Class 12 Biology - ISC
Microbes in Human Welfare
Microbes in Human Welfare explores the beneficial roles of microorganisms in everyday life, industry, agriculture, and medicine. For Class 12 ISC board exams, this chapter is high-yield, focusing on specific scientific names of microbes, their commercial products like antibiotics, enzymes, and organic acids, and their applications in sewage treatment and biofertilisers. Students must memorize key binomial nomenclature and specific metabolic processes, as questions frequently test direct factual recall, scientific naming, and matching-type applications in both objective and descriptive sections.
Start Learning FreeKey Concepts
Microbes in Household Products
Lactobacillus converts milk to curd by producing lactic acid, while Saccharomyces cerevisiae (brewer's yeast) is used for fermenting dough to make bread and idli.
Industrial Production and Fermentors
Microbes are grown on a large scale in vessels called fermentors to produce beverages, antibiotics like penicillin from Penicillium notatum, and bioactive molecules like cyclosporin A and statins.
Sewage Treatment Plants (STPs)
Primary treatment involves physical removal of particles, while secondary treatment relies on aerobic and anaerobic microbes to break down organic matter, significantly reducing the Biological Oxygen Demand (BOD).
Microbes as Biocontrol Agents
Natural methods of pest and disease control include using bacteria like Bacillus thuringiensis to control butterfly caterpillars and fungi like Trichoderma against plant pathogens.
Microbes as Biofertilisers
Organisms such as Rhizobium, Azospirillum, and Mycorrhiza enrich the nutrient quality of the soil by fixing atmospheric nitrogen and forming symbiotic associations with plant roots.
Important Formulas
Board Exam Info
In the ISC Class 12 Biology examination, this chapter typically carries around 3 to 5 marks. Questions generally appear as direct theoretical questions, identification of specific microbes and their commercial products, expansion of acronyms like BOD, or distinguishing between primary and secondary sewage treatment.
Frequently Asked Questions
Why is BOD important in sewage treatment?
BOD measures the amount of organic matter in water; higher BOD indicates higher pollution potential, and secondary treatment aims to lower this BOD before releasing water into natural bodies.
Do we need to memorize the exact scientific names of microbes?
Yes, ISC board exams strictly require correct binomial nomenclature (Genus and species) for microbes, and spelling errors can lead to loss of marks.
What is the difference between a biofertiliser and chemical fertilizer?
Biofertilisers are living organisms that enrich soil nutrients naturally through nitrogen fixation and solubilisation without causing chemical pollution, unlike synthetic fertilizers.
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