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

The NCERT Solutions for Class 12 Biology Chapter 8 Microbes in Human Welfare explains the importance of microbes. Microorganisms, as the name indicates, are organisms that are not seen with the naked eye. These organisms are present everywhere in soil, water, air, and food items. Microbes play a very important role in the production of valuable medicines like penicillin. All the explanations included in the NCERT Solutions are provided by subject experts in a simple manner. This makes the learning more effective and enjoyable.

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1. Download PDF of NCERT Solutions for Class 12 Biology Chapter 8
2. Get Class 12 Biology Chapter 8 Solutions (Exercise Questions)
3. Approach to Solve Class 12 Biology Chapter 8 Question Answer
4. Important Question from Class 12 Biology Chapter 8 Solutions
5. What Extra Should Students Study Beyond the NCERT for NEET?
6. NCERT Solutions for Class 12 Biology- Chapter-wise

Through the regular practice of the Class 12 Biology Chapter 8 Solutions, students can gain knowledge about microbes. This chapter makes them understand that although there are some harmful microbes, most microbes play a positive role. Microorganisms also help in the production of food products like bread, cheese, etc. With the use of NCERT Solutions Class 12 Biology, students can improve their performance in theory and practical questions. For quick revision, they can also download the Microbes in Human Welfare NCERT PDF.

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NCERT Exemplar For Class 12 Biology: Microbes in Human Welfare

Download PDF of NCERT Solutions for Class 12 Biology Chapter 8

Students can download the PDF of the Microbes in Human Welfare chapter from the link given below. This PDF can be used offline for revision and to score well in exams.

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Get Class 12 Biology Chapter 8 Solutions (Exercise Questions)

Given below are the solved exercise questions of the Microbes in Human Welfare chapter. Practising the Class 12 Biology Chapter 8 question answer 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:

• It improves the nutritional quality of curd by increasing the amount of vitamin B12.

• 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, leprosy, etc.

• 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 notatum.

2) Cephalosporins - These are derived from the fungus source Cephalosporium acremonium, having relieving activity against typhoid.

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 malaria and dengue and also causes 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 the solution of 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 fertilisers 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 is 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, 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: synthetically produced by microbial transformations and used mainly as a preservative of food items.

Q15. How do biofertilisers 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

• NCERT Solutions for Class 12 Maths

• NCERT Solutions for Class 12 Chemistry

• NCERT Solutions for Class 12 Physics

Approach to Solve Class 12 Biology Chapter 8 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. Recognise how microbes are used in household products, industries, agriculture, and sewage treatment. Students can use the NCERT Solutions for Class 12 Biology Chapter 8 Microbes in Human Welfare 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 Microbes in Human Welfare NCERT PDF.

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 Question from Class 12 Biology Chapter 8 Solutions

Microorganisms are tiny organisms that are present everywhere. Given below is a question from this chapter along with the answer. To gain clarity, students should practice more questions given in Microbes in Human Welfare Class 12 NCERT Solutions.

Question: 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 flavouring properties.

NCERT Exemplar Class 12 Solutions

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• NCERT Exemplar Class 12 Mathematics Solutions

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• NCERT Exemplar Class 12 Biology Solutions

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 Microbes in Human Welfare Class 12 NCERT Solutions.

NCERT Solutions for Class 12 Biology- Chapter-wise

Here is the complete chapter-wise table provided for easy access: