CBSE Class 12 Biology Microbes In Human Welfare Worksheet Set A

MULTIPLE CHOICE QUESTIONS

Very Short Answer Type Questions

Question. Why are blue-green algae not popular as biofertilisers?
Answer : Blue-green algae add organic matter to the soil and increase its fertility still these are not popular as biofertilisers. This is due to several constraints that limit the application or implementation of the biofertiliser technology. The constraints may be environmental, technological, infrastructural, financial, unawareness, quality, marketing etc.

Question. Which species of Penicillium produces Roquefort cheese?
Answer : Roquefort cheese is formed by ripening of cheese with the fungi Penicillium roqueforti for a particular flavour.

Question. Name the states involved in Ganga Action Plan.
Answer : Ganga runs from Gangotri in the Himalayas to Ganga Sagar in the Bay of Bengal. The Ganga Action Plan (GAP) was a program launched in April 1986 in order to reduce the pollution load on the River Ganga. The states involved in Ganga Action Plan are— Uttaranchal, UP, Bihar, West Bengal and Jharkhand.

Question. Name any two industrially important enzymes.
Answer : (i) Lipases are used in detergent formulations and are helpful in removing oily stains from the laundry. (ii) Pectinases and proteases that are used as clarifying agents in making commercial fruit and vegetable juices.

Question. Name an immune immunosupressive agent?
Answer : Cyclosporin-A, produced by the fungus Trichoderma polysporum is used as an immunosupressive agent in organ transplant patients.

Question. Given an example of a rod-shaped virus.
Answer : Tobacco mosaic virus is a rod-shaped virus. This is the first plant virus to be discovered.

Question. What would happen if our intestine harbours microbial flora exactly similar to that found in the rumen of cattle?
Answer : If our intestine harbors microbial flora exactly similar to that found in the rumen of cattle, we would be able to digest the cellulose present in our foods because the microbes present in the rumen (a part of stomach) of cattle, collectively called methanogens, are capable of digesting cellulose as they have cellulase enzyme.

Question. Give any two microbes that are useful in biotechnology.
Answer : Two microbes that are useful in biotechnology are (i) Bacillus thuringiensis a gene isolated from this bacterium is introduced in cotton plants to make them able to kill butterfly caterpillars. (ii) Escherichia coli is a bacterium that is used in many biotechnology procedures. Their plasmid is used as vector to introduce foreign DNA segment in desired organisms.

Question. What is the source organism for Eco RI, restriction endonuclease?
Answer : Escherichia coli strain RY 13 is the source organism for Eco RI.

Question. Name any genetically modified crop.
Answer : Bt cotton is a genetically modified plant that has been modified to resist attack by insect pests e.g., cotton ball worm). These are developed by introducing a gene from Bacillus thuringiensis which produces toxin is plants which is lethat to insects.

Question. What is the group of bacteria found in both the rumen of cattle and sludge of sewage treatment?
Answer : Methanogens (Methanobacterium), anaerobically break down cellulosic material to produce CO2 and H2, and are found in (i) Anaerobic sludge in sewage treatment plants. (ii) Rumen (a part of stomach) of cattles, thus providing nutrition to cattles.

Question. Name a microbe used for the production of swiss cheese.
Answer : Cheese is formed by partial degradation of milk by different microorganisms. Swiss cheese is formed by the bacterium Propionibacterium sharmanii. Its characteristic feature is formation of large holes due to production of large amount of CO2

Short Answer Type Questions

Question. What roles do enzymes play in detergents that we use for washing clothes? Are these enzymes produced from some unique microorganisms?
Answer : Enzymes like lipases are used in detergent which formulations, cause breakdown of oils and thus help in removing oily and greasy stains from the clothes in laundry. These are obtained from Candida lipolytica and Geotrichum candidum.

Question. What is the chemical nature of biogas. Name an organism which is involved in biogas production?
Answer : The chemical nature of biogas is CH4, CO2, H2 and a trace amount of H S 2 Methanobacteria, a type of methanogen is employed for biogas production.

Question. How do microbes reduces the environmental degradation causes by chemicals?
Answer : Chemicals from fertilisers and pesticides are highly toxic to human beings and animals alike, and have been polluting our environment. To reduce the environmental degradation caused by chemicals, microbes can be used both as fertilisers and pesticides and can be called biofertilisers and biopesticides, respectively. Microbes are used as biofertilisers to enrich the soil nutrients, e.g., 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, fungal species, is effective bicontrol agent of several plant pathogens. Baculovirus used as biological control agents in genus Nucleopolyhedrovirus are excellent for species-specific, narrow spectrum insecticidal applications.

Question. Why are flocs important in biological treatment of waste water?
Answer : Flocs are masses of bacteria associated with fungal filaments that form mesh like structures. These are important in biological treatment of waste water, as they help in digestion of organic matter, remove pathogens and release nutrients in the sewage effluent.

Question. How has the bacterium Bacillus thuringiensis helped us in controlling caterpillars of insect pests?
Answer : Bacillus thuringiensis produces an are endotoxin which, when ingested and released in the gut of the larvae of insect pest disrupts the insect gut lining thereby killing them.

Question. What is a broad spectrum antibiotic? Name one such antibiotic.
Answer : A broad spectrum antibiotic is one which can inhibit the growth of both Gram positive and Gram negative bacteria e.g.,Tetracyclines, phenicols, fluoroquinolones, third-generation and fourth-generation antibiotivcs is cephalosporins.

Question. What are viruses parasitising bacteria called? Draw a well labelled diagram of the same.
Answer : Viruses parasitising bacteria are called bacteriophages. These viruses do not actually eat bacteria. They infect and replicate within the bacteria.

Long Answer Type Questions

Question. Draw a diagrammatic sketch of biogas plant and label its various components given below gas holder, sludge chamber, digester, dung + water chamber.
Answer : The raw material for biogas production is excreta (dung) of cattle. The biogas plant has a concrete tank (10-15 feet deep) in which bio-wastes and slurry of dung is collected. (Image 195) The tank has a floating cover which rises on production of gas in the tank. Methanobacterium in the dung act on the bio-wastes to produce biogas. The gas produced is supplied to nearby houses by an outlet. Through another outlet, the spent slurry is removed to be used as fertiliser. Biogas is used as fuel for cooking and lighting.

Question. Describe the main ideas behind the biological control of pests and diseases.
Answer : It’s a natural and eco-friendly concept. If employs the use of organisms to control the population of pathogens and pests in an ecosystem. Classical examples are Trichoderma which is antagonist, i.e., against many soil borne plant pathogens. Similarly, Penicillium inhibits the growth of Staphylococcus and therefore has been successfully used in the production of penicillin antibiotic to control many human bacterial pathogens. Bacillus thuringiensis acts as biopesticide to control insect. Baculovirus used as biological control agents in genus Nucleo-polyhedrovirus are excellent for species-specific-narrow spectrum insecticidal application. The overall biological control of pest is considered much more beneficial in an ecological sensitive area.

Question. Why is aerobic degradation more important than anaerobic degradation for the treatment of large volumes of wastewaters rich in organic matter. Discuss.
Answer : Aerobic degradation is more important as naturally occurring aerobic and facultative microbes (bacteria, fungi, Protozoa and others) in the waste water can rapidly oxidise soluble organic and nitrogenous compounds. Mechanical addition of oxygen makes the process faster and most of the pathogenic content of the effluent is removed.

Question. (a) Discuss about the major programs that the Ministry of Environment and Forests, Government of India, has initiated for saving major Indian rivers from pollution. (b) Ganga has recently been declared the national river. Discuss, the implication with respect to pollution of this river.
Answer : (a) Prior to year 1985, only few cities and towns had sewage treatment plants. Most of the sewage water of urban as well as rural areas was discharged directly into rivers resulting in their pollution. Importance of microbial treatment of sewage was then realised and more sewage treatment plants were established. Still, they are not sufficient due to increasing urbanisation and production of much larger quantities of sewage as compared to earlier days. Realising the importance of microbes in pollution control, the Ministry of Environment and forests has initiated development of sewage treatment plants under the National River Conservation Authority. e.g., Ganga Action Plan (GAP) and Yamuna Action Plan (YAP) to save these major rivers of our country from pollution.
(b) The Ganga Action Plan (GAP) was a program launched in April, 1986 in order to reduce the pollution load on the river. A steering committee of the National River Conservation Authority reviewed the progress of the GAP and necessary correction. Scientists and religious leaders have speculated on the causes of the river’s apparent self-purification effect, in which water-borne diseases such as dysentery and cholera are eliminated by killing thin caused organisms. Thus preventing large-scale epidemics. Some studies have reported that the river retains more oxygen than is typical for comparable rivers; this could be a factor leading to fewer disease agents being present in the water. National River Ganga Basin Authority (NRGBA) was established by the Central Government of India, on 20th February 2009 Under Section 3(3) of The Environment Protection Act, 1986. It also declared Ganges as the National, river of India.

Question. (a) What would happen if a large volume of untreated sewage is discharged into a river? (b) In what way anaerobic sludge diagestion is important in sewage treatments?
Answer : (a) If untreated sewage is discharged directly into rivers it will lead to serious pollution of the waters with organic matter and pathogenic bacteria, Protozoa and many other diseaser. This water, if used, will cause outbreaks of water borne diseases. (b) In anaerobic sludge digestion, anaerobic bacteria, digest the aerobic bacteria and the fungi in the sludge and the remaining organic matter. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases (biogas) can be used as source of energy as it is inflammable.

Question. Which type of food would have lactic acid bacteria? Discuss their useful application.
Answer : The most common food item that are curd, and yoghurt contain Lactic Acid Bacteria (LAB) of Lactobacillus species. Curd is formed by adding a small amount of curd to milk, which acts as a starter. Microbes present in starter multiply at suitable temperature and convert milk into curd. Acids released by LAB during the growth coagulate and partially digest milk protein, casein thus increases the digestibility of milk protein. Application of LAB (i) Improves nutritional quality of milk by increasing vitamin-B12. (ii) Checks disease-causing microbes in stomach.