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Karnataka 2nd PUC Biology Question Bank Chapter 10 Microbes in Human Welfare
2nd PUC Biology Microbes in Human Welfare One Mark Questions and Answers
Give examples to prove that microbes release gases during metabolism.
The dough, which is used for making foods such as dosa and idli is fermented by bacteria (Leuconostoc and Streptococcus sp.). After fermentation the dough shows puffed appearance due to the production of CO2 gas .
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Lactic acid bacteria (LAB) are present in foods like curd and yoghurt.
LAB are used in the preparation of food items like curd, yoghurt, butter, butter-milk and sour cream.
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Microbes are the source of antibiotic drugs. Antibiotics have greatly improved our capacity to treat deadly diseases such as plague, whooping cough, diphtheria, tuberculosis, leprosy, cholera etc.
Name any two species of fungus, which are used in the production of the antibiotics.
Penicillium notatum and P. griseofulvum.
Name the chemical process involved in the preparation of ethanol.
What are antibiotics?
Antibiotics are antibacterial compounds that are secreted by some microorganisms which inhibit the growth and development of other microbes (pathogenic).
Name any two antibiotics.
Which bacterium is used in the preparation of acetic acid?
Name the fungus that produces statins.
Name an organism producing pectinase.
Name the enzyme used to clarify fruit juices.
How do biofertilizers enrich the fertility of the soil?
Biofertilizers are organisms (certain fungi, bacteria and cyanobacteria) that enrich the nutrient quality of the soil by fixing atmospheric nitrogen into the soil.
What is the role of Baker’s yeast in the production of bread?
Saccharomyces cerevisiae (Bakers yeast) causes the alcoholic fermentation of sugars of wheat flour and produce ethanol and CO2. CO2 causes doughing and when the dough is baked, CO2 evaporates.
Name the two symbiotic and free living N2 fixing microbes.
Symbiotic: Rhizobium and Frankia.
Free living: Azatobacter and Clostridium butylicum.
Lactic acid Bacteria.
Name the fungus which produces cyclosporin A
Why lipase are used in detergents?
Lipase in detergents are helpful in removing oily stains from the laundry.
2nd PUC Biology Microbes in Human Welfare Two Marks Questions and Answers
What is sewage? In which way can sewage be harmful to us?
The municipal waste water is called sewage. It contains a number of pathogenic microbes, which cause a number of water borne diseases like cholera, dysentry, diarrhoea, jaundice and typhoid etc.
What is the key difference between primary and secondary sewage treatment?
Primary treatment of sewage:
- It involves physical removal of solid particles from the sewage.
- The solids are removed through Alteration and sedimentation.
Secondary treatment of sewage :
- It involves aerobic oxidation of organic matter present in the primary effluent by microbes.
- The effluent is constantly agitated mechanically for aeration, to allow vigorous growth of microbes to decompose the organic matter.
Do you think microbes can also be used as sources of energy? If yes, how?
Yes. There are certain bacteria which grow anaerobically on cellulosic material and produce large amount of methane along with CO2 and H2. These bacteria are called methanogens.
The excreta of cattle (dung) commonly called ‘gobar’ is rich in these bacteria and undigested cellulose. Therefore, dung can be used to generate a gaseous fuel called biogas or gobar gas.
Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished.
The use of chemical fertilizers and pesticides can be reduced by the use of biofertilizers and biological pest control methods. Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi and cyanobacteria.
Many bacteria and cyanobacteria fix the atomospheric nitrogen into organic forms, thus enriching the nitrogen content of the soil. In paddy fields, cyanobacteria serve as an important biofertilizer. Similarly, some microbes (fungi, bacteria and viruses) can be used to control a number of crop pests.
Find out the name of the microbes from which CyclosporinA (animmuno-suppressive drug) and Statins (blood chloesterollowering agents) are obtained.
Cyclosporin in A is obtained from – Trichodermapolysporum (a fungus) statins are obtained from Monascus purpureus (a yeast).
What are methanogens? Mention its compsoition.
Methanogens are special types of bacteria which grow anaerobically on cellulose material. They produce large quantities of methane with CO2 and H2 during the decomposition of organic matter, e.g. methanobacterium.
When was Ganga Action plan started? What is the aim of Ganga Action Plan?
- Ganga action plan was started in 1985.
- Its aim as to clean the Ganga river and to install Sewage treatment plants at various points along the banks of the river, to treat the sewage before its discharge into the river.
What is dairy technology? Mention any two dairy products.
It is the scientific management of milk producing animals for milk and its products for human consumption.
a) Mention the major sources of biofertilizers,
b) What is biocontrol ? Give any two examples.
(a) Biofertilizers are the organisms that enrich the nutrient quality of the soil. The main source of biofertilizers are bacteria, fungi and cyanobacteria. Bacteria and cyanobacteria have the property of nitrogen fixation, while mycorrhizal fungi help in the mineral uptake by the plant.
Rhizobium forms a symbiotic association with the roots of leguminous plants. They develop the ability to fix nitrogen when they are present inside that root nodules.
Note : Some non-legume plants also show symbiotic association with some other nitrogen fixing bacteria.
Example: Frankia is associated symbiotically with the root nodules of several non-legume plants like Casuarina, Alnus.
- Biocontrol refers to the use of biological methods for controlling plant diseases and pests. These methods rely on natural predation rather than on the introduced chemicals.
- An organic gardener works to create a system where the insects (that are pests) are not eradicated, but are kept at manageable levels by a complex system of checks and balances
within the ecosystem.
- The beneficial predatory and parasitic insects which depend on these insect pests are able to survive; for example beetle is useful to get rid aphids and dragonflies control mosquitoes.
- Bacillus thuringiensis is a bacterium whose spores are toxic to certain insect larvae and kill them, but is not harmful to other insects.
- The toxin-producing genes of this bacterium are transferred (genetic engineering) into crop plants, which become resistant to insect pests; Bt cotton is an example.
- Another biological control being developed for treatment/control of plant diseases in the fungus Trichoderma, which is free-living in the soil and root ecosystems and is effective against several plant pathogens.
2nd PUC Biology Microbes in Human Welfare Three Marks Questions and Answers
Write the scientific name of microbes that produces Streptokinase, Statin and Citric acid.
(a) Streptokinase – Streptococcus
(b) Statin – Monascus pupureus
(c) Citric acid – Aspergillus niger.
a) What is biochemical oxygen demand (BOD)?
BOD is the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria.
b) Differentiate between primary sludge and activated sludge.
|Primary sludge||Activated sludge|
|The sediment obtained due to primary treatment of sewage by alum or iron sulphate.||The sediment obtained due to action of bacterial floss during secondary treatment.|
2nd PUC Biology Microbes in Human Welfare Five Marks Questions and Answers
What are biofertilisers? Write the main sources of biofertilisers and explain their functions.
Biofertilizers are the organisms that enrich the nutrient quality of the soil. The main source of biofertilizers are bacteria, fungi and cyanobacteria. Bacteria and cyanobacteria have the property of nitrogen fixation, while mycorrhizal fungi help in the mineral uptake by the plant.
Rhizobium forms symbiotic association with the roots of leguminous plants. They develop the ability to fix nitrogen when they are present inside that root nodules.
Note: Some non-legume plants also show symbiotic association with some other nitrogen fixing bacteria.
Example : Frankia is associated symbiotically with the root nodules of several non-legume plants like Casuarina, Alnus.
Symbiotic nitrogen fixing cyanobacteria: A number of cyanobacteria (blue green algae) form symbiotic association with several plants, e.g., Lichens, hornworts, Azolla (fern), Cycas roots. Azolla is a small fast growing fern that occurs floating on water.
Anctbaena azollae, (a cyanobacterium) lives in the cavities of Azolla leaves. Azolla – Anabaena symbiotic association is of great importance to agriculture. The fern can grow in rice fields, because it does not interfere with the growth of crop plants.
Mycorrhiza: Mycorrhiza (pi. mycorrhizae) is a symbiotic association of certain fungi with the roots of certain seed bearing plants. Many members of the genus Glomus form mycorrhiza. The fungal symbiont in these associations absorbs phosphorus from soil and passes it to the plant. Plants having such associations show other benefits also, like
(a) resistance to root borne pathogens,
(b) tolerance to salinity and drought, and
(c) an overall increase in plant growth and development.
Mycorrhizae can be broadly classified into two types: ectomycorrhizae and endomycorrhizae.
- Ectomycorrhiza: The mycelium of the fungus forms a mantle on the surface of the root. Ectomycorhizae commonly occur on the roots of trees such as pine, oak, peach and eucalyptus.
- Endomycorrhiza : The fungus lives between and within the cells of the cortex of the roots.
Define sewage. Explain the two stages of treatment of sewage water.
Sewage refers to the municipal waste water generated in cities and towns that contains human and animal excreta and other domestic wastes. Large quantities of waste water are generated every day in cities and towns. Sewage contains large amount of organic matter and microbes. Many of the microbes present in sewages are pathogenic.
Therefore, the sewage cannot be discharged into natural water bodies like rivers and streams directly. To make the sewage less polluting, it has to be treated in Sewage Treatment Plants (STPs). Treatment of waste water is done by the heterotrophic microbes naturally present in the sewage.
This treatment is carried out in two stages: Primary treatment and secondary treatment. The waste water can be passed into rivers after secondary treatment. In some cases, tertiary treatment is also carried out which removes nutrients by chemical process.
Primary Treatment: This step involves physical removal of floating and suspended solids from sewage through filtration and sedimentation. Initially, floating debris is removed through sequential Alteration. The filtrate is kept in large open settling tanks where grit (sand, silt and small pebbles) are removed by sedimentation.
Sometimes, alum or iron sulphate is added for flocculation and settling down of solids. The sediment is called primary sludge, while the supernatant is called effluent. The primary sludge is subjected to composting or land fill. The effluent from the primary settling tank is taken for secondary treatment.
Secondary treatment or Biological treatment: The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into floes (masses of bacteria associated with fungal filaments to form mesh like structures).
While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (biochemical oxygen demand) of the effluent. BOD refers to the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidised by bacteria.
The sewage water is treated till the BOD is reduced. The BOD test measures the rate of uptake of oxygen by micro-organisms in a sample of water and thus, indirectly. BOD is a measure of the organic matter present in the water. The greater the BOD of waste water, more is its polluting potential.
Once the BOD of sewage or waste water is reduced significantly, the effluent is then passed into a settling tank where the bacterial ‘floes’ are allowed to sediment. This sediment is called activated sludge. A small part of the activated sludge is pumped back into the aeration tank to serve as the incolulum.
The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here, other kinds of bacteria, which grow anaerobically, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas . and can be used as a source of energy as it is inflammable.
The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams.
Describe the role of microbes in the production of industrial products.
Microbes in Industrial Products : A number of industrial products valuable to human beings are produced with the help of microbes. The two common ones are alcoholic beverages and antibiotics.
Alcoholic Fermentation: Microbes especially yeasts have been used for the production of alcoholic beverages from time immemorial. Yeast species used in alcoholic fermentation are Saccharomyces cerevisiae (Brewer’s yeast). S. ellipsoides (wine yeast), S. cake (sake yeast) and S. pireformis (Ginger Beer / Ale yeast).
Substrates containing starch juice from sugar cane or molasses or sugar beet are the common substrates for the production of ethanol. Ethanol is produced by continuous fermentation. The process is carried out in large fermenters. Fermentation is carried out at pH5, at a temperature of 35°C, but the cultures and culture conditions are different.
Varieties of alcoholic drinks are made from the same microorganism using different substrates. Starch from barley grains is used in the preparation of beer. Wine is produced from the sugar in grapes.
Note: After fermentation is over, the cells are separated to get a biomass of yeast cells which are used as SCP (single Cell Protein) for animal feed.
Depending upon the raw material and the type of processing, the alcoholic drinks are of two types:
- Without Distillation: Wine and beer are produced without distillation. Beer is an undistilled product of grain mash fermentation, while wine is produced from fruit juice without distillation.
- With Distillation : Whisky, brandy and rum are produced by distillation of the fermented
Explain the role of microbes in the production of household products.
Microbes in Household Products : Microbes have been used in different ways by mankind from time immemorial in the preparation of household products. Some of the household products obtained from microbial activity are:
Dairy Products: A number of bacteria like Lactobacillus and some others commonly called Lactic Acid Bacteria (LAB) are used in the preparation of several dairy products.
Lactic acid fermentation : Lactic acid causes coagulation of milk protein casein. Milk is converted into products like curd, yoghurt and cheese.
1. Curd: For making curd, milk is boiled and then the temperature of milk is brought to about 40°C by keeping it in a cool place. Now a small amount of curd (the innoculum or starter containing Lactobacillus acidophilus) is added to the milk. The fermentation process begins which converts milk sugar lactose into lactic acid.
The acid coagulates milk protein by partially digesting it so that a thick concentrated curd is prepared. Curd is more nutritious than milk as it contains increased quantity of vitamin B12
2. Yoghurt (= Yogurt): It is prepared by curdling milk with the help of Streptococcus thermophilus and Lactobacillus bulgaricans. The temperature is maintained at about 45°C for four hours.
3. Butter Milk: The acidulated liquid left after churning out butter from curd is butter milk.
4. Cheese: It is a protein rich nutritive preparation obtained after fermentation and curdling of milk. It consists of milk curd that has separated from liquid part or whey. Depending upon the water content present in milk/curd, cheese is of three types.
- Raw cheese,
- Unripened cheese (cottage cheese), and
- Ripened cheese.
Bread: A small amount of baker’s yeast (Saccharomyces cerevisiae) is added to wheat flour at the time of its kneading. The kneaded flour or dough is kept for a few hours in a warm place. It results in swelling of the dough called leavening. The leavening is caused by the actions of three types of enzymes secreted by the yeast. These are amylase, maltase and zymase.