Microbes in Human Welfare Exam Questions Class 12 Biology

Please see Chapter 10 Microbes in Human Welfare Exam Questions Class 12 Biology below. These important questions with solutions have been prepared based on the latest examination guidelines and syllabus issued by CBSE, NCERT, and KVS. We have provided Class 12 Biology Questions and answers for all chapters in your NCERT Book for Class 12 Biology. These solved problems for Microbes in Human Welfare in Class 12 Biology will help you to score more marks in upcoming examinations.

Exam Questions Chapter 10 Microbes in Human Welfare Class 12 Biology

Objective Type Question

Question. Baculoviruses are excellent candidates for
(a) Species- specific norrow spectrum pesticidal
(b) Species specific broad spectrum pesticidal
(c) Species- specific narrow spectrum insecticidal application
(d) Species -specific broad spectrum insecticidal application

Question. The following bacteria help in nitrogen fixation from atmosphere .
A. Azotobacter
B. Rhizobium
C. Azospirillum
D. Lactobacillus
Identify the correct bacteria
(a) A, C, D
(b) A, B, C, D
(c) B, C, D
(d) A, B, C

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

Question. The diagram below shows a typical biogas . with few structure labelled as A,B and .C Identify A,B and C
(a) A-Sludge,B-Methane, Oxygen,C-Dung water
(b) A-Sludge,B-Methane,Carbon dioxide C-Dung water
(c) A-Sludge,B-Ethylene,Carbon dioxide, C-Dungwater
(d) A-Sludge,B-Methane,B-Carbon dioxide,C-Sewage

Question. Microbes are a diverse group which includes.
A. Bacteria
B. Mosses
C. Protozoans
D. Fungi
Options :
(a) A, C, D
(b) A, D
(c) A, B
(d) C, D

Question. The given figure shows the sewage treatment with few steps are marked as 1,2,3 and 4 . In which of the following options correct word for all the four number (1,2,3and4) are indicated
(a) 1 – Large aeration tanks, 2 – Chemical agitation, 3 – High,4-Anaerobic
(b) 1- Large aeration tanks,2-Mechanical agitation , 3-Low 4 – Anaerobic
(c) 1-Large aeration tanks, 2 -Chemical agitation, 3-High,4-Aerobic
(d) 1- Large aeration tanks,2-Mechanical agitation, 3-Low 4 – Anaerobic

Question. Read the following statement
‘‘A drug used for _____(A)_____patients is obtained from a species of the organism ______(B)______” Identify A and B

A	B
(a) Heart	Penicillium
(b) Organ-transplant	Trichoderma
(c) Swine flu	Monascus
(d) AIDS	Pseudomonas

Question. Antibodies in our body are complex
(a) Prostaglandins
(b) Glycoprotein
(c) Lipoproteins
(d) Streptomyces

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

Question. Which among these are produced by distillation of fermented broth?
A. Whisky
B. Wine
C. Beer
D. Rum
E. Brandy
Options :
(a) B and C alone
(b) A and B alone
(c) C and E alone
(d) A, D and E alone
(e) C and D alone

Question. Flemming Chain and Florey were awarded the Nobel Prize in 1945 for the discovery of
(a) HIV
(b) CT scan
(c) Penicillin
(d) Staphyloccus

Question. Read the following statements and choose the incorrect ones
A. Physical removal of large and small particles through filteration and sedimentation is called primary sewage treatment
B. Secondary sewage treatment is mainly a mechanical process
C. Activated sludge sediment in a sewage treatment plant is a rich soure of aerobic bacteria
D. Biogas, commonly called as gobar gas, is pure methane
Options :
(a) A and B
(b) B and D
(c) B and C
(d) C and D

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

Question. Which of these following methods is the most suitable for disposal of nuclear waste?
(a) Shoot the nuclear waste into space
(b) Bury the waste under Antarctic ice-cover
(c) Dump the waste within rocks under deep ocean
(d) Bury the waste within rocks deep below the Earth’s surface

Question. Which one of the following pairs is wrongly matched?
(a) Methanogens – Gobar gas
(b) Yeast – Ethanol
(c) Streptomycetes – Antibiotic
(d) Coliform – Vinegar

Question. In developing countries, the heaviest demand on forests is for
(a) Fuel wood
(b) Petroleum and oil
(c) Coal
(d) Charcoal

Question. Cow dung is appropriately used as
(a) Manure
(b) Fuel
(c) Medicine
(d) Building material

Question. Farmer have reported 50% higher yield of rice by using biofertilizer
(a) Azolla pinnata
(b) Legume -rhizobium symbiosis
(c) Cyanobacteria
(d) Mycorrhiza

Question. Biofertilizers include
(a) Cowdung manure and farmyard waste
(b) A quick growing crop ploughed back
(c) BGA/Anabaena and Azolla
(d) All the above

Question. Latest trend in plant disease control is
(a) Biological control
(b) Pesticides
(c) Confusion technique
(d) Biofertilizer

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. 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

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

Question. Which gas is responsible for the puffed up appearance of dough?
(a) CO₂
(b) O₂
(c) SO₂
(d) NO₂

Question. Which one is used in production of alcohol /ethanol
(a) Saccharomyces cerevisiae
(b) Torulopsis utilis
(c) Clostridium botulinum
(d) Leuconostoc citrovorum

Question. Bioactive molecules produced from Monascus purpureus which inhibit cholestrol synthesis in blood are
(a) Gluconic acid
(b) Statins
(c) Gibberellins
(d) Bacitracin

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

Very Short Answer Questions

Question. What for Nucleopolyhedroviruses are being used nowadays? 
Ans. Nucleopolyhedroviruses are used for the biological control of insect pests.

Question. What causes doughing of wheat flour?
Ans. Production of CO₂ gas during yeast fermentation of bacteria.

Question. How is the presence of cyanobacteria in the paddy fields beneficial to rice crop?
Ans. Cyanobacteria can fix atmospheric nitrogen. In paddy fields, the cyanobacteria act as an important biofertiliser. They also add organic matter to soil and increase its fertility.

Question. What are biofertilisers? Give two examples. 
Ans. Biofertilisers are organisms that enrich the nutrients in the soil. e.g. Rhizobium, Azotobacter.

Question. Why are drinks like Whisky and Rum more intoxicating than wine?
Ans. This is because wine is produced without distillation whereas whisky and rum are produced by distillation of the fermented broth.

Question. In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Ans. The major role of microbes in controlling the diseases is the ‘antibiotic production’. Antibiotics have been used against pathogenic bacteria, e.g., penicillin from Penicillium notatum, streptomycin from Streptomyces griseus, etc.

Short Answer Questions

Question. Mention the importance of Lactic acid bacteria to humans other than setting milk into curd.
Ans. Lactic acid bacteria increase vitamin B12 absorption and also checks disease-causing microbes.

Question. Give the scientific name of the microbes from which cyclosporin A and statin are obtained.Write one medical use of each one of these drugs.
Ans. Cyclosporin A that is used as an immuno-suppressive agent during organ transplantation in patients is produced by the fungus Trichoderma polysporum. Statins produced by yeast Monascus purpureus have been commercialised as blood cholesterol lowering agents.

Question. To reduce the percentage of population suffering from hunger and malnutrition, microbes are grown on a large scale to act as food supplements. Mention any two microbes used as food supplement and suggest their role. 
Ans. Spirulina and Methylophilus methylotrophus are used as food supplements.
Spirulina produces large quantities of food rich in protein, minerals, fats, carbohydrates and vitamins.
250 gm of Methylophilus methylotrophus produces 25 tonnes of protein per day.

Question. Name the blank spaces a, b, c and d given in the following table:

Type of microbe	Name	Commercial product
Bacterium	a	Clot buster enzyme
b	Aspergillus niger	Citric acid
Fungus	Trichoderma polysporum	c
Bacterium	d	Butyric acid

Ans. (a) Streptococcus
(b) Fungus
(c) Cyclosporin A
(d) Clostridium butylicum

Question. Write the binomials of two fungi and mention the products/bioactive molecules they help to produce.
Ans. 

Fungi	Products/Bioactive molecules produced
Trichoderma polysporum	Cyclosporin A
Aspergillus niger	Citric Acid
Monascus purpureus	Statin
Saccharomyces cerevisiae	Ethanol/alcohol
Penicillium notatum	Penicillin

Question. What is the key difference between primary and secondary sewage treatment?
Ans. The key difference between primary and secondary treatment of sewage is that primary treatment is the physical process of removing grit and floating debris while secondary treatment is a biological process that involves digestion of organic matter by microbes.

Question. Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. 
Biogas, Citric acid, Penicillin and Curd.
Ans. (i) Penicillin: It is an antibiotic used in curing numerous bacterial diseases.
(ii) Biogas: It is a source of energy in rural areas, produced by anaerobic degradation of organic matter.
(iii) Curd: It is vitamin-rich milk preparation which is easily digested.
(iv) Citric acid: It is an organic acid used as preservative in juices, jams and jellies, etc.

Question. Why are some molecules called bioactive molecules? Give two examples of such molecules.
Ans. Some molecules are called bioactive molecules, because microbes like bacteria or fungi are used in their production.
e.g., Citric acid produced by Aspergillus niger Butyric acid produced by Clostridium butylicum Ethanol produced by Saccharomyces cerevisiae Streptokinase produced by Streptococcus (Any two)

Question. Give the binomials of two types of yeast and the commercial bioactive products they help to produce. 
Ans.

Yeast	Their bioactive products
Saccharomyces cerevisiae	Ethanol/alcohol
Monascus purpureus	Statin

Question. Name the source of statin and state its action on the human body. 
OR
Name a microbe used for statin production. How do statin lower blood cholesterol level?
Ans. Statin is produced by the yeast Monascus purpureus. It acts as a blood-cholesterol lowering agent,by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

Question. Describe the main ideas behind the biological control of pests and diseases.
Ans. Biological control means life against life. It is a natural and ecofriendly concept. It employs natural organisms to control the population of pathogens and pests in an ecosystem. Classical examples are Trichoderma which is antagonist against many soil-borne plant pathogens. Similarly,Penicillium inhibits the growth of Staphylococcus and therefore has been successfully used in the production of penicillin antibiotic to control many human bacterial pathogens.
Ladybirds used to control aphids and dragonflies used to control mosquitoes.

Question. (a) Patients who have undergone myocardial infarction are given clot buster. Mention the clot buster administered and its microbial source.
(b) A person recuperating from illness is advised to have curd regularly. Why?
Ans. (a) Streptokinase is the clot buster and its microbial source is Streptococcus.
(b) Curd contains Lactic Acid Bacteria, which play beneficial role in checking disease-causing microbes. It is also a source of vitamin B12.

Long Answer Questions

Question. (a) Why are the fruit juices bought from market clearer as compared to those made at home?
(b) Name the bioactive molecules produced by Trichoderma polysporum and Monascus purpureus. 
Ans. (a) The fruit juices bought from market are clearer because they have been clarified by pectinases and proteases.
(b) Trichoderma polysporum: Cyclosporin A Monascus purpureus: Statins

Question. (a) Name the category of microbes occurring naturally in sewage and making it less polluted during the treatment.
(b) Explain the different steps involved in the secondary treatment of sewage. 
Ans. (a) Aerobic microbes
(b) Secondary treatment or biological treatment
• Primary effluent is passed into large aeration tanks with constant mechanical agitation and air supply.
• Useful aerobic microbes grow rapidly and form flocs.
• Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
• The growing microbes consume organic matter and thus reduce the biochemical oxygen demand (BOD).
• When BOD of sewage has reduced, the effluent is passed into settling tank.
• Here, the bacterial flocs settle and the sediment is called activated sludge.
• A small part of the sludge is used as an inoculum in the aeration tank and the remaining part is passed into large tanks called anaerobic sludge digesters.
• In the digesters, heterotrophic microbes anaerobically digest bacteria and fungi in sludge producing mixture of gases such as methane, hydrogen sulphide (H₂S) and CO₂, which form the biogas.
• Effluent is now released into rivers and streams.

Question. Explain the function of “anaerobic sludge digester” in a sewage treatment plant.
Ans. Anaerobic sludge digester has anaerobic bacteria that digests the aerobic bacteria and fungi present in the sludge. During the digestion these bacteria produce mixture of gases such as methane, H₂S and CO₂ (biogas).

Question. Explain the different steps involved during primary treatment phase of sewage. 
Ans. Primary treatment or physical treatment
• It is the physical removal of large and small particles from sewage.
• First, the floating debris is removed by sequential filtration by passing through wire mesh screens.
• Then, the grit (soil and small pebbles) are removed by sedimentation in settling tanks. The sediment is called primary sludge and the supernatant is the effluent.
• The effluent is taken for secondary treatment.

Question. (i) List the components of biogas.
(ii) What makes methanogens suitable for biogas production?
Ans. (i) Biogas is a mixture of inflammable gases like methane, carbon dioxide and hydrogen.
(ii) Methanogens grow anaerobically and help in breakdown of cellulosic material to produce large amount of methane, carbon dioxide and hydrogen and so it is suitable for biogas production.

Question. How can sewage be used to generate biogas? Explain.
Ans. When biochemical oxygen demand (BOD) of sewage is reduced, effluent is passed into a settling tank for bacterial flocs to settle down. The sediment is called activated sludge. Activated sludge is pumped into anaerobic sludge digesters. In the digesters, heterotrophic microbes anaerobically digest bacteria and fungi in the sludge producing a mixture of gases which form the biogas.