Class 12 Biology - WEST-BENGAL
Microbes in Human Welfare
Microbes in Human Welfare for Class 12 West Bengal Council of Higher Secondary Education (WBCHSE) explores the beneficial aspects of microorganisms in daily life and industry. Students learn about microbes in household products like curd and bread, industrial production of antibiotics and beverages, sewage treatment plants, biogas production, and as biocontrol agents and biofertilizers. This chapter holds significant weightage in board exams for both objective and descriptive questions, testing conceptual clarity on eco-friendly biological applications.
Start Learning FreeKey Concepts
Microbes in Household Products
Lactic acid bacteria (LAB) like Lactobacillus convert milk to curd, improving its nutritional quality by increasing vitamin B12, while baker's yeast (Saccharomyces cerevisiae) is used to ferment dough for breads and idlis.
Microbes in Industrial Products
Microorganisms are grown in large vessels called fermentors to produce valuable products such as beverages (wine and beer via yeast fermentation) and life-saving antibiotics like penicillin from Penicillium notatum.
Microbes in Sewage Treatment
Primary treatment involves physical removal of particles, while secondary (biological) treatment uses aerobic and anaerobic microbes to digest organic matter, significantly reducing the Biochemical Oxygen Demand (BOD) of wastewater.
Microbes as Biocontrol Agents
Biological control refers to the use of natural methods to control plant pests and diseases, such as using Bacillus thuringiensis bacteria to protect crops from caterpillar pests without chemical pesticides.
Microbes as Biofertilizers
Organisms that enrich the nutrient quality of the soil include Rhizobium in legume root nodules for nitrogen fixation, Azospirillum, and Mycorrhiza fungi that absorb phosphorus from soil.
Important Formulas
Board Exam Info
In the WBCHSE Class 12 Biology examination, this chapter typically carries around 3 to 5 marks. Questions commonly include short answer questions (SAQ) about specific microbe names and their products, multiple-choice questions (MCQ), and 3-mark descriptive questions on sewage treatment or biogas production.
Frequently Asked Questions
What is BOD and why is it important in sewage treatment?
BOD stands for Biochemical Oxygen Demand. It represents the amount of oxygen required by bacteria to oxidize organic matter in a given water sample. Higher BOD indicates higher organic pollution.
Name the bacterium used in the production of curd from milk.
Lactic Acid Bacteria (LAB), such as Lactobacillus, are used to convert milk into curd.
What are biofertilizers and name one example?
Biofertilizers are organisms that enrich soil nutrient quality through biological processes. An example is Rhizobium, which fixes atmospheric nitrogen in the root nodules of leguminous plants.
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