Biology Important Questions for Chapter 8 Microbes in Human Welfare Class 12 - FREE PDF Download
Prepare for Class 12 Biology preparation with Vedantu’s Important Questions for Chapter 8: Microbes in Human Welfare. This Chapter explores the vital role that microorganisms play in various aspects of human life. From their use in food production to their applications in medicine, microbes are essential for maintaining human health and enhancing daily life. This chapter covers how microbes contribute to processes like fermentation, the production of antibiotics, and their role in environmental sustainability. , making it a crucial part of both board and competitive exams.
Table of Content
This FREE PDF for Class 12 Biology Important Questions is carefully designed to include the most relevant and frequently asked questions, along with solutions, as per the CBSE Class 12 Biology Syllabus. Download the FREE PDF now and prepare with Vedantu.
Very Short Questions and Answers (1 Mark Questions)
1. How does a small amount of curd added to fresh milk convert it into curd? Mention a nutritional quality that gets added to the curd.
Ans: In a small amount of curd, a huge number of lactic acid bacteria can be detected. By creating lactic acid, proliferate and turn the milk into curd. Increased Vitamin B12 enhances nutritional quality.
2. Why is the secondary treatment of water in sewage treatment plants called biological treatment?
Ans: Organic wastes from sewage water are digested by particular bacteria in this treatment In the presence of water, microorganisms.
3. An antibiotic called Wonder Drug was used to treat the wounded soldiers of America during World War II. Name the drug and the scientist who discovered it.
Ans: Alexander Fleming invented penicillin.
4. You have observed that fruit juice in bottles bought from the market is clearer as compared to those made at home. Give a reason.
Ans: Pectinase and proteases are used to clarify bottle juices.
5. Alexander Fleming discovered Penicillin, but its full potential an effective antibiotic was established by other scientists. Name the two scientists.
Ans: Howard Florey and Ernest Chain were the two scientists.
6. Name the plant whose sap is used in making Toddy. Mention the process involved in this.
Ans: The sap of a palm tree is used in making Toddy and the process is called fermentation.
7. What is the medical use of cyclosporin A?
Ans: During organ transplantation, cyclosporin A is used as an immunosuppressive drug.
8. Name the pests that ladybirds & dragonflies help to get rid of respectively.
Ans: Aphids are controlled by ladybird beetles, and mosquitoes are controlled by dragonflies.
9. Give an example to prove that microbes release gases during metabolism.
Ans: Bread and Puffed dough are suitable examples of bacteria releasing gases during metabolism.
10. What are interferons?
Ans: The Interferons are those proteins that are released by the cells in response to the viral infection and they help in the fight against viral infection.
11. Name the enzyme which is used as a clot buster" to remove a blood clot from the blood vessels of patients.
Ans: Streptokinase is used.
14. Expand LAB?
Ans: Lactic acid Bacteria is the full form of LAB.
15. Name any two free-living nitrogen-fixing bacteria.
Ans: Two free-living nitrogen bacteria are Azotobacter and Azospirillum
16. Name the organism used in the dough for making bread.
Ans: Saccharomyces cerevisiae.
17. Name the fungus used as a biocontrol of plant diseases.
Ans: The fungus used as a biocontrol of plant diseases is known as Trichoderma.
18. Name any two gases produced during the secondary treatment of Sewage?
Ans: Methane, Hydrogen sulphide & carbon dioxide.
Short Questions and Answers (2 Marks Questions)
1. Name two alcoholic drinks produced in each of the following ways.
(i) by distillation and (ii) without distillation.
Ans:
(i) Distillation produces whisky, brandy, and rum.
(ii) Wine and beer that has not been distilled.
2. Lactic Acid Bacteria (LAB) is commonly used in the conversion of milk into curd. Mention any two other functions of LAB that are useful to humans.
Ans:
(i) Vitamin B12 is synthesised by LAB in the human gut.
(ii) The presence of LAB in the human stomach inhibits the growth of dangerous microorganisms.
3. How do mycorrhizae function as biofertilizers? Explain with examples.
Ans: Fungi connected with plant roots are known as mycorrhizae. Mycorrhizae are formed by many species of the Glomus genus. These fungal symbionts collect water and minerals such as phosphorus from the soil and pass them on to the plant.
Long Questions and Answers (3 Mark Questions)
1. Fill in the blanks spaces a, b, c, d, e, and given in the following table:
Ans:
(a) to kill disease-causing bacteria
(b) Lactobacillus
(c) remove clots from blood vessels
(d) Cyclosporin A
(e) Beverage/medicines
(f) Propionibacterium Shermanii.
2. What is the biochemical oxygen demand (BOD) test? At what stage of Sewage treatment this test is performed? The BOD levels of three samples of water labelled as A, B and C are 30 mg/L and10mg/L and 500 mg/L respectively. Which sample of water is most polluted?
Ans:
The BOD test determines how quickly microorganisms in a sample of water absorb oxygen.
Secondary treatment or biological treatment.
Sample C is the most polluted of the three water samples since it has the greatest BOD level.
3. Given below is the Flow chart of Sewage treatment. Fill in the blank spaces marked
'a' to f.
Ans:
(a) Primary treatment.
(b) Aeration
(c) Flocs
(d) Biochemical Oxygen Demand (BOD)
(e) Activated sludge
(f) Water bodies like river streams.
4. What are biofertilisers? A farmer is advised to add a culture of bacterium in the soil before sowing the crop. Name the bacterium in the culture. How is this bacterium useful to the crop?
Ans: Some points on biofertilisers are:
Biofertilizers are organisms that improve the soil's nutrient quality.
Azotobacter/Azospirillum is a bacteria found in the bacterium Azotobacter/Azospirillum (free living)
This bacterium converts atmospheric nitrogen into organic molecules that are used as a fertiliser by plants.
5. What are statins? Name the microorganism that produces this substance. How is it medically important?
Ans: The Monascuspurpureus produces statins, which are cholesterol-lowering drugs (Yeast). They operate as blood cholesterol-lowering drugs by competitively blocking the enzymes involved in cholesterol production.
6. Describe the procedure involved in Sewage treatment?
Ans: The following technique is performed for the treatment of sewage waste:
i) Primary Treatment- This entails physically separating suspended materials in settling tanks in order to reduce BOD. The raw sewage is routed into massive open tanks where it is subjected to anaerobic digestion to remove the solid fraction.
ii) Secondary Therapy- Secondary treatment relies on microbial activity, either aerobic or anaerobic. Secondary treatment techniques include:
Sand filters for filtration
Process of aeration
Application of oxidation ponds:
After drying, the sludge that collects after secondary treatment is disposed of, and the efferent is allowed to be used for tertiary treatment.
iii) Tertiary Treatment- This treatment comprises chemical treatment to eliminate inorganic chemicals as well as pathogenic microorganisms. Chlorination is the most common disinfection procedure.
7. What is Biogas? How is it produced & Name the microbes invaded in Biogas production.
Ans: Biogas is the gas produced by anaerobic fermentation of waste biomass. It is made up of methane, CO2, hydrogen, nitrogen, oxygen, and hydrogen sulphide, among other things. Microbes that are often employed in the production of biogas-
i) Hydrolytic Bacteria, such as cellulosomes, clostridium, etc.
ii) Bacteria that produce hydrogen sulphide, such as Syntrophomonas wolfei
iii) Methanobacterium Omelianskii is an example of a methanogenic bacteria.
The biogas plant is fed by a concrete tank. The slurry is covered with a floating cover, which continues to rise when gas is created in the tank owing to microbial activity. The biogas plant includes an output that connects to a pipe that distributes biogas to surrounding residences. Microbes transform the organic part of biodegradable organic solid waste and trash into energy in the form of biogas and humus during biogas production.
$ CO + H_2O \to CO_2 + H_2 $
$ CO_2 + 4H_2 \to CH_4 + 2H_2O $
$ CH_3OH \to CH_4 + O_2 $
8. Microbes can be used to decrease the use of chemical fertilisers & pesticides. Explain how this can be accomplished.
Ans: Below are some of the ways that microbes can be used to decrease the use of chemical fertilisers & pesticides:
Chemicals are commonly used to control plant diseases and pests in modern society.
However, these chemicals can be harmful to humans and the environment due to their toxicity.
In agriculture, natural predation can be used as a form of pest control instead of pesticides.
Bacillus thuringiensis (Bt) is a type of bacteria that can be used to control butterflies, caterpillars, and other insects.
Dried spores of Bt are mixed with water and sprayed onto sensitive plants such as brassicas.
The toxin released by Bt in the intestines of larvae kills them, but it does not harm other insects.
This natural form of pest control can help to reduce the use of harmful chemicals in agriculture and minimise their impact on the environment.
9. How do Bio fertilisers enrich the fertility of soil? How do cyanobacteria act as biofertilisers?
Ans: Microorganisms employ biological channels to improve soil fertility for optimal crop development, and they are referred to as "BIOFERTILISERS." These microorganisms can boost crop output in one of two ways.
i) By removing nitrogen from the atmosphere
ii) Insoluble fertiliser solubilisation
iii) By promoting the growth of plants.
iv) Through phosphorus absorption.
v) By allowing plant remnants to decompose.
Anabaena, a cyanobacterium found in the leaf cavity of the water fern Azolla, fixes nitrogen from the air and excretes nitrogenous compounds into the leaf cavity.
10. How does primary sludge differ from activated sludge? What type of changes in the sludge is carried out in an anaerobic sludge digester? Give the composition of biogas produced in the sewage treatment plant.
Ans:
Primary sludge consists of all solids, such as soil and small stones, that settle in the settling tank during sewage treatment.
Activated sludge is the sediment of bacterial flocs that settle in the settling tank after biological treatment during sewage treatment.
Bacteria, slime and fungal filaments bind together to form flocs in the activated sludge.
A portion of the activated sludge is used as inoculum in the aeration tank and the remaining is sent to the anaerobic sludge digester.
In the anaerobic sludge digester, bacteria that grow anaerobically consume the bacteria, fungus and cellulose in the sludge.
Biogas is a mixture of methane, hydrogen and carbon dioxide that is produced in sewage treatment plants.
Points to Remember From Class 12 Biology Chapter 8: Microbes in Human Welfare
Microorganisms like yeast are used in the fermentation process to produce food items such as bread, alcoholic beverages, and dairy products like curd and cheese.
Microorganisms are crucial in producing antibiotics (e.g., penicillin) and vaccines for diseases like polio and hepatitis.
Microbes like Rhizobium enhance soil fertility by fixing nitrogen, while others act as biopesticides, reducing the need for harmful chemicals.
Microbes decompose organic waste, produce biogas, and help in sewage treatment, contributing to environmental sustainability.
Microbes are used in the production of enzymes, vitamins, and biofuels, benefiting various industries.
Microorganisms play a vital role in ecological balance by cleaning up pollutants, such as in oil spills, and promoting overall environmental health.
Benefits of Important Questions for Class 12 Biology Chapter 8
Helps students concentrate on key topics like microbes in food production, medicine, and agriculture, ensuring effective revision before exams.
Promotes a deeper understanding of how microorganisms impact various aspects of human life, from medicine to waste management.
Familiarises students with commonly asked questions, boosting confidence and ensuring readiness for both board exams and competitive tests like NEET.
Provides a concise set of important questions for quick yet comprehensive revision, saving time in the lead-up to exams.
Regular practice of these questions reinforces key concepts, improving long-term retention and application of knowledge.
Helps students develop the ability to answer a range of question types, including conceptual and application-based questions, effectively.
Conclusion
Understanding the role of microbes in human welfare is essential for mastering Class 12 Biology. With Vedantu's Important Questions for Chapter 8: Microbes in Human Welfare, students can learn critical topics such as fermentation, antibiotic production, and the role of microbes in agriculture and waste management. These questions, available in a FREE PDF download, provide focused practice and conceptual clarity to help you perform well in your exams. Rely on Vedantu for comprehensive, exam-ready preparation and ensure your success in both board exams and competitive tests like NEET.
Related Study Materials for Class 12 Biology Chapter 8 Microbes in Human Welfare
Chapter-wise Important Questions for Biology Class 12
Additional Study Materials for Class 12 Biology
FAQs on Microbes in Human Welfare Class 12 Important Questions: CBSE Biology Chapter 8
1. From a board exam perspective, what are the key differences between primary and activated sludge produced during sewage treatment?
The key differences between primary and activated sludge are crucial for understanding the sewage treatment process:
- Origin: Primary sludge is the solid material, including soil and small pebbles, that settles down during the primary treatment in the primary settling tank. In contrast, activated sludge is the sediment of bacterial 'flocs' (masses of bacteria associated with fungal filaments) that settles down in the settling tank after the secondary or biological treatment.
- Composition: Primary sludge consists mainly of settled organic and inorganic solids. Activated sludge is rich in aerobic microbial life that is used as an inoculum back in the aeration tank.
- Disposal: A major part of the activated sludge is passed into a large tank called an anaerobic sludge digester, while the primary sludge is also disposed of. The remaining activated sludge is pumped back into the aeration tank to serve as an inoculum.
2. Why is the secondary stage of sewage treatment often referred to as 'biological treatment'?
The secondary stage of sewage treatment is called biological treatment because it primarily uses living microorganisms to break down organic waste. The primary effluent is pumped into large aeration tanks where heterotrophic microbes grow rapidly and consume the major part of the organic matter in the effluent. This significantly reduces the Biochemical Oxygen Demand (BOD) of the wastewater, relying entirely on a biological process rather than physical or chemical means.
3. Name the microbes that produce statins and cyclosporin A. What are their specific medical applications?
These are two very important bioactive molecules for medical use:
- Statins: Produced by the yeast Monascus purpureus. They are used as blood-cholesterol lowering agents. They act by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.
- Cyclosporin A: Produced by the fungus Trichoderma polysporum. It is used as an immunosuppressive agent in organ-transplant patients to prevent the body from rejecting the new organ.
4. How can microbes be used as biocontrol agents to reduce dependency on chemical pesticides? Provide two distinct examples as per the CBSE syllabus.
Microbes can be used as biocontrol agents by using their natural predatory or pathogenic properties against specific pests, which is a more ecological approach than using chemical pesticides. Two important examples are:
- The bacterium Bacillus thuringiensis (Bt): This bacterium is used to control butterfly caterpillars. Dried spores are mixed with water and sprayed onto vulnerable plants. When the insect larvae eat the plant, the toxin is released in their gut and kills them, but it is harmless to other insects and humans.
- The fungus Trichoderma: Species of this fungus are free-living in root ecosystems and act as effective biocontrol agents for several plant pathogens, protecting the plant from root-borne diseases.
5. What is Biochemical Oxygen Demand (BOD), and how does it help in assessing the level of pollution in a water body?
Biochemical Oxygen Demand (BOD) refers to the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria. BOD is a measure of the organic matter present in the water. A higher BOD value indicates a greater amount of organic waste, which means the water is more polluted. Conversely, a low BOD value signifies that the water is less polluted or cleaner.
6. Explain the dual role of Lactic Acid Bacteria (LAB) in the production of curd and in promoting human health.
Lactic Acid Bacteria (LAB), such as Lactobacillus, play a dual role:
- In Curd Production: LAB grow in milk and convert it to curd. They produce acids that coagulate and partially digest the milk proteins (casein), changing the texture and flavour.
- In Human Health: LAB are beneficial in the human stomach as they check the growth of disease-causing microbes. They also improve nutritional quality by increasing Vitamin B12 content.
7. A farmer is advised to add a culture of Azospirillum to the soil before sowing a cereal crop. How does this microbe benefit the crop?
Azospirillum is a type of free-living bacterium that lives in the soil and fixes atmospheric nitrogen into organic forms, such as ammonia, which can be absorbed by plants. By adding Azospirillum, the farmer enriches the soil's nitrogen content naturally. This acts as an excellent biofertilizer, enhancing the growth and yield of the cereal crop while reducing the need for synthetic nitrogen fertilizers.
8. Why are commercially bottled fruit juices clearer than those made at home? Name the key enzymes involved in this process.
Commercially bottled fruit juices are clearer because they are treated with specific enzymes to break down substances that cause cloudiness. The key enzymes used are pectinase and protease. These enzymes digest the pectin and proteins present in the raw juice, leading to a clearer final product. Juices made at home are not treated with these enzymes and thus retain their natural, cloudy appearance.
9. How do mycorrhizae function as effective biofertilizers for plants?
Mycorrhizae are symbiotic associations between a fungus (like those from the genus Glomus) and the roots of higher plants. The fungus helps the plant in several ways:
- It absorbs essential nutrients, particularly phosphorus, from the soil and passes it on to the plant.
- It enhances the plant's resistance to root-borne pathogens.
- It increases the plant's tolerance to salinity and drought.
In return, the fungus gets energy-yielding carbohydrates from the plant. This mutualistic relationship significantly boosts plant growth and makes mycorrhizae excellent biofertilizers.
10. Differentiate between the production of alcoholic drinks with and without distillation, providing an example for each.
The key difference lies in the process used after fermentation by the yeast, Saccharomyces cerevisiae:
- Without Distillation: Beverages like wine and beer are produced directly through the fermentation of fruit juices or malted cereals. The alcohol concentration is relatively low as it is limited by the yeast's tolerance.
- With Distillation: Beverages like whisky, brandy, and rum are produced by fermenting a mash, and then distilling it. Distillation is a process that separates components based on different boiling points, which is used to increase the concentration of alcohol in the final product.
11. Name the enzyme used as a 'clot-buster'. Which microbe produces it, and what is its specific medical function?
The enzyme used as a 'clot-buster' is streptokinase. It is produced by the bacterium Streptococcus. Its primary medical function is to dissolve blood clots (thrombi) that have formed in the blood vessels. It is administered to patients who have suffered a myocardial infarction (heart attack) to clear the blockages and restore blood flow.
12. What are the main gaseous components of biogas? Why is it considered a valuable resource, especially in rural areas?
The main gases produced during anaerobic digestion in a biogas plant are methane (CH₄), which is the predominant component, along with carbon dioxide (CO₂) and traces of hydrogen sulphide (H₂S). Biogas is considered a valuable resource because it is inflammable and can be used as a clean, low-cost fuel for cooking and lighting, reducing dependency on firewood and fossil fuels. The slurry left behind is an excellent fertilizer, rich in nutrients.
