CBSE Class 12 Biology Microbes In Human Welfare Worksheet Set B

Very Short Answer

Question. What are the uses of microbes?

Question. How the Roquefort cheeses are ripened?

Question. Where microbes are present?

Question. What are fermentors?

Question. What are lactic acid bacteria?

Short Answer

Question. What do you mean by antibiotics?

Question. Define microbes?

Question. What do you meant by fermented beverages?

Question. What do you understand by bioactive molecules?

Question. What is the difference between primary sewage treatment and secondary sewage treatment?

Long Answer

Question. Explain why microbes used in production of biogas?

Question. What are the bio control agents in microbes?

Question. What is the use if microbes in sewage treatment?

Question. How can we define microbes as bio fertilizers?

Question. State the difference between conventional farming and organic farming?

Very Short Answer Questions

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

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

Question. How is the presence of cyanobacteria in the paddy fields beneficial to rice crop?
Answer. 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. 
Answer. 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?
Answer. 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?
Answer. 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.
Answer. 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.
Answer. 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. 
Answer. 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:

Answer. (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.
Answer. 

Question. What is the key difference between primary and secondary sewage treatment?
Answer. 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.
Answer. (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.
Answer. 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. 
Answer.

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?
Answer. 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.
Answer. 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?
Answer. (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.

Question. Name the group of bacteria involved in setting milk into curd. Explain the process they carry in doing so. Write another beneficial role of such bacteria. 
Answer. (group of) LAB / (group of) Lactic acid Bacteria / Lactobacillus species 1
LAB produce acids that coagulate and partially digest the milk proteins. 1 Increases Vitamin B12 / Checks disease causing microbes in the stomach.

Question. (a) Match the microbes listed under Column-A with the products mentioned under Column-B.
Column-A                                        Column-B
(H) Penicillium notatum                     (i) Statin
(I) Trichoderma polysporum              (ii) ethanol
(J) Monascus purpureus                   (iii) antibiotic
(K) Saccharomyces cerevisiae         (iv) Cyclosporin-A
(b) Why does ‘Swiss Cheese’ develop large holes ?
Answer. ( a) The correct matches are as follows :
(H) Penicillium notatum                 (iii) Antibiotic
(I) Trichoderma polysporum          (iv) Cyclosporin–A
(J) Monascus purpureus                 (i) Statin
(K) Saccharomyces cerevisiae        (ii) Ethanol
(b) Due to production of large amount of CO₂ (by Propionibacterium shermanii) 

Question. Effluent from the primary treatment of sewage is passed for secondary treatment. Explain the process till the water is ready to be released into natural water bodies.
Answer. During treatment (after adding a small amount of inoculum) primary effluent is constantly agitated mechanically in (large) aeration tanks and the air is pumped into it, this allows the vigorous growth of useful microbes into flocs, the microbes consume the major part of the organic matter in the effluent, it reduces the BOD of the effluent, the effluent is then passed into a settling tank where the bacterial flocs are allowed to sediment, major part of theactivated sludge is pumped into aerobic sludge digester and the remaining water is released into natural water bodies.

Question. “Determination of Biological Oxygen Demand (BOD) can help in suggesting the quality of a water body.” Explain.
Answer. High BOD in a water body indicates more number of micro-organisms in water, resulting in bad quality of water / death of aquatic creatures, more polluting potential.
Lower BOD of water body indicates less number of micro-organisms in water, good quality of water / aquatic life flourishes / less polluting potential. 

Question. Describe how do ‘flocs‘ and ‘activated sludge‘ help in Sewage Treatment.
Answer. Flocs : Aerobic microbes consume the major part of the organic matter in the effluent, which significantly reduces BOD.
Activated sludge : Small part of activated sludge is used as inoculum and pumped back to aeration tank / pumped into anaerobic sludge digesters where microbes or bacteria grow anaerobically to produce CH₄ or H₂S or CO₂ or biogas. 

Question. The three microbes are listed below. Name the product produced by each one of them and mention their use.
(a) Aspergillus niger
(b) Trichoderma polysporum
(c) Monascus purpureus
Answer. (a) Aspergillus niger - Citric Acid, natural preservative / flavouring agent.
(b) Trichoderma polysporum - Cyclosporin A , immunosuppressive agent.
(c) Monascus purpureus - Statin, blood cholesterol lowering agent.

Question. Baculoviruses are good example of biocontrol agents. Justify giving three reasons.
Answer. i. Species specific / narrow spectrum insecticidal application. 1
ii. They have no negative impact on plants / mammals / birds / fish / non-target insects. 1
iii. They are beneficial for IPM (Integrated Pest Management ) / Pest Management Programme.

Question. Some microbes act as biofertilizers. Explain with the help of three suitable examples.
Answer. (i) Rhizobium : Symbiotically fix atmospheric nitrogen into organic forms which can be used by the plant as nutrients.
(ii) Azospirillum / Azotobacter : Free living bacteria fix atmospheric nitrogen.
(iii) Glomus / Fungi : Symbiotic with plants absorbs phosphorus from soil and passes it to plant.
(iv) Cyanobacteria / Anabaena / Nostoc / Oscillatoria
: Fix atmospheric nitrogen in aquatic and terrestrial environment.

Question. ​​​​​​​How does the activity of each one of the following help in organic farming ?
(a) Mycorrhiza
(b) Cyanobacteria
(c) Rhizobium 
Answer. (a) Mycorrhiza : The fungal symbionts in these association absorb phosphorous from soil and pass it to plant. Plants also show resistance to root borne pathogens , tolerance to salinity / drought , an overall increase in plant growth and development. (Any two)
(b) Cyanobacteria : Serve as an important biofertilizers by fixing atmospheric nitrogen, also add organic matter to the soil, and increase its fertility. (Any two)
(c) Rhizobium : Fix atmospheric nitrogen into organic forms , which is used by plant as nutrient / increase soil fertility / symbiotic association in root nodules of leguminous plants.

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