2nd PUC Biology Question Bank Chapter 10 Microbes in Human Welfare

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Karnataka 2nd PUC Biology Question Bank Chapter 10 Microbes in Human Welfare

2nd PUC Biology Microbes in Human Welfare NCERT Text Book Questions and Answers

Question 1.
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?
Answer:
Microbes or microorganisms like bacteria, fungi, and protozoans are omnipresent (i.e., found everywhere) but are not visible to the naked eye because they have a size of 0.1 mm or less. The common household product that shows the presence of bacteria is curd. Milk is converted to curd by Lactobacillus bulgaricus and Streptococcus thermophilous.

Question 2.
Give examples to prove that microbes release gases during metabolism.
Answer:
The examples of bacteria that release gases during metabolism are:

• Bacteria and fungi carry out the process of fermentation and during this process, they release carbon dioxide.
• 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.

Question 3.
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Answer:
Microorganisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk. They convert lactose sugar of milk into lactic acid. Lactic acid causes coagulation of milk protein casein. Milk is changed into curd, yogurt and cheese etc.

• Curd – Indian curd is prepared by inoculating cream and skimmed milk with Lactobacillus acidophilus at a temperature of about 40°C or less.
• Yogurt – It is produced by curdling milk with the help of Streptococcus thermophilus and Lactobacillus bulgaricus. It has a flavor of lactic acid and acetaldehyde. It is often sweetened and flavored with fruit.
• Cheese – It consists of milk curd separated from liquid part. In preparation for raw cheese milk is curdled with the help of lactic acid bacteria.
  In our stomach too, the LAB play very beneficial role in checking disease-causing microbes.

Question 4.
Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve the use of microbes.
Answer:

• Wheat product: Bread, Cake etc.
• Rice product: Idli, dosa.
• Bengal gram Product: Dhokla, Khandvi.

Question 5.
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Answer:
Microbes are very useful to combat disease-causing harmful bacteria. A number of antibiotics have been isolated from microorganisms. An antibiotic is a substance which in low concentration inhibits the growth and metabolic activity of pathogenic organisms without harming the host. Penicillin was the first antibiotic to be discovered by Alexander Fleming from fungus Penicillium notation. Antibiotics are obtained from lichens, fungi, eubacteria, and actinomycetes. Some common antibiotics and their sources are as follows :

1. Polymyxin – Bacillus polymyxa
2. Chloramphenicol – Streptomyces venezuelae
3. Neomycin – Streptomyces fradiae
4. Tetracycline (Terramycin) – Streptomyces rimosus
5. Cephalosporin – Cephalosporium acremonium

Question 6.
Name any two species of fungus, which are used in the production of antibiotics.
Answer:

• Penicillin – Penicillin chrysogenum
• Griseofulvin – Penicillin griseofulvin
• Fumagillin – Aspergillus puniyatus
• Cephalosporin – Cephalosporium acremonium.

Question 7.
What is sewage? In which way can sewage be harmful to us?
Answer:
Sewage is a collective term used to represent municipal wastewater (both liquid and solid wastes) generated in cities and towns which is carried off in sewers. Chemically, the sewage consists of approximately 99% water and 1% solid waste including inorganic and organic matter. The microorganisms present in sewage include bacteria (coliforms, streptococci, clostridia, lactobacilli), microfungi, protozoa, and microalgae. Proper sewage disposal is of prime importance, because disposal of untreated sewage in the river and other water bodies may be harmful in the following ways:

• It results in the dissemination of water-borne diseases caused by microorganisms.
• It may cause depletion of dissolved oxygen (DO) in water.
• Reduction in oxygen availability may kill aerobic aquatic microorganisms.
• Untreated sewage produces an offensive odor.

Question 8.
What is the key difference between primary and secondary sewage treatment?
Answer:
Primary treatment is physical and removes grit and large prices of organic matter while secondary treatment is Biological causing digestion of organic matter by microbes.

Question 9.
Do you think microbes can also be used as source of energy? If yes, how?
Answer:
Microbes can be used as a source of energy. Biogas is a mixture of gases produced from degradable organic matter by the activity of various anaerobic microorganisms and it may be used as fuel.

The microorganisms involved in biogas production are mainly facultative and strictly anaerobic bacteria. The most important among them are methanogenic archaebacteria, represented by Methanobacterium. The major component of biogas is methane (about 50-68%) which is highly inflammable. The other gases are CO₂ (25-35%), hydrogen (1-5%), nitrogen (2-7%), oxygen (0-0.1%) and H₂S (traces).

Biogas is commercially produced inside the biogas plant. The plant is fed with a mixture of dung and water (1 : 1 ratio). Dung is an excreta of cattle, commonly called ‘gobar’, it is because of this, the plant is commonly called ‘gobar gas plant’. Cattle dung is a rich source of cellulosic material from plants. Biogas is used as fuel for heating, cooking, lighting, power for irrigation, and other purposes as an alternative to firewood, kerosene, dung cakes, or even electricity and LPG. It is considered an eco-friendly and pollution-free source of energy.

Question 10.
Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
Answer:
Microbes play an important role in organic farming which is done without the use of chemical fertilizers and pesticides. Bio-fertilizers are living organisms that help increase the fertility of soil. It involves the selection of beneficial microorganisms that help in improving plant growth through the supply of plant nutrients. Bio-fertilizers are introduced in seeds, roots or soil to mobilize the availability of nutrients. Thus, they are extremely beneficial in enriching the soil with organic nutrients.

Many species of bacteria and cyanobacteria have the ability to fix free atmospheric nitrogen, 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. Bio-fertilizers are cost-effective and eco-friendly.

Microbes can also act as bio-pesticides to control insect pests in plants. An example of bio-pesticides is Bacillus thuringiensis, which produces a toxin that kills insect pests. Dried bacterial spores are mixed in water and sprayed in agricultural fields. When larvae of insects feed on crops, these bacterial spores enter the gut of the larvae and release toxins, thereby it. Similarly, Trichoderma is free-living fungi. They live in the roots of higher plants and protect them from various pathogens. Baculoviruses are another bio-pesticides that is used as a biological control agent against insects and other arthropods.

Question 11.
Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/ L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
Answer:
BOD (Biological Oxygen Demand) refers to the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria. BOD is a measure of the organic matter present in the water. The greater the BOD of wastewater, the more are the pollutants. BOD value of clean water is generally between 1 and 2 mg/L. As the amount of pollution increases, BOD is also increased and grossly polluted waters may have the BOD around 20 mg/L.

In the given problem BOD values of the three samples A, B and C are 20 mg/L, 8 mg/L and 400 mg/L, respectively. Here sample C has the greatest BOD value hence it is the most polluted. If we correctly label the three samples, then sample A should be secondary effluent discharged from a sewage treatment plant (20 mg/L), sample B should be river water (8 mg/L) and sample C should be untreated sewage water (400 mg/L).

Question 12.
Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol-lowering agents) are obtained.
Answer:

• Cyclosporin A is produced by the fungus Trichoderma polysporum.
• Statins are produced by die yeast Monascus purpureus which acts as a blood cholesterol-lowering agent.

Question 13.
Find out the role of microbes in the following and discuss it with your teacher.
(a) Single-cell protein (SCP)
(b) Soil
Answer:
(a) Single-cell protein (SCP) – Microorganisms (e.g., bacteria, yeast, filamentous fungi, algae etc.) can be cultured on a commercial scale in a fermenter, treated in various ways, dried or used as food source or as animal feed are called single-cell protein. The term SCP, however, is misleading as it sounds as if the protein is obtained from single cell. In fact, the biomass obtained from uni and the multicellular organism is considered as SCP.

Some common microorganisms, used in the production of SCP are as follows:

• Bacteria (e.g., Methylophilus, Brevibacterium, etc.)
• Cyanobacteria (e.g., Spirulina)
• Yeasts (e.g., Saccharomyces cerevisiae, Candida utilis, etc.)
• Filamentous fungi (e.g., Fusarium graminearum)
• Algae (e.g., Chlorella)

There are several advantages of SCP using as food. Some of them are listed below :

• SCP is rich in high-quality protein and poor in fat content.
• The SCP can be produced in laboratories all year round. Its production is not dependent on climatic factors.
• The microorganisms, used in the production of SCP, are very fast-growing and produce a large amount of SCP from a relatively very small area of land.

(b) Soil – Microbes are very useful to maintain and restore soil fertility. The fertility of soil depends not only on its chemical composition but also on the quantity and quality of useful microbes present in it. Moreover, if the composition of the soil is not upto the mark and poor in fertility, materials of biological origin are added to it to improve and maintain its fertility. These materials are grouped under the two broad categories manures and’ biofertilisers. Manures are of three types, farmyard manure, compost and green manure.

Farmyard manure is the oldest manure known to mankind which is made up of dung of farm animals and plant remains etc, which are allowed to partially decay with the help of soil microorganisms. These microorganisms decompose complex organic debris into a dark amorphous substance (humus) and degradation products are easily assimilated by plants. The manure loosens the soil, increases its aeration, and makes the soil more fertile. Biofertilisers are the microorganisms which bring about soil nutrient enrichment, maximize the ecological benefits and minimize environmental hazards.

Question 14.
Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd.
Answer:
The order of arrangement of products according to their decreasing importance is:
Penicillin—Biogas—Citric acid—Curd

Penicillin is the most important product for the welfare of human society. It is an antibiotic, which is used for controlling various bacterial diseases. The second most important product is biogas. It is an eco-friendly source of energy. The next important product is citric acid, which is used as a food preservative. The least important product is curd, a food item obtained by the action of lactobacillus bacteria on milk Hence, the products in the decreasing order of their importance are as follows:

Penicillin—Biogas—Citricacid—Curd.

Question 15.
How do biofertilizers enrich the fertility of the soil?
Answer:
Bio fertilizers are the microorganisms which bring about soil nutrient enrichment, maximize the ecological benefits and minimize environmental hazards. The main sources of biofertilizers are bacteria, fungi, and cyanobacteria. Some of the biofertilizers and their importance in maintaining soil fertility are as follows:

1. Free-living nitrogen-fixing bacteria fix atmospheric nitrogen in the soil and make it available for the higher plants. The best example is Azolobncter. Apart from this Clostridium, Bacillus polymyxa, Derxia, etc., are also known to fix atmospheric nitrogen.
2. Symbiotic nitrogen-fixing bacteria, Rhizobium, form an efficient symbiotic relationship with leguminous plants and can fix upto 500 kg nitrogen per hectare of land. Rhizobium forms nodules on the roots of legume plants.
3. Free-living nitrogen-fixing cyanobacteria ‘include Anabaena, Nostoc, Aulosira, Stigonema, etc. Aulosira fertilissimma is considered to be the most active nitrogen fixer of rice fields in India.
4. Nitrogen-fixing cyanobacteria form a symbiotic association with several plants, e.g., cycad roots, lichens, liverworts, Azolla (fern). Out of these, the Azollci-Amibaena association is of great importance to agriculture. Anabaena azollae resides in the leaf cavities of fern. It fixes nitrogen.
5. Fungi are also known to form symbiotic associations with plants (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, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.

2nd PUC Biology Microbes in Human Welfare Additional Questions And Answers

2nd PUC Biology Microbes in Human Welfare One Mark Questions

Question 1.
What is LAB?
Answer:
The microorganisms which commonly grow in milk and converted into curd are called Lactic Acid Bacteria or LAB.

Question 2.
Name the fungus which gave gibberellins hormone.
Answer:
Gibberellin is found by Gibberella fujikuroi.

Question 3.
Who discovered penicillin?
Answer:
Alexander Fleming.

Question 4.
Which microbes are given antibiotics?
Answer:
Generally, bacteria and fungus give us antibiotics.

Question 5.
What are fermentors?
Answer:
Fermentors are very large vessels used for growing microbes for the production of microbial products on an industrial scale.

Question 6.
What are antibiotics?
Answer:
The chemical substances which are produced by certain microbes can kill or retard the growth of other microbes.

Question 7.
What is BOD?
Answer:
The amount of oxygen that would be consumed for the oxidation or decomposition of the biodegradable organic waste present in the water is called BOD or biological oxygen demand.

Question 8.
Why does the river Ganga water not spoil even kept for a long-time?
Answer:
Bacteriophages are present in the Ganga river’s water, they feed bacteria which spoil water. So, this water does not spoil in long-time.

Question 9.
Name the enzyme used “clot buster” is to remove blood clots from blood vessels and which organism produces this enzyme.
Answer:
Streptokinase is known as clot buster. It is produced by Streptococcus bacteria.

Question 10.
Name the microorganism/fungi which gave penicillin.
Answer:
Penicillium notatum.

Question 11.
What is STP stands for?
Answer:
Sewage Treatment Plant.

Question 12.
Write the name of methanogen bacteria.
Answer:
Methano bacterium species.

Question 13.
Which of the following is a Cyanobacteria that can fix atmospheric nitrogen? Spirulina, Azospirillum, Sonalika.
Answer:
Azospirillum.

Question 14.
Milk starts to coagulate when Lactic Acid Bacteria is added to warm milk as a starter. Mention any other two benefits LAB provides. (AI CBSE – 2009)
Answer:
Increase vitamin B₁₂ and also check disease-causing microbes in stomach.

Question 15.
Name the group of organisms and the substrate they act on to produce biogas.
(CBSE 2009)
Answer:
Methanogens, Cellulose present in cattle excreta (cow dung)

Question 16.
What are floes?
Answer:
The masses of bacteria associated with fungal filaments forming the mesh-like structures are the floes.

Question 16.
Give the name of autotrophic nitrogen-fixing microbes.
Answer:
Anabaena.

Question 18.
Name the fungus that is being developed as biocontrol.
Answer:
Trichoderma.

Question 19.
What is the key differences between primary and secondary sewage treatment?
Answer:
Primary treatment of sewage is a physical process, while secondary treatment is a biological process.

Question 20.
Name a genus of a fungus that forms mycorrhiza.
Answer:
Glomus is the fungus that forms mycorrhiza.

Question 21.
List 2 advantages that a mycorrhizal association provides to the plant. (AI2008)
Answer:

• The fungal partner in mycorrhiza absorbs
• Phosphorus from the soil and passes it on to the plant.
• The plants having mycorrhizal association show resistance to root borne pathogens and tolerance to salinity

2nd PUC Biology Microbes in Human Welfare Two Marks Questions

Question 1
(a) Name an eco-friendly hloherhicide that interferes with amino add synthesis and resistance to which has been obtained through transgenic culture.
(b) Name the first biopesticide. (CBSE 2004)
Answer:
Basta or phosphinothricin (ppt)
(a) It obtained from a product of Streptomyces species. Crop plants have been made resistant to it by transferring bar gene into them (e.g. wheat)
(b) Divine and college.

Question 2.
Match the columns

Answer:

Question 3.
Name the blank spaces ‘a’, ‘b’, ‘c’ and ‘d’ give in the following label.

Type of microbe	Scientific Name	Commercial or Product
Bacterium	a	Lactic acid
Fungus	b	Cyclosporin A stains
C	Monascus Purpur
Fungus	Penicillin Nolaltisin	d

Answer:

• a – Laetobaellhts
• b – Triehodmna polysptmtm
• c – Yeast (fungus)
• d – Penicillin

Question 4.
Name the blank spaces a, b, c, and d given in the following label. (CBSE – 2008)

Type of microbe	Scientific Name	Commercial or Product
Bacterium	a	Clot buster
b	Aspergillus Trichoderma	Enzyme citric acid
Fungus	Polysporum	c
Bacterium	d	Enzyme citric acid

Answer:
a – Streptococcus
b – Fungus
c – Cyclosporin A
d – Clostridium butylicum.

Question 5.
Fill in the blanks from Cephalosporin, Cyclosporin, Cycas, Soybean, Nepiatode, Fungus, Rhizobium. (CBSE 2008)
(a) Potent immunosuppressant drug is ………….. which is obtained from a …………..
(b) Roots pines and ………….. are associated will Amanita and …………..respectively.
Answer:
(a) Cyclosporin A, Fungus
(b) Soybean, Rhizobium.

Question 5.
“BOD must be low in freshwater”
a. Expand BOD.
b. Define BOD.
c. Write the importance of BOD.
Answer:
a. Biological Oxygen Demand
b. This is the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by the microbes.
c. BOD is the measure of the organic matter present in water because BOD test measures the rate of uptake of oxygen by microbes in sample water. The greater the BOD in sewage, more is its polluting potential.

Question 7.
Name the blank spaces a, b, c and d from the table given below (CBSE 2007)

Type of Microbes	Scientific Name	Product	Medical Application
Fungus	a	Cyclosporin	b
c	Monascus	statin	d
	purpureus

Answer:
(a) Trichoderma polysporum
(b) Organs transplant patients
(c) Yeast (fungus)
(d) lowering blood cholesterol level.

Question 8.
What is baker’s yeast?
Answer:
Saccharomyces cerevisiae

Question 9.
What are harmful effects of using chemical pesticides?
Answer:

• The chemical pesticides are harmful to many organisms (maybe useful) other than the pests for which they used.
• They enter the food chain and cause diseases/disorders in various organism
• They are also highly toxic to man
• They cause pollution of our soil, water and air.

Question 10.
How do bacteria function as biofertilizers? Name 2 free-living soil bacteria that are biofertilizers.
Answer:

• Bacteria can fix atmospheric nitrogen into those nitrogen compounds which are used by the plants as their nutrients.
• Soil bacteria that are biofertilizers includes – Azotobacter and azospirillum.

2nd PUC Biology Microbes in Human Welfare Three Marks Questions

Question 1.
What are methanogens? Where are they generally found? Give examples.
Answer:
Methanogens are a group of anaerobic bacteria, which produce large quantities of methane from cellulosic materials.
E.g.: Methano bacterium Methanogens are found in

• The sewage wager
• Marshy place
• The rumen of cattle.

Question 2.
Describe the functions of anaerobic sludge in a sewage treatment plant.
Answer:

• A portion of the activated sludge from anaerobic sludge digester is pumped back to the aeration tank to serve as inoculum.
• The anaerobic bacteria digest the bacteria and fungi of the floes.
• The anaerobic bacteria in the sludge release CO₂, methane etc. during decomposition; these gases from the biogas is used as a source of energy, as it is inflammable.

Question 3.
What are mycorrhizae? How do they serve as biofertilizers or how are they useful to plants?
Answer:
Mycorrhizae are the symbiotic association between certain fungi and roots of higher plants.

• The fungus absorbs phosphorous from the soil and passes it to the plants
• Plants with mycorrhiza show resistance to root borne pathogens
• They show increased tolerance to salinity and drought
• There is an overall increase in plant growth and development.

Question 4.
Biocontrol is the best alternative for chemical control. Justify your answer.
Answer:
The use of biological methods for controlling plant diseases and pests is called biocontrol. This method has been replaced by the indiscriminate use of chemicals used in the chemical control of pests. The chemicals used for killing pests are toxic and extremely harmful to men and domestic animals. They also pollute the environment and our crop plants.

2nd PUC Biology Microbes in Human Welfare Five Marks Questions

Question 1.
Write seven useful activities of Bacteria.
Answer:
Useful activities of bacteria:

1. N₂ fixation: Some bacterias play an important role in nitrogen fixation e.g., Azotobacter, Clostridium, Rhizobium. These bacterias increase the fertility of soil by the fixation of atmospheric nitrogen.
2. Lactic acid synthesis: Lactobacillus lacti converts the milk sugar into lactic acid.
3. Acetic acid synthesis: Acetobacter aceti takes part in the synthesis of acetic acid or vinegar.
4. Rating of fibers: Isolation of wood fibres from the stem of plants is called rating. Clostridium butyricum is used in the rating of fibres.
5. Tobacco and Tea industry: Some bacteria like Micococcus canadiens is used to increase the flavour of the leaves of tobacco and tea. This process is called seasoning.
6. Medicine production: Bacteria are the chief source of antibiotics, hence, they are used to extract antibiotics, e.g., Streptomyces gresius (Streptomycin).
7. As symbionts: Bacteria present in our body, helps in the various metabolic reactions e.g, E.coli.