Class 12 Biology Chapter 10 Notes: Microbes In Human Welfare
Class 12 Biology Chapter 10 Notes define Biology as the study of life, from single-celled to complex organisms. It includes the study of genes and DNA that give organisms their unique characteristics.
Microbes are one of the most essential components for life on earth. Some microbes are pathogenic and some are beneficial. In Class 12 Biology Chapter 10, ‘Microbes In Human Welfare’, students will see the benefits of microbes in various processes like changing milk to curd, fermentation of idli and Dosa, and imparting flavour to the cheese, as well as medicinal purposes. Microbes exist everywhere, even in deep layers of the earth or in geysers where temperatures can be as high as 100 degrees Celsius or under the layers of the snow. Microbes include protozoa, bacteria, fungi and microscopic viruses. To study microorganisms, they can be grown in a nutrition-rich environment to form colonies that are visible to naked eyes.
In Class 12 Biology Chapter 10 Notes, students will learn how microbes are used to treat sewage by activated sludge formation and how methanogens produce Biogas while degrading plant waste. Biology Chapter 10 Class 12 Notes also shed light on the use of microbes to kill harmful pests and how microbes play an essential role in the welfare of human society.
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Key topics covered in Class 12 Biology Chapter 10 Notes:
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Given below are a few of the key elements covered in our Class 12 Biology Chapter 10 Notes:
- Microbes in Household Products.
- Microbes in Industrial Products.
- Microbes in Sewage Treatment.
- Microbes in Production of Biogas.
- Microbes as Biocontrol Agents.
- Microbes as Biofertilizers.
Microbes in Household Products:
- Lactic acid bacteria(LAB) such as lactobacillus convert milk into curd. LAB produces acids that coagulate and digest the milk proteins. On adding a small amount of curd to fresh milk, millions of LAB multiply at a suitable temperature, converting milk to curd. This also enhances the nutritional quality by increasing vitamin B12.
- Moreover, LAB is essential in eliminating disease-causing microbes in our stomach.
- Microbes are used in the fermentation of the dough. The carbon dioxide gas produced gives a spongy and puffy appearance. The dough used for dosa and idli is also prepared from fermentation by bacteria.
- Todi is a traditional drink found in some parts of Southern India among several drinks fermented by bacteria. It is prepared from the fermentation of palm sap.
- Microbes are also used in the fermentation of fish, soybean and bamboo shoots.
- The application of microbes achieves different varieties of cheese with various characteristics and textures. The large holes in Swiss cheese are due to carbon dioxide production by a bacterium named Propionibacterium shamanic.
More examples of how microbes are used in preparation of household products are given in our Class 12 Biology Chapter 10 Notes.
Microbes In Industrial Products:
Class 12 Biology Chapter 10 Notes explains the importance of Microbes, as they synthesise various products that are significant for human use. For example, beverages and antibiotics. In Industries, microbes are grown in large vessels called fermentors to increase production.
Fermented Beverages:
Microorganisms produce wine, beer, whisky, brandy or rum, for example, yeast. Saccharomyces cerevisiae, also known as brewers yeast, is used to ferment malted cereals and fruit juices. Depending on the type of processes and raw material used, different alcoholic drinks are obtained. For instance, beer and wine are produced without distillation, while whisky, brandy and rum are produced by distillation of the fermented broth.
Antibiotics:
- ‘Anti’ means’ Against’, and ‘Bio’ means life. Together antibiotics represent life. But in the human context, they are known as pro-life. Why? Antibiotics are chemical substances produced by microbes that kill other microbes or retard their growth and protect us from disease.
- Alexander Fleming discovered the first antibiotic called Penicillin while working on Staphylococci bacteria. Furthermore, Ernest Chain and Howard Florey harnessed Penicillin as an effective antibiotic during World war II to treat American soldiers. They were awarded the Nobel prize in 1945.
The study of usage of microbes in antibiotics is very important for students to understand. They can register on Extramarks’ website and get access to our Class 12 Biology Chapter 10 Notes.
Chemical Enzymes and other Bioactive Molecules:
Microbes are an excellent boon for commercial and industrial purposes. They produce chemicals like alcohol, enzymes and organic acids. Few of the applications of microbes as discussed in our Class 12 Biology Chapter 10 Notes are given in the table below:
| Microbe |
Name |
Product |
| Fungi |
Aspergillus niger |
Citric acid |
| Bacterium |
Acetobacter aceti |
Acetic acid |
| Bacterium |
Clostridium butylicum |
Butyric acid |
| Bacterium |
Lactobacillus |
Lactic acid |
| Yeast |
Saccharomyces cerevisiae |
Ethanol |
- The enzymes produced by bacteria, such as lipases, are used in detergent formulations and help remove oil stains from the laundry.
- The fruit juice producers use pectinases and proteases to soften fruits, facilitate the process of extraction which will increase the juice yield and also clarify the bottled juice.
- Streptokinase is used as a clot-buster for removing clots from blood vessels of patients who had myocardial infarction leading to heart attack.
- Cyclosporin A, produced by the fungus Trichoderma polypore, is an immunosuppressive agent in organ transplant patients.
- Statins produced by yeast Monascus purpureus are used as a blood cholesterol-lowering agent.
Microbes in Sewage Treatment:
Large amounts of wastewater are generated every day in towns and cities. Since this water is mainly rich in human excreta, it is also known as sewage. Sewage contains a large amount of organic matter and pathogenic microbes; thus, the water cannot be directly discharged into natural water bodies. Before disposal, they have to go through the sewage treatment plants to make them less polluting.
Heterotrophic microbes are present naturally in the sewage for the treatment of wastewater. The treatment is carried out in two stages: primary treatment and secondary treatment.
Primary treatment:
Following measures are to be taken for the primary sewage treatment:
- This process involves physically removing large and small debris through filtration or sedimentation.
- Floating debris is removed by sequential filtration, while small pebbles and grids are separated by sedimentation.
- All solids that settle become the primary sludge and the supernatant is called the effluent.
- The effluent from the Primary Setting Tank then goes for secondary treatment.
Secondary treatment:
- This process is also known as biological treatment.
- The effluent is passed through large aeration tanks where the air is pumped into it and is constantly agitated.
- This aids the growth of aerobic microbes into flocs.
- The microbes consume most of the organic matter in the effluent and reduce the BOD (Biochemical Oxygen Demand).
- Biochemical Oxygen Demand is the number of oxygen bacteria consume when it oxidizes all organic matter in 1 litre of water.
- In simple words, BOD is a measure of organic matter present in the water. The water is said to have a High polluting potential if BOD is more incredible in wastewater.
- The effluent is passed on into a settling tank once the BOD of sewage is reduced. The bacterial flocs called activated sludge are allowed to sediment.
- A little part of the activated sludge is pumped back and serves as an inoculum aeration tank.
- Anaerobic sludge digesters receive a significant part of the sludge where various kinds of bacteria grow anaerobically to digest the bacteria and fungi in the sledge. In this process, the bacteria produce a mixture of methane, hydrogen sulphide and carbon dioxide. These gases together form the Biogas. Biogas, being inflammable, is used as a source of energy.
- Due to large quantities of sewage water and limited sewage treatment plants, untreated sewage is often discharged into rivers leading to pollution and water-borne diseases.
- The Ministry of Environment and Forest has launched the Ganga Action Plan and Yamuna Action Plan to save these rivers from pollution.
Both primary and secondary treatment processes are further given in detail in our Class 12 Biology Chapter 10 Notes. Students can refer to our study resources to learn more about all subjects and prepare well for their final examinations.
Microbes in Production of Biogas:
- Certain bacteria grow anaerobically on cellulose material and produce a large amount of methane, carbon dioxide, and hydrogen. These bacteria are called methanogens.
- Methanobacterium is a common bacteria found in anaerobic sludge during sewage treatment. They are also found in the rumen of cattle to help break down cellulose.
- The dung of cattle, commonly called Gobar, is rich in these bacteria. The dung is commonly used to generate Biogas, also called gobar gas.
The structure of the biogas plant is explained at full-length in our Class 12 Biology Chapter 10 Notes. We have given a brief description of the same below:
- The Biogas is a concrete tank of 10 to 15 feet in depth.
- The bio-wastes are collected, and a dung slurry is fed into the plant.
- A floating cover over the slurry rises when gas is produced during microbial activity.
- The biogas plant consists of an outlet. The outlet is connected to a pipe to supply Biogas to nearby houses.
- Through another outlet, the remaining slurry is removed and used as fertiliser.
Cattle dung is available in rural areas and is used for various purposes. The Biogas produced is used for household purposes such as cooking and lighting. The Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC) put effort into developing Biogas technologies in India.
Microbes as Biocontrol Agents:
The application of biological methods to control plant diseases and pests is termed as Biocontrol. The increased use of insecticides and pesticides is toxic and highly harmful to animals, humans, and the environment.
Biological Control of Pests and Diseases:
In agriculture, farmers use biocontrol methods to control pests rather than chemicals. A farmer’s goal in organic farming is to design a system where the pest is not eradicated, which helps balance the ecosystem. This way, a holistic approach is introduced to the myriad of organisms that constitute flora and fauna. The use of chemicals often kills both valuable and harmful life forms.
Examples of Biocontrol Agents:
- The ladybird and dragonflies assist the farmers in getting rid of aphids and mosquitoes, respectively.
- Bacteria Bacillus thuringiensis (Bt) control the growth of butterfly caterpillars. They release toxins that kill the larvae once they eat them.
- Fungus Trichoderma is used to treat plant disease and protects against plant pathogens.
- Baculoviruses are pathogens that attack insects. The genus Nucleopolyhedrovirus is the majority of baculoviruses used in biological control. These viruses are excellent suitors for species-specific, narrow spectrum insecticidal applications. They have no adverse effect on plants, animals, birds, fish and other insects. Beneficial insects are conserved to assist in an integrated pest management program(IPM).
Microbes as Biofertilisers:
With the increase in the demand for agriculture, overuse of chemical fertilisers has led to the rise in pollution. Hence, there is a need for biofertilizers.
- Biofertilizers are organisms that improve the nutrient quality of the soil. Bacteria, fungi and cyanobacteria are the primary sources of biofertilizers.
- The bacteria in nodules on the roots of leguminous plants fix atmospheric nitrogen into organic forms, which the plant uses as a nutrient.
- Fungi also form symbiotic associations with plants (mycorrhiza). The fungal symbionts absorb phosphorus from soil and offer it to the plant.
- Cyanobacteria are autotrophic microbes. They are widely distributed in aquatic and terrestrial environments and can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, etc.
- Cyanobacteria serve as an essential biofertilizer in paddy fields.
- Blue-green algae also increases fertility.
- Farmers use bio-fertilizers in their fields to enrich soil nutrients.
The chapter covers a variety of usage of microbes in both household and industrial settings. Our expert team of Biology academicians have prepared study notes and other study materials for helping students gain a better understanding and familiarity with the Biology chapters. Students can refer to our Class 12 Biology Chapter 10 Notes to study the chapter Microbes for Human Welfare in detail.
Class 12 Biology Chapter 10 Notes: Exercise & Answer
Class 12 students can visit the Extramarks’ website for the best study materials. Class 12 Biology Chapter 10 Notes – Exercises & Answer covers all the critical concepts in ‘Microbes of Human Welfare’. Professors appointed by the Extramarks use a comprehensive approach to provide easy-to-understand solutions that help students in their examination preparation. Students should register on the Extramarks website to access Exercise and Answer for Biology Chapter 10 based on NCERT Books.
Students can click on the links below to access the solutions for various exercises they will need to prepare for the examination.
Chapter 10: Exercise 10.1 Solutions
Chapter 10: Exercise 10.2 Solutions
Chapter 10: Exercise 10.3 Solutions
Chapter 10: Exercise 10.4 Solutions
Chapter 10: Exercise 10.5 Solutions
Chapter 10: Exercise 10.6 Solutions
Chapter 10: Exercise 10.7 Solutions
Chapter 10: Exercise 10.8 Solutions
Chapter 10: Exercise 10.9 Solutions
Chapter 10: Exercise 10.10 Solutions
Chapter 10: Exercise 10.11 Solutions
Chapter 10: Exercise 10.12 Solutions
Chapter 10: Exercise 10.13 Solutions
Chapter 10: Exercise 10.14 Solutions
Chapter 10: Exercise 10.15 Solutions
Chapter 10: Exercise 10.16 Solutions
NCERT Exemplar Class 12 Biology
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Key features of Class 12 Biology Chapter 10 Notes
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- It is based on NCERT books and covers the entire CBSE Syllabus.
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- Team of academicians with decades of experience in Biology has prepared Class 12 Biology Chapter 10 Notes and other study resources.