Microbes In Human Welfare ncert solutions: Class 12th biology chapter 8 ncert solutions
| Textbook | NCERT |
| Class | Class 12 |
| Subject | Biology |
| Chapter | Chapter 8 |
| Chapter Name | Microbes In Human Welfare class 12 ncert solutions |
| Category | Ncert Solutions |
| Medium | English |
Are you looking for Ncert Solutions for Class 12 Biology Chapter 8 Microbes In Human Welfare? Now you can download Ncert class 12 biology chapter 8 questions and answers pdf from here.
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 with the help of a microscope, which sample would you carry and why?
Solution 1: I would carry a sample of soil from my garden to the biology laboratory to demonstrate the presence of microbes. Soil is teeming with a diverse range of microorganisms, including bacteria, fungi, and protozoa, which play crucial roles in nutrient cycling and soil health.
When observed under a microscope, soil samples can reveal a variety of bacterial shapes and arrangements, providing an excellent opportunity to study microbial diversity and their ecological functions. Additionally, soil samples are easy to collect and handle, making them practical for laboratory analysis.
Question 2: Give examples to prove that microbes release gases during metabolism.
Solution 2: Microbes release gases during metabolism, and several examples illustrate this process:
Fermentation by Yeast: Yeast, particularly Saccharomyces cerevisiae, undergoes alcoholic fermentation where glucose is converted into ethanol and carbon dioxide (CO₂). The CO₂ produced is responsible for the bubbles seen in fermenting dough and the carbonation in alcoholic beverages.
Anaerobic Bacteria in Digestion: In the human gut, anaerobic bacteria such as Bacteroides and Clostridium break down complex carbohydrates through fermentation, producing gases like methane (CH₄), hydrogen sulfide (H₂S), and carbon dioxide. This gas production can lead to flatulence.
Decomposition of Organic Matter: During the decomposition of organic matter, bacteria and fungi metabolize dead plant and animal material, producing gases such as methane and carbon dioxide. This process is essential in ecosystems for nutrient cycling.
Question 3: In which food would you find lactic acid bacteria? Mention some of their useful applications.
Solution 3: Lactic acid bacteria (LAB) are commonly found in fermented foods such as yogurt, kefir, sauerkraut, kimchi, pickles and Cheese. These bacteria are beneficial for several reasons:
- Probiotics: LAB, particularly strains like Lactobacillus and Bifidobacterium, are used as probiotics, promoting gut health by balancing the intestinal microbiota and improving digestion.
- Food Preservation: The lactic acid produced during fermentation helps preserve food by lowering the pH, which inhibits the growth of harmful bacteria and extends shelf life.
- Nutrient Enhancement: LAB can enhance the nutritional profile of foods by increasing the bioavailability of vitamins and minerals, as well as producing beneficial compounds like vitamins B and K during fermentation.
- Flavor Development: They contribute to the characteristic flavors and textures of fermented foods, making them more palatable and enjoyable.
Question 4: Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Solution 4: Here are some traditional Indian foods made from wheat, rice, and Bengal gram that involve the use of microbes in their preparation:
Wheat-based Foods:
- Idli: A steamed cake made from fermented rice and urad dal (black gram) batter, often served with chutney and sambar.
- Dosa: A thin, crispy pancake made from a fermented batter of rice and urad dal, commonly enjoyed with chutney and sambar.
- Bread (Roti or Naan): Leavened and unleavened flatbreads often made with wheat flour, which may use yeast for fermentation in some recipes.
Rice-based Foods:
- Pongal: A savory dish made from rice and lentils, which is sometimes fermented to enhance flavor and texture.
- Uttapam: A thick pancake made from fermented rice and urad dal batter, topped with vegetables like tomatoes and onions.
- Puttu: A steamed rice cake, typically layered with coconut, which can involve fermentation in some regional variations.
Bengal Gram-based Foods:
- Besan Cheela: A savory pancake made from fermented besan (gram flour), often mixed with spices and vegetables.
- Dhokla: A steamed snack made from fermented besan, often flavored with mustard seeds and green chilies.
- Vada: A deep-fried snack made from fermented lentil (urad dal) batter, sometimes mixed with Bengal gram flour for added texture.
Question 5: In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Solution 5: Microbes play a major role in controlling diseases caused by harmful bacteria through the use of probiotics and antibiotics. Probiotics, such as Lactobacillus and Bifidobacterium, help maintain gut health by competing with pathogenic bacteria for resources and producing substances that inhibit their growth. Additionally, certain microbes, like the mold Penicillium, produce antibiotics that can effectively kill or inhibit harmful bacteria, providing a critical means of treating bacterial infections. Together, these mechanisms help prevent and manage bacterial diseases, promoting overall health.
Question 6: Name any two species of fungus, which are used in the production of the antibiotics.
Solution 6: Two species of fungi that are used in the production of antibiotics are:
1. Penicillium chrysogenum: This fungus is the source of penicillin, the first widely used antibiotic, discovered by Alexander Fleming. Penicillin is effective against a variety of bacterial infections.
2. Cephalosporium acremonium (now known as Acremonium chrysogenum): This fungus produces cephalosporins, a class of antibiotics that are effective against a broad spectrum of bacteria and are often used to treat infections when penicillin is not suitable.
Question 7: What is sewage? In which way can sewage be harmful to us?
Solution 7: The term sewage refers to the municipal waste material which is carried away in drains and sewers. Sewage includes both solid and liquid wastes that are rich in microbes and organic matter.
Most of these microbes are pathogenic, i.e., they are capable of causing diseases such as water-borne diseases. This sewage water is one of the major causes of contaminating drinking water. Therefore, it is vital to treat sewage water by collecting and disposing of it.
Question 8: What is the key difference between primary and secondary sewage treatment?
Solution 8: The key differences are as follows:
| Primary Sewage Treatment | Secondary Sewage Treatment |
|---|---|
| Involves the physical removal of solids through sedimentation. | Involves biological processes to degrade dissolved organic matter. |
| Primarily removes large solids and debris from wastewater. | Focuses on the breakdown of organic matter by microorganisms. |
| Typically a faster process that requires less energy. | Generally takes longer and requires aeration or other biological methods. |
| Results in primary sludge and clarified water. | Produces secondary sludge and further purified water. |
| Often the first step in the sewage treatment process. | Follows primary treatment and is essential for nutrient removal. |
Question 9: Do you think microbes can also be used as source of energy? If yes, how?
Solution 9: Yes, microbes can be used as a source of energy. Bacteria such as Methane bacterium is used for the generation of gobar gas or biogas.
The generation of biogas is an anaerobic process in a biogas plant, which consists of a concrete tank (10−15 feet deep) with sufficient outlets and inlets. The dung is mixed with water to form the slurry and thrown into the tank. The digester of the tank is filled with numerous anaerobic methane-producing bacteria, which produce biogas from the slurry. Biogas can be removed through the pipe which is then used as a source of energy, while the spent slurry is removed from the outlet and is used as a fertilizer.
Question 10: Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
Solution 10: Microbes can be used to decrease the use of chemical fertilizers and pesticides. This can be accomplished by the use of biofertilizers. The main source of biofertilizers are bacteria, fungi and cyanobacteria. They can provide plant nutrients at cheaper cost when compared with the chemical fertilizers. e.g.
(i) Use of leguminous plant with Rhizobium.
(ii) Use of sulphur fixing bacteria.
(iii) Use of hydrogen fixing bacterium.
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?
Solution 11: BOD or biochemical oxygen demand refers to the amount of oxygen which would be consumed if all the organic matter in one litre of water were to be oxidized by bacteria. This BOD test measures the rate of uptake of oxygen by microbes in a sample of water; hence BOD is said to be a measure of the organic matter found in water. Therefore, the greater the BOD of wastewater, the greater the polluting potential.
- Sample A with BOD 20mg/L can be assigned as the secondary effluent discharged from a sewage treatment plant.
- Sample B with BOD 8mg/L can be assigned as river water
- Sample C with BOD 400mg/L can be assigned as untreated sewage water.
This assignment is on the basis that the highest BOD value is the sample carrying the most polluted water.
Question 12: Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
Solution 12: Cyclosporin A (an immuno suppressive drug) is obtained from fungus Trichoderma polysporum while statins (blood cholesterol lowering agent) is obtained from yeast Monascus purpureus.
Question 13: Find out the role of microbes in the following and discuss it with your teacher.
(a) Single cell protein (SCP)
(b) Soil
Solution 13:
Single Cell Protein (SCP) :refers to harmless microbial cells that can be used as an alternate source of good protein.Just like mushrooms (a fungus) is eaten by many people and yeast isused by athletes as a protein source;similarly, other forms of microbial cells can also be used as food rich in protein, minerals, fats, carbohydrate and vitamins.Microbes like Spirulina and Methylophilus methylotrophus are being grown on an industrial scale on materials containing starch like wastewater from potato processing plants, straw,molasses, animal manure and even sewage. These single cell microbes can be used as source.
Soil: Microbes play an important role in maintaining soil fertility. They help in the formation of nutrient-rich humus by the process of decomposition. Many species of bacteria and cyanobacteria have the ability to fix atmospheric nitrogen into usable form. Rhizobium is a symbiotic bacteria found in the root nodules of leguminous plants. Azospirillium and Azotobocter are free living nitrogen-fixing bacteria, whereas Anabena, Nostoc, and Oscillitoria are examples of nitrogen-fixing cyanobacteria.
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
Solution 14: The order of arrangement of products according to their decreasing importance is: Penicillin- Biogas − Citric acid − Curd
Penicillin is the most important product for the welfare of human society. It is an antibiotic, which is used for controlling various bacterial diseases. The second most important product is biogas. It is an eco-friendly source of energy. The next important product is citric acid, which is used as a food preservative. The least important product is curd, a food item obtained by the action of lactobacillus bacteria on milk
Hence, the products in the decreasing order of their importance are as follows: Penicillin- Biogas − Citric acid − Curd
Question 15: How do biofertilisers enrich the fertility of the soil?
Solution 15: Biofertilizers enrich soil fertility by enhancing the availability of essential nutrients, improving soil structure, and promoting beneficial microbial activity. They contain live microorganisms, such as bacteria, fungi, and cyanobacteria, which work symbiotically with plants. These microorganisms facilitate nitrogen fixation, converting atmospheric nitrogen into forms that plants can absorb, thus reducing the need for synthetic nitrogen fertilizers.
Additionally, biofertilizers help solubilize nutrients like phosphorus and potassium, making them more accessible to plant roots. They also enhance soil health by increasing microbial diversity and activity, which can improve organic matter decomposition and nutrient cycling. Furthermore, biofertilizers improve soil structure by promoting the formation of soil aggregates, enhancing aeration and water retention. Overall, the use of biofertilizers contributes to sustainable agriculture by improving soil fertility, promoting plant growth, and reducing chemical inputs.