Students of class 12 Biology should refer to MCQ Questions Class 12 Biology Microbes in Human Welfare with answers provided here which is an important chapter in Class 12 Biology NCERT textbook. These MCQ for Class 12 Biology with Answers have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 12 Biology. The following MCQs can help you to practice and get better marks in the upcoming class 12 Biology examination

Chapter 10 Microbes in Human Welfare MCQ with Answers Class 12 Biology

MCQ Questions Class 12 Biology Microbes in Human Welfare provided below have been prepared by expert teachers of grade 12. These objective questions with solutions are expected to come in the upcoming Standard 12 examinations. Learn the below provided MCQ questions to get better marks in examinations.

Question. Which of the following toxic substance is responsible for the malarial fever.
(A) Haemocyanin
(B) Haemozoin
(C) Haemoglobin
(D) Haemoriden R

Question. When an apparently healthy person is diagnosed as unhealthy by a psychiatrist, the reason could be that
(A) The patient was not efficient at his work.
(B) The patient was not economically prosperous.
(C) The patient shows behavioural and social maladjustment.
(D) He does not take interest in sports.

Question. Diseases are broadly grouped into infectious and non-infectious diseases. In the list given below, identify the infectious diseases. (i) Cancer
(ii) Influenza (iii) Allergy (iv) Small pox
(A) (i) and (ii)
(B) (ii) and (iii)
(C) (iii) and (iv)
(D) (ii) and (iv)

Question. The chronic intake of ……… causes Cirrhosis of liver.
(A) Opium
(B) Alcohol
(C) Cocaine
(D) Tobacco

Question. One of the following is not the causal organism for ringworm.
(A) Microsporum
(B) Trichophyton
(C) Epidermophyton
(D) Macrosporum

Question. _______ is a CNS stimulant as it interferes with the transport of the neuro-transmitter, dopamine.
(A) Valium
(B) Barbituarate
(C) Cocaine
(D) Opium

Question. The term ‘Health’ is defined in many ways.
The most accurate definition of the health would be
(A) Health is the state of body and mind in a balanced condition.
(B) Health is the reflection of a smiling face.
(C) Health is a state of complete physical, mental, and social well-being.
(D) Health is the symbol of economic prosperity.

Question. Non-specific host defence that exists prior to the exposure of an antigen is called :
(A) Acquired immunity
(B) Passive immunity
(C) Innate immunity
(D) Active immunity

Question. Marijuana is extracted from
(A) Dried leaves and flowers of hemp plant
(B) Ergot fungus
(C) Roots of hemp plant
(D) Cocoa plant.

Question. A person with sickle cell anaemia is
(A) More prone to malaria.
(B) More prone to typhoid.
(C) Less prone to malaria.
(D) Less prone to typhoid.

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.

Question. A common biocontrol agent for the control of plant diseases is 
(a) baculovirus
(b) Bacillus thuringiensis
(c) Glomus
(d) Trichoderma

Question. Biogas can be a good substitute for
(a) fuel wood
(b) petroleum and oil
(c) coal
(d) charcoal

Question. A lake with an inflow of domestic sewage rich in organic waste may result in
(a) drying of the lake very soon due to algal bloom.
(b) an increased production of fish due to lot of nutrients.
(c) death of fish due to lack of oxygen.
(d) increased population of aquatic food web organization.

Question. Secondary sewage treatment is mainly a
(a) physical process
(b) mechanical process
(c) chemical process
(d) biological process\

Question. Which of the following is common to Azospirillum, Azotobacter, Anabaena, Nostoc and Oscillatoria?
(a) Prokaryotes
(b) Nitrogen-fixers
(c) Both (a) and (b)
(d) Eukaryotes

Question. What would happen if oxygen availability to activated sludge flocs is reduced?
(a) It will slow down the rate of degradation of organic matter
(b) The center of flocs will become anoxic, which would cause death of bacteria and eventually breakage of flocs.
(c) Flocs would increase in size as anaerobic bacteria would grow around flocs.
(d) Protozoa would grow in large numbers.

Question. 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.

Question. Which one of the micro-organism is used for production of citric acid in industries?
(a) Lactobacillus bulgaricus
(b) Penicillium citrinum
(c) Aspergillus niger
(d) Rhizopus nigricans

Question. A good producer of citric acid is
(a) Clostridium
(b) Sacchaaromyces
(c) Aspergillus
(d) Pseudomonas.

Question. Consider the following statements about organic farming.
(i) It utilizes genetically modified crops like Bt cotton.
(ii) It uses only naturally produced inputs like compost.
(iii) It does not use pesticides and urea.
(iv) It produces vegetables rich in vitamins and minerals.
Which of the above statements are correct?
(a) (ii), (iii) and (iv)
(b) (iii) and (iv) only
(c) (ii) and (iii) only
(d) (i) and (ii) only

Question. What are the advantages of gobar gas over conventional utilization?
(i) It is most efficient source of energy.
(ii) It is used as good fertilizer.
(iii) It reduces the chances of spreading of pathogens.
(a) (i) and (ii) only
(b) (ii) and (iii) only
(c) (i) and (iii) only
(d) all of these

Question. Methanogenic bacteria are not found in
(a) rumen of cattle
(b) gobar gas plant
(c) bottom of water-logged paddy fields
(d) activated sludge.

Question. Match the following list of bacteria and their commercially important products Bacterium Product
A. Aspergillus niger (i) Lactic acid
B. Acetobacter aceti (ii) Butyric acid
C. Clostridium butylicum (iii) Acetic acid
D. Lactobacillus (iv) Citric acid
Choose the correct match.
(a) A-(ii), B-(iii), C-(iv), D-(i)
(b) A-(ii), B-(iv), C-(iii), D-(i)
(c) A-(iv), B-(iii), C-(ii), D-(i)
(d) A-(iv), B-(i), C-(iii), D-(ii)

Question. Lactic acid bacteria convert milk into curd and improves its nutritional quality by enhancing
(a) vitamin A
(b) vitamin B
(c) vitamin C
(d) vitamin D

Question. The bacterium that commonly lives in animal and human intestine is
(a) Bacillus anthracis
(b) Vibrio cholerae
(c) Escherichia coli
(d) Corynebacterium

Question. The primary treatment of waste water involves the removal of
(a) dissolved impurities
(b) stable particles
(c) toxic substances
(d) harmful bacteria.

Question. Big holes in Swiss cheese are made by
(a) a machine
(b) a bacterium that produces methane gas
(c) a bacterium producing a large amount of carbon dioxide
(d) a fungus that releases a lot of gases during its metabolic activities.

Question. The residue left after methane production from cattle dung is
(a) burnt
(b) burried in land fills
(c) used as manure
(d) used in civil construction.

Question. The free-living fungus Trichoderma can be used for
(a) insects
(b) biological control of plant diseases
(c) controlling butterfly caterpillars
(d) producing antibiotics

Question. Methanogens do not produce
(a) oxygen
(b) methane
(c) hydrogen sulfide
(d) carbon dioxide.

Question. The technology of biogas production from cow dung was developed in India largely due to the efforts of
(a) Gas Authority of India
(b) Oil and Natural Gas Commission
(c) Indian Agricultural Research Institute and Khadi & Village Industries Commission
(d) Indian Oil Corporation.

Question. Which of these is/are symbiotic N2 fixing organisms?
(a) Rhizobium
(b) Clostridium
(c) Azotobacter
(d) All of these

Question. Primary treatment of sewage waste involves which processes ?
(a) Filtration and incubation
(b) Sedimentation and decantation
(c) Filtration and sedimentation
(d) Sedimentation and microbial proliferation

Question. Activated sludge should have the ability to settle quickly so that it can
(a) be rapidly pumped back from sedimentation tank to aeration tank
(b) absorb pathogenic bacteria present in waste water while sinking to the bottom of the settling tank
(c) be discarded and anaerobically digested
(d) absorb colloidal organic matter.

Question. 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

Question. Which one of the following alcoholic drinks is produced without distillation?
(a) Wine
(b) Whisky
(c) Rum
(d) Brandy

Question. Match the items in Column ‘A’ and Column ‘B’ and choose correct answer.
     Column I                     Column II
A. Lady bird             (i) Methanobacterium
B. Mycorrhiza           (ii) Trichoderma
C. Biological control  (iii) Aphids
D. Biogas                 (iv) Glomus
The correct answer is:
(a) A-(ii), B-(iv), C-(iii), D-(i)
(b) A-(iii), B-(iv), C-(ii), D-(i)
(c) A-(iv), B-(i), C-(ii), D-(iii)
(d) A-(iii), B-(ii), C-(i), D-(iv)

Question. Saccharomyces cerevisiae is employed in production of
(a) idli
(b) beer
(c) bread
(d) all of these

Question. Which bacterium helps in the production of ‘Swiss cheese’?
(a) Propionibacterium sharmanii
(b) Trichoderma polysporum
(c) Saccharomyces cerevisiae
(d) Aspergillus niger

Question. Streptokinase, used as a ‘clot buster’ is obtained from
(a) Streptococcus
(b) Staphylococcus
(c) Lactobacillus
(d) Saccharomyces

Question. BOD refers to
(a) bacteria oxygen demand
(b) biochemical oxygen demand
(c) biochemical operation demand
(d) biological organism demand

Question. Sewage treatment process in which part of decomposer bacteria is recycled into starting of the process is called __________ .
(a) cyclic treatment
(b) primary treatment
(c) tertiary treatment
(d) activated sludge treatment

Question. Cyclosporin A is used for
(a) dissolving blood clots
(b) lowering cholesterol level
(c) immunosuppression
(d) enhancing tenderness of meat

Question. The large vessels for growing microbes on an industrial scale are called _________ .
(a) petridish
(b) digestors
(c) biogas vessel
(d) fermentors

Question. Sewage purification is done by
(a) microbes
(b) fertilizers
(c) antibiotics
(d) antiseptics

Question. Insect resistant transgenic cotton has been produced by inserting a piece of DNA from
(a) an insect
(b) a wild relative of cotton
(c) a bacterium
(d) a virus]

Question. Microbe used for biocontrol of pest butterfly caterpillars is
(a) Trichoderma sp.
(b) Saccharomyces cerevisiae
(c) Bacillus thuringiensis
(d) Streptococcus sp.

Question. Bottled fruit juices from market are clearer than that at home because of
(a) antibiotics
(b) hormones
(c) enzymes
(d) filtration

Question. Match the following list of bioactive substances and their roles Bioactive Substance Role
A. Statin (i) Removal of oil stains ]
B. Cyclosporin A (ii) Removal of clots from blood vessels
C. Streptokinase (iii) Lowering of blood cholesterol
D. Lipase (iv) Immuno-suppressive agent
Choose the correct match.
(a) A-(ii), B-(iii), C-(i), D-(iv)
(b) A-(iv), B-(ii), C-(i), D-(iii)
(c) A-(iv), B-(i), C-(ii), D-(iii)
(d) A-(iii), B-(iv), C-(ii), D-(i)

Question. Symbiotic asociation is exhibited by
I. Mycorrhiza II. Rhizobium
III. Heterocyst IV. Yeast
(a) I, III, IV
(b) I, II, III, IV
(c) II, III, IV
(d) I, II

Question. The symbiotic association between fungi and roots of higher plants is called __________ .
(a) lichen
(b) mycorrhiza
(c) biofertilizer
(d) BOD

Question. Which one of the following is not true about antibiotics?
(a) First antibiotic was discovered by Alexander Flemming.
(b) The term ‘antibiotic’ was coined by S. Waksman in 1942.
(c) Some persons can be allergic to a particular antibiotic.
(d) Each antibiotic is effective only against one particular kind of germ.

Question. Pollution from animal excreta and organic wastes from kitchen can be most profitably minimised by
(a) storing them in underground storage tanks.
(b) using them for producing biogas.
(c) vermiculture.
(d) using them directly as biofertilizers

Question. The following bacteria help in nitrogen fixation from atmosphere.
I. Azotobacter II. Rhizobium
III. Azospirillum IV. Lactobacillus
Identify the correct bacteria.
(a) I, III, IV
(b) I, II, III, IV
(c) II, III, IV
(d) I, II, III

Question. The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is
(a) vitamin C
(b) vitamin D
(c) vitamin B12
(d) vitamin E.

Question. Wastewater treatment generates a large quantity of sludge, which can be treated by
(a) anaerobic digesters
(b) floc
(c) chemicals
(d) oxidation pond

Question. Which of the following is used as biofertilizer ?
I. Cyanobacteria II. Yeast
III. Symbiotic bacteria IV. Free living bacteria
(a) I, II, III
(b) I, II, IV
(c) I, III, IV
(d) II, III, IV

Question. Antibiotics are drugs commonly used to cure diseases of
(a) fungi
(b) viruses
(c) protozoans
(d) bacteria

Question. An organism used as a biofertilizer for raising soyabean crop is
(a) Azotobacter
(b) Azospirillum
(c) Rhizobium
(d) Nostoc

Question. Monascus purpureus is a yeast used commercially in the production of
(a) ethanol
(b) streptokinase for removing clots from the blood vessels
(c) citric acid
(d) blood cholesterol lowering statins.

Assertion and Reason Based MCQs

Directions : In the following questions a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as :
(A) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(B) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(C) Assertion (A) is true but reason (R) is false.
(D) Assertion (A) is false but reason (R) is true.

Question. Assertion (A) : Bottled fruit juices bought from the market are clearer as compared to those made at home.
Reason (R) : They are clarified by pectinases and proteases.
Answer : (A)

Question. Assertion (A) : Members of the genus Glomus form mycorrhiza.
Reason (R) : Mycorrhiza is an association of plants and fungi.
Answer : (A)

Question. Assertion (A) : Statins is produced by a yeast called Trichoderma polysporum.
Reason (R) : It lowers the blood cholesterol level in the body.
Answer : (D)

Question. Assertion (A) : Cyanobacteria increases the soil fertility and also add the organic matter to the soil.
Reason (R) : They can fix free nitrogen in the atmosphere.
Answer : (A)

Question. Assertion (A) : Blue green algae are popular as biofertilisers.
Reason (R) : Blue green algae cause algal bloom in polluted water bodies.
Answer : (D)

We hope the above multiple choice questions for Class 12 Biology for Chapter 10 Microbes in Human Welfare provided above with answers based on the latest syllabus and examination guidelines issued by CBSE, NCERT and KVS are really useful for you. Microbes in Human Welfare is an important chapter in Class 12 as it provides very strong understanding about this topic. Students should go through the answers provided for the MCQs after they have themselves solved the questions. All MCQs have been provided with four options for the students to solve. These questions are really useful for benefit of class 12 students. Please go through these and let us know if you have any feedback in the comments section.