Case Study Questions Class 12 Biology Microbes In Human Welfare

Case Study Questions Class 12 Biology Chapter 10 Microbes In Human Welfare

CBSE Class 12 Case Study Questions Biology Microbes In Human Welfare. Term 2 Important Case Study Questions for Class 12 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Microbes In Human Welfare.

At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.

CBSE Case Study Questions Class 12 Biology Microbes In Human Welfare

Case Study 1

Besides macroscopic plants and animals, microbes are the major components of biological systems on this earth. You have studied about the diversity of living organisms in Class XI. Microbes like bacteria and many fungi can be grown on nutritive media to form colonies, that can be seen with the naked eyes. Such cultures are useful in studies on micro-organisms.A common example is the production of curd from milk. Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins.

A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin B12. In our stomach too, the LAB play very beneficial role in checking diseasecausing microbes. The dough, which is used for making foods such as dosa and idli is also fermented by bacteria. The puffed-up appearance of dough is due to the production of CO2 gas. Can you tell which metabolic pathway is taking place resulting in the formation of CO2 ? Where do you think the bacteria for these fermentations come from? Similarly the dough, which is used for making bread, is fermented using baker’s yeast (Saccharomyces cerevisiae). A number of traditional drinks and foods are also made by fermentation by the microbes. ‘Toddy’, a traditional drink of some parts of southern India is made by fermenting sap from palms. Microbes are also used to ferment fish, soyabean and bamboo shoots to make foods. Cheese, is one of the oldest food items in which microbes were used. Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity coming from the microbes used. For example, the large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii. The ‘Roquefort cheese’ are ripened by growing a specific fungi on them, which gives them a particular flavour.

Que. 1) Which of the following are the major components of biological system?

(a) Tigers

(b) Microbes

(c) Geysers

(d) Goat

Que. 2) ……………………………………………………………………….. is a part of bacteriophage.

(a) Prongs

(b) Collar

(c) Fins

(d) Both (a) and (b)

Que. 3) In the preparation of dough for Dosa and idli, …………………………………………………………………………………. is used for the fermentation.

(a) Dye

(b) Bacteria

(c) Honey

(d) Wax

Que. 4) Which bacteria is responsible for converting milk into curd?

Que. 5) Why dough get puffed up like appearance?

Answer Key

Que. 1)(b) Microbes.

Que. 2) (d) Both (a) and (b).

Que. 3) (b) Bacteria

Que. 4) Answer: Lactobacillus or Lactic acid bacteria is responsible for converting milk into curd.

Que. 5) Answer: The dough is mainly fermented by bacteria. Due to CO2 production, a dough get puffed up like appearance.

Case Study 2

Microbes especially yeasts have been used from time immemorial for the production of beverages like wine, beer, whisky, brandy or rum. For this purpose the same yeast Saccharomyces cerevisiae used for bread-making and commonly called brewer’s yeast, is used for fermenting malted cereals and fruit juices, to produce ethanol. Depending on the type of the raw material used for fermentation and the type of processing (with or without distillation) different types of alcoholic drinks are obtained. Wine and beer are produced without distillation whereas whisky, brandy and rum are produced by distillation of the fermented broth.

Antibiotics produced by microbes are regarded as one of the most significant discoveries of the twentieth century and have greatly contributed towards the welfare of the human society. Anti is a Greek word that means ‘against’, and bio means ‘life’, together they mean ‘against life’ (in the context of disease causing organisms); whereas with reference to human beings, they are ‘pro life’ and not against. Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes. You are familiar with the commonly used antibiotic Penicillin. Do you know that Penicillin was the first antibiotic to be discovered, and it was a chance discovery? Alexander Fleming while working on Staphylococci bacteria, once observed a mould growing in one of his unwashed culture plates around which Staphylococci could not grow. He found out that it was due to a chemical produced by the mould and he named it Penicillin after the mould Penicillium notatum. However, its full potential as an effective antibiotic was established much later by Ernest Chain and Howard Florey. This antibiotic was extensively used to treat American soldiers wounded in World War II. Fleming, Chain and Florey were awarded the Nobel Prize in 1945, for this discovery.

Que. 1) What is meant by ‘Anti’?

(a) At the top

(b) Apical

(c) Against

(d) Life

Que. 2) Which of the following microbe is used for the production of beverages?

(a) Yeast

(b) Algae

(c) Salmonella

(d) Virus

Que. 3) ……………………………………………………………………………… is a yeast which is useful in bread-making.

(a) Musca domestica

(b) Culicidae

(c) Saccharomyces cerevisiae

(d) None of these

Que. 4) What is the name of firstly discovered antibiotic?

Que. 5) Why Fleming, Chain and Florey were awarded?

Answer Key

Que. 1)(c) Against.

Que. 2) (a) Yeast.

Que. 3) (c) Saccharomyces cerevisiae

Que. 4) Answer: Penicillin was the firstly discovered antibiotics.

Que. 5) Answer: An effective antibiotic which is used to treat wounds of soldiers in world war. This antibiotic was discovered by Fleming, chain and Florey. Hence, they were awarded.

Case Study 3

We know that large quantities of waste water are generated everyday in cities and towns. A major component of this waste water is human excreta. This municipal waste-water is also called sewage. It contains large amounts of organic matter and microbes. Many of which are pathogenic. Have you ever wondered where this huge quantity of sewage or urban waste water is disposed off daily? This cannot be discharged into natural water bodies like rivers and streams directly – you can understand why. Before disposal, hence, sewage is treated in sewage treatment plants (STPs) to make it less polluting. 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: These treatment steps basically involve physical removal of particles – large and small – from the sewage through filtration and sedimentation. These are removed in stages; initially, floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge, and the supernatant forms the effluent. 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 flocs (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.

Que. 1) BOD stands for ………………………………………………………………………………………….

(a) Biosynthesis of Diphenol

(b) Biochemical of Demand

(c) Biological oxygen Degree

(d) Biochemical oxygen demand

Que. 2) Secondary treatment is also referred as ……………………………………………………………………………………….

(a) Biohazards team

(b) Biological treatment

(c) Biomes team

(d) Biochemical flocs

Que. 3) ………………………………………………………………………….. is the major component of waste water.

(a) Bird feather

(b) Human excreta

(c) Fish excreta

(d) All of them

Que. 4) Mention other word for municipal waste water.

Que. 5) What happens when sewage is treated in STPs or Sewage treatment plants?

Answer Key

Que. 1)(d) Biochemical oxygen demand.

Que. 2) (b) Biological treatment.

Que. 3) (b) Human excreta.

Que. 4) Answer: Sewage

Que. 5) Answer: When sewage is treated in Sewage treatment plants, it makes sewage less polluting. And this treatment occurs before disposal.

Case Study 4

Biogas is a mixture of gases (containing predominantly methane) produced by the microbial activity and which may be used as fuel. You have learnt that microbes produce different types of gaseous end-products during growth and metabolism. The type of the gas produced depends upon the microbes and the organic substrates they utilise. In the examples cited in relation to fermentation of dough, cheese making and production of beverages, the main gas produced was CO2. However, certain bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with CO2 and H2. These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium. These bacteria are commonly found in the anaerobic sludge during sewage treatment. The technology of biogas production was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC).

Biocontrol refers to the use of biological methods for controlling plant diseases and pests. In modern society, these problems have been tackled increasingly by the use of chemicals – by use of insecticides and pesticides. These chemicals are toxic and extremely harmful, to human beings and animals alike, and have been polluting our environment (soil, ground water), fruits, vegetables and crop plants. Our soil is also polluted through our use of weedicides to remove weeds

Que. 1) A mixture of gases or Biogas contains predominantly ……………………………………………………………………………………….

(a) Oxygen

(b) Sulphur

(c) Methane

(d) None of these.

Que. 2) Which of the following technique is developed in India?

(a) Biogas

(b) Nuclear energy

(c) Polymerase chain reaction

(d) Probing

Que. 3) ……………………………………………………………………………….. control method is mainly responsible for polluting soil.

(a) Insecticides

(b) Pesticides

(c) Both (a) and (b)

(d) Weedicides

Que. 4) What is produced in large amount by the bacteria while growing anaerobically on cellulosic materials?

Que. 5) Define ‘Biocontrol’.

Answer Key

Que. 1)(c) Methane.

Que. 2) (a) Biogas.

Que. 3) (d) Weedicides.

Que. 4) Answer: Methane is produced in large amount by the bacteria while growing anaerobically on cellulosic materials. 

Que. 5) Answer: Biocontrol is defined as the use of biological methods which helps to control diseases and pests of the plants.

Case Study 5

The bacterial disease will kill the caterpillars, but leave other insects unharmed. Because of the development of methods of genetic engineering in the last decade or so, the scientists have introduced B. thuringiensis toxin genes into plants. Such plants are resistant to attack by insect pests. Bt-cotton is one such example, which is being cultivated in some states of our country. You will learn more about this in chapter 12. A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens. Baculoviruses are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications. They have been shown to have no negative impacts on plants, mammals, birds, fish or even on non-target insects. This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management (IPM) programme, or when an ecologically sensitive area is being treated.

We have now realised that there are problems associated with the overuse of chemical fertilisers and there is a large pressure to switch to organic farming – the use of biofertilisers. Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria. You have studied about the nodules on the roots of leguminous plants formed by the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as nutrient. Other bacteria can fix atmospheric nitrogen while free-living in the soil.

Que. 1) The bacterial disease will not harm ……………………………………………………………………………………..

(a) Caterpillars

(b) Insects

(c) Both (a) and (b)

(d) None of them

Que. 2) Biofertilizers will …………………………………………………………………… nutrient quality of the soil.

(a) Keep as it is

(b) Remains constant

(c) Decreases

(d) Increases

Que. 3) Which is the free-living fungi mainly found in the root ecosystem?

(a) Trichoderma

(b) Nucleovirus

(c) Retrovirus

(d) Thuringiensis

Que. 4) Give an example of plant which is resistant to attacks by insect pest?

Que. 5) What are the sources of Bio-fertiliser?

Answer Key

Que. 1) (b) Insects.

Que. 2) (d) Increases.

Que. 3) (a) Trichoderma.

Que. 4) Answer: Bt-cotton.

Que. 5) Answer: The sources of Bio-fertiliser include cyanobacteria, bacteria and fungi.

Updated: February 18, 2022 — 10:32 pm

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