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NCERT Class 12 Biology Chapter 10 Microbes in Human Welfare
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Microbes in Human Welfare
Chapter: 10
BIOLOGY
UNIT – III BIOLOGY AND HUMAN WELFARE
TEXT BOOK QUESTIONS ANSWERS
Q. 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?
Ans: Curd can be used as a sample to demonstrate the presence of microbes under a microscope because curd contains numerous lactic acid bacteria (LAB) or Lactobacillus.
Q. 2. Give examples to prove that microbes release gases during metabolism.
Ans: DOSA and IDLI:
(i) Dough used for making dosa and idli is fermented by bacteria Streptococcus and Leuconostoc.
(ii) The puffed-up appearance of dough is due to the production of CO 2 gas.
CHEESE:
(i) Cheese is made from milk with the help of microbes.
(ii) Large holes in ‘Swiss cheese’ are due to production of CO 2 by a bacterium Propionibacterium sharmanii.
Q. 3. In which food would you find lactic acid bacteria? Mention some of their useful applications.
Ans: (i) Curd is produced from milk with Lactobacillus commonly called lactic acid bacteria (LAB).
(ii) Inoculum or starter of small amount of curd added to milk has millions of LAB.
(iii) LAB converts lactose sugar into lactic acid that coagulates and partially digests milk protein casein.
(iv) LAB improves nutritional value of curd by increasing vitamin B 12.
(v) LAB checks disease causing microbes in stomach.
Q. 4. Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Ans: Wheat: Bread, cake.
Rice: Idli, dosa.
Bengal gram: Dhokla, Khandvi.
Q. 5. In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Ans: Antibiotics are produced by several bacteria and fungi which are used to kill other disease-causing microorganisms. Streptomycin, tetracycline, and penicillin are common antibiotics.
Q. 6. Name any two species of fungus, which are used in the production of the antibiotics.
Ans: Two antibiotics are: Penicillin- Penicillium notatum and Cephalosporin- Cephalosporium acremonium.
Q. 7. What is sewage? In which way can sewage be harmful to us?
Ans: Sewage is the municipal waste water that contains human excreta, organic matter and microbes. Many of these microbes cause water-borne diseases. Sewage water is a major cause of water pollution.
Q. 8. What is the key difference between primary and secondary sewage treatment?
Ans: Primary sewage treatment is physical process involving the removal of solid materials through filtration and sedimentation.
Secondary sewage treatment: It is a biological process carried out by the action of microorganisms.
Q. 9. Do you think microbes can also be used as source of energy? If yes, how?
Ans: Yes, microbes can be used as a source of energy. Methanogens are used for the generation of gobar gas or biogas.
Q. 10. Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
Ans: MICROBES AS BIOCONTROL AGENTS:
(i) Biocontrol is use of biological methods for controlling plant diseases and pests.
(ii) Biocontrol measures reduce the dependence on toxic chemicals and pesticides.
(ii) Eg: Ladybird beetle and Dragonflies are
useful to get rid of aphids and mosquitoes, respectively.
MICROBES AS BIOFERTILIZERS:
(i) Biofertilizers are organisms that enrich the nutrient quality of the soil.
(ii) Biofertilizers replenish soil nutrients and reduce dependence on chemical fertilizers.
(iii) The main sources of biofertilisers are bacteria, fungi and cyanobacteria.
Q. 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 20 mg/L, 8 mg/L and 400 mg/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?
Ans: 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.
Q. 12. Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
Ans: Cyclosporine A-Trichoderma polysporum and Statin-Monascus purpureus.
Q. 13. Find out the role of microbes in the following and discuss it with your teacher.
(a) Single cell protein (SCP).
Ans: Single cell protein (SCP):
The cells from microorganism like bacteria, yeasts, filamentous fungi which are processed and used as food are called Single Cell Protein (SCP). Single Cell Protein (SCP) are rich in high quality protein and poor in fats. SCP production based on industrial wastes help to reduce environmental pollution.
(b) Soil.
Ans: Soil: Microbes play an important role in maintaining soil fertility. They act as biofertilisers. Biofertilisers replenish soil nutrients and reduce dependence on chemical fertilizers by nitrogen fixation. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.
Q. 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
Ans: 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
Q. 15. How do biofertilizers enrich the fertility of the soil?
Ans: Biofertilizers replenish soil nutrients and reduce dependence on chemical fertilizers by nitrogen fixation. The main sources of biofertilizers are bacteria, fungi and cyanobacteria.
