Microbes play a crucial role in human welfare. They are used in various industrial processes, agriculture, food production, sewage treatment, and even in antibiotics. Understanding the beneficial aspects of microorganisms helps us realize their importance in maintaining ecological balance and improving human life.
In this article, we present 50 important objective questions from “Microbes in Human Welfare Objective Question” (Class 12 Biology, Bihar Board) — with options and one-word answers to help you prepare effectively for your exams.
Bihar Board Class 12th Biology – Microbes in Human Welfare Objective Questions & Answers (50 MCQs)
1. Which microbe is used in the production of curd?
a) Rhizobium
b) Lactobacillus
c) Azotobacter
d) Penicillium
Answer: Lactobacillus
2. Penicillin was discovered by —
a) Alexander Fleming
b) Louis Pasteur
c) Robert Koch
d) Edward Jenner
Answer: Alexander Fleming
3. The source organism for penicillin is —
a) Aspergillus
b) Penicillium notatum
c) Rhizopus
d) Yeast
Answer: Penicillium notatum
4. Which bacteria is used in nitrogen fixation in leguminous plants?
a) Azospirillum
b) Rhizobium
c) Clostridium
d) Nitrobacter
Answer: Rhizobium
5. Methanogens produce —
a) Carbon dioxide
b) Methane
c) Nitrogen
d) Oxygen
Answer: Methane
6. Yeast is used in the production of —
a) Bread
b) Cheese
c) Curd
d) Butter
Answer: Bread
7. The scientific name of Baker’s yeast is —
a) Saccharomyces cerevisiae
b) Lactobacillus bulgaricus
c) Penicillium chrysogenum
d) Rhizopus stolonifer
Answer: Saccharomyces cerevisiae
8. Antibiotics are produced by —
a) Fungi and bacteria
b) Viruses
c) Protozoa
d) Algae
Answer: Fungi and bacteria
9. Biofertilizers increase —
a) Soil acidity
b) Soil fertility
c) Water content
d) Soil salinity
Answer: Soil fertility
10. BOD stands for —
a) Biological Oxygen Demand
b) Biochemical Oxygen Demand
c) Basic Oxygen Density
d) Biological Organic Density
Answer: Biochemical Oxygen Demand
11. Methanogens are found in —
a) Paddy fields
b) Cow dung
c) Sewage
d) All of these
Answer: All of these
12. Antibiotic from Streptomyces is —
a) Penicillin
b) Streptomycin
c) Tetracycline
d) Both b and c
Answer: Both b and c
13. Cheese is produced by the activity of —
a) Bacteria
b) Fungi
c) Yeast
d) Virus
Answer: Bacteria
14. Which microbe is used in alcohol production?
a) Lactobacillus
b) Yeast
c) Rhizobium
d) Azospirillum
Answer: Yeast
15. The first antibiotic discovered was —
a) Streptomycin
b) Tetracycline
c) Penicillin
d) Chloramphenicol
Answer: Penicillin
16. Microbes used in sewage treatment are —
a) Pathogens
b) Useful bacteria
c) Viruses
d) Parasites
Answer: Useful bacteria
17. The biofertilizer for rice fields is —
a) Azolla and Anabaena
b) Rhizobium
c) Azotobacter
d) Clostridium
Answer: Azolla and Anabaena
18. Which microbe is used in the production of vinegar?
a) Acetobacter aceti
b) Saccharomyces
c) Lactobacillus
d) Penicillium
Answer: Acetobacter aceti
19. SCP stands for —
a) Single Cell Protein
b) Single Cell Process
c) Simple Cell Protein
d) Soluble Cell Product
Answer: Single Cell Protein
20. Spirulina is rich in —
a) Protein
b) Fat
c) Carbohydrate
d) Vitamin C
Answer: Protein
21. Microbes used in biogas production are called —
a) Methanogens
b) Nitrifiers
c) Denitrifiers
d) Decomposers
Answer: Methanogens
22. Citric acid is produced by —
a) Aspergillus niger
b) Rhizopus
c) Penicillium
d) Yeast
Answer: Aspergillus niger
23. Vinegar contains —
a) Lactic acid
b) Acetic acid
c) Citric acid
d) Hydrochloric acid
Answer: Acetic acid
24. Which microbe helps in sewage treatment?
a) Methanobacterium
b) Bacillus
c) Rhizobium
d) Lactobacillus
Answer: Methanobacterium
25. Which fungus produces citric acid?
a) Aspergillus niger
b) Rhizopus
c) Penicillium
d) Yeast
Answer: Aspergillus niger
26. Microbes in dairy industry convert milk into —
a) Alcohol
b) Curd
c) Sugar
d) Butter
Answer: Curd
27. Which of the following is a biofertilizer?
a) Rhizobium
b) Yeast
c) Virus
d) Penicillium
Answer: Rhizobium
28. The process of fermentation was discovered by —
a) Louis Pasteur
b) Robert Koch
c) Alexander Fleming
d) Edward Jenner
Answer: Louis Pasteur
29. Alcoholic fermentation produces —
a) Ethanol and CO₂
b) Methanol and O₂
c) Lactic acid
d) Acetic acid
Answer: Ethanol and CO₂
30. Which microorganism is used in the production of antibiotics?
a) Bacteria and fungi
b) Algae
c) Virus
d) Protozoa
Answer: Bacteria and fungi
31. Biogas mainly contains —
a) Carbon dioxide
b) Methane
c) Oxygen
d) Nitrogen
Answer: Methane
32. Citric acid is used in —
a) Soft drink industry
b) Dairy industry
c) Textile industry
d) All of these
Answer: All of these
33. Lactic acid bacteria convert milk sugar into —
a) Lactic acid
b) Alcohol
c) Glucose
d) Acetic acid
Answer: Lactic acid
34. Which organism produces acetic acid?
a) Acetobacter
b) Rhizopus
c) Aspergillus
d) Penicillium
Answer: Acetobacter
35. Which gas indicates active sewage treatment?
a) Methane
b) Hydrogen
c) Oxygen
d) Carbon dioxide
Answer: Methane
36. Antibiotics are used to —
a) Kill pathogens
b) Increase immunity
c) Supply vitamins
d) Produce enzymes
Answer: Kill pathogens
37. Microbes used in biofertilizer for non-legumes —
a) Azotobacter
b) Rhizobium
c) Anabaena
d) Nostoc
Answer: Azotobacter
38. Spirulina is an example of —
a) Cyanobacteria
b) Green algae
c) Protozoa
d) Fungi
Answer: Cyanobacteria
39. The main function of microbes in sewage treatment is —
a) Decomposition of organic matter
b) Water purification
c) Gas production
d) All of these
Answer: All of these
40. SCP is a rich source of —
a) Protein
b) Fat
c) Carbohydrate
d) Vitamin A
Answer: Protein
41. Which microbe is used in Swiss cheese production?
a) Propionibacterium shermanii
b) Rhizobium
c) Yeast
d) Lactobacillus
Answer: Propionibacterium shermanii
42. Ethanol is produced by —
a) Saccharomyces cerevisiae
b) Lactobacillus
c) Penicillium
d) Rhizobium
Answer: Saccharomyces cerevisiae
43. The main component of biogas is —
a) Methane
b) Carbon dioxide
c) Oxygen
d) Hydrogen
Answer: Methane
44. Which microbe is used in antibiotics production?
a) Streptomyces
b) Aspergillus
c) Rhizopus
d) Lactobacillus
Answer: Streptomyces
45. Rhizobium lives in —
a) Root nodules of legumes
b) Soil surface
c) Water
d) Leaf surface
Answer: Root nodules of legumes
46. Biogas plant sludge is rich in —
a) Nutrients
b) Oil
c) Metals
d) Acids
Answer: Nutrients
47. Microbes convert milk into curd by —
a) Fermentation
b) Digestion
c) Respiration
d) Photosynthesis
Answer: Fermentation
48. The full form of LAB is —
a) Lactic Acid Bacteria
b) Light Absorbing Bacteria
c) Large Aerobic Bacteria
d) Lignin Assimilating Bacteria
Answer: Lactic Acid Bacteria
49. Which microbe is used in antibiotic chloramphenicol production?
a) Streptomyces venezuelae
b) Penicillium notatum
c) Aspergillus niger
d) Rhizopus
Answer: Streptomyces venezuelae
50. Which microbe helps in biogas formation from dung?
a) Methanobacterium
b) Rhizobium
c) Azotobacter
d) Lactobacillus
Answer: Methanobacterium
Conclusion
Microbes are truly the unseen heroes of our environment and daily life. From producing curd, cheese, and alcohol to cleaning sewage and generating biogas, their contributions to human welfare are endless.
For Bihar Board Class 12th Biology students, understanding this chapter — Microbes in Human Welfare — is crucial, as it connects biology to real-life applications in health, industry, and agriculture.
By practicing these 50 objective questions with one-word answers, students can strengthen their concept clarity and score better in board examinations. Remember, microbes may be microscopic, but their benefits to humanity are massive!
FAQs –Microbes in Human Welfare Objective Questions
1. What is the main role of microbes in human welfare?
Microbes play a major role in human welfare by helping in food production, sewage treatment, biogas generation, antibiotics formation, and soil fertility improvement. They are essential for sustainable development and environmental balance.
2. Which microbe is used in curd formation?
Lactic acid bacteria, specifically Lactobacillus, are responsible for converting milk into curd by the process of fermentation.
3. What is the importance of methanogens in biogas production?
Methanogens like Methanobacterium help in breaking down organic waste to produce methane gas, which is the main component of biogas used as fuel.
4. Which microbe is used in the production of antibiotics?
Antibiotics are produced by certain fungi and bacteria such as Penicillium notatum (produces Penicillin) and Streptomyces species (produce Streptomycin and Tetracycline).
5. What are biofertilizers and why are they important?
Biofertilizers are living microorganisms like Rhizobium, Azotobacter, and Anabaena that improve soil fertility by fixing nitrogen and enhancing plant growth naturally without chemicals.
6. What is Single Cell Protein (SCP)?
Single Cell Protein refers to protein-rich biomass obtained from microorganisms such as Spirulina and Methylophilus methylotrophus. It is a cheap and nutritious food supplement.
7. How do microbes help in sewage treatment?
Microbes decompose organic matter in sewage, reducing the Biochemical Oxygen Demand (BOD) and purifying water before it is released into natural sources.
8. What is the industrial use of Aspergillus niger?
Aspergillus niger is widely used in the fermentation industry for the production of citric acid, which is used in soft drinks, food processing, and pharmaceuticals.
9. Which microbes are used in cheese production?
Microbes like Lactobacillus and Propionibacterium shermanii are used in cheese production to give flavor, aroma, and texture to different types of cheese such as Swiss cheese.
10. What are the main benefits of microbes in agriculture?
In agriculture, microbes improve soil fertility, enhance nutrient availability, promote plant growth, and reduce dependence on chemical fertilizers. Examples include Rhizobium and Azospirillum.
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