NCERT Exemplar Class 12 Biology Chapter 10 Microbes In Human Welfare
NCERT Exemplar for Class 12 Biology Chapter 10
Exemplar Class 12 Biology Chapter 10 will help students to deepen their knowledge related to the topic of Microbes in Human Welfare. This provided exemplar by SimplyAcad allows students to cover all the areas and sections comprising the chapter 10 of the biology textbook. The subject experts have prepared several answer type questions such as MCQs based, very short, short and long answer type questions. It will be an advantage for students as they become more familiar with these different patterns. Students can easily access this NCERT Exemplar Class 12 Biology Chapter 10 in this article below to perform incredibly well in their upcoming 12th board examinations. Along with this, there are several other NCERT exemplar for class 12 science of all the chapters provided in a detailed manner.
NCERT Exemplar Class 12 Biology Chapter 10: Microbes in Human Welfare
MCQ Type Questions
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
Ans: Option (c) is the answer. Lactic acid bacteria are used to transform milk into curd. This process increases the nutritional value by raising vitamin B12 concentration.
2. Wastewater treatment generates a large quantity of sludge, which can be treated by:
a. Anaerobic digesters
b. Floc
c. Chemicals
d. Oxidation pond
Ans: Option (a) is the answer. During secondary treatment, activated sludge is treated anaerobically using anaerobic digesters, where bacteria generate biogas.
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
Ans: Option (d) is the answer. Methanogenic bacteria are not present in activated sludge, which typically contains aerobic bacteria.
4. Match the following list of bacteria and their commercially important products:
| Bacterium | Product |
|---|---|
| A. Aspergillus niger | i. Lactic acid |
| B. Acetobacter aceti | ii. Butyric acid |
| C. Clostridium butylicum | iii. Acetic acid |
| D. Lactobacillus | iv. Citric acid |
Choose the correct match:
a. A-ii, B-iii, C-iv, D-i
b. A-ii, B-iv, C-iii, D-i
c. A-iv, B-iii, C-ii, D-i
d. A-iv, B-i, C-iii, D-ii
Ans: Option (c) is the answer.
| Bacterium | Product |
|---|---|
| Aspergillus niger | Citric acid |
| Acetobacter aceti | Acetic acid |
| Clostridium butylicum | Butyric acid |
| Lactobacillus | Lactic acid |
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. Immuno-suppressive agent |
Choose the correct match:
a. A-ii, B-iii, C-i, D-iv
b. A-iv, B-ii, C-i, D-iii
c. A-iv, B-i, C-ii, D-iii
d. A-iii, B-iv, C-ii, D-i
Ans: Option (d) is the answer.
| Bioactive Substance | Role |
|---|---|
| Statin | Lowering of blood cholesterol |
| Cyclosporin A | Immuno-suppressive agent |
| Streptokinase | Removal of clots from blood vessels |
| Lipase | Removal of oil stains |
6. The primary treatment of wastewater involves the removal of:
a. Dissolved impurities
b. Stable particles
c. Toxic substances
d. Harmful bacteria
Ans: Option (b) is the answer. Primary treatment involves the removal of stable particles from sewage through filtration and sedimentation.
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
Ans: Option (d) is the answer. BOD (Biological Oxygen Demand) is estimated by measuring the amount of oxygen consumed by bacteria during the oxidation of organic matter.
8. Which one of the following alcoholic drinks are produced without distillation?
a. Wine
b. Whisky
c. Rum
d. Brandy
Ans: Option (a) is the answer. Wine is produced without distillation, whereas whisky, rum, and brandy are produced by distillation.
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
Ans: Option (c) is the answer. The technology of biogas production from cow dung was developed by the Indian Agricultural Research Institute (IARI) and Khadi & Village Industries Commission (KVIC).
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
Ans: Option (b) is the answer. Trichoderma is used as a biological control agent against plant diseases.
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 center of flocs will become anoxic, which would cause the death of bacteria and eventually breakage of flocs
c. Flocs would increase in size as anaerobic bacteria would grow around flocs
d. Protozoa would grow in large numbers
Ans: Option (b) is the answer. Reduced oxygen leads to anoxic conditions in the center of the flocs, causing bacterial death and floc breakage.
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
Ans: Option (d) is the answer. Mycorrhizae help in phosphorus uptake, drought tolerance, and resistance to root pathogens, but not in insect resistance.
13. Which one of the following is not a nitrogen-fixing organism?
a. Anabaena
b. Nostoc
c. Azotobacter
d. Pseudomonas
Ans: Option (d) is the answer. Pseudomonas is not a nitrogen-fixing organism; it is a bacterium involved in biodegradation.
14. 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
Ans: Option (c) is the answer. The bacterium Propionibacterium shermanii produces carbon dioxide, creating big holes in Swiss cheese.
15. The residue left after methane production from cattle dung is:
a. Burnt
b. Buried in landfills
c. Used as manure
d. Used in civil construction
Ans: Option (c) is the answer. The residue left after methane production from cattle dung is used as manure.
16. Methanogens do not produce:
a. Oxygen
b. Methane
c. Hydrogen sulphide
d. Carbon dioxide
Ans: Option (a) is the answer. Methanogens produce methane, hydrogen sulphide, and carbon dioxide but not oxygen.
17. Activated sludge should have the ability to settle quickly so that it can:
a. Be rapidly pumped back from sedimentation tank to 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
Ans: Option (a) is the answer. Activated sludge must settle quickly to be pumped back to the aeration tank.
18. Match the items in Columns ‘A’ and Column ‘B’ and choose the correct answer.
| Column I | Column II |
|---|---|
| A. Ladybird | i. Methane bacterium |
| B. Mycorrhiza | ii. Trichoderma |
| C. Biological control | iii. Aphids |
| D. Biogas | iv. Glomus |
The correct answer is:
a. A-ii, B-iv, C-iii, D-i
b. A-iii, B-iv, C-ii, D-i
c. A-iv, B-i, C-ii, D-iii
d. A-iii, B-ii, C-i, D-iv
Ans: Option (b) is the answer.
Very Short Answer Type Questions
Very Short Answer Type Questions: NCERT Exemplar Class 12 Biology Chapter 10: Microbes in Human Welfare
1. Why does ‘Swiss cheese’ have big holes?
Ans: The big holes in ‘Swiss cheese’ are made by a bacterium known as Propionibacterium shermanii which produces a large amount of carbon dioxide during fermentation.
2. What are fermentors?
Ans: Fermentors are large vessels used for the commercial production of fermented products by growing microorganisms.
3. Name a microbe used for statin production. How do statins lower blood cholesterol levels?
Ans: A microbe used in the production of statin is Monascus purpureus. Statins lower blood cholesterol by inhibiting the enzyme HMG-CoA reductase, which plays a central role in the production of cholesterol in the liver.
4. Why do we prefer to call secondary wastewater treatment a biological treatment?
Ans: Secondary wastewater treatment is called biological treatment because it involves the use of microorganisms to decompose organic matter.
5. What are Nucleopolyhedroviruses being used for nowadays?
Ans: Nucleopolyhedroviruses (NPVs) are used as biological insecticides to kill insects that harm plants and crops, such as caterpillars and butterflies.
6. How has the discovery of antibiotics helped in the field of medicine?
Ans: The discovery of antibiotics has helped by providing effective treatments for bacterial infections, significantly reducing mortality rates.
7. Why is distillation required for producing certain alcoholic drinks?
Ans: Distillation is required for producing certain alcoholic drinks because it increases the alcohol content by separating alcohol from the fermented broth.
8. Write the most important characteristic that Aspergillus niger, Clostridium butylicum, and Lactobacillus share.
Ans: The most important characteristic is that they all produce commercially valuable acids: Aspergillus niger produces citric acid, Clostridium butylicum produces butyric acid, and Lactobacillus produces lactic acid.
9. What would happen if our intestine harbours microbial flora exactly similar to that found in the rumen of cattle?
Ans: If our intestines harboured microbial flora similar to that in the rumen of cattle, we would be able to digest cellulose and produce methane in our digestive system.
10. Give any two microbes that are useful in biotechnology.
Ans: Escherichia coli (E. coli) and Agrobacterium tumefaciens are two microbes useful in biotechnology.
11. What is the source organism for ECORI restriction endonuclease?
Ans: The source organism for ECORI is Escherichia coli.
12. Name any genetically modified crop.
Ans: Bt cotton is a genetically modified (GM) crop that produces an insecticide to protect against bollworm.
13. Why are blue-green algae not popular as biofertilizers?
Ans: Blue-green algae are not popular as biofertilizers because they can create a slippery mucus and cause algal blooms, which are harmful to aquatic life.
14. Which species of Penicillium produces Roquefort cheese?
Ans: The species of Penicillium that produces Roquefort cheese is Penicillium roqueforti.
15. Name the states involved in the Ganga action plan.
Ans: The states involved in the Ganga Action Plan are Jharkhand, Uttar Pradesh, Bihar, and West Bengal.
16. Name any two industrially important enzymes.
Ans: Two industrially important enzymes are:
- Lipase: Used in detergents for removing oily stains.
- Amylase: Used in the food and fermentation industry.
17. Name an immune-suppressive agent.
Ans: Cyclosporin A, produced by the fungus Trichoderma polysporum, is an immune-suppressive agent.
18. Give an example of a rod-shaped virus.
Ans: The Tobacco Mosaic Virus (TMV) is an example of a rod-shaped virus.
19. What is the group of bacteria found in both the rumen of cattle and the stage of sewage treatment?
Ans: Methanogens are the group of bacteria found in both the rumen of cattle and in sewage treatment, where they produce methane gas.
20. Name a microbe used for the production of Swiss cheese.
Ans: Propionibacterium shermanii is the microbe used for the production of Swiss cheese, creating the characteristic holes by producing carbon dioxide during fermentation.
Short Answer Type Questions: NCERT Exemplar Class 12 Biology Chapter 10 Microbes in Human Welfare
1. Why are flocs important in the biological treatment of wastewater?
Ans: Flocs are crucial in biological wastewater treatment because they help reduce Biological Oxygen Demand (BOD) in the water, making it less polluted and more suitable for aquatic life. They also reduce pathogens and decompose organic waste, contributing to the overall purification process.
2. How has the bacterium Bacillus thuringiensis helped us in controlling caterpillars of insect pests?
Ans: The bacterium Bacillus thuringiensis helps control insect pest caterpillars by producing an endotoxin that, when ingested by the pest, gets activated in the caterpillar’s midgut. This endotoxin destroys the midgut lining, leading to the insect’s death.
3. How do mycorrhizal fungi help the plants harboring them?
Ans: Mycorrhizal fungi assist plants by increasing nutrient uptake from the soil, especially phosphorus, and transferring it to the host plant. They also help the plant absorb more water, enhancing the plant’s ability to withstand environmental conditions like drought.
4. Why are cyanobacteria considered useful in paddy fields?
Ans: Cyanobacteria are beneficial in paddy fields because they fix atmospheric nitrogen and provide organic matter, which improves soil fertility, supporting better crop growth.
5. How was penicillin discovered?
Ans: Penicillin was discovered by Alexander Fleming in 1928. He accidentally observed that a mold, later identified as Penicillium notatum, inhibited the growth of Staphylococcus bacteria on a culture plate. This led to the discovery of penicillin as an antibiotic.
6. Name the scientists who were credited for showing the role of penicillin as an antibiotic?
Ans: Alexander Fleming discovered penicillin, but the scientists credited for demonstrating its role as an antibiotic are Howard Florey and Ernst Boris Chain, who further developed and purified penicillin for medical use.
7. How do bioactive molecules of fungal origin help in restoring the good health of humans?
Ans: Bioactive molecules of fungal origin help restore human health in several ways:
- Statins: Lower blood cholesterol levels.
- Cyclosporin A: Acts as an immunosuppressive drug, especially useful in organ transplants.
- Lipase: Aids in the digestion of fats and also helps remove oil stains in detergents.
8. What roles do enzymes play in detergents that we use for washing clothes? Are these enzymes produced from some unique microorganisms?
Ans: Enzymes such as lipases in detergents help break down oils and fats, making it easier to remove greasy stains from clothes. These enzymes are produced by microorganisms such as Candida lipolytica and Geotrichum candidum.
9. What is the chemical nature of biogas? Name an organism involved in biogas production.
Ans: Biogas is primarily composed of methane (CH4) (60-70%), carbon dioxide (CO2) (30-40%), and trace amounts of hydrogen sulphide (H2S). The organisms involved in biogas production are methanogens, such as Methanobacterium.
10. How do microbes reduce the environmental degradation caused by chemicals?
Ans: Microbes reduce environmental degradation by breaking down harmful chemicals in processes like bioremediation. For example, biofertilizers like Rhizobium enrich the soil with nitrogen, and biopesticides like Bacillus thuringiensis produce toxins that kill pests without harming the environment.
11. What is a broad-spectrum antibiotic? Name one such antibiotic.
Ans: A broad-spectrum antibiotic is one that is effective against a wide range of bacterial infections. An example of a broad-spectrum antibiotic is Ampicillin.
12. What are viruses parasitizing bacteria called? Draw a well-labeled diagram of the same.
Ans: Viruses that parasitize bacteria are called bacteriophages.
13. Which bacterium has been used as a clot-buster? What is its mode of action?
Ans: The bacterium Streptococcus produces an enzyme called streptokinase, which is used as a clot-buster. It breaks down blood clots by converting plasminogen to plasmin, thereby preventing heart attacks and other clot-related diseases.
14. What are biofertilizers? Give two examples.
Ans: Biofertilizers are natural fertilizers that enrich the soil by fixing nitrogen or decomposing organic matter, thus enhancing soil fertility. Examples include:
- Rhizobium: A nitrogen-fixing bacterium that forms symbiotic relationships with leguminous plants.
- Nostoc: A cyanobacterium that also fixes atmospheric nitrogen.
Long Answer Type Questions: NCERT Exemplar Class 12 Biology Chapter 10 Microbes in Human Welfare
1. Why is aerobic degradation more important than anaerobic degradation for the treatment of large volumes of wastewaters rich in organic matter? Discuss.
Ans: Aerobic degradation is more significant than anaerobic degradation for the treatment of large volumes of organic-rich wastewaters due to the following reasons:
- Efficient Breakdown of Organic Matter: In aerobic degradation, microorganisms utilize oxygen to break down organic matter more efficiently. This process is faster and more complete, leading to a significant reduction in the volume of organic sludge.
- Reduction of Biological Oxygen Demand (BOD): Aerobic degradation effectively reduces the Biological Oxygen Demand (BOD) of wastewater, which is a key measure of pollution. Lower BOD indicates that the wastewater is less polluted and safer for discharge into natural water bodies.
- Activated Sludge Formation: During aerobic degradation, the process forms activated sludge, which contains a high concentration of beneficial microorganisms. This sludge can be recycled back into the treatment process to enhance the efficiency of wastewater treatment.
- Biogas Production: Although biogas production is more associated with anaerobic degradation, aerobic degradation helps in reducing pathogens and organic waste, making the subsequent anaerobic process more effective for biogas generation.
Overall, aerobic degradation is preferred for treating large volumes of wastewater because it is more effective at reducing pollutants and making the water safer for release into the environment.
2.
(a) Discuss the major programs that the Ministry of Environment and Forests, Government of India, has initiated for saving major Indian rivers from pollution.
Ans: The Ministry of Environment and Forests, Government of India, has initiated several programs to save major Indian rivers from pollution. The two key programs are:
- Ganga Action Plan (GAP): Launched in 1986, the Ganga Action Plan aimed to reduce the pollution levels in the Ganges River. The plan involved setting up sewage treatment plants (STPs) to treat wastewater before it enters the river, promoting public awareness, and controlling industrial pollution.
- Yamuna Action Plan (YAP): Similar to the Ganga Action Plan, the Yamuna Action Plan was initiated to clean the Yamuna River, which flows through several states, including Delhi. The plan included the construction of STPs, interception and diversion of sewage, and public participation in river cleaning activities.
Both programs aim to involve local communities and governments in pollution control efforts and promote sustainable practices to protect these vital water resources.
(b) Ganga has recently been declared the national river. Discuss the implication with respect to the pollution of this river.
Ans: Declaring the Ganga as the national river of India emphasizes the importance of preserving and restoring the river’s ecological health. This designation comes with increased responsibility for the government and citizens to protect the river from pollution. It implies stricter enforcement of environmental laws, increased funding for cleanup efforts, and a national commitment to ensuring the river remains free from pollutants. The status also raises awareness and fosters a sense of pride among Indians, encouraging them to actively participate in conserving the Ganga.
3. Draw a diagrammatic sketch of the biogas plant, and label its various components given below: Gas Holder, Sludge Chamber, Digester, Dung + water chamber.
Ans:
4. Describe the main ideas behind the biological control of pests and diseases.
Ans: The main ideas behind the biological control of pests and diseases involve the use of natural predators, parasites, or pathogens to manage pest populations. This approach reduces the reliance on chemical pesticides, which can have harmful environmental and health effects. Key concepts include:
- Introduction of Natural Predators: For example, ladybird beetles are introduced to control aphid populations.
- Use of Pathogens: Nucleopolyhedroviruses (NPVs) are used to target specific pests like caterpillars, which cause damage to crops.
- Conservation of Natural Enemies: Encouraging the presence of natural predators in the environment helps maintain a balanced ecosystem, reducing the need for external interventions.
- Sustainability: Biological control is a sustainable approach as it minimizes the ecological footprint and promotes long-term pest management.
Overall, biological control is an environmentally friendly and sustainable method for managing pests and diseases.
5.
(a) What would happen if a large volume of untreated sewage is discharged into a river?
Ans: If a large volume of untreated sewage is discharged into a river, it would lead to several detrimental effects:
- Increased Biological Oxygen Demand (BOD): The organic matter in sewage would increase the BOD of the river, depleting the oxygen levels, which is essential for aquatic life.
- Fish and Aquatic Life Mortality: Low oxygen levels would result in the death of fish and other aquatic organisms, disrupting the ecosystem.
- Spread of Waterborne Diseases: Untreated sewage contains pathogens, leading to the spread of diseases like cholera, dysentery, and typhoid among communities that rely on the river for drinking water.
- Eutrophication: The excess nutrients from sewage can cause algal blooms, leading to eutrophication, which further depletes oxygen and harms aquatic life.
(b) In what way is anaerobic sludge digestion important in sewage treatments?
Ans: Anaerobic sludge digestion is crucial in sewage treatment as it helps in:
- Reduction of BOD: Anaerobic digestion reduces the BOD of sludge, making it safer for disposal.
- Biogas Production: During anaerobic digestion, microorganisms break down organic matter in the absence of oxygen, producing biogas (mainly methane), which can be used as a renewable energy source.
- Pathogen Reduction: The process also reduces the number of pathogens in the sludge, making it safer for use as fertilizer.
Anaerobic sludge digestion is an essential step in sewage treatment for reducing environmental impact and generating energy.
6. Which type of food would have lactic acid bacteria? Discuss their useful applications.
Ans: Lactic acid bacteria (LAB) are commonly found in fermented foods, such as curd, yogurt, and sauerkraut. Their useful applications include:
- Fermentation: LAB are used to ferment milk into curd and yogurt. They convert lactose into lactic acid, giving these foods their characteristic sour taste.
- Probiotics: LAB are considered probiotics, which help maintain gut health by balancing the microbial flora in the digestive system.
- Lactose Intolerance: LAB help people with lactose intolerance by breaking down lactose in dairy products, making them easier to digest.
- Nutritional Enhancement: LAB increase the nutritional value of foods by enhancing the production of vitamins, such as vitamin B12.
Overall, LAB play a significant role in food processing, health, and nutrition.
NCERT Exemplar For Class 12 Science
Students must practise these additional questions for their own benefits, the ncert exemplar are curated by the best subject-matter experts to boost your knowledge on the presented topic. Students can easily access the ncert exemplar for class 12 science by visiting our website SimplyAcad and solve all the questions listed to secure maximum marks.
Here are some other NCERT exemplar for class 12 biology:
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| NCERT exemplar for class 12 biology Chapter 3 | NCERT exemplar for class 12 biology Chapter 12 |
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