CBSE Class 12 Biology Microbes in Human Welfare MCQs Set B

Question. Dough kept overnight in warm weather becomes soft and spongy because of
(a) absorption of carbon dioxide from atmosphere
(b) fermentation
(c) cohesion
(d) osmosis.

Answer : B

Question. Which of the following is a commercial blood cholesterol lowering agent?
(a) Lipases
(b) Cyclosporin A
(c) Statin
(d) Streptokinase

Answer : C

Question. The guts of cow and buffalo possess
(a) methanogens
(b) cyanobacteria
(c) Fucus sp.
(d) Chlorella sp

Answer : A

Question. Select the correct statement from the following.
(a) Biogas is produced by the activity of aerobic bacteria on animal waste.
(b) Methanobacterium is an aerobic bacterium found in rumen of cattle.
(c) Biogas, commonly called gobar gas, is pure methane.
(d) Activated sludge-sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria.

Answer : D

Question. Which one of the following is not used in organic farming?
(a) Glomus
(b) Earthworm
(c) Oscillatoria
(d) Snail

Answer : D

Question. Which one of the following plants are used as green manure in crop fields and in sandy soils ?
(a) Crotalaria juncea and Alhagi camelorum
(b) Calotropis procera and Phyllanthus niruri
(c) Saccharum munja and Lantana camara
(d) Dichanthium annulatum and Azolla nilotica

Answer : A

Question. Name an example of a rod-shaped virus.
(a) Ebola virus
(b) Tobacco mosaic virus
(c) Influenza virus
(d) Both (a) and (c)

Answer : B

Question. In the sewage treatment, bacterial flocs are allowed to sediment in a settling tank. This sediment is called as
(a) activated sludge
(b) primary sludge
(c) anaerobic sludge
(d) secondary sludge

Answer : A

Question. The diagram given below represents a typical biogas plant. Select the correct option for A, B and C, respectively. (Image 29)
(a) A–Sludge, B–Dung + Water, C– Gas holder
(b) A–Dung + Water, B–Sludge, C–CH₄ +CO₂
(c) A–Sludge, B–Gas holder, C–Dung + Water
(d) A–CH₄ +CO₂, B–Dung + Water, C–Sludge

Answer : C

Question. 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 the above

Answer : D

Question. Which of the following microorganisms is used for production of citric acid in industries?
(a) Aspergillus niger
(b) Rhizopus nigricans
(c) Lactobacillus bulgaris
(d) Penicillium citrinum

Answer : A

Question. The citric acid is produced by
(a) Candida utilis
(b) Azotobacter suboxydans
(c) Aspergillus niger
(d) Streptococcus lactis.

Answer : C

Question. Which one of the following pairs is correctly matched?
(a) Rhizobium – Parasite in the roots of leguminous plants.
(b) Mycorrhizae – Mineral uptake from soil.
(c) Yeast – Production of biogas.
(d) Myxomycetes – The ringworm diseases.

Answer : B

Question. Consider the following statements (A–D) about organic farming.
(A) Utilizes genetically modified crops like Bt cotton
(B) Uses only naturally produced inputs like compost
(C) Does not use pesticides and urea
(D) Produces vegetables rich in vitamins and minerals Which of the above statements are correct?
(a) B, C and D
(b) C and D only
(c) B and C only
(d) A and B only

Answer : C

Question. Given below is the flowchart of sewage treatment.
Identify A, B, C, D and E and select the correct option.
(a) A–Small aeration tank, B–Microbial digestion, C–High BOD, D–Activated sludge, E–Aerobic sludge digesters
(b) A–Large aeration tank, B–Mechanical agitation,C–Increased BOD, D–Activated sludge, E–Aerobic sludge digesters
(c) A–Small aeration tank, B–Microbial digestion, C–Low BOD, D–Activated sludge, E–Anaerobic sludge digesters
(d) A–Large aeration tank, B–Mechanical agitation, C–Reduced BOD, D–Activated sludge, E–Anaerobic sludge digesters

Answer : D

Question. The BOD test measures the rate of uptake of oxygen by microbes in water bodies. The greater BOD of sample water, indicates that
(a) it is highly polluted
(b) it is not polluted
(c) it is moderately polluted
(d) pollution level cannot be determined

Answer : A

Question. Continuous addition of sugars in ‘fed batch’ fermentation is done to
(a) produce methane
(b) obtain antibiotics
(c) purify enzymes
(d) degrade sewage.

Answer : C

Question. A patient brought to a hospital with myocardial infarction is normally immediately given
(a) penicillin
(b) streptokinase
(c) cyclosporin-A
(d) statins.

Answer : B

Question. Which one of the following helps in absorption of phosphorus from soil by plants?
(a) Glomus
(b) Rhizobium
(c) Frankia
(d) Anabaena

Answer : A

Question. Due to which of the following organism, yield of rice is increased?
(a) Sesbania
(b) Bacillus popilliae
(c) Anabaena
(d) Bacillus subtilis

Answer : C

Question. Match the following columns.
Codes
A B C D A B C D
(a) 4 3 2 1
(b) 3 2 1 4
(c) 4 1 2 3
(d) 1 4 3 2

Answer : A

Question. Curd is formed by adding a small amount of curd to milk. This small amount is referred to as inoculum
(a) True
(b) False
(c) Cannot say
(d) Partially true or false

Answer : A

Question. Which of the following is used to manufacture ethanol from starch?
(a) Penicillium
(b) Saccharomyces
(c) Azotobacter
(d) Lactobacillus

Answer : B

Question. Which of the following is put into anaerobic sludge digester for further sewage treatment?
(a) Primary sludge
(b) Floating debris
(c) Effluents of primary treatment
(d) Activated sludge

Answer : D

Question. Which of the following is not used as a biopesticide?
(a) Bacillus thuringiensis
(b) Trichoderma harzianum
(c) Nuclear Polyhedrosis Virus (NPV)
(d) Xanthomonas campestris

Answer : D

Question. A fungus which is used as a method of biocontrol is
(a) Glomus
(b) Trichoderma
(c) Penicillium
(d) Aspergillus

Answer : B

Question. Antibiotics are the most effective on:
Bacteria
Virus
Fungi
None of the above

Answer : A

Question. Microbes are used in
1. primary treatment of sewage
2. secondary treatment of sewage
3. anaerobic sludge digester
4. production of bioactive molecules
(a) 1, 3 and 4
(b) 1, 2, 3 and 4
(c) 2, 3 and 4
(d) 3 and 4

Answer : C

Question. Big holes in Swiss cheese are formed as a result of
(a) machine used for making the cheese
(b) a bacterium producing a large amount of carbon dioxide
(c) a bacterium that is visible to naked eyes
(d) a fungus that produces large amount of carbon dioxide

Answer : B