The source organism for the EcoRI restriction endonuclease is Escherichia coli (E. coli).
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Do you know that microbes, though invisible, make up more than 90% of the total biomass on Earth and play an important role in human survival? The NCERT Exemplar Class 12 Biology Solutions Chapter 10 Microbes in Human Welfare has different types of questions like multiple choice, very short, short and long answer with proper answers. These NCERT exemplar solutions help students to learn the chapter in an organised way and make their concepts stronger.
The topics covered in the NCERT Exemplar Solutions for Class 12 Biology are about role of microbes in medicine, industries, environmental safety and also how they support evolution and daily human life. If students do these questions regularly, they can remember the important facts and small terms better and also improve their problem-solving skills. Regular revision with these resources helps to build confidence and makes the Microbes in Human Welfare chapter easy enough to face the exam with help of the NCERT Exemplar Solutions for Class 12.
A set of question formats, like MCQs, short answers, and long answers, is provided to help students strengthen their understanding and perform better in exams.
Question:1
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
Answer:
Milk, when converted into curd by lactic acid bacteria, sees an increase in the content of vitamin B12. This vitamin is crucial for red blood cell formation and neurological function. The fermentation process enhances its bioavailability.
Hence, the correct answer is option (c) Vitamin B12.
Question:2
Wastewater treatment generates a large quantity of sludge, which can be treated by:
a. anaerobic digesters
b. floc
c. chemicals
d. oxidation pond
Answer:
The sludge formed during wastewater treatment is biologically degraded in anaerobic digesters. These digesters use anaerobic microbes that break down the organic matter, producing biogas.
Hence, the correct answer is option (a) Anaerobic digesters.
Question:3
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:
Methanogenic bacteria are obligate anaerobes and are found in oxygen-free environments like the rumen of cattle, gobar gas plants, and paddy fields. Activated sludge, however, contains aerobic microbes.
Hence, the correct answer is option (d) Activated sludge.
Question:4
Match the following list of bacteria and their commercially important products:
Bacterium | Product |
---|---|
A. Aspergillus niger | i. Lactic acid |
B. Acetobacter acetic | ii. Butyric acid |
C. Clostridium bretylium | iii. Acetic acid |
D. Lactobacillus | iv. Citric acid |
Answer:
Aspergillus niger produces citric acid, Acetobacter aceti produces acetic acid, Clostridium butylicum produces butyric acid, and Lactobacillus produces lactic acid. These are used in commercial fermentation processes.
Hence, the correct answer is option (c) A-iv, B-iii, C-ii, D-i.
Question:5
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. Immunosuppressive agent |
Answer:
Statins (from Monascus purpureus) lower cholesterol, Cyclosporin A is an immuno-suppressant, Streptokinase helps dissolve blood clots, and Lipases remove oil stains. Each has a bioactive industrial or therapeutic application.
Hence, the correct answer is option (d) A-iii, B-iv, C-ii, D-i.
Question:6
The primary treatment of wastewater involves the removal of:
a. dissolved impurities
b. stable particles
c. toxic substances
d. harmful bacteria
Answer:
Primary wastewater treatment is physical. It removes solid and stable particles through filtration and sedimentation. Chemical and biological impurities are handled in later stages.
Hence, the correct answer is option (b) Stable particles.
Question:7
BOD of wastewater is estimated by measuring the amount of:
a. total organic matter
b. biodegradable organic matter
c. oxygen evolution
d. oxygen consumption
Answer:
BOD or biochemical oxygen demand is the amount of oxygen required by microbes to break down biodegradable organic matter in water. It indirectly measures pollution.
Hence, the correct answer is option (d) Oxygen consumption.
Question:8
Which one of the following alcoholic drinks is produced without distillation?
a. Wine
b. Whisky
c. Rum
d. Brandy
Answer:
Wine is prepared by fermentation of fruit juices like grapes and is not distilled. Whisky, rum, and brandy are distilled alcoholic drinks.
Hence, the correct answer is option (a) Wine.
Question:9
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
Answer:
Biogas technology in India was pioneered by the Indian Agricultural Research Institute and KVIC. They promoted the use of cow dung as a renewable energy source.
Hence, the correct answer is option (c) Indian Agricultural Research Institute and KVIC.
Question:10
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
Answer:
Trichoderma is a fungus used as a biocontrol agent against plant pathogens. It inhibits harmful fungi and promotes plant growth.
Hence, the correct answer is option (b) Biological control of plant diseases.
Question:11
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 centre of flocs will become anoxic, which would cause the death of bacteria and eventually the breakage of flocs.
c. Flocs would increase in size as anaerobic bacteria would grow around flocs.
d. Protozoa would grow in large numbers
Answer:
Activated sludge flocs require oxygen for the aerobic bacteria within them. If oxygen is limited, anoxic conditions kill bacteria and break down the floc structure.
Hence, the correct answer is option (b) Centre of flocs becomes anoxic, causing breakdown.
Question:12
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
Answer:
Mycorrhiza helps in nutrient and water absorption and disease resistance, but not in fighting insect pests.
Hence, the correct answer is option (d) Increasing resistance to insects.
Question:13
Which one of the following is not a nitrogen-fixing organism?
a. Anabaena
b. Nostoc
c. Azotobacter
d. Pseudomonas
Answer:
Pseudomonas is generally non-nitrogen-fixing. It includes pathogenic species. Anabaena, Nostoc, and Azotobacter fix nitrogen.
Hence, the correct answer is option (d) Pseudomonas.
Question:14
Big holes in Swiss cheese are made by a:
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:
Swiss cheese holes are due to carbon dioxide production by Propionibacterium shermanii during fermentation. Methane and other gases are not involved.
Hence, the correct answer is option (c) Bacterium producing carbon dioxide.
Question:15
The residue left after methane production from cattle dung is:
b. buried in landfills
c. used as manure
d. used in civil construction
Answer:
The leftover slurry after biogas production is rich in nutrients and is used as organic manure in agriculture.
Hence, the correct answer is option (c) used as manure.
Question:16
Methanogens do not produce:
a. Oxygen
b. Methane
c. Hydrogen sulfide
d. Carbon dioxide
Answer:
Methanogens produce methane, CO2, and H2S but not oxygen. They are anaerobic organisms.
Hence, the correct answer is option (a) Oxygen.
Question:17
Activated sludge should have the ability to settle quickly so that it can:
a. be rapidly pumped back from the sedimentation tank to the aeration tank
b. absorb pathogenic bacteria present in wastewater while sinking to the bottom of the settling tank
c. be discarded and anaerobically digested
d. absorb colloidal organic matter
Answer:
Activated sludge must settle quickly to allow proper separation from treated water and enable anaerobic digestion of the sludge.
Hence, the correct answer is option (c) Be discarded and anaerobically digested.
Question:18
Column I | Column II |
---|---|
A. Ladybird | i. Methane bacterium |
B. Mycorrhiza | ii. Trichoderma |
C. Biological control | iii. Aphids |
D. Biogas | iv. Glomus |
Answer:
Ladybird controls aphids (iii), Mycorrhiza involves Glomus (iv), Trichoderma (ii) is a biocontrol agent, and biogas involves methane bacteria (i).
Hence, the correct answer is option (b) A-iii, B-iv, C-ii, D-i.
To make the basic concepts strong students can go through the very short answers provided here:
Question:1
Why does ‘Swiss cheese’ have big holes?
Answer:
A bacterium called Propionibacterium sharmanii produces a large amount of carbon dioxide during fermentation. This is the reason for the big holes in Swiss cheese.Question:2
Answer:
Exceptionally large vessels, which are used for industrial-scale fermentation, are called fermenters.Question:3
Name a microbe used for statin production. How do statins lower blood cholesterol levels?
Answer:
The yeast Monascus purpureus is used for the commercial production of stains. Stain competitively inhibits the enzyme responsible for cholesterol formation and thus helps in lowering the blood cholesterol level.Question:4
Why do we prefer to call secondary wastewater treatment a biological treatment?
Answer:
Secondary treatment of wastewater involves action by microbes. Due to this, secondary treatment is called biological treatment.Question:5
What Nucleopolyhydro viruses are being used nowadays?
Answer:
Nucleopolyhydro viruses are used for controlling pests and other arthropods in farms. These are narrow-spectrum viruses and do not harm plants, cattle humans or even non-target insects.Question:6
How has the discovery of antibiotics helped mankind in the field of medicine?
Answer:
Antibiotics have created a revolution in the treatment of diseases.Question:7
Why is distillation required for producing certain alcoholic drinks?
Answer:
Distillation is done to remove most of the water and impurities from certain alcoholic drinks.Question:8
Answer:
All of them produce organic acids. Aspergillus niger produces citric acid, Clostridium butylicum produces butyric acid, and Lactobacillus produces lactic acid.Question:9
Answer:
The microbial flora in the rumen of cattle facilitates the digestion of cellulose. If such microbial flora is present in our intestines, then humans will also be able to digest cellulose.Question:10
Give any two microbes that are useful in biotechnology.
Answer:
Streptococcus, Bacillus thuringiensisQuestion:11
What is the source organism for EcoRI restriction endonuclease?
Answer:The source organism for the EcoRI restriction endonuclease is Escherichia coli (E. coli).
Question:12
Name any genetically modified crop.
Answer:
BT cotton is a GM crop and contains a gene from Bacillus thuringiensis which helps in killing pests.
Question:13
Why are blue-green algae not popular as biofertilisers?
Answer:
Blue-green algae can proliferate in water and can carry out nitrogen fixation. However, paddy is the only crop which grows in stagnant water. Most of the other crops do not need stagnant water to grow. This is the main reason for the low popularity of blue-green algae as biofertiliser.Question:14
Which species of Penicillium produces Roquefort cheese?
Answer:
The species of Penicillium that produces Roquefort cheese is Penicillium roqueforti.Question:15
Name the states involved in the Ganga action plan.
Answer:
Uttarakhand, Uttar Pradesh, Bihar, Jharkhand and West BengalQuestion:19
What is the group of bacteria found in both the rumen of cattle and the stage of sewage treatment?
Answer:
The group of bacteria found in both the rumen of cattle and the stage of sewage treatment is Methanogen.Question:20
Name a microbe used for the production of Swiss cheese.
Answer:
A microbe used for the production of Swiss cheese is Propionibacterium sharmanii.Students can go through the short answers for a better understanding of concepts:
Question:1
Why are flocs important in the biological treatment of wastewater?
Answer:
Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures. Flocs digest most of the organic material from the sludge. Thus, floc helps in reducing the BOD (Biochemical Oxygen Demand) of the effluent. This helps in the further treatment of sludge.Question:2
How has the bacterium Bacillus thuringiensis helped us in controlling caterpillars of insect pests?
Answer:
Bacillus thuringiensis produces an endotoxin which when ingested and released in the gut of the larvae of insect pest disrupts its gut lining, and thus caterpillars are killed. By killing the caterpillars, it helps in pest control.Question:3
How do mycorrhizal fungi help the plants harbouring them?
Answer:
Mycorrhizal fungi absorb phosphorus from soil and pass it to the plant. These fungi also help the plant to develop resistance against root-borne pathogens and develop sustainability against salinity and drought.Question:4
Why are cyanobacteria considered useful in paddy fields?
Answer:
Cyanobacteria are important biofertilisers in paddy fields. They add organic matter to the soil and enhance soil fertility. Hence, they are considered useful in paddy fields.Question:5
How was Penicillin discovered?
Answer:
Penicillin was discovered accidentally. Alexander Fleming was working on Staphylococci when he observed that in one of the unwashed culture plates, bacteria did not grow around a mould. He could observe that it was because of a chemical released by the mould. He named it Penicillin after the mould Penicillium notatum.Question:6
Name the scientists who were credited for showing the role of Penicillin as an antibiotic.
Answer:
Alexander Fleming first discovered penicillin in 1928. Later, Howard Florey and Ernst Boris Chain worked out how to purify and produce it on a large scale. Together, their work proved penicillin’s role as an antibiotic that could treat bacterial infections. Their discovery saved millions of lives.
Question:7
How do bioactive molecules of fungal origin help in restoring the good health of humans?
Answer:
Following are some bioactive molecules of fungal origin which help in restoring good health in humans:Question:8
Answer:
Lipase is used in detergent formulations because it helps in removing oily stains from laundry. Lipases are prepared from the yeast Saccharomyces cerevisiae.Question:9
What is the chemical nature of biogas? Name an organism which is involved in biogas production.
Answer:
Biogas is mainly composed of methane; other gases are CO2 and H2. It is highly inflammable and is used as fuel, especially in rural areas. Methanogen bacteria are involved in the production of biogas.Question:10
How do microbes reduce the environmental degradation caused by chemicals?
Answer:
Many harmful chemicals are produced as a byproduct of modern lifestyle. These chemicals are finally dumped in the soil and end up contaminating the soil. Soil contamination can be removed with the help of microbes.Question:11
What is a broad-spectrum antibiotic? Name one such antibiotic.
Answer:
An antibiotic which is effective against most of the common pathogenic bacteria is called a broad-spectrum antibiotic. Cefoperazone and Ceftazidime are examples of broad-spectrum antibiotics.Question:12
What are viruses parasitising bacteria called? Draw a well-labelled diagram of the same.
Answer:
Question:13
Which bacterium has been used as a clot-buster? What is its mode of action?
Answer:
Streptococcus is genetically modified to make streptokinase which is used as a clot buster. Streptokinase carries out thrombolysis which breaks the clot into smaller fragments, and thus, the clot is dissolved.Question:
What are biofertilisers? Give two examples.
Answer:
Organisms which enrich nutrients in the soil are called bio-fertilisers. Azotobacter and Rhizobium are examples of biofertilizers.The long answers will help the students understand the complex concepts very well to secure good marks in any examination:
Question:1
Answer:
Organic matter in wastewater consumes a lot of oxygen to carry on various biological processes. It results in a reduction of oxygen levels in the surrounding air and thus can increase air pollution. Consumption of oxygen by organic matter in wastewater is measured by BOD (Biochemical Oxygen Demand). A higher level of BOD indicates a higher polluting potential of wastewater. It is important to reduce the BOD so that pollution can be reduced. Hence, aerobic degradation is more important than anaerobic degradation for the treatment of large volumes of wastewater rich in organic matter.Question:2
(b) Ganga has recently been declared the national river. Discuss the implications with respect to the pollution of this river.
Answer:
(a) The Government has launched the Ganga Action Plan and Yamuna Action Plan to reduce pollution levels in these rivers. Under the Ganga Action Plan, dredging and cleaning of the riverbed are being carried out. These activities are especially intensified at places where the river passes through a major urban centre. The current government has named the Ganga Action Plan Namami Gange.Question:4
Describe the main ideas behind the biological control of pests and diseases.
Answer:
Biological control of pests and diseases is based on the interdependency among various components of an ecosystem. This approach is also based on the acknowledgement of potential harm caused by chemical control of pests and diseases.Question:5
(a) What would happen if a large volume of untreated sewage is discharged into a river?
(b) In what way anaerobic sludge digestion is important in sewage treatments?
Answer:
(a) The following are the harmful effects of untreated sewage being discharged into a river:Question:6
Which type of food would have lactic acid bacteria? Discuss their useful application.
Answer:
Lactic acid bacteria are present in milk products which are prepared by fermentation. They are also found in pickled vegetables and wines. The following are some useful applications of lactic acid bacteria:NCERT Exemplar Class 12 Solutions Subject Wise
Some points to understand before solving the questions of the chapter are given below:
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Also, read the NCERT Solution subject-wise
The important topics of the Microbes in Welfare Chapter are given below-
Also Check NCERT Books and NCERT Syllabus here
Below is an important question of the chapter:
Question:
Which of the following is used as a bioinsecticide to control caterpillar pests in crops?
a) Rhizobium leguminosarum
b) Trichoderma harzianum
c) Bacillus thuringiensis
d) Azotobacter chroococcum
Answer:
Bacillus thuringiensis Bt acts as a natural pest controller in crops as it produces a protein crystal that disrupts the gut of caterpillar larvae leading to their death without harming humans or beneficial insects farmers prefer Bt because it is eco friendly and safe for the environment the other options listed work for nitrogen fixation or fungal control but Bt remains the most effective for managing caterpillar pests
Hence, the correct answer is option (c) Bacillus thuringiensis.
Must Read NCERT Notes subject-wise
The chapter-wise solutions for all chapters of Class 12 Biology are given below:-
The students can study each section of the chapter completely and attempt the question bank given with the NCERT exemplar Class 12 Biology solutions to study and get the answer format completely.
The topics included in the NCERT exemplar solutions for Class 12 Biology Chapter 10 are -
1. Microbes in Household Products
2. Microbes in Industrial Products
3. Microbes in Sewage Treatment
4. Microbes in the Production of Biogas
5. Microbes as Biocontrol Agents
6. Microbes as Biofertilizers
And other detailed explanations of related topics too are mentioned.
Yes, along with the textbooks the student can rely on NCERT Exemplar Class 12 Biology solutions chapter 10, for any reference and guidance.
Microbes are vital in industrial production, used in processes like fermentation to create food, biofuels, enzymes, and pharmaceuticals, as well as in bioremediation and single-cell protein production.
Biofertilizers are substances containing living microorganisms that, when applied to soil or plants, promote plant growth by increasing nutrient availability and improving soil health, making agriculture more sustainable.
In sewage treatment, microbes, particularly bacteria, play a crucial role in breaking down organic matter, reducing pollution, and producing biogas, as outlined in NCERT Class 12 Biology.
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Changing from the CBSE board to the Odisha CHSE in Class 12 is generally difficult and often not ideal due to differences in syllabi and examination structures. Most boards, including Odisha CHSE , do not recommend switching in the final year of schooling. It is crucial to consult both CBSE and Odisha CHSE authorities for specific policies, but making such a change earlier is advisable to prevent academic complications.
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