GSEB Class 12 Biology Solutions Chapter 10 Microbes in Human Welfare

GSEB Solutions Class 12 Biology Chapter 10 Microbes In Human Welfare

GSEB Class 12 Biology Microbes In Human Welfare Text Book Questions And Answers

 

Question 1. Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why?
Answer: Curd contains Lactic Acid Bacteria (LAB), such as *Lactobacillus acidophilus*, making it an ideal sample.
In simple words: To observe microbes, one could bring a sample of curd from home, as it is rich in beneficial lactic acid bacteria easily visible under a microscope.

🎯 Exam Tip: Remember to specify *curd* and the reason (*Lactic Acid Bacteria*) to get full marks for identifying a suitable sample.

 

Question 2. Give examples to prove that microbes release gases during metabolism.
Answer: Examples demonstrating gas release by microbes during metabolism include the rising of dough and the formation of characteristic holes in Swiss cheese.
In simple words: The expansion of dough and the holes in Swiss cheese are clear signs that microbes produce gas while they metabolize.

🎯 Exam Tip: When providing examples, ensure they clearly illustrate the production of gas as a metabolic byproduct by microorganisms.

 

Question 3. In which food would you find lactic acid bacteria? Mention some of their useful applications.
Answer: Lactic acid bacteria are found in curd. Their useful applications include:
- These bacteria facilitate the conversion of milk into curd by fermenting lactose to produce lactic acid, which coagulates casein protein.
- They contribute to curd's nutritional value by increasing Vitamin B12 content and inhibit the growth of spoilage-causing and pathogenic microorganisms.
In simple words: Lactic acid bacteria are present in curd and help turn milk into curd, increase Vitamin B12, and prevent harmful bacteria from growing.

🎯 Exam Tip: Always list both the food source and at least two distinct beneficial applications of Lactic Acid Bacteria to achieve comprehensive scoring.

 

Question 4. Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Answer: Traditional Indian foods like bread, dosa, idli, and various fermented beverages utilize microbial action in their preparation.
In simple words: Many Indian dishes such as bread, dosa, and idli, along with drinks, rely on microbes for their making.

🎯 Exam Tip: Provide a diverse range of examples from different food categories (e.g., bread, fermented batters, beverages) to show a broad understanding.

 

Question 5. In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Answer: Microorganisms have significantly contributed to disease control by serving as a source of antibiotics. These antimicrobial agents effectively combat pathogenic bacteria. Notable examples include streptomycin (derived from *Streptomyces griseus*), erythromycin (from *Streptomyces erythreus*), and bacitracin (from *Bacillus licheniformis*).
In simple words: Microbes help fight diseases by producing antibiotics, which are powerful medicines used to kill bad bacteria.

🎯 Exam Tip: Focus on the concept of antibiotics as microbial products and provide specific examples of both the antibiotic and its microbial source for a complete answer.

 

Question 6. Name any two species of fungus, which are used in the production of antibiotics.
Answer: Two fungal species commonly employed in antibiotic production are *Penicillium notatum* and *Cephalosporium*.
In simple words: Fungi like *Penicillium notatum* and *Cephalosporium* are important for making antibiotics.

🎯 Exam Tip: Ensure correct scientific names (genus and species) are provided for full accuracy when identifying organisms.

 

Question 7. What is sewage? In which way can sewage be harmful to us?
Answer: Sewage, or municipal wastewater, comprises human excreta and diverse organic wastes, carrying numerous pathogenic microorganisms and detrimental chemicals. Its harmful effects on us arise because it:
- Acts as a source of contamination for various water bodies.
- Contributes to eutrophication in water ecosystems.
- Leads to the formation of scum and sludge, imparting an unpleasant taste, foul odor, and turbidity to the water where it is discharged.
In simple words: Sewage is dirty water with waste and germs; it harms us by polluting water, causing excessive algae growth, and making water look and smell bad.

🎯 Exam Tip: Define sewage accurately and list at least three distinct negative impacts on human health and the environment to cover all aspects of the question.

 

Question 8. What is the key difference between primary and secondary sewage treatment?
Answer: The primary distinction between primary and secondary sewage treatment lies in their methods.
- **Primary treatment:** This stage focuses on the physical separation of particles. It begins with sequential filtration to eliminate floating debris, followed by sedimentation to remove grit (soil and small pebbles). The settled solids form primary sludge, and the liquid portion, known as effluent, then proceeds to secondary treatment.
- **Secondary treatment:** This biological process involves transferring the primary effluent into large aeration tanks, where it is continuously stirred. This agitation promotes the vigorous proliferation of aerobic microorganisms, which form aggregates called 'flocs' (masses of bacteria intertwined with fungal filaments). These microbes actively consume the majority of organic matter in the effluent, thereby reducing its Biological Oxygen Demand (BOD). BOD quantifies the amount of oxygen microbes would consume to oxidize organic matter in a water sample; a higher BOD indicates greater pollution potential. Treatment continues until the BOD is significantly lowered.
In simple words: Primary sewage treatment physically removes large particles, while secondary treatment uses microbes to biologically break down organic matter and reduce pollution levels.

🎯 Exam Tip: Clearly delineate primary (physical) and secondary (biological) treatment steps, focusing on the main objective and processes of each, including the role of BOD in secondary treatment.

 

Question 9. Do you think microbes can also be used as source of energy? If yes, how?
Answer: Microbes themselves are not directly used as a primary energy source. However, their metabolic fermentation products, such as biogas and alcohol, are widely utilized as sources of energy.
In simple words: While microbes themselves aren't direct energy sources, the biogas and alcohol they produce through fermentation are used for energy.

🎯 Exam Tip: Differentiate between microbes as *direct* energy sources and their *products* as energy sources, citing specific examples like biogas or alcohol.

 

Question 10. Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
Answer: Microorganisms play a crucial role in reducing the reliance on chemical fertilizers and pesticides through biological control, also known as biocontrol. This approach involves using natural enemies or microbial agents to manage plant diseases and pests. Unlike chemical pesticides, which are toxic, harmful to humans and animals, and pollute the environment and crops, biocontrol methods offer a sustainable and eco-friendly alternative, thereby mitigating the negative impacts of synthetic chemicals.
In simple words: Microbes help reduce chemical use by acting as natural pest controllers and biofertilizers, offering a safer and eco-friendly way to manage crops compared to toxic chemicals.

🎯 Exam Tip: Emphasize the concept of biocontrol and biofertilizers, explaining how these microbial actions replace chemical inputs and lead to environmental benefits.

 

Question 11. 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 labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the 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 the river water is relatively clean?
Answer: The most polluted water sample is C, which has the highest BOD value of 400 mg/L, indicating untreated sewage water. Sample B, with the lowest BOD of 8 mg/L, represents the relatively clean river water. Sample A, having a BOD of 20 mg/L, is the secondary effluent discharged from the sewage treatment plant.
In simple words: Sample C (400 mg/L BOD) is the most polluted (untreated sewage), Sample B (8 mg/L BOD) is the cleanest (river water), and Sample A (20 mg/L BOD) is treated sewage.

🎯 Exam Tip: Remember that a higher BOD value indicates greater organic pollution. Rank the samples by BOD to assign labels correctly, starting with the least polluted (lowest BOD) and most polluted (highest BOD).

 

Question 12. Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol-lowering agents) are obtained.
Answer: Cyclosporin A, an immunosuppressive agent, is obtained from the fungus *Trichoderma polysporum*. Statins, which are blood cholesterol-lowering agents, are produced by the yeast *Monascus purpureus*.
In simple words: Cyclosporin A comes from *Trichoderma polysporum*, and Statins are made by *Monascus purpureus*; both are vital medicines from microbes.

🎯 Exam Tip: Precisely recall the microbial source for each bioactive molecule and its specific medical application (immunosuppressive or cholesterol-lowering).

 

Question 13. Find out the role of microbes in the following: a. Single-cell protein (SCP) b. Soil
Answer: The roles of microbes are significant in:
(i) **Single-cell protein (SCP):** Microbes like *Spirulina*, yeast, and mushrooms are cultivated to produce SCP, which serves as a rich source of food and animal feed, containing essential amino acids and being low in fat.
(ii) **Soil:** Microorganisms perform several vital functions in soil:
- They facilitate humification, the process of forming humus from organic matter.
- They contribute to mineralization, releasing essential minerals during the decomposition of organic substances.
- They act as biofertilizers, enhancing soil fertility and nutrient availability for plants.
- They are involved in denitrification, a process that converts nitrates back into gaseous nitrogen.
In simple words: Microbes are used to make protein-rich food (SCP) and are essential in soil for creating humus, releasing minerals, fertilizing plants, and converting nitrogen.

🎯 Exam Tip: When describing microbial roles, provide concrete examples for SCP and detail multiple processes (humification, mineralization, biofertilization, denitrification) for their function in soil.

 

Question 14. Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd
Answer: The decreasing order of importance for human welfare is: Penicillin, Biogas, Curd, and Citric acid.
- **Penicillin:** Discovered by Alexander Fleming, this pioneering antibiotic is crucial for eradicating pathogenic bacteria and has revolutionized the control of infectious diseases such as diphtheria, whooping cough, and pneumonia. Its significance in modern medicine is paramount, making a world without antibiotics almost inconceivable.
- **Biogas:** This microbial product serves as a valuable renewable energy source, particularly in rural settings.
- **Curd:** A nutritious food product, curd plays an important role in gut health by inhibiting the proliferation of disease-causing microbes in the digestive system.
- **Citric acid:** This compound is a beneficial source of Vitamin C.
In simple words: Penicillin is most important for fighting deadly diseases, followed by biogas for energy, then curd for nutrition and gut health, and finally citric acid as a vitamin source.

🎯 Exam Tip: Justify your ranking by explaining the profound impact of each item, especially highlighting life-saving benefits for the highest-ranked items.

 

Question 15. How do biofertilizers enrich the fertility of the soil?
Answer: Biofertilizers are microbial preparations that enhance soil fertility and nutrient availability for crop plants through various mechanisms:
- **Nitrogen-fixing bacteria and Cyanobacteria:** These microorganisms convert atmospheric nitrogen (N₂) into usable nitrogen compounds (salts of N₂), making this essential nutrient accessible to plants.
- **Phosphate-solubilizing bacteria:** They secrete phosphatase enzymes that dissolve insoluble phosphate forms in the soil, converting them into a plant-absorbable form.
- **Mycorrhizae:** These symbiotic fungi form associations with plant roots, particularly in forest plants, and effectively solubilize and absorb nutrients from organic matter, greatly improving the plant's nutrient uptake capacity.
In simple words: Biofertilizers make soil fertile by fixing nitrogen, dissolving locked-up phosphates, and helping plants absorb nutrients better through fungi partnerships.

🎯 Exam Tip: Detail at least two distinct mechanisms by which biofertilizers improve soil fertility, such as nitrogen fixation and phosphate solubilization, and provide relevant microbial examples.

GSEB Class 12 Biology Microbes In Human Welfare Additional Important Questions And Answers

 

Question 1. Do you agree with the statement that microbes are omnipresent?
Answer: Yes, the statement that microbes are omnipresent is accurate. Microorganisms are found in virtually every part of the biosphere, including diverse environments such as water, soil, hot springs, the ocean floor, high atmospheric layers, and deep within Earth's crust. For instance, *Methanopyrus kandleri* can thrive at temperatures up to 122°C, and *Trichosporonoides nigerescens* is a microbe known to survive for nearly a decade without water exposure, highlighting their remarkable adaptability and widespread presence.
In simple words: Yes, microbes are everywhere – in water, soil, extreme temperatures, and even the air – showing their incredible ability to live in almost any environment.

🎯 Exam Tip: To support your agreement, provide examples of diverse and extreme habitats where microbes are found, demonstrating their adaptability.

 

Question 2. A person complained to the doctor about the myocardial infraction he suffered and about a doctor he consulted earlier. The earlier doctor told about curing of the diseases using microbes. Will the doctor support the earlier doctor or not? Substantiate your answer.
Answer: Yes, the current doctor would support the earlier doctor's approach. This is because streptokinase, an enzyme produced by *Streptococcus* bacteria, can be genetically engineered and is effectively used as a 'clot-buster' medication. It helps dissolve blood clots in patients who have experienced a myocardial infarction (heart attack) by clearing blockages in their blood vessels.
In simple words: The doctor would agree because microbes can produce medicines like streptokinase, which can break down blood clots and treat heart attacks.

🎯 Exam Tip: Provide a specific example of a microbially derived therapeutic agent (like streptokinase) and its medical application to substantiate the answer effectively.

 

Question 3. "Antibiotics are chemical substances produced from microbes". a. What is the meaning of the term antibiotics? b. Name the first antibiotic. c. Who discovered antibiotics?
Answer:
(a) The term 'antibiotics' literally means 'against life,' specifically referring to substances that are effective 'against the life' of pathogens.
(b) The first antibiotic discovered was Penicillin.
(c) Antibiotics were discovered by Alexander Fleming.
In simple words: Antibiotics mean 'against life' (for germs); Penicillin was the first, discovered by Alexander Fleming.

🎯 Exam Tip: Ensure precise definitions and accurate historical facts for these fundamental concepts in microbiology.

 

Question 4. Some discoveries are made unexpectedly. a. What is it known as? b. Give one example.
Answer:
(a) Such unexpected discoveries are referred to as serendipity.
(b) A prime example is the discovery of penicillin by Alexander Fleming. While culturing *Staphylococcus* bacteria, Fleming fortuitously observed that a blue-green mold contaminating one of his petri dishes inhibited the growth of the bacteria around it. He deduced that this inhibition was caused by a chemical substance produced by the mold, which he subsequently named penicillin, after the mold *Penicillium notatum*.
In simple words: Unexpected discoveries are called serendipity; a famous example is Alexander Fleming accidentally discovering penicillin from mold on a bacterial plate.

🎯 Exam Tip: Define serendipity accurately and use the discovery of penicillin as a classic, detailed example, explaining the key observations that led to it.

 

Question 5. (a) What is the source of statins and how they reduce the level of cholesterol in our body. (b) Write the technical terms for VAM. Pickup examples of endomycorrhiza and ectomycorrhiza from sclerosis, Laccaria, Gigaspora, glomas, Hebeloma, Psilocybes.
Answer:
(a) Statins, which are effective in lowering cholesterol levels in the body, are synthesized through the metabolic activity of the yeast *Monascus purpureus*. Examples of statins include Lovastatin, Simvastatin, Pravastatin, and Fluvastatin.
(b) The technical term for VAM is Vesicular-Arbuscular Mycorrhiza. This type of mycorrhiza involves fungal hyphae that form vesicular and branched arbuscular structures within the root cortical cells, facilitating nutrient exchange.
- **Ectomycorrhiza examples:** *Laccaria*, *Hebeloma*, *Psilocybes*
- **Endomycorrhiza examples:** *Gigaspora*, *Glomus*
In simple words: (a) Statins for cholesterol reduction come from *Monascus purpureus* yeast. (b) VAM stands for Vesicular-Arbuscular Mycorrhiza, a fungus-root partnership; *Laccaria* is ectomycorrhiza, and *Gigaspora* is endomycorrhiza.

🎯 Exam Tip: For statins, identify the microbial source and their general function. For VAM, provide the full form and clearly distinguish examples of ecto- and endomycorrhiza from the given list.

 

Question 6. Complete the following.

Microbes	Products
i. ............(a)	(a) Penicillin
ii. Trichoderma polysporum	...........(b)..........
iii. Propionibacterium Sharmanii	...........(c)..........
iv. ............(d)............	Statin

Answer:

Microbes	Products
i. Penicillium notatum	(a) Penicillin
ii. Trichoderma polysporum	(b) Cyclosporin A
iii. Propionibacterium Sharmanii	(c) Swiss Cheese (Carbon Dioxide for holes)
iv. Monascus purpureus	(d) Statin

The following table matches microbes with the acids they produce:

Microbes	Acids
i. Aspergillus niger	a. Citric acid
ii. Acetobacter aceti	b. Acetic acid
iii. Lactobacillus	c. Lactic acid

In simple words: This question asks to complete two tables: one matching microbes to their medical/food products like Penicillin, Cyclosporin A, Swiss Cheese, and Statin; and another matching microbes like *Aspergillus niger*, *Acetobacter aceti*, and *Lactobacillus* to the acids they produce: Citric, Acetic, and Lactic acid, respectively.

🎯 Exam Tip: Accurately recall the specific microbial species and their corresponding primary products, whether they are antibiotics, enzymes, food items, or organic acids.

 

Question 7. The puffed-up appearance of dough is due to the production of CO2 gas. Can you tell which metabolic pathway is taking place resulting in the formation of CO2?
Answer: The metabolic pathway responsible for the production of CO2 gas, leading to the puffed-up appearance of dough, is alcoholic fermentation.
In simple words: The puffy look of dough comes from CO2 gas made during alcoholic fermentation.

🎯 Exam Tip: Link the observed phenomenon (puffed dough) directly to the specific biochemical process (alcoholic fermentation) and its gaseous product (CO2).

 

Question 8. Name the organism that causes large holes in "Swiss cheese". How are these cause?
Answer: The bacterium responsible for the characteristic large holes in Swiss cheese is *Propionibacterium shermanii*. These distinct holes are formed by the substantial amount of carbon dioxide gas released during the bacterium's metabolic processes.
In simple words: *Propionibacterium shermanii* makes the big holes in Swiss cheese by producing lots of carbon dioxide gas.

🎯 Exam Tip: State the exact bacterial name and the gas produced as the reason for the holes to ensure a complete answer.

 

Question 9. Which among the following is used for making Roquefort cheese? a. Propionibacterium sharmanii b. LAB c. Saccharomyces cerevisiae d. None of these
Answer: The correct option is (d) None of these, as Roquefort cheese is typically made using the fungus *Penicillium roqueforti*, which is not listed.
In simple words: Roquefort cheese is made with *Penicillium roqueforti*, so none of the given options are correct.

🎯 Exam Tip: For MCQ questions, even if the answer is "None of these," it's beneficial to know the correct answer (e.g., *Penicillium roqueforti* for Roquefort cheese) for deeper understanding.

 

Question 10. Curd is more nutritious than milk. Justify the statement.
Answer: Curd is often considered more nutritious than milk primarily because the fermentation process, driven by Lactic Acid Bacteria (LAB), significantly increases its Vitamin B12 content.
In simple words: Curd is healthier than milk because the bacteria that make it increase its Vitamin B12 content.

🎯 Exam Tip: Focus on the specific nutritional enhancement (Vitamin B12 increase) due to microbial activity as the key justification.

 

Question 11. What is alcoholic fermentation?
Answer: Alcoholic fermentation is a biological process where glucose is converted into ethyl alcohol (ethanol) and carbon dioxide, releasing energy. This conversion can be represented by the chemical equation: \( C_6H_{12}O_6 \)
\( \implies 2C_2H_5OH + 2CO_2 + \text{energy} \).
In simple words: Alcoholic fermentation is when glucose turns into alcohol, carbon dioxide, and energy, a process used by yeast.

🎯 Exam Tip: Provide both a clear definition and the balanced chemical equation to fully explain alcoholic fermentation.

 

Question 12. Penicillin was a chance discovery. Is it true or not? If the answer is true, give reason.
Answer: Yes, it is true that penicillin was a chance discovery, an excellent example of serendipity in the scientific method-the ability to make valuable discoveries unexpectedly. In 1928, Alexander Fleming, while studying *Staphylococcus* bacteria, fortuitously observed that a blue-green mold contaminating one of his petri dishes inhibited the bacterial growth around it. He deduced that this inhibition was caused by a chemical substance produced by the mold, which he subsequently named Penicillin, after the mold, *Penicillium notatum*. This accidental observation paved the way for the development of antibiotics, revolutionizing the treatment of bacterial infections like staphylococcal throat infections.
In simple words: Yes, penicillin was discovered by accident when Alexander Fleming noticed a mold preventing bacterial growth, a classic example of serendipity in science.

🎯 Exam Tip: Clearly define serendipity and provide a concise yet comprehensive account of Alexander Fleming's discovery, emphasizing the accidental nature of the observation.

 

Question 13. Today, we cannot imagine a world without antibiotics. Justify the statement.
Answer: The statement that we cannot imagine a world without antibiotics today is well-justified. Antibiotics have been instrumental in saving countless lives by effectively combating deadly bacterial diseases such as plague, diphtheria, whooping cough, and leprosy. Given that humans constantly coexist with various bacteria, many of which can cause fatal illnesses, antibiotics have significantly enhanced our ability to treat and control these severe diseases, becoming an indispensable part of modern medicine.
In simple words: We can't live without antibiotics because they are crucial for treating severe bacterial infections like plague and diphtheria, saving countless lives.

🎯 Exam Tip: Emphasize the historical impact of antibiotics on infectious disease mortality and their continued necessity in managing bacterial infections for a strong justification.

 

Question 14. Observe the table and fill in the blanks.

Microbes	Acids
i. Aspergillus niger	a.
ii. Acetobacter aceti	b.
iii. ..........................	c. Lactic acid

Answer:

Microbes	Acids
i. Aspergillus niger	a. Citric acid
ii. Acetobacter aceti	b. Acetic acid
iii. Lactobacillus	c. Lactic acid

In simple words: The table shows which microbes produce specific acids: *Aspergillus niger* makes citric acid, *Acetobacter aceti* makes acetic acid, and *Lactobacillus* makes lactic acid.

🎯 Exam Tip: Be precise in matching each microbe with the exact acid it is known to produce industrially or biologically.

 

Question 15. Name a bioactive molecule produced by *TrichocLerma polysporum*. Mention the significance also.
Answer: The bioactive molecule produced by *Trichoderma polysporum* is Cyclosporin A. Its significance lies in its role as a potent immunosuppressive agent, critically used in organ-transplant patients to prevent rejection of the transplanted organ.
In simple words: *Trichoderma polysporum* produces Cyclosporin A, an important drug that suppresses the immune system to prevent organ rejection in transplant patients.

🎯 Exam Tip: Correctly identify the molecule and its medical purpose (immunosuppression) in organ transplantation.

 

Question 16. Expand the following. a. Bt cotton b. BOD c. LAB
Answer:
(a) Bt cotton: *Bacillus thuringiensis* cotton
(b) BOD: Biological Oxygen Demand
(c) LAB: Lactic Acid Bacteria
In simple words: Bt cotton means *Bacillus thuringiensis* cotton, BOD is Biological Oxygen Demand, and LAB refers to Lactic Acid Bacteria.

🎯 Exam Tip: Accurately provide the full form for each abbreviation, ensuring correct spelling and capitalization where appropriate.

 

Question 17. What are methanogens?
Answer: Methanogens are a group of anaerobic bacteria and archaea that are responsible for producing biogas, primarily methane, through their metabolic activities.
In simple words: Methanogens are microbes that live without oxygen and produce methane gas, a key component of biogas.

🎯 Exam Tip: Define methanogens by their anaerobic nature and their role in methane production, linking them to biogas.

 

Question 18. What are baculoviruses?
Answer: Baculoviruses are a family of viruses that act as pathogens, specifically targeting and infecting insects and other arthropods.
In simple words: Baculoviruses are viruses that naturally attack and infect insects and other similar creatures.

🎯 Exam Tip: Identify baculoviruses as pathogens that specifically target insects and arthropods, often used in biological pest control.

 

Question 19. Identify the figure and write a short note on it.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक बायोगैस संयंत्र को दर्शाता है, जिसमें जैविक कचरे को अवायवीय रूप से किण्वित करके बायोगैस का उत्पादन किया जाता है। इसमें एक बड़ा डाइजेस्टर टैंक होता है जहाँ गोबर और पानी का घोल डाला जाता है, जिससे मीथेन और कार्बन डाइऑक्साइड जैसी गैसें बनती हैं, जो ऊपर गैस-होल्डर में जमा होती हैं और उपयोग के लिए निकाली जाती हैं।
Answer: This figure represents a Biogas plant. A biogas plant utilizes anaerobic microorganisms to decompose organic waste, like animal dung, producing biogas (primarily methane) used as fuel. The process occurs in a digester, and the gas is collected in a gas-holder.
In simple words: The picture shows a biogas plant, which uses microbes to turn animal waste into biogas for fuel in a special tank.

🎯 Exam Tip: When asked to identify a diagram, state its name clearly and provide a concise explanation of its function and key components.

 

Question 20. Name a microbial biocontrol agent.
Answer: A notable microbial biocontrol agent is *Bacillus thuringiensis*, often referred to as Bt.
In simple words: *Bacillus thuringiensis*, or Bt, is a microbe used to control pests naturally.

🎯 Exam Tip: Provide a specific and well-known example of a microbial biocontrol agent, ensuring correct scientific naming.

 

Question 21. Rhizobium, Azospirillum and Azotobacter act as biofertilisers. How?
Answer: *Rhizobium*, *Azospirillum*, and *Azotobacter* function as biofertilizers by fixing atmospheric nitrogen. They convert inert gaseous nitrogen into usable forms like nitrates and ammonium, thereby enriching the soil's nitrogen content and making it available for plant uptake.
In simple words: These bacteria act as biofertilizers by taking nitrogen from the air and changing it into a form plants can use, enriching the soil.

🎯 Exam Tip: Explain that these bacteria are nitrogen-fixers, converting atmospheric nitrogen into plant-available forms, which is their primary mode of action as biofertilizers.

 

Question 22. Do you think that fungi can help the plant to grow and develop resistance? If yes, how?
Answer: Yes, fungi can indeed assist plants in growth and resistance development through symbiotic associations, specifically mycorrhizae. In this relationship, the fungi absorb phosphorus and other nutrients from the soil, effectively transferring them to the plant, which enhances plant vigor and often improves resistance to certain stresses.
In simple words: Yes, fungi help plants grow and become stronger by forming partnerships (mycorrhizae) that allow them to absorb more nutrients like phosphorus from the soil.

🎯 Exam Tip: Acknowledge the symbiotic relationship (mycorrhiza) and explain the mechanism (nutrient absorption, especially phosphorus) by which fungi benefit plants.

 

Question 23. Name a microbe which serves as a biofertilizer in the paddy field.
Answer: *Anabaena*, a type of cyanobacterium (blue-green alga), is a microbe that serves as an effective biofertilizer in paddy fields.
In simple words: *Anabaena*, a blue-green alga, is a microbe used as a biofertilizer in rice paddies.

🎯 Exam Tip: Identify *Anabaena* or another relevant cyanobacterium known for nitrogen fixation in flooded conditions for this specific crop.

 

Question 24. Write about "Organic farming”.
Answer: Organic farming represents a holistic and integrated agricultural management system that prioritizes understanding and nurturing the intricate interactions among the diverse organisms comprising the field's flora and fauna. Key aspects include:
- This method aims to establish an ecosystem where insect populations are not eliminated but rather maintained at manageable levels through natural checks and balances, fostering a vibrant and self-sustaining environment.
- It acknowledges that completely eradicating pests is often impractical and undesirable, as many beneficial predatory and parasitic insects rely on these populations for survival. This approach significantly minimizes the reliance on chemical pesticides, thereby reducing environmental pollution.
In simple words: Organic farming is a natural way to grow food that focuses on working with the environment and its creatures to control pests and keep the ecosystem healthy without harsh chemicals.

🎯 Exam Tip: Define organic farming as a holistic system and elaborate on its principles, such as maintaining ecological balance and reducing chemical inputs, instead of just stating it's chemical-free.

 

Question 25. Match the following.

Microbe	Uses
i. Anabaena	a. Biogas
ii. Penicillium notation	b. Cheese
iii. Methanobacterium	c. Penicillin
iv. Monascus purpureus	d. Biofertiliser

Answer:

Microbe	Uses
i. Anabaena	d. Biofertiliser
ii. Penicillium notatum	c. Penicillin
iii. Methanobacterium	a. Biogas
iv. Monascus purpureus	b. Cheese

In simple words: This table matches microbes with their uses: *Anabaena* is a biofertilizer, *Penicillium notatum* makes penicillin, *Methanobacterium* produces biogas, and *Monascus purpureus* is used in cheese production.

🎯 Exam Tip: Ensure precise pairing of each microbe with its correct application or product based on established biological functions.

 

Question 26. Name a fungus used for the control of pests.
Answer: A fungus commonly utilized for pest control purposes is the *Trichoderma* species.
In simple words: *Trichoderma* species are fungi used to naturally control pests.

🎯 Exam Tip: Provide a specific and widely recognized fungal genus (*Trichoderma*) known for its biological pest control properties.

 

Question 27. You have been deputed by your school Principal to a local village to explain the use of a biogas plant. With the help of a labelled sketch, explain the various parts of the biogas plant.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक बायोगैस संयंत्र की संरचना को दर्शाता है, जिसमें एक गहरा कंक्रीट टैंक (डाइजेस्टर) होता है जहाँ पशुओं का गोबर और अन्य जैव-अपशिष्ट एक घोल के रूप में डाले जाते हैं। अवायवीय सूक्ष्मजीव इस घोल को किण्वित करते हैं, जिससे मीथेन और कार्बन डाइऑक्साइड युक्त बायोगैस उत्पन्न होती है। गैस को ऊपर एक फ्लोटिंग गैस-होल्डर में जमा किया जाता है और फिर पाइपलाइनों के माध्यम से घरों में खाना पकाने और रोशनी के लिए वितरित किया जाता है।
Answer: The development of biogas production technology in India was largely driven by the initiatives of the Indian Agricultural Research Institute (IARI) and the Khadi and Village Industries Commission. A typical biogas plant comprises a deep concrete tank, usually 10-15 feet deep, which serves as the digester. Organic wastes, primarily a slurry of animal dung, are introduced into this tank. A floating cover rests on the slurry, collecting the biogas produced by anaerobic microbial activity. This biogas plant features an outlet connected to a pipeline, facilitating the supply of biogas to local households. Biogas plants are predominantly constructed in rural areas, where the generated biogas is utilized for cooking and lighting purposes.
In simple words: A biogas plant uses a deep tank to break down animal waste with microbes, producing biogas that is collected under a floating cover and then piped to homes for cooking and lighting, especially in rural areas.

🎯 Exam Tip: Include a clear description of the biogas plant's main components (digester, inlet, outlet, gas-holder) and the anaerobic process, along with its practical applications (cooking, lighting).

 

Question 28. How are biofertilizers different from fertilizers such as NPK that we buy from the market? Justify the role of rhizobium as a biofertilizer.
Answer: Biofertilizers differ significantly from synthetic chemical fertilizers like NPK in their composition and mechanism. Chemical fertilizers are manufactured inorganic compounds, whereas biofertilizers are living microorganisms that naturally enhance soil fertility.
The indiscriminate use of chemical fertilizers contributes substantially to environmental pollution, prompting a shift towards organic farming practices that incorporate biofertilizers. These biological agents, derived from bacteria, fungi, and cyanobacteria, naturally enrich the soil's nutrient quality.
*Rhizobium* serves as an excellent example of a biofertilizer. It forms a symbiotic association within the root nodules of leguminous plants, where it performs atmospheric nitrogen fixation. This process converts gaseous nitrogen into organic forms, making this vital nutrient directly available for plant uptake and growth.
In simple words: Biofertilizers are living microbes that naturally enrich soil, unlike chemical NPK fertilizers. *Rhizobium* is a biofertilizer because it helps plants get nitrogen from the air.

🎯 Exam Tip: Clearly distinguish biofertilizers (living organisms) from chemical fertilizers (synthetic compounds) and thoroughly explain *Rhizobium*'s specific role in nitrogen fixation within leguminous plants.

 

Question 29. Bacteria that convert milk into curd play two other beneficial roles. What are they?
Answer: Besides converting milk to curd, Lactic Acid Bacteria (LAB) offer two additional beneficial roles:
(i) They enhance the nutritional profile of curd by notably increasing its Vitamin B12 content.
(ii) LAB actively inhibit the growth of harmful, disease-causing microorganisms, contributing to gut health and food safety.
In simple words: Lactic Acid Bacteria (LAB) in curd also boost its Vitamin B12 and fight off bad microbes, improving nutrition and gut health.

🎯 Exam Tip: Focus on distinct benefits beyond curd formation, such as nutritional enrichment (e.g., Vitamin B12) and antimicrobial properties.

 

Question 30. What are 'floes'? State their role in effluent treatment and their ultimate fate in the sewage treatment tanks.
Answer: Flocs (often misspelled as 'floes' in the text) are distinct masses of aerobic bacteria that grow in association with fungal filaments, forming a mesh-like structure during secondary sewage treatment.
Their role in effluent treatment is crucial: these microbial flocs actively consume organic matter in the wastewater, thereby significantly reducing the Biological Oxygen Demand (BOD) of the sewage. A lower BOD indicates less polluting potential.
The ultimate fate of these bacterial flocs in sewage treatment tanks is sedimentation. After the biological treatment, the effluent containing the flocs is transferred to a settling tank, where the heavy flocs are allowed to settle. This settled material is then referred to as 'activated sludge'.
In simple words: Flocs are clumps of microbes that clean sewage by eating organic waste, reducing pollution. After cleaning, they settle down and become activated sludge.

🎯 Exam Tip: Define flocs accurately, describe their function in reducing BOD in secondary treatment, and explain their final state as activated sludge in settling tanks.

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