Class 12 Biology Chapter 10 Microbes in Human Welfare

Class 12 Biology Chapter 10 Microbes in Human Welfare The answer to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 10 Microbes in Human Welfare Question Answer.

Class 12 Biology Chapter 10 Microbes in Human Welfare

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Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board Class 12 Biology Chapter 10 Microbes in Human Welfare Solutions for All Subjects, You can practice these here.

Microbes in Human Welfare

Chapter – 10


Very Short Answer Type Questions

Q.1. What is biofertilizer? What are its sources? 

Ans: Biofertilizer are live or latents cell of specific microbes which are inoculated in seeds or seedlings with the purpose of their multiplying in soil and in turn increasing the nutrient availability to crops. Thes-e are collected from son, multiplied and preserved for use as inoculant. 

Q.2. What do you meant by biopesticide? Name a biopesticide obtained from Neem. 

Ans : Any organic substance like plants, microorganisms, insects etc which are used to destroy pests is called biopesticide. 

Azadirachtin in a chemical substance extracted from neem to be used as biopesticide. 

Q.3. What are bioreactors? 

Ans : These are growth chambers for large scale multiplication of microorganism for obtaining products like proteins, enzymes, antibiotics etc. Such growth chamber is provided with nutrition, suitable temperature, moisture, pH, etc. so that the desired microbes can grow continuously. 

Q.4. Which one is the first organic acid produced by microbial fermentation? 

Ans : Lactic acid. 

Q.5. Expand the term TPA. 

Ans : Tissue Plaşminogen Activator. 

Q.6. Name the blue green algae which is used as human food and its importance. 

Ans : Spirulina which is a blue green algae. It is very rich in protein. 

Q.7. Which one is the world’s most problematic aquatic weed. At what condition it grows abundantly? 

Ans : Water hyacinth. It grows profusely when eutrophication is caused by excessive presence of nitrogen and phosphate in water. 

Q.8. Name the group of organisms and the substrates they act on to produce biogas? 

Ans : Methanomonas bacteria. They act on deng, organic waste etc. to produce biogas. 

Q.9. Name the organism that fixes Nitrogen in symbiotic association with a water fern. 

Ans : Anabaena azollae. 

Q.10. What is mycorrhiza? 

Ans : A kind of fungi that live in symbiotic association with the roots of higher plants. They help the plants to overcome physical and chemical stress and in addition supply phosphate to the plants. 

Q.11. Name the curd forming bacteria. Mention at what temperature it can convert the milk to curd.

Ans : Lactobacillus bulgaricus. It forms curd best at 25°-30° C. 

Q.12. What is SCP? 

Ans : It means singlé cell protein. It is obtained from microbial cells, particularly yeast. 

Q.13. Why are pectinases and proteases added to fruit juices? 

Ans : These are used to clear the fruit juice by dissolving debris of fruit. 

Q.14. Define organic farming. 

Ans : Farming in which no chemical fertilizer, chemical pesticide, herbicide are used and only organic manure, biofertilizer and biopesticides are used is called organic farming. Rotation of crop and other sustainable measures are followed.

Q.15. What is pesticides? 

Ans : The Chemicals which kill the pest are called pesticides. 

Q.16. Name the first organic acid produced by microbial fermentation. 

Ans : Lactic acid. 

Q.17. What is the scientific name of Baker’s yeast? 

Ans : Saccharomyces cerevisae.

Q.18. How do the differently written ‘Cry’ and ‘cry’ represent respectively? 

Ans : To represent different endotoxins. 

Q.19. Who coined the term antibiotic? 

Ans : S.A. Waksman.

(B). Fill up the blanks : 

Q.1. Yeast is used in preparation of ____

Ans : Wine. 

Q.2. Biogas mainly contains _____and is used for cooking.

Ans : Methane. 

Q.3.  Vinegar is prepared from alcohol with the help of organism. 

Ans : Acetobacter. 

Q.4. The nutrient material for Wine and Brandy is_____ juice. 

Ans : Fruit.

Q.5. Chemical fertilizers and ____ are the sources of wide spread pollution. 

Ans : Pesticide.

Q.6. Single Cell Protein (SCP) provides a valuable____ rich supplement in human dict. 

Ans : Protein.

Q.7. The sewage water is treated till the BOD is found to be _____

Ans : Low. 

Q.8. ___ and ____ are the two biotechnologically manufactured vitamins.

Ans : Vitamin A& D.

Q.9. ____ is an antibiotic which is active against fungus.

Ans : Trichostatin. 

Q.10. Trichoderma species are potentially useful as_____

Ans : Biopesticide.

Q.11. The biopesticides Azadirachtin obtained from____ plant. 

Ans : Neem. 

Q.12. _____ a blue green algae used as human food. 

Ans : Spirulina.

Q.13. ____ grow in milk and convert it to curd. 

Ans : Lactobacillus acidophilus.

Q.14. Enzyme zymase convert the sugar into _____ during fermentation. 

Ans : Ethanol and Co₂.

(C). True and False : 

Q.1. Aquatic fern Marsilea is an excellent biofertilizer. 

Ans : False. 

Q.2. Extensive use of chemical fertilizers may lead to eutrophi- cation of near by water bodies. 

Ans : True.

Q.3. People recovering from long illness are often advised to take spirulina in their diet because it makes food easy to digest. 

Ans : False. 

Q.4. Dish washing powder contains an enzyme amylase. 

Ans : True.

Q.5. Primary treatment of sewage is a biological process. 

Ans : False. 

Q.6. The free living fungus Trichoderma can be used for killing insects.

Ans : True.

Q.7. The most important role of microorganisms for the well being of human is sewage treatment. 

Ans : False. 

Q.8. Biogas is produced by the activity of aerobic bacteria on animal waste.

Ans : False. 

Q.9. Saccharomyces cerevisiae is Bakers yeast. 

Ans : True. 

Q.10. DDT is the first commercially developed bioinsecticide. 

Ans : True. 

Q.11. Biofertilizers includes Blue green algae, Rhizobia and Mycorrhiza fungi. 

Ans : True.

Q.12. Mycorrhiza is the association of Algae and Fungi. 

Ans : False. 

Q.13. Methanobacterium is used in the production of biogas. 

Ans : True.

Q.14. Vit B,₁₂ content increases during the conversion of milk into curd by Lactobacillus bacteria. 

Ans : False.

II. Short Questions (2 Marks): 

Q.1. Explain how cyanobacteria serve as a main source of biofertilizers. Give the names of two cyanobacteria. 

Ans : Cyanobacteria like NOSTOC, Anabaena etc. have ability to fix atmospheric nitrogen into soil and water. Therefore these are extensively used as biofertilizer particularly in rice field. These are easy to grow and multiply and no financial expenditure is involved. They grow easily. 

Q.2. Identify the organisms. 

(a) A microbes responsible for the preparation of alcohol from molasses. 

Ans : Yeast. 

(b) A soil microbe that forms symbiotic association with the roots of bean plants. 

Ans : Rhizobium. 

Q.3. What kind of microbes are present in our intestine? What are their role? 

Ans : Lactobacillus bulgaricus, Lactobacillus acidophilus, bifidobacterium breve. 

These bacteria secrete vitamins and maintain balance of acid and alkali, keep intestinal environment free from pathogens. 

Q.4. Write notes on : 

(a) Baker’s yeast.

Ans : Saccharomyces cerevisiae popularly known as yeast is used to prepare bead and therefore it is called baker’s yeast. The fungi acts on the flour and sugar and ferment them to produce the dough. 

Some particular varieties of scenevisia is used to produce wine from fruit juice, malt, potato etc. and therefore such yeast are called brewer’s yeast. 

Q.5. What are antibiotics? How they are able to prevent the growth of other microbes in media. 

Ans : Antibiotics are substances of microbial origin which kill or inhibit the growth of other organisms. During cultural of particular microorganism in media some other unwanted microbes may grow. Therefore to prevent growth of unwanted bacteria particular antibiotic is used in the medium. 

Q.6. What is sewage? In which way can sewage be harmful?

Ans : Sewage is the discharge coming out from houses, factories, slaughter house, cow shed, open toilets and such other places and ultimately flow into nearby water bodies, lake or river.

Sewage contains harmful substances, pathogens, toxins etc. and therefore if it mixes up with drinking water it may cause serious harm. Bathing in such polluted water also harmful. 

Q.7. Discuss giving examples the statement ‘Legumes fertilize the soil but cereals do not’. 

Ans : Leguminous plants herbour nitrogen fixing symbiotic bacteria called Rhizobium and therefore cultivation of legumes fertilize the soil by adding nitrogen. Cereals do not possess any nitrogen fixing bacteria in their roots and therefore they cannot enrich the soil with nutrients. 

Q.8. What is mycorrhiza? How does it help as a biofertilizer? 

Ans : Mycorrhiza is a symbiotic association of some types of fungi with the roots of higher plants. They not only help in phosphate nutrition of the plants but also help in overcoming of resistance due to draught, cold and other environmental stress. Therefore suitable types of mycorrhiza are used as biofertilizer for crop cultivation and in silviculture. 

Q.9. Are microbes can be used as a source of energy? If yes how? 

Ans : Methane gas is inflammable and can be used as fuel for various purposes. Methane is obtained from decomposing organic matter, sewage and from reserve under the earth. Methanomonas bacteria are used for biogas production from decomposition of organic waste. Ethanol is another kind of fuel which can be obtained from fermentation of carbohydrate by yeast and some specific microbes. It is popularly called biofuel. 

Q.10. Discuss the biological significance of Azolla pinnata in agriculture. 

Ans : Azolla Pinnata is a free floating aquatic pteridophyte which contains a symbiotic cyanobacteria Anabaena azollae which has the capacity to fix atmospheric N, and excretes the nitrogenous compounds in to the cavity of ferm. In agricultural field specially in rice field it increases the nitrogen content. 

Q.11. What is the chemical nature of bio-gas? Name an organism involved in biogas production. 

Ans : Biogas is a mixture of methane carbon dioxide, hydrogen sulphide and ammonia.

The biogas is produced by a special category of bacteria called methanogens and common methanogens are methanobacterium and methanococcus. 

Q.12. Name the microbes used for the production of following-

(a) Citric acid.

(b) Acetic acid.

(c) Butyric acid 

(d) Lactic acid.

Ans :     

(a) Citric acidAcetobacter aceti 
(b) Acetic acid.Aspergillus niger
(c) Butyric acidClostridium butylicum
(d) Lactic acid.Lactobacillus delbrueckii

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