azotobactor
(d) Rhizobium

Answer: (c) Azotobactor

Question 30:  For retting of jute, the fermenting microbe is:

(a) Methanophilic bacteria
(b) Butyric acid bacteria
(c) Helicobactor pylon
(d) Streptococcus lactin

Answer: (b) Butyric acid bacteria

Question 31:  Antibiotics are the most effective on:

(a) Bacteria

(b) Virus

(c) Fungi

(d) None of the above

Answer: (a) Bacteria

Question 32:  Which of the following microbes is a proteinacious infectious agent ?

(a) Fungi
(b) Prions
(c) Bacteria
(d) Protozoa

Answer: (b) Prions

Question 33: The nutritive medium for growing bacteria and many fungi in laboratory is called

(a) growth media
(b) suspension media
(c) culture media
(d) colonial media

Answer: (c) culture media

Question 34:  The inoculum is added to the fresh milk in order to convert milk into curd, the term ‘inoculum’ here refers to

(a) a starter rich in vitami Bp
(b) a starter rich in proteins
(c) a starter containing milions of LAB
(d) an aerobic digester

Answer: (c) a starter containing milions of LAB

Question 35:  Which one of the following alcoholic drinks is produced without distillation? 

(a) Wine
(b) Whisky
(c) Rum
(d) Brandy

Answer: (a) Wine

Question 36: Which of the following organisms is used in the production of beverages ?

(a) Penicillium notatum
(b) Saccharomyces cerevisiae
(c) Aspergilus niger
(d) Clostridium butylicum

Answer: (b) Saccharomyces cerevisiae

Question 37:  Which of the following options contains the end products formed during anaerobic respiration in yeast ?

(a) H₂O, CO₂ and energy
(b) H₂S, C₆H₁₂O₆ and energy
(c) CO₂, C₂H₅OH and energy
(d) H₂O and CO₂

Answer: (c) CO₂, C₂H₅OH and energy

Question 38:  Streptomycin is obtained from

(a) Streptomyces griseus
(b) S. cerevisiae
(c) S. venezuelae
(d) S. rimosus

Answer: (a) Streptomyces griseus

Question 39: Integrated Pest Management (IPM) discourages the excessive used of

(a) biological methods
(b) chemical pesticides
(c) mechanical methods
(d) all of these

Answer: (b) chemical pesticides

Question 40: The residue left after methane production from cattle dung is

(a) burnt
(b) burned in land fills
(c) used as manure
(d) used in civil construction.

Answer: (c) used as manure

Question 41:  Methanogens, growing anaerobically on cellulosic material, produce

(a) methane gas
(b) methane and carbon dioxide
(c) methane and hydrogen
(d) methane, carbon dioxide, hydrogen.

Answer: (d) methane, carbon dioxide, hydrogen.

Question 42: Which one of the following is used in the manufacture of alcohol ?

(a) Bacteria

(b) Bread molds

(c) Yeasts

(d) Slime molds

Answer: (a) Bacteria           

Question 43: Which of the following bacteria converts milk into curd ?

(a) Propionibacterium

(b) Lactobacillus

(c) Streptococcus

(d) Bacillus

Answer: (b) Lactobacillus

Question 44:  Which role is played by lactic acid bacteria (LAB) in our stomach ?

(a) Beneficial

(b) Harmful

(c) Neutral

(d) All of these

Answer : (a) Beneficial 

Question 45:  Organic farming includes

(a) use of fertilisers and pesticides of biological origin
(b) IPM (Integrated Pest Management)
(c) locally developed pest resistant varieties
(d) all of these

Answer: (d) all of these

Question 46: Living organisms used to enrich the nutrient quality of the soil are called as

(a) biocontrol agents
(b) biofertilisers
(c) synthetic fertilisers
(d) natural fertilisers

Answer: (d) natural fertilisers

Question 47: Biofertilisers are the living organisms which

(a) bring about soil nutrient enrichment
(b) maximise the ecological benefits
(c) minimise the environmental hazards
(d) all of these

Answer: (d) all of these

Question 48: Which one of the following can be used as biofertiliser in cotton field ?

(a) Azolla-Anabaena
(b) Streptococcus
(c) Azospirillum
(d) Azotobacter chroococcum

Answer: (d) Azotobacter chroococcum

Question 49: The primary treatment of waste water involves the removal of:

(a) dissolved impurities
(b) stable particles
(c) toxic substances
(d) harmful bacteria.

Answer: (b) stable particles

Question 50: The residue left after methane production from cattle dung is:

(a) burnt
(b) buried in land-fills
(c) used as manure
(d) used in civil construction.

Answer: (c) used as manure

Question 51: Statins used for lowering blood cholesterol level are extracted from

(a) algae
(b) bacteria
(c) viruses
(d) yeast

Answer: (d) yeast

Question 52:  Monascus purpureus is a yeast commercially used in the production of

(a) citric acid
(b) ethanol
(c) blood cholesterol lowering statins
(d) streptokinase for removing clots from blood vessels

Answer: (c) blood cholesterol lowering statins

Question 53: In the sewage treatment, bacterial floes are allowed to sediment in a settling tank. This sediment is called as

(a) inactivated sludge
(b) activated sludge
(c) primary sludge
(d) secondary sluge

Answer: (b) activated sludge

Question 54:  Which of the following steps is taken by the Ministry of Environment and Forests to protect rivers from water pollution ?

(a) Ganga Action Plan
(b) Narmada Action Plan
(c) Yamuna Action Plan
(d) Both (a) and (c)

Answer: (d) Both (a) and (c)

-: End of MCQ Microbes in Human Welfare for ISC Class 12 Biology :-

-: also visit :-

• ISC Class-12 Text book Solutions, Notes , Syllabus, Paper
• MCQ Type Questions ISC Class-12 Semester-1 Session 2021-22

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