Every Book Back multiple-choice question from Microbes in Human Welfare (12th Standard Zoology, Samacheer Kalvi) — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Which of the following microorganism is used for production of citric acid in industries?
A. Lactobacillus bulgaris
B. Penicillium citrinum
C. Aspergillus nigerCorrect
D. Rhizopus nigricans
Explanation. Aspergillus niger is a fungus commonly utilized in industrial biotechnology for the mass production of citric acid. This organic acid is widely used in food, beverage, and pharmaceutical industries.
Q2
Which of the following pair is correctly matched for the product produced by them?
A. Acetobacter aceti - Antibiotics
B. Methanobacterium - Lactic acid
C. Penicilium notatum - Acetic acid
D. Saccharomyces cerevisiae - EthanolCorrect
Explanation. Saccharomyces cerevisiae, also known as brewer's yeast, is widely utilized to ferment sugars into ethanol and carbon dioxide. This process is essential for producing industrial alcohol and alcoholic beverages.
The most common substrate used in distilleries for the production of ethanol is_________
A. Soyameal
B. Groundgram
C. MolassesCorrect
D. Corn meal
Explanation. Molasses, a byproduct of sugar refining, contains high concentrations of sucrose and other fermentable sugars. This makes it the most economical and widely used raw material for industrial ethanol production.
Q4
Cyclosporin - A is an immunosuppressive drug produced from _______
A. Aspergillus niger
B. Manascus purpureus
C. Penicillium notatum
D. Trichoderma polysporumCorrect
Explanation. Cyclosporin-A is an important immunosuppressive agent that prevents organ transplant rejection. It is naturally synthesized as a metabolite of the fungus Trichoderma polysporum.
Q5
CO2 is not released during
A. Alcoholic fermentation
B. Lactate fermentationCorrect
C. Aerobic respiration in animals
D. Aerobic respiration in plants
Explanation. Lactate fermentation converts pyruvate into lactic acid without producing carbon dioxide. In contrast, alcoholic fermentation and aerobic respiration release carbon dioxide as a product.
The purpose of biological treatment of waste water is to _______
A. Reduce BODCorrect
B. Increase BOD
C. Reduce sedimentation
D. Increase sedimentation
Explanation. Biological sewage treatment uses aerobic microorganisms to decompose organic waste in wastewater. This active decomposition consumes dissolved organic matter, thereby significantly reducing the biological oxygen demand.
Q7
The gases produced in anaerobic sludge digesters are
A. Methane, oxygen and hydrogen sulphide.
B. Hydrogen sulphide, methane and sulphur dioxide.
C. Hydrogen sulphide, nitrogen and methane.
D. Methane, hydrogen sulphide and CO2.Correct
Explanation. During anaerobic digestion of sewage sludge, methanogenic bacteria break down organic matter in the absence of oxygen. This process releases a mixture of methane, carbon dioxide, and hydrogen sulphide gases.
These are the Book Back multiple-choice questions for Microbes in Human Welfare from the Tamil Nadu State Board (Samacheer Kalvi) 12th Standard Zoology syllabus. Each question shows the correct option and an original, step-by-step explanation so you understand the method, not just the answer. Use the answer key above to jump to any question, then take the practice test to check yourself under exam-like conditions.
Frequently asked questions
How many MCQs are there in Microbes in Human Welfare?
This chapter has 7 book-back multiple-choice questions, each with the correct answer and a step-by-step explanation.
Are these 12th Standard Zoology MCQs free to practise online?
Yes. Every question, answer and explanation here is free, and you can also take them as a timed practice test.
Where can I find the Microbes in Human Welfare book-back answers?
The correct option for each question is highlighted on this page with a worked explanation, plus a quick answer-key summary at the top.
