Microbes in Human Welfare Class 12 Important Questions and Answers Biology Chapter 8

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Microbes In Human Welfare Question And Answers

Question 1. Bacteria cannot be seen with the naked eye, 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?
Answer:

The most common household product that we would like to carry is curd which is common in Lactic acid bacteria (Lactobacillus sp.).

Question 2. Give examples to prove that microbes release gases during metabolism.
Answer:

The puffed-up appearance of dough is used for making dosa, idli, and bread due to gas production.

  • Methanogens (bacteria) in the biogas plant produce methane and carbon dioxide.
  • Also large holes in the ‘Swiss cheese’ are due to the production of a large amount of CO2 during its production.

Question 3. In which food would you find lactic acid bacteria? Mention some of their useful applications.
Answer:

The lactic acid bacteria (LAB) are found in curd.

  • LAB converts the lactose sugar of milk into lactic acid.
  • Lactic acid coagulates the milk protein called casein.
  • It also increases the nutritional quality of curd as the curd contains vitamin B12 along with other vitamins. They also check the growth of other harmful microbes.

Question 4. Name some traditional Indian foods made of wheat, rice, and Bengal gram (or their products) that involve the use of microbes.
Answer:

‘Dosa’ and ‘idli’ (from rice), bread (from wheat), and ‘dhokla’ (from Bengal gram) are traditional Indian foods that involve the use of microbes.

Read and Learn More Class 12 Biology Chapter Wise

CBSE Class 12 BioIogy Chapter 8 Microbes In Human Welfare Questions And Answers

Question 5. In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Answer:

The major role of microbes in controlling diseases is ‘antibiotic production, Antibiotics have been used against pathogenic bacteria, for example, penicillin from streptomycin from Streptomyces griseus, etc.

Question 6. Name any two species of fungus, which are used in the production of antibiotics.
Answer:

  1. Penicillium notatum (for penicillin production).
  2. Aspergilus fumigatus(for fumagillin production).

Question 7. What is sewage? In which way can sewage be harmful to us?
Answer:

Sewage is the municipal waste water containing large quantities of human excreta and other organic wastes.

  1. Sewage could be harmful to us as it contains many pathogenic microbes and produces a foul smell. It is the cause of many water-borne diseases.
  2. It is also the cause of the eutrophication of water bodies thereby killing many aquatic organisms.

Question 8. What is the key difference between primary and secondary sewage treatment?
Answer:

The key difference between primary and secondary treatment of sewage is that primary treatment
is the physical process of removing grit and floating debris while secondary treatment is a biological process that involves digestion of organic matter by microbes.

Question 9. Do you think microbes can also be used as a source of energy? If yes, how?
Answer:

Yes, microbes can be used to produce energy indirectly.

Methanogens (bacteria) like Methanobacterium are involved in the production of biogas which is used as a source of energy.

Question 10. Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished.
Answer:

Microbes can be used both as fertilizers and pesticides called biofertilizers and biopesticides respectively.

  • Microbes are used as biofertilizers to enrich the soil nutrients, eg Rhizobium, Azotobacter, Azospirillum, etc. which can fix atmospheric nitrogen in the soil.
  • Bacillus thuringiensis bacteria act as biopesticides to control the growth of insect pests.
  • Trichoderma, a fungal species, is an effective biocontrol agent for several plant pathogens.
  • Baculoviruses used as control agents in the genus are excellent for species-specific, narrow-spectrum insecticidal applications.

Question 11. Three water samples namely river water, untreated sewage water, and secondary effluent discharged from a sewage treatment plant were subjected to the BOD test The samples were labeled 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/1., 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?
Answer:

Sample C is the most polluted (Highest BOD).

Sample A-River water

Sample B- Secondary effluent (Least BOD)

Sample C- Untreated sewage (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:

  1. Cyclosporin A is obtained from Trichoderma polysporum.
  2. Statins are obtained from the yeast Monascus purpureus.

Question 13. Find out the role of microbes in the following and discuss it with your teacher.

  1. Single-cell protein (SCP)
  2. Soil

Answer:

1. Single-cell protein (SCP): It is a protein-rich microbial biomass that can be used as food. Microbes are being grown on an industrial scale as a source of good protein. For example, Blue-green algae like Spirulina

  • Methylophilus methylotrophic bacteria
  • Mushrooms

2. Soil: Soil is the habitat of numerous microbes. Microbes in the soil increase the fertility of soil by decomposing organic matter. Some microbes convert nitrates into free nitrogen that escapes into the atmosphere for replenishment.

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.
Answer:

  1. Penicillin
  2. Biogas
  3. Curd
  4. Citric acid.
    1. Penicillin:- It is an antibiotic used in curing numerous bacterial diseases.
    2. Biogas:- It is a source of energy in rural areas, produced by anaerobic degradation of organic matter
    3. Curd:- It is a vitamin-rich milk preparation that is easily digested.
    4. Citric acid:- It is an organic acid used as a preservative in juices, jams jellies, etc.

Question 15. How do biofertilizers enrich the fertility of the soil?
Answer:

Biofertilizers are microorganisms that bring about nutrient enrichment of soil by enhancing the availability of nutrients to crops. They are of the following types:

  1. Nitrogen-fixing bacteria and cyanobacteria- They form symbiotic associations with plants. They get food and shelter from plants and on the other hand, plants get nitrogen fixed by these bacteria. For example Rhizobium and A nabena.
  2. Mycorrhiza: It is an association between a fungus and the roots of higher plants. It takes pan in the solubilization and absorption of nutrients from organic matter. Many members of the genus Glomus form mycorrhiza.
  3. Manures: They are semi-decayed organic remains of various types-manure, green manure compost, and vermicompost.

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