RBSE Solutions for Class 12 Biology Chapter 10 Microbes in Human Welfare

Rajasthan Board RBSE Solutions for Class 12 Biology Chapter 10 Microbes in Human Welfare Textbook Exercise Questions and Answers.

RBSE Class 12 Biology Solutions Chapter 10 Microbes in Human Welfare

RBSE Class 12 Biology Microbes in Human Welfare Textbook 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 with the help of microscope, which sample would you carry and why?
Answer:
The most common household product that we would like carry is curd which contains lactic acid bacteria (LAB; i.e., Lactobacillus).

Question 2. 
Give example to prove that microbes release gases during metabolism.
Answer:
Methane is largely products of incomplete decomposition and is produced by a group of bacteria called methanogens, under anaerobic conditions. The major sources of methane include; freshwater wetlands, enteric fermentation in cattle, and flooded rice fields. Biomass, especially animal waste can also be converted into biogas digesters by using the process of anaerobic microbial decomposition.

Question 3. 
In which food would you find lactic acid bacteria? Mention some their useful applications. 
Answer:
Lactic acid bacteria (LAB) present in curd. These bacteria convert lactose sugar into lactic acid. They also improve the nutritional quality of curd by adding vitamin B12. LAB are also found in our stomach where they check disease causing microbes.

Question 4. 
Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Answer:
Idli, Dosa, Jalabi, Dhokla etc.

Question 5. 
In which way have microbes played a major role in controlling disease caused by harmful bacteria?
Answer:
The major role of microbes in controlling the disease is the antibiotic production. Antibiotics have been used against pathogenic bacteria e.g., penicilline from Penicillium notatum P. chrysogenum, streptomycin from Streptomyces griseus etc.

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

• Penicillin is produced from the fungal culture of Penicillium notatum and P. chrysogenum.
• Cephalosporin are a group antibiotics produced by a fungus known as Cephalosparium acremonium.

Question 7. 
What is sewage? In which way can sewage be harmful to us?
Answer:
Sewage is the municipal waste water containing large amount of human and animal excreta and other organic wastes. Sewage could be harmful to us as it contains many pathogenic microbes and produces foul small. It is the cause of many water borne diseases. It is also the cause of 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 sewage treatment is that primary treatment is the physical process of removing grit and large pieces of organic matter while secondary treatment is a biological process that involves digestion of organic matter by microbes in effluent.

Question 9. 
Do you think microbes can also be used as source of energy? If yes, how?
Answer:
Yes, microbes can be used to produce energy indirectly, Methanogens (bacteria) like Methanobacterium is involved in the production of biogas which is used as 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. Biofertilizers are used to enrich the soil nutrients. These microbes are Rhizohium, Azotobacter, Azospirillum etc., which can fix atmospheric nitrogen in the soil. Some microbes like Bacillus thuringiensis bacteria act as biopesticide to control the growth of insect pests, Trichoderma, a fungal species, is effective biocontrol agent of several plant pathogens. Baculoviruses used as biological control agents in genus Nucleopolyhedrovirus 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 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?
Answer:
Sample C is most polluted (Highest BOD).
Sample A, having BOD 20 mg / L, is secondary effluent discharged from a sewage treatment plant.
Sample B, having BOD 8 mg / L, is river water.
Sample C, having BOD 400 mg / L, is untreated sewage water.

Question 12. 
Find out the name of the microbes from which cyclosporin A (a immunosuppressive drug) and statins (blood cholesterol lowering agents) are obtained.
Answer:

• Cyclosporin A is obtained from Trichoderma polysporum.
• 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:
(a) Single Cell Protein (SCP).
(b) Soil.
Answer:
(a) Single Cell Protein (SCP): It is a protein - rich microbial biomass which can be used as food. SCP contains essential amino acids and low fat. Bacteria, filamentous fungi, algae, yeast, etc., are used as single cell proteins. Spirulina (An unicellular algae) is taken as a tablet having 60% proteins, all minerals, vitamins, etc.

(b) Soil: Soil is the habitat of numerous microbes. Microbes increase the fertility of soil by decomposing organic matter. Some microbes convert nitrates into free nitrogen that escapes into 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.
Biogas, Citric acid, Penicillin and Curd.
Answer:
Penicillin, Biogas, Curd and Citric acid.

Question 15. 
How do biofertilizers enrich the fertility of the soil?
Answer:
Biofertilizers are microbes which bring about nutrient enrichment of soil by enhancing the availability of nutrients to crops. They are of following types:

• Nitrogen Fixing bacteria and Cyano bacteria: They form symbiotic association with plants. They get food and space from plants and on the other hand, they provide fixed nitrogen to plants. For example, Rhizobium, Frankia etc.
• Mycorrhiza: It is an association between a fungus and roots of higher plants. It takes part in the solubilisation and absorption of nutrients from organic matter. Many members of the genus Glomus form mycorrhiza.
• Manures: They are semi - decayed organic remains of various types: manure, green manure, compost and vermicompost.