CBSE Class 12 Biology Microbes In Human Welfare Worksheet Set A

Question. Nutritionally curd is more suitable then milk. Which of the following reason not supporting to this view
(a) It increasing vitamin B12
(b) It checks disease causing microbes
(c) LAB convert lactose into lactic curd
(d) It provide additional proteins

Answer: D

Question. Full potential of penicillin as an effective antibiotic was established by
(a) Alexander Flemming
(b) Ernest chain
(c) Howard florey
(d) Both 2 and 3

Answer: D

Question. Which of the following is "Clot buster"
(a) Citric acid
(b) Streptokinase
(c) Cyclosporin
(d) Statins

Answer: B

Question. Large holes in "Swiss cheese" are due to production of large amount of CO2 by ............... bacterium
(a) Leuconostoc mesenteroides
(b) Propionibacterium sharmanii
(c) Thermococcus proteus
(d) Staphylococcus thermophilus

Answer: B

Question. Functioning of statin is based on
(a) Competitive inhibition
(b) Endproduct inhibition
(c) Allosteric inhibition
(d) Negative feed back inhibition

Answer: A

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

Answer : D

Question. A nitrogen-fixing microbe associated with Azolla in rice fields is :
(a) Spirulina
(b) Anabaena
(c) Frankia
(d) Tolypothrix

Answer : B

Question. Which one of the following is not a nitrogenfixing organism?
(a) Anabaena
(b) Nostoc
(c) Azotobacter
(d) Pseudomonas

Answer : D

Question. Which gases are produced in anaerobic sludge digesters ?
(a) Methane and CO₂ only
(b) Methane, hydrogen sulphide and CO₂
(c) Methane, hydrogen sulphide and O₂
(d) Hydrogen Sulphide and CO₂

Answer : B

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 and Village Industries Commission
(d) Indian Oil Corporation

Answer : C

Question. Bacillus thuringiensis is widely used as :
(a) Insecticide
(b) Weedicides
(c) Rodenticide
(d) All of the above

Answer : A

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

Answer : D

Question. Which pigment gives a pinkish hue to rhizobium induced root nodules.
(a) Leghaemoglobin
(b) Carotenoid
(c) Mauveine
(d) None of the above

Answer : A

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.

Answer : C

Question. Conversion of milk to curd improves its nutritional value by increasing the amount of :
(a) Vitamin D
(b) Vitamin E
(c) Vitamin B12
(d) Vitamin A

Answer : C

Question. The technology of biogas production was developed in India mainly due to efforts of
(a) IARI
(b) KVIC
(c) IPM
(d) Both 1 and 2

Answer: D

Question. Which of the following bacteria was associated with discovery of penicillin
(a) Streptococus
(b) Staphylococcus
(c) Saccharomyces cerveisiae
(d) Propionobacterium

Answer: B

Question. Bacillus thuringiensis show their inhibitory effect on which part of the insect body
(a) Gut
(b) Respiratory tract
(c) Nervous system
(d) Circulatory system

Answer: A

Question. Which of the following biological agents are used for species specific, narrow spectrum insecticidal applications
(a) Adenoviruses
(b) Nucleopolyhedrosis viruses
(c) Retroviruses
(d) Trichoderma

Answer: B

Question. Members of which of the following fungal genus mainly participate in the mycorrhiza formation
(a) Azotobacter
(b) Fusarium
(c) Rhizopus
(d) Glomus

Answer: D

Question. A prokaryotic autotrophic nitrogen fixing symbiont is found in
(a) Alnus
(b) Cycas
(c) Cicer
(d) Pisum. 

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. Which one of the following is not a biofertiliser?
(a) Agrobacterium
(b) Rhizobium
(c) Nostoc
(d) Mycorrhiza 

Answer: A

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

Answer: C

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. The common nitrogen-fixer in paddy fields is
(a) Rhizobium
(b) Azospirillum
(c) Oscillatoria
(d) Frankia.

Answer: B

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

Answer: D

Question. An example of endomycorrhiza is
(a) Nostoc
(b) Glomus
(c) Agaricus
(d) Rhizobium.

Answer: B

Question. Nitrogen fixation in root nodules of Alnus is brought about by
(a) Frankia
(b) Azorhizobium
(c) Bradyrhizobium
(d) Clostridium. 

Answer: A

Question. Which one of the following pairs is not correctly matched?
(a) Streptomyces - Antibiotic
(b) Serratia - Drug addiction
(c) Spirulina - Single cell protein
(d) Rhizobium - Biofertilizer 

Answer: B

Question. A free living nitrogen-fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is
(a) Tolypothrix
(b) Chlorella
(c) Nostoc
(d) Anabaena. 

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. Which of the following is the pair of biofertilizers?
(a) Azolla and BGA
(b) Nostoc and legume
(c) Rhizobium and grasses
(d) Salmonella and E.coli

Answer: A

Question. Which aquatic fern is used to increase the yield in paddy crop?
(a) Azolla
(b) Salvinia
(c) Marsilea
(d) Isoetes

Answer: A

Question. Which of the following fern is an excellent biofertilizer?
(a) Marsilea
(b) Pteridium
(c) Azolla
(d) Salvinia 

Answer: C

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. Which of the following is non-symbiotic biofertilizer?
(a) Anabaena
(b) Rhizobium
(c) VAM
(d) Azotobacter 

Answer: D

Question. Farmers have reported over 50% higher yields of rice by using which of the following biofertilizer?
(a) Cyanobacteria
(b) legume-Rhizobium symbiosis
(c) Mycorrhiza
(d) Azolla pinnata 

Answer: D

Question. The biofertilizers are
(a) Anabaena and Azolla
(b) cow dung, manure and farmyard waste
(c) quick growing crop ploughed under soil
(d) none of these. 

Answer: A

Question. Which of the following species does not have the ability to fix atmospheric nitrogen?
(a) Azotobactor
(b) Anabaena
(c) Nostoc
(d) Spirogyra 

Answer: D

Question. Which one of the following statements is correct?
(a) Legumes fix nitrogen only through the specialized bacteria that live in their roots.
(b) Legumes fix nitrogen independently of the specialized bacteria that live in their roots.
(c) Legumes fix nitrogen only through specialized bacteria that live in their leaves.
(d) Legumes are incapable of fixing nitrogen.

Answer: A

Question. Identify the organism which cannot fix atmospheric nitrogen.
(a) Nostoc
(b) Oscillatoria,
(c) Anabaena
(d) Spirogyra.

Answer: D

Question. Identify the process involved in making ― Toddy‖ .
(a) Lactic acid fermentation,
(b) Alcoholic fermentation
(c) Distillation,
(d) All the above

Answer: B

Question. Activated sludge formed in STP is used in :
(a) Aeration tank to serve as inoculums
(b) Anaerobic sludge digester p
(c) Used in aeration tank as well as anaerobic sludge digester
(d) Used in sedimentation tank.

Answer: C

Question. Which of the following is immediately given to a patient brought to a hospital with myocardial infarction?
(a) Streptokinase,
(b) Statin,
(c) Penicillin,
(d) Cyclosporin –A

Answer: A

Question. Big holes in Swiss cheese are made by ---------- .
(a) a fungus that releases carbondioxide.
(b) a bacterium that produces methane gas.
(c) Yeast
(d) a bacterium that produces large amount of carbondioxide.

Answer: D

Question. The use of biocontrol agents in farming will greatly reduce our dependence on….. .
(a) Fertilisers,
(b) manure,
(c) chemical pesticides
(d) weedicides.

Answer: C

Question. Which of the following is/are used in organic farming?
(a) Anabaena,
(b) Azospirillum,
(c) Trichoderma,
(d) All

Answer: D

Question. Baculoviruses are pathogens that :
(a) Attack viruses and bacteria,
(b) attack insect pests,
(c) kill useful insects,
(d) Kill nucleopolyhedrovirus.

Answer: B

Question. Identify the wrong pair:
(a) Statin : Monascus,
(b) Cyclosporin : Trichoderma
(c) Penicillin : Staphylococci,
(d) Ethanol : Yeast

Answer: C

Question. Match the following list of microbes and their commercially important products:
Microbe Product
A).Aspergillusniger i) Lactic acid
B).Lactobacillus ii) Citric acid
C).Acetobacteraceti iii) Butyric acid
D).Clostridium butylicum iv)Acetic acid
(a) A-ii, B-i, C-iii, D-iv
(b) A-ii, B-iii, C-i, D-iv,
(c) A-ii, B-iv, Ci, D-iii
(d) A-ii, B- i, C-iv, D-iii

Answer: D

Question. The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is :
(a) Vitamin E,
(b) Vitamin B 12 ,
(c) Vitamin C ,
(d) Vitamin D

Answer: B

Question. The events of sewage treatment is given below
(a) Filtration
(b) Chlorination
(c) Biological treatment
(d) Sedimentation
Which one is the correct sequence of steps involved in sewage treatment?
(a) Steps A, B, C and D
(b) Step B C, A, and D
(c) Steps A, D, C and B
(d) Steps A, D, B and C

Answer: C

Question. Bottled juices are clarified by the use of ……… and ……… .
(a) Pectinase and lipase
(b) Protease and lipase
(c) Protease and amylase
(d) Protease and pectinase

Answer: D

Question. The spent slurry from the biogas plant is used as ………. .
(a) cooking fuel
(b) biofertiliser
(c) manure
(d) inoculum.

Answer: C

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

Answer: D

Assertion – Reason Type Questions:

Answer these questions selecting the appropriate option given below: -
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Question. Assertion (A) : Saccharomyces cerevisiae is used for making bread.
Reason (R) : Fermentation carried out by Yeast enzymes produces CO₂ .

Answer: C

Question. Assertion (A) : Cyanobacteria like Nostoc and Anabaena are used as biofertilisers.
Reason (R) : Cyanobacteria absorb phosphorus from soil and passes it to crop.

Answer: C

Question. Assertion(A): Methanogens are present in the rumen of cattle.
Reason (R) : The break down of cellulosic materials in the rumen is carried out by methanogens.

Answer: C

Question. Assertion (A) : Azospirillum can enrich nitrogen content in the soil.
Reason (R) : Ammonia is converted into free nitrogen by Azospirillum .

Answer: A

Question. Assertion (A) : Dough used for making dosa and idli is fermented by bacteria.
Reason (R)) :The puffed-up appearance of dough is due to production of lactic acid.

Answer: C

Question. Assertion (A): Bacillus thuringiensis and Trichoderma are used as biocontrol agents by organic farmers.
Reason (R) : The use of biocontrol agents helps to reduce pollution caused by excessive use of fertilizers.

Answer: A

Question. Assertion(A) : Statins produced by Monascus is used for lowering blood cholesterol.
Reason (R) : Statins stimulate the enzyme responsible for synthesis of cholesterol.

Answer: A

Short Answer Type Questions:

Question. What are flocs in STP? Mention the role of flocs in STP. 
Answer: Masses of bacteria associated with fungal filaments to form mesh like structures in aeration tank. These microbes consume the major part of the organic matter in the effluent and reduces the BOD.

Question. As a part of Swatch Vidyalaya programme, the Panchayath has donated a biogas plant and a single burner stove. The Panchayath authorities instructed to add 10 bags of cow dung initially in the biogas plant.
a. Mention the main constituents of biogas.
b. What is the use of spent slurry?
c. Give reason for adding cow dung in the biogas plant.
Answer: a) Methane, hydrogen sulphide, carbondioxide, hydrogen.
b) Used as manure.
c) Cow dung is rich in methanogens which help to produce biogas.

Question. How are the following microbes useful to us?
a. Trichodermapolysporum b.Monascuspurpureus
Answer: Trichoderma polysporum is the source of Cyclosporin which is used as immunosuppressive agent. Monascuspurpureus is the source of statins which is used for lowering cholesterol.

Question. An organic farmer added fungal genus Glomus in his crop field. How does it help in improving the yield? 
Answer: Glomus forms mycorrhiza , It helps to absorb phosphorus from the soil and pass it to plant, resistant to root borne pathogen, tolerance to salinity and drought.

Question. Organ-transplant patients need a medicine called cyclosporine. How is it useful for the patient?
Answer: Cyclosporin is used as an immunosuppressant, It prevent the rejection of transplanted organ.

Question. a) What is activated sludge ?
b) Explain the fate of activated sludge in the sludge digester. 
Answer: a)The effluent from aeration tank is passed into a settling tank where the bacterial flocs are allowed to sediment. This sediment is called activated sludge.
b) A small part of it is passed into aeration tank to serve as inoculums. The remaining part is pumped into anaerobic sludge digester.Here, the anaerobic bacteria digest bacteria and fungi in the sludge and forms methane, hydrogen sulphide and carbondioxide. These gases form biogas. 

Question31. a) Name two photosynthetic biofertilisers. How do they improve soil fertility?
b) How is it different from mycorrhizae ?
Answer: a) Anabaena, Nostoc, Oscillatoria (Any two), Fix atmospheric nitrogen- also add organic material to the soil.
b) Mycorrhizae are symbiotic association between fungi and roots of higher plants.
Photosynthetic biofertilisers are free living or symbiotic.

Question. Alexander Fleming while working on Staphylococci bacteria, once observed a mould growing in one of his unwanted culture plate around which Staphylococci could not grow. Which was the mould that contaminated his culture plate. Mention the significance of this observation.
Answer: Penicillium notatum , The chemical produced by the mould (Penicillium) inhibited the growth of Staphylococci. This led to the discovery of antibiotic – penicillium.

Question. Suggest an eco-friendly and pollution free alternative source of energy for rural areas which is dependent on microbial activity. Name the microbe involved in the production of this cooking fuel and mention the chemical composition of it.
Answer: Biogas plant, Methanogens/ methanobacterium, Methane, carbondioxide, Hydrogen etc.

Question. The excessive use of chemical pesticides causes soil pollution and adversely affect human health. An alternative to pesticide is use of biocontrol agents. Name a bacterium and a virus which are used as biocontrol agents and mention their action.
Answer: Bacterium –Bacillus thuringiensis, Toxin released by his bacterium kill the pest larvae.
Virus _ Baculoviruses/Nucleopolyhedrovirus attack insects and other arthropods.

Long Answer Type Questions:

Question. a) Differentiate between biofertilisers and chemical fertilizers?
b) Explain the three types of biofertilisers.
Answer: a)Any two differences – biofertilisers are organisms/ but fertilizers are chemicals produced in factories, Use of biofertilisers do not cause pollution/ but excessive use of fertilizers causes pollution.
b) i.Bacteria – symbiotic (Rhizobium) fix atmospheric nitrogen.
Free living nitrogen fixers – Azospirillum and Azotobacter.
ii) Mycorrhizae –symbiotic association of fungi with roots of higher plants –any one role (absorb Phosphorus and pass it to plant, resistant to root borne pathogens, tolerance to salinity
and drought.
● Cyanobacteria – Nostoc,Anabaena, Oscillatoria –can fix atmospheric nitrogen.

Question.a) Secondary treatment of the sewage is also called 'Biological treatment‘. Justify the statement and explain the process. 
Answer: Aerobic and anaerobic microbes used in secondary treatment.
Primary effluent is passed into aeration tank- constantly agitated mechanically and air is pumped into it-Flocs formation- these microbes consume major part of the organic matter in the effluent- reduces BOD – Effluent is passed into settling tank – forms activated sludge- small part is pumped back into aeration tank – major part is passed into anaerobic sludge digester – Anaerobic bacteria digest flocs into mixture of gases (methane, carbondioxide, hydrogen etc ) forms biogas –Effluent from the secondary treatment plant is released into natural water bodies.

Diagram Based / Case Based Questions:

Question. The given diagram shows the root system of a leguminous plant. 
a. Name the microbe present inside the root nodule and mention the role of it.
b.How is this microbe differ from Nostoc?
c. The application of fertilizers and pesticides has improved our food production. But excessive use of these agrochemicals have adverse effect on environment and human health. So many farmers are moving away from the use of agrochemicals and started practicing organic farming.
Answer: a) Rhizobium, Can fix atmospheric nitrogen.
b) Rhizobium is symbiotic nitrogen fixer, But Nostoc is photosynthetic free living

Question. Observe the given diagram and answer the questions : 
a) What is a and how is it useful to us?
b) Name the main gases collected in b.
c) Name the microbes present in the digester part. 
Answer: a) Spent slurry/ sludge, used as manure.
b) CH₄ , CO₂ , H₂S , H₂
c) Methanogens / Methanobacterium

Question. Organic farmers use a number of microbes for crop protection from pests.
a. Mention one benefit of microbial biocontrol method over pesticides.
b. Name a fungus and a bacteria which act as biocontrol agents.
Answer: a) No pesticide pollution, No impact on health
Fungus- Trichoderma , Bacterium: Bacillus thuringiensis

Sewage treatment plants are compulsory for all newly constructed residential apartments with many family accommodations. Sewage treatment aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding environment or can be reused for watering plants. Untreated sewage discharged into water bodies adversely affect the quality of water. The presence of high amount of organic matter in water increases the BOD. The two stages in sewage treatment are physical treatment and biological treatment. The secondary /biological treatment requires the action of aerobic and anaerobic microbes. The flocs formed in the aeration tank help to reduce the BOD. The biogas generation is also possible through STPs.

Question. Give reason for pumping a part of activated sludge in to aeration tank?
Answer: It acts as inoculums

Question. Where is activated sludge formed in STP?
Answer: In settling tank

Question. The effluent from the primary settling tank is taken to --------
i. Anaerobic sludge digester,
ii. Aeration tank ,
iii. Natural water bodies ,
iv.Biogas plant
Answer: Aeration tank

Question. Name two major categories of microbes which consume organic matter in the aeration tank.
Answer: Bacteria and fungi

Microbes  in Human Welfare Questions and Answers

Question. The immune system of a person is suppressed. In the ELISA test, he was found positive to a pathogen. Which cells of the body are affected by the pathogen?
Answer. Helper T lymphocytes 

Question. What would happen to immune system, if thymus gland is removed from the body of a person?
Answer. Thymus is the primary lymphoid organ. In thymus gland, immature lymphocytes differentiate into antigen-sensitive lymphocytes. If thymus gland is removed from the body of a person, his immune system becomes weak. As a result the person's body becomes prone to infectious diseases.

Question. If a regular dose of drugs or alcohol is not provided to an addicted person, he shows some withdrawl symptoms. List any four such withdrawal symptoms.
Answer. The withdrawal symptoms are:
a. Anxiety b. Shakiness c. Nausea d. Sweating 

Question. In the metropolitan cities of India, many children are suffering from allergy/asthma. What are the main causes of this problem. Give some symptoms of allergic reactions.
Answer. Allergy is the exaggerated response of the immune system of certain antigens present in the environment. In metropolitan cities life style is responsible in lowering of immunity and sensitivity to allergens. More polluted environment increases the chances of allergy in children. Some symptoms of allergic reactions are sneezing, watery eyes, running nose and difficulty in breathing. 

Question. Life style diseases are increasing alarmingly in India. We are also dealing with large scale malnutrition in the population. Is there any method by which we can address both these problems?
Answer. The answer to address both these problems is called biofortification. This area looks at improving food quality with respect to protein, oil, vitamin, micro nutrient and mineral content. The oils need to be rich in omega 3 fatty acids which are good for heart. Similarly, proteins should have more of lysine and tryptophan (essential amino acids). Many varieties of maize, carrots and spinach have been released which fulfill the above criteria.

Biology in Human Welfare Questions and Answers

Question. Do you think we, human beings, are able to digest the cellulose present in our foods? Why or why not ?
Answer. We lack cellulase enzyme for digestion due to nonfunctioning of appendix. 

Question. Baculoviruses are the pathogens that attack on plants and also are used for biocontrol. How both antagonistic functions are performed ?
Answer. Baculovirus like Nucleopolyhedral virus are- species specific, narrow spectrum, effective only against insects and arthropods. 

Question. Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river
water is relatively clean?
Answer. Most polluted water : 400 mg/L of secondary effluent (c). A (River water) : 08 mg/L; b (Untreated sewage water) : 20 mg/L. 

Question. The Ministry of Environment and Forests has initiated Ganga Action Plan and Yamuna Action Plan to save these major rivers. How was the target fulfilled ?
Answer. Decreasing pollution, Sewage treatment and utilization of treated water. 

Question.  What are the negative impacts of biological control ?
Answer. May develop resistant insect varieties, may be lethal / harmful for human beings.