NCERT Solutions for Class 12 Biology Chapter 8 Microbes in Human Welfare

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Get Class 12 Biology Chapter 8 Microbes in Human Welfare Question Answer

Given below are the solved exercise questions of the Microbes in Human Welfare chapter. Practicing the Class 12 Biology Chapter 8 Microbes in Human Welfare question answers that are prepared according to the latest NCERT curriculum will help students answer the questions effectively.

Q1. Bacteria cannot be seen with the naked eye, but they 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 with the help of a microscope, which sample would you carry and why?

Answer:

To demonstrate the presence of microbes with the help of a microscope, the best sample we can carry is curd. Curd contains lactic acid bacteria (LAB), such as Lactobacillus, and is safe. A small portion of curd contains millions of bacteria, which can easily be observed under the microscope.

Q2. Give examples to prove that microbes release gases during metabolism.

Answer:

There are many examples where we find that microbes release gases during metabolism:

• The dough that is used for making foods such as dosa and idlis is fermented by bacteria. The puffed appearance of dough is due to the production of CO₂ gas.

• The dough that is used for making bread is fermented by using baker’s yeast (Saccharomyces cerevisiae).

The large holes in Swiss cheese are due to the production of a large amount of CO₂ by the bacteria.

Q3. In which food would you find lactic acid bacteria? Mention some of their useful applications.

Answer:

• Lactic acid bacteria grow in milk and convert it to curd. Besides this, there are other applications of lactic acid bacteria given below:

• LAB improves nutritional quality (e.g., some B-vitamins, better digestibility) and acts as probiotics that check pathogenic microbes.

• In our stomachs, too, the LAB plays a very beneficial role in checking disease-causing microbes.

Q4. Name some traditional Indian foods made of wheat, rice, and Bengal gram (or their products) that involve the use of microbes.

Answer:

Traditional Indian foods made of wheat, rice, and Bengal gram are:-

• Wheat- Bread, Bathura, and cake are prepared from wheat.

• Rice - Dosa and idlis involve the use of microbes.

• Bengal gram- Dhokla and khandvi are made from the Bengal gram

Q5. In which way have microbes played a major role in controlling diseases caused by harmful bacteria?

Answer:

Microorganisms have several characteristics that make them ideal organisms for the production of various products, including medicines, vaccines, and antibiotics that help in controlling diseases caused by harmful bacteria, which are given below:

• Many medicines like Ergot, Cyclosporin A, and Statins are produced from the fungus and bacteria, which are used to induce uterine contractions, immunosuppressive agents, and blood cholesterol-lowering agents, respectively.

• Penicillin, Cephalosporins, Streptomycin, Erythromycin, etc. Antibiotics are prepared from microbes for the treatment of diseases like pneumonia, cough, diphtheria, and leprosy.

• Inactivated strains of microbes are used for producing vaccines.

Q6. Name any two species of fungus that are used in the production of antibiotics.

Answer:

Microorganisms possess several characteristics and are used in various fields, one of which is the important field where microbes are used in the production of antibiotics. Two species of fungus which are used in the production of antibiotics are:-

1) Penicillin - It's the first antibiotic to be discovered from the fungus Penicillium chrysogenum.

2) Cephalosporins - These are derived from the fungus source Acremonium, used as antibiotics that are effective against a wide range of bacterial infections.

Q7. What is sewage? In which way can sewage be harmful to us?

Answer:

Large quantities of wastewater are generated every day in cities. A major component of this wastewater is human excreta. This municipal wastewater is called sewage. It contains a large amount of organic matter and microbes.

Hence, proper sewage disposal is of prime importance; otherwise, untreated sewage, if disposed of in water bodies, results in waterborne diseases such as cholera and typhoid, which also cause depletion of dissolved oxygen in the water.

Q8. What is the key difference between primary and secondary sewage treatment?

Answer:

The differences between the primary and secondary treatment of sewage are as follows:

Q9. Do you think microbes can also be used as a source of energy? If yes, how?

Answer:

Several microbes have been found helpful in solving energy crises. Synthetic fuels are produced by the activity of microbes, including ethanol, methane, hydrogen, and hydrocarbons.

Gasohol- Gasohol is a mixture of 90% gasoline and 10% alcohol and is used in several countries to combat the energy shortage.

Production of Biogas- Biogas is a mixture of gases containing mainly methane produced by microbial activity. Livestock waste is used for the generation of biogas through microbial fermentation.

Hydrogen is a valuable fuel; several algae have the capability of producing hydrogen from water in sunlight.

Q10. Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished.

Answer:

Chemical fertilizers and pesticides are made up of a few minerals, thus making the soil toxic and also exploiting its nutrients. To overcome these problems, the use of biofertilizers is being encouraged. Biofertilizers are organisms that enrich the nutrient quality of the soil. They promote growth by increasing the supply or availability of primary nutrients to the plant. They mostly include nitrogen-fixing microorganisms. Some of them are given below:

Legume-Rhizobium symbiosis- Certain nitrogen-fixing bacteria, for example, rhizobium, live in symbiosis where the legume provides carbohydrates to the bacteria. Rhizobium not only increases the production of crops but also leaves a fair amount of nitrogen in the soil, which benefits the crop.

Another example of this type of symbiosis is the Azolla-Anabaena symbiosis. Apart from them, Azotobacter and Azospirillum are free-living bacteria that fix nitrogen and make it available for crop plants.

Q11. Three water samples, namely river water, untreated sewage water, and secondary effluent discharged from a sewage treatment plant, were subjected to the 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:

Biological oxygen demand (BOD) is a measure of the organic matter present in the water. The greater the BOD of wastewater, the more its polluting potential.

Q12. 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, which is an immunosuppressive drug, and statins from the yeast Monascus purpureus, which are blood cholesterol-lowering agents.

Q13. Find out the role of microbes in the following

a) Single cell protein (SCP)

Answer:

Single-cell protein

SCP is a protein-rich biomass produced from microbes. It is used as a food supplement for both humans and animals.

• Microbes like algae, bacteria, fungi, and yeast are used.

• These microbes grow fast and contain a high amount of protein.

• It can be grown on waste, so it also helps in waste management.

• Does not depend on the climate, so production is easy and cheap.

• Used in animal feed and also as a protein source for people

Q13. Find out the role of microbes in the following

b) Soil

Answer:

Soil

• The microbes present in the soil increase the fertility of the soil by decomposing organic matter.

• The bacteria Rhizobium live symbiotically in the nodules of the roots of leguminous plants, fixing atmospheric nitrogen into organic forms, which are used by the plant as a nutrient.

• Similarly, some free-living bacteria in the soil, like Azospirillum and Azotobacter, fix atmospheric nitrogen, thus enriching the nitrogen content of the soil.

Q14. 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:

• Penicillin: Penicillin is the first antibiotic to be discovered, and it is an effective antibiotic to treat deadly diseases

• Biogas: a mixture of gases (mainly containing methane) produced by the microbial activity on excreta (dung) of cattle, an eco-friendly source of energy, particularly in rural areas.

• Curd: a portion of nutritious and easily digestible food for all age groups obtained from milk by the action of lactic acid bacteria (LAB).

• Citric acid: It is produced industrially by microbial fermentation (Aspergillus niger).

Q15. How do biofertilizers enrich the fertility of the soil?

Answer:

• Biofertilizers are organisms that enhance the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi, and cyanobacteria.

• Rhizobia bacteria live in a symbiotic association on the roots of leguminous plants. These bacteria fix atmospheric nitrogen into organic forms, which are used by the plant as a nutrient.

• Other bacteria like Azospirillum and Azotobacter can also fix atmospheric nitrogen while free-living in the soil, thus enriching the nitrogen content of the soil and improving its quality.

• Cyanobacteria (e.g., Anabaena, Nostoc, etc.) can also fix atmospheric nitrogen. In paddy fields, cyanobacteria add organic matter to the soil and increase its fertility.

NCERT Solutions for Class 12- Subject-wise

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Approach to Solve Microbes in Human Welfare Class 12 Question Answer

Microbes play an important role in human welfare by contributing to food production, medicine, agriculture, etc. Understanding their uses helps in solving questions related to this topic.

1. Recognize how microbes are used in household products, industries, agriculture, and sewage treatment. Students can use the Class 12 Biology Chapter 8 Microbes in Human Welfare question answer to understand clearly.

2. Recall microbes such as Lactobacillus for curd, yeast for bread, and Rhizobium for nitrogen fixation.

3. Linked microbes with their uses, such as biofertilizers, biocontrol agents, and the synthesis of antibiotics.

4. Use simple definitions for terms such as biofertilizers, biogas, and single-cell protein. These are well-explained in the Class 12 Biology Microbes in Human Welfare question answer.

5. Learn from the solved exercises given in the NCERT Solutions for Class 12 to understand the question pattern.

Also, check the NCERT Books and the NCERT Syllabus here:

• NCERT Books Class 12 Biology

• NCERT Syllabus Class 12 Biology

• NCERT Books Class 12

• NCERT Syllabus Class 12

Important Questions from Class 12 Biology Chapter 8 Microbes in Human Welfare

Microorganisms are tiny organisms that are present everywhere. Given below are the important questions from this chapter, along with the answers. To gain clarity, students should practice more questions given in the NCERT Solutions for Class 12 Biology Chapter 8 Microbes in Human Welfare.

Question 1: Which of the following microbes is used for the commercial production of citric acid?

a) Lactobacillus
b) Aspergillus niger
c) Penicillium notatum
d) Rhizobium

Answer: The correct answer is option (b) Aspergillus niger

Explanation:
Aspergillus niger is a fungus widely used in industry to produce citric acid through fermentation. It efficiently converts sugars into citric acid under controlled conditions. This citric acid is then used in food, beverages, pharmaceuticals, and cleaning products due to its preservative and flavoring properties.

Question 2: Activated sludge should have the ability to settle quickly so that it can:

a) Be rapidly pumped back from the sedimentation tank to the aeration tank.
b) Absorb pathogenic bacteria present in wastewater while sinking to the bottom of the settling tank
c) Be discarded and anaerobically digested.
d) Absorb colloidal organic matter.

Answer: The correct answer is option (c) Be discarded and anaerobically digested.

Explanation:

• For activated sludge to be isolated from treated water, it must settle rapidly.
• By doing this, extra sludge can be disposed of and sent for anaerobic digestion.
• It is broken down by bacteria during digestion to produce biogas.
• This recycles energy and lessens waste.

Question 3: Methanogens do not produce:

a) Oxygen
b) Methane
c) Hydrogen sulfide
d) Carbon dioxide

Answer: The correct answer is option (a) Oxygen

Explanation:
Yes, methanogens are a group of anaerobic microorganisms that produce methane as a byproduct of their metabolic process. During the breakdown of organic matter, methanogens primarily convert carbon compounds into methane (CH₄), but they also produce other gases, including carbon dioxide (CO₂) and hydrogen sulfide (H₂S).

Question 4: The primary treatment of wastewater involves the removal of:

a) dissolved impurities
b) stable particles
c) toxic substances
d) harmful bacteria

Answer: The correct answer is option (b) stable particles

Explanation:
Dissolved impurities, toxic substances, and harmful bacteria are usually removed during the later parts of purification treatments for water or drinking water. The term "stable particles" indicates that what is left after purification does not have an inherent ability to be harmful to health or the environment. If the use of water or the solution is to be made safe to utilize, that can result in an effective purification method by maintaining safety and quality.

Question 5: Big holes in Swiss cheese are made by a:

a) a machine
b) a bacterium that produces methane gas
c) a bacterium producing a large amount of carbon dioxide
d) a fungus that releases a lot of gases during its metabolic activities

Answer: The correct answer is option (c) a bacterium producing a large amount of carbon dioxide

Explanation:
The bacterium Propionibacterium sharmanii plays a key role in the production of Swiss cheese by fermenting lactic acid into carbon dioxide (CO₂) and propionic acid. The release of a large amount of CO₂ during this process creates the characteristic big holes or "eyes" in Swiss cheese. The propionic acid also contributes to the unique flavor of the cheese.

NCERT Exemplar Class 12 Solutions

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What Students Learn from Microbes in Human Welfare NCERT Solutions

This chapter explains how different microorganisms play a vital role in our daily lives and environment.

1. Students learn how microbes are used in household products like curd, cheese, and fermented foods.

2. Through the Microbes in Human Welfare Class 12 question answer, they understand the role of microorganisms in the industrial production of beverages and antibiotics.

3. The chapter helps them explore how sewage treatment plants use microbes to purify wastewater.

4. With the help of the Class 12 Biology Microbes in Human Welfare question answer, learners study how microbes act as biocontrol agents and biofertilizers in sustainable agriculture.

5. Learners also gain knowledge about biogas production and the contribution of microbes in generating renewable sources of energy.

Why Class 12 Biology Chapter 8 Microbes in Human Welfare NCERT Solutions are Important?

Microbes in Human Welfare is an important chapter as it allows students to understand the benefits of microorganisms in different fields, such as in producing medicines, agriculture, waste management, etc.

• Class 12 Biology Chapter 8 Microbes in Human Welfare NCERT Solutions clearly explain the industrial use of microbes in producing alcohol, antibiotics, and enzymes.
• Students also learn about the use of microbes in sewage treatment and biogas production by using the solutions.
• Microbes play an important role in food production, such as curd, cheese, and bread formation, which is explained in detail in the solutions.
• Topics like biofertilizers and biocontrol agents are described, which are frequently asked in the NEET or board exams.

What Extra Should Students Study Beyond the NCERT for NEET?

Here is a table for all the topics students study beyond the NCERT for the NEET exam. Along with this, to score well, students can refer to the NCERT Solutions for Class 12 Biology Chapter 8 Microbes in Human Welfare.

NCERT Solutions for Class 12 Biology- Chapter-wise

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