CBSE Class 12 Biology HOTs Microbes In Human Welfare

Please refer to CBSE Class 12 Biology HOTs Microbes In Human Welfare. Download HOTS questions and answers for Class 12 Biology. Read CBSE Class 12 Biology HOTs for Chapter 10 Microbes In Human Welfare below and download in pdf. High Order Thinking Skills questions come in exams for Biology in Class 12 and if prepared properly can help you to score more marks. You can refer to more chapter wise Class 12 Biology HOTS Questions with solutions and also get latest topic wise important study material as per NCERT book for Class 12 Biology and all other subjects for free on Studiestoday designed as per latest CBSE, NCERT and KVS syllabus and pattern for Class 12

Chapter 10 Microbes In Human Welfare Class 12 Biology HOTS

Class 12 Biology students should refer to the following high order thinking skills questions with answers for Chapter 10 Microbes In Human Welfare in Class 12. These HOTS questions with answers for Class 12 Biology will come in exams and help you to score good marks

HOTS Questions Chapter 10 Microbes In Human Welfare Class 12 Biology with Answers

Question. Given below is the diagram of a bacteriophage. In which one of the option, all the six parts A, B, C, D, E and F are correct? (Image 4)
(a) A–Head, B–Tail, C–Collar, D–Pins, E–Plate, F–Prongs
(b) A–Head, B–Collar, C–Tail, D–Plate, E–Pins, F–Prongs
(c) A–Head, B–Tail, C–Collar, D–Plate, E–Prongs, F–Pins
(d) A–Head, B–Collar, C–Tail, D–Pins, E–Plate, F–Prongs
5 Which of the following bacteria convert milk into curd?
(a) Propionibacterium shermanii
(b) Saccharomyces cerevisiae
(c) Lactobacillus
(d) Thermophilic bacteria
Answer : B

Question. Microorganisms such as Lactobacillus are commonly called
(a) Citric Acid Bacteria (CAB)
(b) Lactic Acid Bacteria (LAB)
(c) Tartaric Acid Bacteria (TAB)
(d) Formic Acid Bacteria (FAB)
Answer : C

Question. Which of the following food items are produced through fermentation by the microorganisms?
I. Idli II. Dosa
III. Toddy IV. Cheese
Choose the correct option.
(a) I, II and III
(b) I, III and IV
(c) II, III and IV
(d) All of these
Answer : B

Question. Which one of the following equipments is essentially required for growing microbes on a large scale, for industrial production of enzymes?
(a) Sludge digester
(b) Industrial oven
(c) Bioreactor
(d) BOD incubator
Answer : C

Question. The most abundant prokaryotes helpful to human in making curd from milk and in the production of antibiotics are the ones categorised as
(a) cyanobacteria 
(b) archaebacteria
(c) chemosynthetic autotrophs
(d) heterotrophic bacteria
Answer : B

Question. The starter or inoculum is added to the fresh milk in order to convert milk into curd and improves its nutritional quality by increasing
(a) vitamin-B12
(b) protein
(c) calcium
(d) All of these
Answer : A

Question. Study the following flowchart that shows curd formation from milk and select the correct option for A and B. (Image 9)
(a) A–citric acid, B–vitamin-B12
(b) A–lactic acid, B–vitamin-B12
(c) A–lactic acid, B–vitamin-C
(d) A–citric acid, B–vitamin-B2
Answer : B

Question. Which gas is released during the process of fermentation that gives the puffy appearance to dough for making bread?
(a) CO2
(b) CO
(c) O2
(d) H2
Answer : A

Question. Toddy, a traditional drink of Southern India is made by ...A... of sap from …B… tree. Here, A and B refer to
(a) A–fermentation, B–palm
(b) A–fermentation, B–bamboo
(c) A–distillation, B–palm
(d) A–distillation, B–bamboo
Answer : A

Question. Swiss cheese is formed by the bacterium
(a) Aspergillus niger
(b) Lactobacillus
(c) Propionibacterium shemanii
(d) Penicillium roqueforti
Answer : C

Question. Roquefort cheese is formed by ripening with ...A...for a particular flavour. Here A refers to
(a) yeast
(b) fungi
(c) bacteria
(d) None of these
Answer : B 

Question. The alcoholic beverages produced by the distillation of the fermented broth are
(a) wine and beer
(b) wine, whisky and brandy
(c) whisky, brandy and rum
(d) whisky, beer and brandy
Answer : C

Question. Which of the following organisms is used in the production of beverages like wine, beer, whisky brandy or rum?
(a) Clostridium butylicum
(b) Aspergillus niger
(c) Saccharomyces cerevisiae
(d) Penicillium notatum
Answer : C

Question. Microorganisms or microbes are found in
(a) soil, air, water and inside the bodies of living organisms
(b) thermal vents deep in soil
(c) under snow and in highly acidic environments
(d) All of the above
Answer : C

Question. The microscopic proteinaceous infectious agents are
(a) viroids
(b) prions
(c) protozoans
(d) bacteria
Answer : B

Question. Identify the blank spaces A, B, C and D given in the following table and select the correct answer.  (Image 29)
(a) A–Trichoderma polysporum, B–As an immunosuppressive agent in organ transplant patients, C–Yeast, D–As blood-cholesterol lowering agent
(b) A–Trichoderma polysporum, B–As blood-cholesterol lowering agent, C–Protozoa, D–As an immunosuppressive agent in organ transplant patients
(c) A–Clostridium butylicum, B–Used as a clot-buster, C–Yeast, D–As blood- cholesterol lowering agent
(d) A–Clostridium butylicum, B–As blood-cholesterol lowering agent, C–Yeast, D–Used as a clot-buster
Answer : A

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 agent, statins
Answer : D

Question. The nutritive medium for growing bacteria and many fungi in the laboratory is called
(a) culture media
(b) fermentation media
(c) baking media
(d) None of the above 
Answer : A

Question. Yeast is used in the production of
(a) citric acid and lactic acid
(b) lipase and pectinase
(c) bread and beer
(d) cheese and butter
Answer : C

Question. Choose the incorrect pair.
(a) Lipases – Used in detergents for removing oil stains
(b) Pectinases and proteases – Used in clarifying bottled juices
(c) Statins – Competitively inhibit the enzyme responsible for cholesterol synthesis
(d) None of the above
Answer : D

Question. Which of the following is used as ‘clot buster’ for removing clots from blood vessels of patient who have undergone myocardial infarction?
(a) Ethanol
(b) Statins
(c) Cyclosporin-A
(d) Streptokinase
Answer : D

Question. Brewer’s yeast is
(a) Penicillium notatum
(b) Trichoderma polysporum
(c) Propionibacterium shermanii
(d) Saccharomyces cerevisiae
Answer : D

Question. Who observed a mould growing in unwashed culture plate while working on Staphylococcus bacterium?
(a) Ernst Chain
(b) Alexander Fleming
(c) Lamarck
(d) Florey
Answer : B 

Question. Antibiotics are used to treat diseases like
(a) diphtheria, whooping cough
(b) plague
(c) leprosy
(d) All of the above
Answer : D

Question. Identify the blank spaces A, B, C and D given in the following table and select the correct answer. (Image 24)
(a) A–Lactobacillus, B–Aspergillus niger, C–Bacterium, D–Penicillin
(b) A–Staphylococcus, B–Clostridium, C–Yeast, D–Penicillin
(c) A–Lactobacillus, B–Microsporum, C–Yeast, D–Penicillin
(d) A–Staphylococcus, B–Microsporum, C–Agaricus, D–Penicillin
Answer : A

Question. Who got Nobel Prize in 1945 for the discovery of penicillin as an antibiotic?
(a) Alexander Fleming
(b) Ernst Chain
(c) Howard Florey
(d) All of these
Answer : D

Question. Which one of the following in sewage treatment removes suspended solids? 
(a) Tertiary treatment
(b) Secondary treatment
(c) Primary treatment
(d) Sludge treatment
Answer : C

Question. Which one of these microbes is used in the commercial production of butyric acid?
(a) Clostridium butylicum
(b) Streptococcus butylicum
(c) Trichoderma polysporum
(d) Saccharomyces cerevisiae
Answer : A

Question. Which of the following is correctly matched for the product produced by them? 
(a) Acetobacter aceti – Antibiotics
(b) Methanobacterium – Lactic acid
(c) Penicillium notatum – Acetic acid
(d) Saccharomyces cerevisiae – Ethanol
Answer : D

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

Question. The dough/ batter out of which Dosa and idly is made, appears to be puffed when kept for some time. What thing is responsible for the puffy appearance? Can you tell the metabolic pathway responsible for giving this puffy appearance? Also, name the microorganism involved in this process?
 
Answer. i) Due to the production of CO2
       ii) Anaerobic Respiration (Alcoholic Fermentation)
      iii) Saccharomyces cerevisiae(yeast)
 
Question. Different variety of cheese is known by their texture, flavors and taste. A variety of cheese is having “pores” in it. State the reason behind this. Name the microbe responsible for it. Also name the variety of cheese?
 
Answer. i) Large amount of CO2 evolving through the cheese
ii) Microbe – A Bacterium - Propionibacterium sharmanii
iii) Swiss Cheese
 
Question. Rama and Shyama are very fond of enjoying fruit juices. Rama likes to drink fresh juice from a local fruit juice shop while Shyama likes bottled juice. When compared, fresh juice appears to be turbid while bottled juice does not. What is the reason for this observation?
 
Answer. i) Fresh juice’s turbidity -cellular remnants
ii) Bottled juice’s clarity – Pectinase and Proteases (of micro organismal origin)
digest them, thus providing clarity.
 
Question. Radha had just undergone a kidney transplant A bioactive molecular drug in administered to oppose kidney rejection by the body. What is the bioactive molecule? Also name the microbe from which this is extracted?
 
Answer. i) Cyclosporin-A ( immunosuppressant )
        ii) A fungus – Trichoderma polysporum.
 
Question. A patient who has been suffering from myocardial infarction is found to be having clots in the blood vessels. “Clot Buster” is used to dissolve the clots. Name the clot buster used to digest the clot and the micro-organism from which it is extracted also?
 
Answer. i) “Clot buster”- an enzyme Streptokinase
       ii) micro-organism-A bacterium - Streptococcus
 
Question. Water samples, three in number namely river water; sewage water and secondary effluent from STP were subjected to BOD test. They were labeled A B & C but the laboratory technician did not note which was which. The BOD values of three samples A, B & C were recorded as 30mg/l, 8mg/l and 500mg/l respectively. Which sample of water is most polluted? Can you assign the correct label to each assuming the river water relatively clear?
 
Answer. BOD value - 30mg/L - Secondary effluent from STP
BOD value - 8mg/L – River Water
BOD value - 500mg/L – Sewage Water
(Fact – The greater the BOD of water, the more is its pollution potential.)
 
Question. A white coloured, dry powdered substances is sprayed on the vulnerable plants to control butterfly caterpillars. Guess what thing of biological origin may be there in. What is the source /micro-organism of it?
 
Answer. i) White powder is “Dry spores”
        ii) Source – Bacillus thuringiensis bacteria
 
Question. A bio- active molecule produced by micro-organism acts by competitively inhibiting the enzyme responsible for cholesterol synthesis .Name the enzyme and the microbe out of which it is extracted?
 
Answer. i) Enzyme – Statins
Microbe – yeast Monascus purpureus.
 
Question. Two villagers were arguing for the nutritive value of milk and curd? Being a normal science student and having studied the biochemistry of both the products, tell which one is more nutritive and justify it ?
 
Answer. Curd / Whey is more nutritious, have vitamin B12, synthesized by LAB (absent in milk).
 
Question. The name virus generally brings in our mind havoc that they are our enemies. There is a category of virus which has species specific narrow spectrum, has insecticidal application, having no impact on plants and other animals. Name the category and give one example?
 
Answer. Baculloviruses is the category. Eg :- Nucleopolyhedrovirus
 
Question. Citric acid is available in the market and acts as an excellent food preservative, can you name the microorganism out of which it is extracted?
 
Answer. Aspergillus niger (A fungus)
 
Question. A farmer was practicing mono culture in his field .Then he was advised to raise paddy crops in his field. He raised after that he observed a boom in the fertility of the field. What can be the reason behind it? Justify your answer.
 
Answer. Nitrogen fixation by autotrophic microbes cyanobacteria e.g. Anabaena, Nostoc ,Oscillatoria. Cyanobacteria enrich the soil with organic matter and nitrogen components.
 
Question. A debate was going on the use of chemical fertilizer and bio-fertilizer. As a student of biology, you have strongly supported the use of bio fertilizer. Acquaint others in what way, you have supported this idea.
 
Answer. Use of Biofertilizers instead of chemical fertilizers because:-
(a) Chemical fertilizers cause pollution.
(b) Biofertilizers- no polution.
(c) Biodegradable (d) Ecofriendly
 
Question. By chance you have been caught by the neighboring country & you have been put with cattle. You have not only given human food to eat, but plentiful straw and green forage was there. As an intellectual student of biology, what thoughts would have come to your mind if you had eaten Straw ?
 
Answer. If I had been cow , I would have rumen , I would be able to eat straw which is a cellulosic material and digest it with the help of Methanogens ( Methane generating bacteria)
 
Question. Assuming you as a chairman of KVIC, suggest the points of maximum utilization of Gobar Gas, the mechanism of its production & ecofriendly aspects of Gobar gas to the villages.
 
Answer. Gobar gas can be abundantly produced in rural areas from gobar with the help of gobar gas plants. Slury acts as an exellent increase of soil fertility. Ecofriendly i.e. it does not cause pollution when burnt.

 

 

Question. Yeast is used in the production of
(a) bread and beer
(b) cheese and butter
(c) citric acid and lactic acid
(d) lipase and pectinase.
Answer : A

Question. A person admitted to hospital as he had myocardial infarction. A cardiologist injected him ‘streptokinase’, why?
(a) It stimulates heart beat.
(b) It reduces hypertension.
(c) It acts as clot buster.
(d) It reduces the level of blood cholesterol.
Answer : C

Question. Ernst Chain and Howard Florey’s contribution was
(a) establishing the potential of penicillin as an effective antibiotic
(b) discovery of streptokinase
(c) production of genetically engineered insulin
(d) discovery of DNA sequence.
Answer : A

Question. Which one of the following is a bacterial biofertiliser?
(a) Anabaena
(b) Nostoc
(c) Rhizobium
(d) Oscillatoria
Answer : C

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. An organism used as a biofertiliser for raising soyabean crop is
(a) Azotobacter
(b) Azospirillum
(c) Rhizobium
(d) Nostoc.
Answer : C

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

Question. Match column I with column II and select the correct option using the codes given below.
Column-I Column-II
A. Citric acid          (i) Trichoderma
B. Cyclosporin A    (ii) Clostridium
C. Statins             (iii) Aspergillus
D. Butyric acid      (iv) Monascus
(a) A-(iii), B-(i), C-(ii), D-(iv)
(b) A-(iii), B-(i), C-(iv), D-(ii)
(c) A-(i), B-(iv), C-(ii), D-(iii)
(d) A-(iii), B-(iv), C-(i), D-(ii)
Answer : B

 

Question. Select the incorrect match.
(a) Citric acid – Aspergillus niger
(b) Streptokinase – Streptococcus
(c) Butyric acid – Clostridium acetobutylicum
(d) Cyclosporin-A – Monascus purpureus
Answer : D

Question. Match the following organisms with the products they produce.
(A) Lactobacillus         (i) Cheese
(B) Saccharomyces     (ii) Curd cerevisiae
(C) Aspergillus niger   (iii) Citric acid
(D) Acetobacter aceti  (iv) Bread
(v) Acetic acid
Select the correct option.
(A) (B) (C) (D)
(a) (ii) (i) (iii) (v)
(b) (ii) (iv) (v) (iii)
(c) (ii) (iv) (iii) (v)
(d) (iii) (iv) (v) (i)
Answer : C

Question. Which of the following microbes is used for the commercial production of ethanol?
(a) Clostridium butylicum
(b) Trichoderma polysporum
(c) Monascus purpureus
(d) Saccharomyces cerevisiae
Answer : B

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

Question. The primary treatment of sewage water involves
(a) anaerobic bacterial activity
(b) sludge digestion
(c) filtration and sedimentation
(d) aerobic bacterial activity.
Answer : C

Question. Identify the organism shown in the given diagram.
(a) Bacteria
(b) Bacteriophage
(c) TMV
(d) HIV
Answer : C

Question. Viruses of the genus Nucleopolyhedrovirus are employed as
(a) gobar gas producers
(b) biological control agents
(c) anaerobic sludge digesters
(d) atmospheric nitrogen fixing agents.
Answer : B

Question. Select the correct pair of microorganism and the product obtained from it.
(a) Monascus purpureus - produces large holes in Swiss cheese.
(b) Saccharomyces cerevisiae - used for making wine and beer after distillation.
(c) Streptococcus - produces streptokinase which is used to remove clots.
(d) Aspergillus niger - produces citric acid and butyric acid.
Answer : C

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

Question. Select the mismatch.
(a) Rhodospirillum – Mycorrhiza
(b) Anabaena – Nitrogen fixer
(c) Rhizobium – Alfalfa
(d) Frankia – Alnus
Answer : A

Question. Refer to the given figure and select the correct match.
CBSE_Class_12_Biology_in_Human_Set_B_1
(a) A-Fungal colony, B-Bacterial colony
(b) A-Viral colony, B-Bacterial colony
(c) A-Bacterial colony, B-Viral colony
(d) A-Bacterial colony, B-Fungal colony
Answer : D

 

Question. As Saccharomyces cerevisiae produces CO2 during fermentation, if fermented dough of Aspergillus niger is used to make bread, then what happens on its consumption ? 
Answer. Food will produce toxicity because Aspergillus niger produce aflatoxins.
 
Question. Raman underwent kidney transplantation after which he observed allergic reactions. Can you suggest the name of microbial product and its source for controlling them.
CBSE_Class_12_Biology_in_Human_Set_B_1
Answer. Product : cyclosporine A, Source : Trichoderma polysporum (fungi)
 
Question. Swati knows that the cow excreta contains a specific bacteria. Name the type of bacteria and how it can be socially used. 
Answer. Methanogens (Archebacteria), Social use: lightening & cooking by using gobar gas.
 
Question. GM crops are favored by some countries, while in India it is still banned. Can you suggest merits and demerits of such crops ? 
Answer. Merits : Enhance the quality & quantity of crops, less requirement of insecticide & pesticides, improve agronomic characteristics. Demerits : Favors new pathogen strain , dependability of farmers on biogenic companies.

 

Q.1. Name the group of bacteria that are capable to live in high temperatures above 100 C (1)
 
Q.2. To which class of fungi does Penicillium belong? (1)
 
Q.3. Which of the steps are related to Nitrogen fixation? (1)
a) N2 NH3
b) N2 NO3
c) N2 Amino acid
d) Both a and b
 
Q.4. Which of the following organisms has Nif Gene? (1)
a) Penicillum b) Rhizobium c) Aspergillus . d) Streptococcus
Ans: b
 
Q.5.Why is whisky more intoxicating than beer?
 
EACH QUESTION CARRIES 2 MARKS
 
Q.6. Biogas plants are more often built in rural areas. Why? (2)
Ans: Cattles are available in plenty & its dung can be used as slurry
 
Q.7. Why are most of the antibiotics sold in combination with lactobacillus, these days? (2)
 
Q.8. Recently Chickungunya cases were reported from various parts of the country. Name the vector and pathogen responsible for this disease. (2)
 
Q.9.In human beings the roughage contains cellulose but in cattles it is not. Why? (2)
 
Q.10. State whether the BOD is High/Low (2)
a) Water after Primary treatment
b)Water after Secondary treatment
 
Q.11. A person has suffered a heart attack due to a floating clot in his coronary artery.
a. Name the bacterium that can save him.
b. Mention its product and its action.
 
EACH QUESTION CARRIES 3 MARKS
 
Q.10. Biocontrol measures are preferred to chemical pesticides. Justify the statement (3)
 
Q.11. Graphically represent the relationship (3)
(a) Organic waste with that of BOD
(b) Dissolved Oxygen with that of BOD.
Ans: More organic waste the more the BOD/More the Oxygen level less the BOD.
 
Q.12. Leguminous plants can thrive well in nitrogen deficient soil. Comment.
 
Q.13. 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 labeled A, B and C. But the lab attendant did not note which was which. The BOD values of A, B and C were recorded as 20 mg/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? (3)
 
Q.14. Give one example and one use of the following (3)
a) Free living fungi
b) Symbiotic fungi
c) Free living bacteria
 
Q.15. Use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides – Elaborate the idea with examples. (Only three) (3)
 
Q.16. How is it that the Cry protein produced by Bacillus thuringiensis (Bt) does harm the bacteria but only kills the insect larvae? (3)
 
Q.17. What according to your opinion is the reason for failure of the major programmes like Ganga Action plan or Yamuna action plan? (3)
 
Ans: a) Illiteracy of people who fail to cooperate in the programmes
       b) Excess of human settlement on the banks of river
       c) Large no. of industries on the banks
       d) Law enforcing agency fails to exercise their power.
       e) Political interference etc.
 
Q.18. Differentiate Antibodies and antibiotics. (3)
 
Q.19. How are biofertilizers different from fertilizers such as NPK that we buy in the market? Justify the role of Rhizobium as a biofertilizer. (3)
 
Q.20. Microbes play a dual role when used for sewage treatment, as they not only help to retrieve usable water but also generate fuel. Write in points how this happens. (3)
 
Q.21. Match the organic acids and the microbial source. (3)
i) Citric acid - Acetobacotor
ii) Acetic acid - Clostridium
iii) Butyric acid - Aspergillus
 

Very Short Answer Questions

Question. Give an example of a rod-shaped virus. 
Answer. Tobacco mosaic virus.

Question. Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Answer. ‘Dosa’ and ‘idli’ (from rice), bread (from wheat) and ‘dhokla’ (from Bengal gram) are the traditional Indian foods which involve use of microbes.

Question. Why is distillation required for producing certain alcoholic drinks?
Answer. Distillation increases the alcohol content in alcoholic drinks.

Question. Mention the role of cyanobacteria as a biofertiliser. 
Answer. It is a biological organism that fixes atmospheric nitrogen.

Question. What would have happened if antibiotics were not discovered?
Answer. If antibiotics were not discovered, bacterial diseases would not have been controllable.

Short Answer Questions

Question. Find out the role of microbes in the following and discuss it with your teacher.
(a) Single cell protein (SCP)
(b) Soil
Answer. (a) Single cell protein (SCP): It is a protein-rich microbial biomass which can be used as food.
SCP contains essential amino acids and low fat. Bacteria, filamentous fungi, algae, yeast,etc., are used as “single cell proteins” (SCPs). Spirulina is taken as a tablet having 60 per cent proteins, all minerals, vitamins, etc.
(b) Soil: Soil is the habitat of numerous microbes. Microbes in the soil increase the fertility of soil by decomposing organic matter. Some microbes convert nitrates into free nitrogen that escapes into atmosphere for replenishment.

Question. Your advice is sought to improve the nitrogen content of the soil to be used for cultivation of a non-leguminous terrestrial crop.
(a) Recommend two microbes that can enrich the soil with nitrogen.
(b) Why do leguminous crops not require such enrichment of the soil? 
Answer. (a) Azospirillum/Azotobacter/Anabaena/Nostoc/Oscillatoria/Frankia. (Any two)
(b) Leguminous crops do not need nitrogen from soil because the nitrogen fixing bacteria (Rhizobium) are present in their root nodules, which can fix atmospheric nitrogen for the crops.

Question. What is the chemical nature of biogas? Name an organism which is known to be employed in biogas. 
Answer. The biogas contains methane, CO2 and H2. Methanobacterium, a type of methanogen is employed for biogas production.

Question. How do mycorrhizae act as biofertilisers? Explain. Name a genus of fungi that forms a mycorrhizal association with plants. 
Answer. Mycorrhizae is a symbiotic association of a fungus with roots of higher plants. The fungus absorbs phosphate from soil and passes it to the plant. It also provides resistance to root-borne pathogen and increase the tolerance of plant to salinity and drought. This way they act as biofertilisers.
Genus of fungi — Glomus.

Question. How was penicillin discovered? 
Answer. Penicillin was an accidental discovery. Sir Alexander Fleming observed that in unwanted culture plates of Staphylococcus a mould of Penicillium was growing This mould inhibited the growth of Staphylococcus around it. Later the antibiotic penicillin was isolated from this fungus.

Question. How does the application of the fungal genus, Glomus, to the agricultural farm increase the farm output? 
Answer. Glomus is a fungus which is found in symbiotic relationship with roots of seed plants. It absorbs phosphorus from the soil and passes it on to the plant, and in turn gets sugars from the plant. Due to increased availability of phosphorus there is an increase in farm output.

Question. Name any two species of fungus, which are used in the production of the antibiotics.
Answer. Two species of fungus, used in the production of the antibiotics:
(i) Penicillium notatum (for penicillin production).
(ii) Aspergillus fumigatus (for fumagillin production).

Question. How does the application of cyanobacteria help to improve agriculture output?
Answer. Cyanobacteria are autotrophic, free-living or symbiotic microbes. They can fix atmospheric nitrogen. Blue-green algae also add organic matter to the soil and increases its fertility. They replenish soil nutrients and reduce dependence on chemical fertilisers.

Question. Name the source of cyclosporin-A. How does this bioactive molecule function in our body?
Answer. Trichoderma polysporum. It acts as an immuno-suppresant and is used in organ transplant patient.

Question. List the events that reduce the Biological Oxygen Demand (BOD) of a primary effluent during sewage treatment. 
OR
Explain the process of secondary treatment given to the primary effluent up to the point it shows significant change in the level of biological oxygen demand (BOD) in it. 
Answer. During secondary treatment of primary effluents, vigorous growth of useful aerobic microbes into flocs occur when it is agitated mechanically and air is pumped into it in a large aeration tank. These microbes while growing consume major part of the organic matter in the effluent. This significantly reduces BOD.

Question. How do mycorrhizal fungi help the plants harbouring them? 
Answer. The mycorrhizal fungi absorb phosphorus from the soil and transfer them to the host cells. They also impart resistance to host plants against root pathogens. They also help plants to tolerate salinity and drought.

Question. Find out the name of the microbes from which cyclosporin A (an immuno-suppressive drug) and statins (blood cholesterol lowering agents) are obtained.
Answer. (a) Cyclosporin A is obtained from Trichoderma polysporum.
(b) Statins are obtained from the yeast Monascus purpureus.

 

Chapter 10. MICROBES IN HUMAN WELFARE

Question. Drinks like Whisky and Rum are more intoxicating than wine. Why? 
Answer
produced without distillation and whisky and rum are produced by distillation of the fermented broth.

Question. Can we imagine a world without antibiotics? Explain briefly. 
AnswerNo, because, Antibiotics are needed to kill millions of microbes which cause many deadly diseases like plague, whooping cough, dysphasia etc.

Question. Bottled juices are clearer compared to homemade juice. Give reason.
AnswerBottled juices are clarified by the use of pectinases and proteases.

Question. Which one of these is a proteinaceous infecting agent? 
AnswerPrions are proteinaceous infecting agents.
a) Viroids, b) prions, c) protern, d) wat.

Question. An organic farmer requires a bio control agent which is species specific and has no negative impact on non-target organism. Suggest the name of such a bio control agent.
Answer. Nucleopolyhedrovirus

Question. Scientists have succeeded in introducing toxin gene of Bacillus thuringiensis into plants like cotton. What purpose is achieved through this action? 
Answer. Pest resistant cotton plant.

Question. A small amount of curd was added to cold milk for converting it into curd. But milk did not get curdled. Why? 
AnswerOptimum temperature is needed for the action of lacto bacillus and to convert milk to curd. Bacteria becomes inactive at low temperature

Question. Consuming curd keeps the gastro-intestinal tract in tact. Give reason. 
AnswerCurd contains lactic acid bacteria which checks the growth of disease causing microbes and protects the gastro intestinal tract

Question. On fermentation the dough of idli and dosa puffs up. Which metabolic pathway is responsible for this process? 
AnswerCellular respiration/anaerobic respiration in bacteria produces CO2 gas which puffs up the dough

Question. How do lactic acid bacteria help in increasing the nutritional quality of curd?
AnswerThe nutritional quality of curd is improved by Lactic acid bacteria by increasing vitamin B12

Question. The excreta of cattle do not contain any cellulose but human excreta may contain cellulose. Why? 
AnswerThe rumen of cattle contains methanogens which help in the digestion of cellulose but these bacteria are not present in human stomach

Question. Antibiotics are always sold in combination with lactobacillus. Why? 
Answer. Antibiotics may kill even the useful bacteria present in the digestive tract LAB will protect some microbes in the digestive tract and enhance the production of vitamin B12.

Question. Why are some microbes useful in detergent formulation? 
AnswerSome microbes produce enzymes like lipases which help in removing oil stain when used in detergent formulation.

Question. Microbes release gases during metabolism. How will it help in the production of energy? 
AnswerSome microbes mainly methanogens release large quantities of methane along with CO2 and H2S during metabolism and these gases are used for the production of biogas which is a good source of energy

Question. Why does 'Swiss-cheese' contain large holes?. 
Answer. The large holes on 'Swiss cheese' are due to production of large amount of CO2 during fermentation by the bacteria Propionibacterium sharmani.

Question. In what way the relationship between BOD and organic matter in Sewage will be useful in ecology?
Answer. To determine pollution it helps. More organic waste BOD increases. 

Question. Why do bottled fruit juices appear clearer than the home made ones?
AnswerBottle fruit juices are treated with the yeast Saccharomyces cervisiae. 

Question. What is the principle behind the conversion of milk into curd and partial digestion of milk protein performed by Lactic Acid Bacteria?
Answer. i) Coagulation
ii) Lactic acid produced by LAB coagulate and partially digest the milk protein.

Question. Wine and beer are different from whisky and brandy though they are all alcoholic beverages. What is the name of the process that brings out this difference?
AnswerWine & Beer is produced without distillation. Whisky & brandy are produced by distilliation.

Question. Name the group of bacteria that are capable of living at high temperature above 1000C. How does it become possible by these bacteria?
Answer. Thermoacidophils. This bacterial Enzyme is resistant to high tem.

Question. Why do doctors prescribe Streptokinases for brain hemorrhage patients? Mention the source of industrial production of this biomolecule.
Answerstreptokinase is a‘clot buster’ for removing the blood clots from blood vessels.Bio molecules are produced from Steptococcus Bacteria.

2 marks

Question. A farmer was suggested to apply certain microbial culture in his field to increase the yield. Suggest the types of microbes he could use in his paddy field and how do they help in increasing the yield. 
AnswerThe microbial culture containing anabaena, Oscillatoria or Nostoc. They act as biofertilizer by fixing the atmospheric nitrogen in the soil and thereby increasing the soil fertility

Question. It was observed that certain plant roots are infected by fungus. in spite of this infection the plant showed increased growth and development. Give reason.
AnswerThe plant roots which are infected by fungi form symbiotic association with them and the fungi help the plant to absorb phosphorus from the soil and the plant becomes resistant to salinity and drought thus this symbiotic association called mycorrhiza help in the development of the plant.

Question. Arrange the steps in sewage treatment in proper sequence. 
a) Anaerobic sludge digestion
b) 'Floc' formation
c) Primary effluent in aeration tank
d) Formation of biogas
e) Constant agitation in presence of oxygen.
f)Digestion by anaerobic bacteria
AnswerThe proper sequence is c-e-b-a-f-d

Question. Bacteria that convert effluent into activated sludge play one more beneficial side.Mention the role.
Answer. A small portion of the activated sludge containing bacteria is pumped back into the aeration tank to act as inoculums.

 CBSE_Class_12_Biology_Human_Welfare_1

Question. In the given figure label X & Y and explain the functioning of the below plant.
Answerx-gas holder, y-Digester.

Question. How does Monascus help in lowering blood-cholesterol? 
Answer. Statin produced by Monascus purpureus competitively inhibit the enzyme responsible for synthesizing cholesterol
 
Question. Complete the given table
CBSE_Class_12_Biology_Human_Welfare_2
 
Answer. i) Citric acid 
ii) saccharomyces cerevisiae 
iii) Trichoderma Polysporum 
iv) Acetobacter aceti 
v) Statin 
vi)Streptokinas
 
 
3 marks

Question. Drinks like Whisky and Rum are more intoxicating than wine. Why? 
Answer. produced without distillation and whisky and rum are produced by distillation of the fermented broth.

Question. For what significant properties the Baculoviruses are considered as best Biological control agent?. Mention its importance in organic farming. 
Answer. I) Baculo viruses attack the specific insects & arthropods. They have no negative impact on plants, birds, mammals or even other non-target insects. The desirable aspect is conservation of beneficial insects. Organic farming uses biopesticides & biofertilizers. Baculo viruses are used as good biopesricides.
 
Question. Give one example and one use of the following:- 
     i) Free living fungi 
     ii) Symbiotic fungi 
     iii) Free living bacteria
 
Answer. I) Free living fugi – Trichoderma – used as biocontrol agent. 
ii) Symbolic fungi – Glomus – helps in absorbtion of nutrients from soil. 
iii) Freeliving bacteria – Azotobactor – helps in increasing yield by fixing atmospheric N2 & making it available to the plants.
 
5 Marks
 
Question. Why is organic farming favoured these days? Describe the methods employed in the process. 
Answer. I) Chemical fertilizers causes environmental pollution. 
ii) It decreases the fertility and productivity of the soil. 
iii) Framing with chemical fertilizers is expensive.
 
Organic farming uses biopesticides and biofertilizers.
 
i)Biopesticides – a) Baculo viruses – attack harmful insects.
                        b) Bacillus thuringiensis – introduced in crop field. (These bacteria are available sackets as dried spores) which are mixed with water & spread over vulnerable plants.
 
ii) Biofertilizers – a) Cyano bacteria are used in crop field to increase the fertility of soil.
                         b) Azolla is used in crop field which is decomposed & increases the fertility of soil.
 
Question. (i) Three water samples namely river water, untreated sewage water and secondary effluent discharge from a sewage treatment plan were subjected to BOD test. The samples were labeled A, B and C but the lab attendant did not note which BOD is for which water. The BOD values of 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 that the river water is relatively clean.
Answer(1)
(ii) Which is not a tool of Recombinant DNA technology. 
a) Restriction enzyme
b) Vector
c) Bioreactor
 
(iii) Label the following diagram & Identify the selectable markers 
 
CBSE_Class_12_Biology_Human_Welfare_3
 
Answer. I) A- 20 mg /L  Secondary effluent
B – 8 mg/L River water
C – 400 mg/L  Untreated sewage water
ii) Bioreactor
iii)
CBSE_Class_12_Biology_Human_Welfare_A_3
iv) Role of polymerase – DNA – polymerase is an enzyme used to make copies of DNA making use of the genomic template DNA and the primer.
Chapter 01 Reproduction in Organisms
CBSE Class 12 Biology HOTs Reproduction In Organisms
Chapter 02 Sexual Reproduction In Flowering Plants
CBSE Class 12 Biology HOTs Sexual Reproduction In Flowering Plants
Chapter 03 Human Reproduction
CBSE Class 12 Biology HOTs Human Reproduction
Chapter 04 Reproductive Health
CBSE Class 12 Biology HOTs Reproductive Health
Chapter 05 Principles of Inheritance and Variation
CBSE Class 12 Biology HOTs Principles Of Inheritance And Variation
Chapter 06 Molecular Basis of Inheritance
CBSE Class 12 Biology HOTs Molecular Basis of Inheritance
Chapter 08 Human Health and Disease
CBSE Class 12 Biology HOTs Human Health and Disease
Chapter 09 Strategies for Enhancement In Food Production
CBSE Class 12 Biology HOTs Strategies For Enhancement In food Production
Chapter 10 Microbes In Human Welfare
CBSE Class 12 Biology HOTs Microbes In Human Welfare
Chapter 11 Biotechnology Principles and Processes
CBSE Class 12 Biology HOTs Biotechnology Principles and Processes
Chapter 12 Biotechnology and Its Application
CBSE Class 12 Biology HOTs Biotechnology And Its Applications
Chapter 13 Organisms and Populations
CBSE Class 12 Biology HOTs Organism And Population
Chapter 15 Biodiversity and Conservation
CBSE Class 12 Biology HOTs Biodiversity And Conservation
Chapter 16 Environmental Issues
CBSE Class 12 Biology HOTs Environmental Issues

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