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|Chapter 10:||Microbes in Human Welfare|
NCERT Solutions for class 12 Biology Chapter 10
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Solutions for 12 Biology Chapter 10
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Important Terms 12 Biology Chapter 10
- Baculovirus: Pathogens that attack insects and other arthropods. They are used to kill harmful pests and arthropods e.g., Nucleopolyhedro virus.
- Flocs: During secondary treatment of effluent, excessive growth of aerobic bacteria and fungi form a mass of mesh like structure called flocs.
- Bio-fertilisers: Microorganisms which produce fertilisers and enrich the soil e.g., bacteria, cyanobacteria and fungi.
- Bioactive Molecules: Molecules produced for commercial use from microbes and used for various purposes e. g., Trichoderma polysporum (fungus) is used to obtain immunosuppressive agent cyclosporine-A.
- Biochemical Oxygen Demand (BOD): Total amount of oxygen consumed by bacteria for oxidation of organic matter present in one litre of water.
- Immunosuppressive Agent: Chemicals which suppress the immunity against organ transplant.
- Organic Farming: Technique of farming, in which bio-fertilisers are used to enrich the soil, without using chemical fertilizers and pesticides to reduce their harmful effect on human health.
- Biological Control: Reduction of pest population by natural enemies minimising the use of harmful chemical pesticide. E.g. lady bird beetle can eradicate aphids.
- Thermal vents: The sites deep inside the geysers/hot springs and oceans where the average temp is as high as 100°C.
- Methanogens: Bacteria producing large quantity of methane during decomposition of organic matter.
- GAP: Ganga Action Plan
- KVIC: Khadi and Village Industries Commission
- TMV: Tobacco Mosaic Virus
- YAP: Yamuna Action Plan
- IPM: Integrated Pest Management.
Microbes as bio-fertilizers.
- Rhizobium: Have symbiotic association with roots of leguminous plants, help in atmospheric nitrogen fixation.
- Azospirillum and Azotobacter: Free living in soil and help in nitrogen 2-fixation enrich nitrogen 2-content of soil.
- Mycorriza: Symbiotic association of fungi with roots of higher plants. Fungi help in absorption of phosphorous from soil. It belong to genus Glomus Provide resistance to root borne pathogens, tolerance to salinity and drought.
- Cyanobacteria: Found in aquatic or terrestrial environment, help in nitrogen fixation, add organic matter to the soil, increase fertility of soil, e.g., Nostoc, Anabaene, Oscillatoria. In paddy fields, these acts as bio-fertilisers.
Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Product: Bread, cake, etc.
Product: Idli, dosa
Product: Dhokla, Khandvi
Give examples to prove that microbes release gases during metabolism.
Bacteria and fungi carry out the process of fermentation and during this process, they release carbon dioxide. Fermentation is the process of converting a complex organic substance into a simpler substance with the action of bacteria or yeast. Fermentation of sugar produces alcohol with the release of carbon dioxide and very little energy.
The dough used for making idli and dosa gives a puffed appearance. This is because of the action of bacteria which releases carbon dioxide. This CO2 released from the dough gets trapped in the dough, thereby giving it a puffed appearance.
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?
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Lactic acid bacteria are also found in our stomach where it keeps a check on the disease-causing micro-organisms.
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
What is sewage? In which way can sewage be harmful to us?
Do you think microbes can also be used as source of energy? If yes, how?
The generation of biogas is an anaerobic process in a biogas plant, which consists of a concrete tank (10−15 feet deep) with sufficient outlets and inlets. The dung is mixed with water to form the slurry and thrown into the tank. The digester of the tank is filled with numerous anaerobic methane-producing bacteria, which produce biogas from the slurry. Biogas can be removed through the pipe which is then used as a source of energy, while the spent slurry is removed from the outlet and is used as a fertilizer.
How do biofertilisers enrich the fertility of the soil?
Rhizobium is a symbiotic bacteria found in the root nodules of leguminous plants.
Azospirillium and Azotobocter are free living nitrogen-fixing bacteria, whereas Anabena, Nostoc, and Oscillitoria are examples of nitrogen-fixing cyanobacteria. Biofertilizers are cost effective and eco-friendly.