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.

III. Short Questions (3 marks each) : 

Q.1. What do you mean by organic farming? Why it is suggested to switch over to organic farming from other types? 

Ans : Organic forming is an agricultural system that seeks to provide the consumer, with fresh, tasty and authentic food while respecting natural life-cycle systems. In this type of farming no unnatural substances like chemical fertilizer, chemical pesticides, chemical herbicides are used.

To achieve this, organic farming relies on a number of objectives and principles, as well as common practices designed to minimise the human impact on the environment, while ensuring the agricultural system operates as naturally as possible. 

Typical organic farming practices include : 

(a) Wide crop rotation as a prerequisite for an efficient use of onsite resources.

(b) Very strict limits on chemical synthetic pesticide and synthetic fertiliser use, livestock antibiotics, food additives and processing aids and other inputs.

(c) Absolute prohibition of the use of genetically modified organisms. 

(d) Taking advantage of on-site resources, such as livestock manure for fertiliser or feed produced on the farm. 

(e) Choosing plant and animal species that are resistant to disease and adapted to local conditions. 

(d) Raising livestock in free-range, open-air systems and providing them with organic feed. 

(e) Using animal husbandry practices appropriate to different livestock species.

Organic farming sustainable use of resources do not pollute the soil and environment and ensure supply of healthy food and therefore it is suggested that farmers should switch over to organic farming. 

Q.2. What are biogas? Give its composition. Why is biogas preferred to other conventional energy fuels. 

Ans : The gas produced by methane bacteria by decomposing organic waste is called biogas. 

The gas mainly composed of methane. Other gases loke carbon dioxide, carbon monoxide, sulphur are also present in minute quantities. 

Biogas is preferred to other fuel as because it is renewable, less costly and easy to produce. The technology is simple and finally the end product of decomposition can be used as manure. We have huge potentiality of producing biogas as we waste a huge sewage which can be used profitably for biogas production. Moreover it is suitable for farmers and villagers because the raw materials needed for the production of biogas is plenty. Conventional energy is costly and non- quantity of organic waste and renewable in the sense that it uses exhaustible natural resources.

Q.3. Lactic acid bacteria inhibit in what kind of food. Mention some of its useful applications. 

Ans : Lactic acid bacteria prefer milk and milk like substances and in. addition it is also found in malt molasses, lactose, maltose etc. 

Lactic acid bacteria are used in 

(a) obtaining lactic acid.

(b) polymer production.

(c) leather industries. and

(d) plastic industries.

Q.4. How are biofertilizers different from fertilizers such as NPK sold in the market. Discuss the role of Rhizobium as a biofertilizer. 

Ans : Biofertilizers are live or latent microbes which on inoculation increase their number in soil or in roots and carry out nutrition enhancement either by fixing atmospheric nitrogen or by dissolving phosphate or by secreting micronutrients etc. Their number gradually increase in soil and continue to help maintain fertility of the soil. NPK on the other hand is a mixture of chemical fertilizer. It serves only limited purpose of supplying a particular type of nutrition and for a specific duration and purpose. It is not multipurpose in nature. It discourage growth and development of indigenous microflora. Excessive use of it destroy the natural biological propertiès of soil. 

Rhizobium is a symbiotic nitrogen fixing bacteria live in association with the roots of legumes. Cultivation of legumes therefore increase nitrogen content of the soil. It is practice to cultivate legumes as inter crop between major crops. It is therefore a kind of biofertilizer and can be inoculated artificially while cropping legumes. 

Q.5. What are flocs? State their role in effluent treatment and their fate in sewage treatment tank? 

Ans : During secondary treatment sewage a huge quantity of microbes grow and consume oxygen. To keep supply required oxygen the water containing sewage is vigorously stirred by rotation. This causes accumulation of waste in the surface in the form of some circles. These are called flocs. 

These flocs contain huge quantities of aerobic microorganisms and are decomposed quickly. Some quantity of it is removed to primary tank for further treatment of fresh sewage. 

Q.6. What is the full form of VAM? What is its role? Give at least two examples each endo and ecto mycorrhiza. 

Ans : Vesicular Arbuscular Mycorrhiza. VAM are symbiotic association of some fungi with the roots of higher plants. They enhance phosphate nutrition of the plants by supplying dissolved phosphate to the plants. So plants in phosphate deficit soil also can grow. In addition to phosphate nutrition the VAM can ameliorate conditions favourable for the growth of plant even under severe physical and chemical stress. 

Example of – Endomycorrhiza : Glomus, Gigaspora, 

Ectomycorrhiza: Boletus, Amanita. 

Q.7. Explain the role of baculoviruses as a biological control agents. Mention their importance in organic farming.

Ans : Baculoviruses are the pathogenic viruses which infect and kill many insect pests and other anthropod pests. Most important baculoviruses involved in biological control is nucleopolyhedro virus. These are species specific and have narron spectrum insecticidal effect so don’t have any negative effect on other organisms, even non-target insects. 

These are used to control the pest of potato like potato beltle, aphids and corn borer etc. It is also used for the production of organic fertilizers and help in organic  farming. 

Q.8. Discuss the role of microbes in sewage treatment. 

Ans : Sewage or waste water contain excreta, industrial and agricultural waste, It contain water and 0.5.-1% organic or inorganic matters. The solid remains, suspended cellulose, lingo cellulose, proteins, fats etc. are found in colloidal form. The inorganic materials remain in dissolved state. Detergent, paints, toxic chemicals. Cellulose matter etc. are discharged by industries chemical fertilizer, pesticides, herbicides, animal excreta etc. are discharged due to agriculture operation. Sewage is a store house of pathogens. It is therefore necessary to treat the sewage before releasing. Removing harmful and polluting substances is difficult. However, microbial treatment can be done to clean it partially. The heterotrophic microbes are used which digest organic residue under aerated condition. 

The treatments are done in two stages : 

(i) Primary treatment : Primary treatment is the physical removal of 20-30% organic materials present in sewage. This is done by screening, precipitation of small particulate matters, filtration and sedimentation. The sludge that form due to such treatment is removed and the required portion is piped into aeration tank for secondary treatment. 

(ii) Secondary treatment : It is a biological treatment done in aeration tank. A large variety of microbes remain present in it. Constant agitation cause aeration which help quicker decomposition of organic substances. A large number of aerobic microbes grow in the process. Sometime, the filamentous microbes and bacteria together form a mesh like structure over the surface. With the gradual consumption of organic materials, the number of microorganisms present in affluent is reduced due to reduced availability of organic substances. This lower the biological oxygen demand (BOD) of the affluent. More the number of microbes more will be the demand for oxygen in the affluent. Till the BOD is significantly reduced the aeration of the tank continues. 

After significant reduction of BOD the affluent is removed to settling tank where all remaining sludge including the aerobic microbes, dead and living will settle down. This sludge is called activated sludge. The remaining sludge is removed to another tank called anaerobic sludge digester. Here the anaerobic bacteria will digest the aerobic microorganisms carried over by the sludge. Anaerobic bacteria while digesting the organic remains produce a mixture of gases such as methane, hydrogen sulphide, carbon dioxide etc. After the anaerobic treatment the affluent is released into natural water bodies. 

Till now no other method of treatment has been successful. This process is carried out all over the world.The treatment of sewage has assumed great importance now as more and more urban localities are coming up all over the globe and as a result more sewage is generated. In India the river Ganga and Yamuna are becoming more and more polluted due to the fact that more urban settlements have grown up on the banks of these rivers. Government has therefore framed two Action plans called Ganga Action Plan and Yamuna action plan to be supervised by the Ministry of Environment and Forests.

Q.9. What are antibiotics? Name any two micro organisms with their products used in the production of antibiotics. 

Ans : Antibiotics are substances, primarily produced by certain harmless micro organism which in law concentrations are antagonistic to the growth of other microorganisms such as pathogenic bacteria. Etymologically, antibiotics means against life’ 

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