They organize important uses and applications of microbes in clear, point-wise answers, making it easier to remember examples commonly tested in MCQs and short questions.
Yes, since NEET is highly NCERT-based, practicing these solutions helps students recall key facts and details for multiple-choice questions.
Yes, the answers follow the current NCERT Class 12 Biology book and CBSE syllabus to ensure students study only relevant content.
Yes, they use correct NCERT terminology and spellings, which improves accuracy in written and objective exams.
Regular practice helps students recognize common question patterns, allowing them to answer faster and more confidently.
NCERT Solutions explain that primary sewage treatment is a physical process that removes solid particles through filtration and sedimentation. Secondary treatment is a biological process in which aerobic microbes break down organic matter and reduce the BOD of sewage.
NCERT Solutions explain that Penicillin is an important antibiotic used to treat bacterial infections. The chapter also explains the importance and uses of Biogas, Curd, and Citric Acid as products obtained through microbial activity.
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NCERT Solutions Class 12 Biology Chapter 8 Microbes in Human Welfare
Class 12 Biology Chapter 8 Microbes in Human Welfare This chapter explains to students how these tiny microorganisms are very important in improving human life and the environment. This chapter deals with the utilisation of microbes in the production of food, medicines, in agriculture and in waste management. It also helps students to know about the role of bacteria and fungi in producing antibiotics, vaccines, biogas and fermented products, thus showing the positive side of microbes in our daily life as well as industry.
ALLEN has provided complete NCERT Solutions for all the questions provided at the end of each chapter in the NCERT Textbooks. Our expert faculty emphasises on clear understanding of biological oxygen demand (BOD) and specific roles of various fungi and bacteria in environmental management. These solutions are designed to help you write accurate point-wise answers that perfectly match the CBSE marking scheme. ALLEN’s professional resources will help you master the technical details of microbiology at the speed and accuracy needed for board exams and NEET preparation.
1.0Key Concepts of Class 12 Biology Chapter 8 Microbes in Human Welfare
The chapter focuses on understanding the beneficial uses of microorganisms. Some of the key lessons covered in this chapter are given below:
Microbes in Household Products: Learn how microorganisms are used in the preparation of curd, bread, cheese, and other fermented food products.
Microbes in Industrial Products: Understand how microbes are used to produce alcohol, organic acids, enzymes, and other commercially useful substances.
Microbes in Medicine: Study the role of microorganisms in producing antibiotics and other medically important products, including therapeutic substances.
Microbes in Sewage Treatment: Understand how microbes break down organic matter during wastewater treatment and help reduce environmental pollution.
Biogas Production: Learn how methanogenic microorganisms break down organic waste and contribute to the production of biogas.
Biological Control: Explore how certain microorganisms and biological agents are used to control agricultural pests and plant diseases.
Biofertilisers: Understand how beneficial microorganisms such as Rhizobium, cyanobacteria, and mycorrhiza help improve soil fertility and support plant growth.
2.0NCERT Class 12 Biology Chapter 8 Microbes in Human Welfare : Detailed Solutions
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 with the help of a microscope, which sample would you Carry and why?
Ans. The most common household product that we would like to carry is curd which common in Lactic acid bacteria (Lactobacillus sp.).
Give examples to prove that microbes release gases during metabolism.
Ans. Puffed-up appearance of dough which is used for making dosa, idli and bread due to gas production.
• Methanogens (bacteria) in the biogas plant produce methane and carbondioxide.
• Also large holes in the 'Swiss cheese' are due to production of a large amount of CO2 during its production.
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Ans. The lactic acid bacteria (LAB) are found in curd.
• LAB convert the lactose sugar of milk into lactic acid.
• Lactic acid coagulates the milk protein called casein.
• It also increases the nutritional quality of curd as the curd contains vitamin B12 along with other vitamins. They also check the growth of other harmful microbes.
Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Ans. 'Dosa' and 'idli' (from rice), bread (from wheat) and 'dhokla' (from Bengal gram) are the traditional Indian foods which involve use of microbes.
In which way have microbes played a major role in controlling diseases caused by harmful bacteria? [IMP.]
Ans. The major role of microbes in controlling the diseases is the 'antibiotic production, Antibiotics have been used against pathogenic bacteria, e.g. penicillin from Penicillium notatum, streptomycin from Streptomyces griseus, etc.
Name any two species of fungus, which are used in the production of the antibiotics.
(ii) Aspergilus fumigatus (for fumagillin production).
What is sewage? In which way can sewage be harmful to us?
Ans. Sewage is the municipal waste water containing large quantities of human excreta and other organic wastes.
wastes.
Sewage could be harmful to us as it contains many pathogenic microbes and produces foul smell. It is the cause of many water-borne diseases.
It is also the cause of eutrophication of water bodies there by killing many aquatic organisms.
What is the key difference between primary and secondary sewage treatment? [IMP.]
Ans. The key difference between primary and secondary treatment of sewage is that primary treatment is the physical process of removing grit and floating debris while secondary treatment is a biological process that involves digestion of organic matter by microbes.
Do you think microbes can also be used as source of energy? If yes, how?
Ans. Yes, microbes can be used to produce energy indirectly.
Methanogens (bacteria) like Methanobacterium are involved in the production of biogas which is used as source of energy.
Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished. [IMP.]
Ans. Microbes can be used both as fertilizers and pesticides called biofertilizers and biopesticides respectively.
Microbes are used as biofertilisers to enrich the soil nutrients, eg Rhizobiun, Azotobacter, Azospirillum, etc. which can fix atmospheric nitrogen in the soil.
Bacillus thuringiensis bacteria act as biopesticide to control the growth of insect pests.
Trichoderma , fungal species, is an effective biocontrol agent of several plant pathogens.
Baculoviruses used as control agents in genus Nucleopolyhedrovirus are excellent for species- specific, narrow spectrum insecticidal applications.
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 20 mg/L, 8 mg/L and 400 mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water isrelatively clean?
Ans. Sample C is most polluted (Highest BOD).
Sample A - River water
Sample B - Secondary effluent (Least BOD)
Sample C - Untreated sewage (Highest BOD)
Find out the name of the microbes from which cyclosporin A (an immuno suppressive drug) and statins (blood cholesterol lowering agents) are obtained.
Ans.
(a) Cyclosporin A is obtained from Trichoderma polysporum.
(b) Statins are obtained from the yeast Monascus purpureus.
Find out the role of microbes in the following and discuss it with your teacher.
(a) Single cell protein (SCP)
(b) Soil
Ans.
(a) Single cell protein (SCP): It is a protein-rich microbial biomass which can be used as food. Microbes are being grown on an industrial scale as source of good protein.
e.g.,
(i) Blue-green algae like Spirulina
(ii) Methylophilus methylotrophus bacteria
(iii) Mushrooms
(b) Soil : Soil is the habitat of numerous microbes. Microbes in the soil increase the fertility of soil by decomposing organic matter. Some microbes convert nitrates into free nitrogen that escapes into atmosphere for replenishment.
Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. [IMP.]
Penicillin, Biogas, Curd and Citric acid.
Ans.
(1) Penicillin :- It is an antibiotic used in curing numerous bacterial diseases.
(2) Biogas :- It is a source of energy in rural areas, produced by anaerobic degradation of organic matter
(3) Curd :- It is vitamin-rich milk preparation which is easily digested.
(4) Citric acid :- It is an organic acid used as preservative in juices, jams and jellies, etc .
How do biofertilizers enrich the fertility of the soil? [IMP.]
Ans. Biofertilizers are microorganisms which bring about nutrient enrichment of soil by enhancing the availability of nutrients to crops. They are of following types:
(a) Nitrogen fixing bacteria and cyanobacteria- They form symbiotic association with plants. They get food and shelter from plants and on the other hand,plants get nitrogen fixed by these bacteria. For example Rhizobium and Anabena.
(b) Mycorrhiza: It is an association between a fungus and roots of higher plants. It takes part in the solubilisation and absorption of nutrients from organic matter. Many members of the genus Glomus form mycorrhiza.
(c) Manures: They are semi-decayed organic remains of various types-manure, green manure compost and vermicompost.
3.0NCERT Solutions for Class 12 Biology | Other Chapter-wise Links
Access chapter-wise NCERT Solutions for Class 12 Biology with detailed answers, clear explanations, and solutions to all textbook questions through the links below.
4.0Key Features and Benefits of Class 12 Biology Chapter 8 Microbes in Human Welfare
Real-World Applications: Understand how microorganisms are used in food production, medicine, agriculture, sewage treatment, and other areas of daily life.
Industrial and Medical Uses: Learn about the role of microbes in producing antibiotics, organic acids, enzymes, fermented products, and other useful substances.
Environmental Applications: Understand how microorganisms help in sewage treatment, waste management, biogas production, and maintaining environmental balance.
NCERT-Based Practice: Practise questions based on important microbial processes, products, examples, and applications covered in the NCERT textbook.
Easy Revision: Revise important microorganisms, products, processes, and their uses to improve recall and strengthen understanding.
Useful for NEET Preparation: Build a strong foundation in microbiology and biotechnology concepts that are important for NEET and higher studies in related fields.
Table of Contents
1.0Key Concepts of Class 12 Biology Chapter 8 Microbes in Human Welfare
2.0NCERT Class 12 Biology Chapter 8 Microbes in Human Welfare : Detailed Solutions
3.0NCERT Solutions for Class 12 Biology | Other Chapter-wise Links
4.0Key Features and Benefits of Class 12 Biology Chapter 8 Microbes in Human Welfare