Hello Students. Are you Searching for NCERT Solutions for Class 12 Biology Chapter 10? If yes then you are most welcome to NCERTian. Here we have provided you with the complete Question and Answers of Chapter 10: Microbes In Human Welfare. These solutions are written by expert teachers and faculties keeping the need of students in mind.
| Chapter | 10. Microbes In Human Welfare |
| Subject | Biology |
| Class | Twelve |
| Category | NCERT Solutions for Class 12 |
Our NCERT Solutions for Class 12 Biology is a great resource for students preparing for boards or competitive exams, such as the NEET. These Biology Class 12 Solutions are made by expert faculties, keeping the latest curriculum in mind. Besides helping students with understanding the concepts of Biology, these solutions are also helpful in writing accurate answers that are vital to score full marks in examinations. On this page, we have given the Class 12 Biology Chapter 10: Microbes In Human Welfare Solutions.
NCERT Solutions for Class 12 Biology Chapter 10
Microbes In Human Welfare Solutions
Q1)
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 can be used as a sample for the study of microbes. Curd contains numerous lactic acid bacteria (LAB) or Lactobacillus. These bacteria produce acids that coagulate and digest milk proteins. A small drop of curd contains millions of bacteria, which can be easily observed under a microscope.
Q2) Give examples to prove that microbes release gases during metabolism.
Answer) The examples of bacteria that release gases during metabolism are:
- (a) Bacteria and fungi carry out the process of fermentation and during this process, they release carbon dioxide. Fermentation is the process of converting a complex organic substance into a simpler substance with the action of bacteria or yeast. Fermentation of sugar produces alcohol with the release of carbon dioxide and very little energy.
- (b) The dough used for making idli and dosa gives a puffed appearance. This is because of the action of bacteria which releases carbon dioxide. This CO2 released from the dough gets trapped in the dough, thereby giving it a puffed appearance.
Q3) In which food would you find lactic acid bacteria? Mention some of their useful applications.
Answer) Lactic acid bacteria can be found in curd. It is this bacterium that promotes the formation of milk into curd. The bacterium multiplies and increases its number, which converts the milk into curd. They also increase the content of vitamin B12 in curd. Lactic acid bacteria are also found in our stomach where it keeps a check on the disease-causing micro-organisms.
Some of their useful applications are as follows:
- It is this bacterium that promotes the formation of milk into curd.
- The bacterium multiplies and increases its number, which converts the milk into curd.
- They also increase the content of vitamin B12 in curd.
- Lactic acid bacteria are also found in our stomach where it keeps a check on the disease-causing micro-organisms.
Q4) Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Answer) Some Indian food made of wheat, rice and Bengal gram are:
- Wheat: Bread, Bhatura and Cake are made of Wheat
- Rice: Idli, Dosa and Uttapam are made of Rice
- Bengal gram: Dhokla and Khandvi are made of Bengal gram
Q5) In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Answer) Several micro-organisms are used for preparing medicines. Antibiotics are medicines produced by certain micro-organisms to kill other disease-causing micro-organisms. These medicines are commonly obtained from bacteria and fungi. They either kill or stop the growth of disease-causing micro-organisms. Streptomycin, tetracycline, and penicillin are common antibiotics. Penicillium notatum produces chemical penicillin, which checks the growth of staphylococci bacteria in the body. Antibiotics are designed to destroy bacteria by weakening their cell walls. As a result of this weakening, certain immune cells such as the white blood cells enter the bacterial cell and cause cell lysis. Cell lysis is the process of destroying cells such as blood cells and bacteria.
Q6) Name any two species of fungus, which are used in the production of the antibiotics.
Answer) Antibiotics are medicines that are produced by certain micro-organisms to kill other disease-causing micro-organisms. These medicines are commonly obtained from bacteria and fungi.
The species of fungus used in the production of antibiotics are:
| Antibiotic | Fungus source |
|---|---|
| Penicillin | Penicillium notatum |
| Cephalosporin | Cephalosporium acremonium |
Q7) What is sewage? In which way can sewage be harmful to us?
Answer) 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 is 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 to contaminate drinking water. Therefore, it is vital to treat sewage water, by collecting and disposing it.
Q8) What is the key difference between primary and secondary sewage treatment?
Answer)
| Primary sewage treatment | Secondary sewage treatment |
|---|---|
| It is a mechanical process involving the removal of coarse solid materials. | It is a biological process involving the action of microbes. |
| It is inexpensive and relatively less complicated. | It is a very expensive and complicated process. |
Q9) Do you think microbes can also be used as source of energy? If yes, how?
Answer) 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.
Q10) Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
Answer) Organic farming is carried out without the use of any pesticides and chemical fertilizers. Microbes play a major role in organic farming. Bio-fertilizers involves picking advantageous microbes to help improve plant growth, by supplying nutrients. Bio-fertilizers are living entities that are known to increase soil fertility. These are introduced into roots, seeds and soil in order to make nutrients available, thus enriching the soil with organic nutrients. Many species of cyanobacteria and bacteria have the potential to fix the free atmospheric nitrogen.
A symbiotic bacteria, Rhizobium, is found in the root nodules of leguminous plants. Some free living nitrogen-fixing bacteria are Azotobacter and Azospirillium, while Nostoc, Oscillitoria, Anabena are examples of nitrogen-fixing cyanobacteria. These bio fertilizers are eco-friendly and cost effective.
On the other hand, microbes can also serve as bio-pesticides to check insect pests in plants. The Bacillus thuringiensis, a bio-pesticide, produces a toxin which kills the insect pests.
Withered bacterial spores are mixed with water and sprinkled in fields. These spores enter the gut of the larvae to release toxins, when larvae of various insects feed on the crops. Likewise, a free living fungi, Trichoderma, are found in the roots of higher plants, safeguarding them from pathogens. Another bio-pesticide, Baculovirus, is used as a biological control agent against other arthropods and insects.
Q11)
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) Biological oxygen demand (BOD) is the method of determining the amount of oxygen required by micro-organisms to decompose the waste present in the water supply. If the quantity of organic wastes in the water supply is high, then the number of decomposing bacteria present in the water will also be high. As a result, the BOD value will increase.
Therefore, it can be concluded that if the water supply is more polluted, then it will have a higher BOD value. Out of the above three samples, sample C is the most polluted since it has the maximum BOD value of 400 mg/L. After untreated sewage water, secondary effluent discharge from a sewage treatment plant is most polluted. Thus, sample A is secondary effluent discharge from a sewage treatment plant and has the BOD value of 20 mg/L, while sample B is river water and has the BOD value of 8 mg/L.
Hence, the correct label for each sample is:
| Label | BOD value | Sample |
|---|---|---|
| A. | 20 mg/L | Secondary effluent discharge from a sewage treatment plant |
| B. | 8 mg/L | River water |
| C. | 400 mg/L | Untreated sewage water |
Q12) Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
Answer)
| Drug | Function | Microbe |
|---|---|---|
| Cyclosporine −A | Immuno suppressive drug | Trichoderma polysporum |
| Statin | Blood cholesterol lowering agent | Monascus purpureus |
Q13) Find out the role of microbes in the following and discuss it with your teacher.
(a) Single cell protein (SCP)
(b) Soil
Answer) The role of microbes in the following are as follows:
a) Single cell protein (SCP):
- It refers to the harmless microbial cells that can be substituted for good proteins.
- Some forms of microbial cells can be consumed as food enriched in minerals, proteins, fats, vitamins and carbohydrates like how mushrooms are consumed and yeast is eaten by athletes as a source of protein.
- Methylophilus methylotrophus, Spirulina are cultivated on large scale on materials comprising starch-like waste water from potato processing plants, molasses, straw, animal manure and sewage
b) Soil:
- The role of microbes is crucial in preserving the fertility of soil
- It helps in forming nutrient-rich humus by the phenomena of decomposition
- Several bacteria and cyanobacteria species have the potential to fix atmospheric nitrogen to a form that can be used by plants
- A symbiotic bacteria, Rhizobium, is found in the root nodules of leguminous plants
- Some free living nitrogen-fixing bacteria, Azotobacter and Azospirillum, and some nitrogen-fixing cyanobacteria – Nostoc, Oscillitoria, and Anabaena are found here.
Q14) 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 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
Q15) How do biofertilisers enrich the fertility of the soil?
Answer) Bio-fertilizers are living organisms which help in increasing the fertility of soil. It involves the selection of beneficial micro-organisms that help in improving plant growth through the supply of plant nutrients. These are introduced to seeds, roots, or soil to mobilize the availability of nutrients by their biological activity. Thus, they are extremely beneficial in enriching the soil with organic nutrients. Many species of bacteria and cyanobacteria have the ability to fix free atmospheric nitrogen. 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. Bio-fertilizers are cost effective and eco-friendly.
That’s it. These were the solutions of NCERT Class 12 Biology Chapter 10 – Microbes In Human Welfare. Our team hopes that you have found these solutions helpful for you. If you have any doubt related to this chapter then feel free to comment your doubts below. Our team will try their best to help you with your doubts.