Microorganisms: Friend and Foe Part 2: MCQs (Q26–Q50)
🦠 Microorganisms: Friend and Foe – MCQs for Class 8 Science
Part 2: Q26 – Q50
Q26. Which disease is caused by Salmonella typhi?
A) Typhoid
B) Tuberculosis
C) Cholera
D) Influenza
✅ Correct Answer: A) Typhoid
Explanation:
- A) Typhoid – ✔ Bacterial infection caused by Salmonella typhi.
- B) Tuberculosis – Caused by Mycobacterium tuberculosis.
- C) Cholera – Caused by Vibrio cholerae.
- D) Influenza – Caused by influenza virus.
Q27. Which of the following is a fungal disease in humans?
A) Ringworm
B) Malaria
C) Typhoid
D) Polio
✅ Correct Answer: A) Ringworm
Explanation:
- A) Ringworm – ✔ Caused by fungi.
- B) Malaria – Protozoa (Plasmodium).
- C) Typhoid – Bacteria.
- D) Polio – Virus.
Q28. Which microorganism is used to prepare antibiotics like streptomycin?
A) Virus
B) Algae
C) Bacteria
D) Protozoa
✅ Correct Answer: C) Bacteria
Explanation:
- A) Virus – Not used in antibiotics.
- B) Algae – Used for food/oxygen, not antibiotics.
- C) Bacteria – ✔ Certain bacteria produce antibiotics like streptomycin.
- D) Protozoa – Not antibiotic producers.
Q29. Which microorganism is used in the production of citric acid?
A) Aspergillus
B) Rhizobium
C) Yeast
D) Lactobacillus
✅ Correct Answer: A) Aspergillus
Explanation:
- A) Aspergillus – ✔ A fungus used in citric acid production.
- B) Rhizobium – Nitrogen-fixing bacteria.
- C) Yeast – Used in alcohol/bread.
- D) Lactobacillus – Converts milk into curd.
Q30. Which microorganism is used to produce alcohol from sugar?
A) Penicillium
B) Yeast
C) Rhizobium
D) Amoeba
✅ Correct Answer: B) Yeast
Explanation:
- A) Penicillium – Produces antibiotics.
- B) Yeast – ✔ Ferments sugar → alcohol + CO₂.
- C) Rhizobium – Nitrogen fixation.
- D) Amoeba – Protozoa, no fermentation role.
Q31. Which disease is caused by virus?
A) Cholera
B) Smallpox
C) Typhoid
D) Tuberculosis
✅ Correct Answer: B) Smallpox
Explanation:
- A) Cholera – Bacterial.
- B) Smallpox – ✔ Viral disease (eradicated by vaccination).
- C) Typhoid – Bacterial.
- D) Tuberculosis – Bacterial.
Q32. Which microorganism causes common cold?
A) Bacteria
B) Virus
C) Fungi
D) Protozoa
✅ Correct Answer: B) Virus
Explanation:
- A) Bacteria – Wrong.
- B) Virus – ✔ Rhinovirus causes common cold.
- C) Fungi – Wrong.
- D) Protozoa – Wrong.
Q33. Which of the following is an example of algae?
A) Spirogyra
B) Amoeba
C) Yeast
D) Lactobacillus
✅ Correct Answer: A) Spirogyra
Explanation:
- A) Spirogyra – ✔ Filamentous green algae.
- B) Amoeba – Protozoa.
- C) Yeast – Fungus.
- D) Lactobacillus – Bacterium.
Q34. Which protozoan causes dysentery?
A) Plasmodium
B) Amoeba
C) Paramecium
D) Rhizobium
✅ Correct Answer: B) Amoeba
Explanation:
- A) Plasmodium – Malaria.
- B) Amoeba – ✔ Entamoeba histolytica causes amoebic dysentery.
- C) Paramecium – Free-living protozoa.
- D) Rhizobium – Nitrogen fixation.
Q35. The edible mushroom is an example of:
A) Virus
B) Fungi
C) Bacteria
D) Protozoa
✅ Correct Answer: B) Fungi
Explanation:
- A) Virus – Not edible.
- B) Fungi – ✔ Mushrooms are fungi (some edible).
- C) Bacteria – Not correct.
- D) Protozoa – Not edible.
Q36. The microorganism used in making vinegar is:
A) Yeast
B) Acetobacter
C) Rhizobium
D) Penicillium
✅ Correct Answer: B) Acetobacter
Explanation:
- A) Yeast – Alcohol fermentation.
- B) Acetobacter – ✔ Converts alcohol → acetic acid (vinegar).
- C) Rhizobium – Nitrogen fixation.
- D) Penicillium – Antibiotics.
Q37. Which disease is caused by protozoa?
A) Polio
B) Dengue
C) Malaria
D) Cholera
✅ Correct Answer: C) Malaria
Explanation:
- A) Polio – Virus.
- B) Dengue – Virus.
- C) Malaria – ✔ Protozoa (Plasmodium).
- D) Cholera – Bacteria.
Q38. The microorganism that fixes nitrogen in soil is:
A) Rhizobium
B) Yeast
C) Amoeba
D) Penicillium
✅ Correct Answer: A) Rhizobium
Explanation:
- A) Rhizobium – ✔ Nitrogen-fixing bacteria in legumes.
- B) Yeast – Fermentation.
- C) Amoeba – Protozoa.
- D) Penicillium – Antibiotic.
Q39. Which method is used to preserve milk at home?
A) Pickling
B) Refrigeration
C) Salting
D) Canning
✅ Correct Answer: B) Refrigeration
Explanation:
- A) Pickling – Not for milk.
- B) Refrigeration – ✔ Prevents microbial growth in milk.
- C) Salting – For fish/meat.
- D) Canning – Industrial preservation.
Q40. Which disease is caused by Vibrio cholerae?
A) Typhoid
B) Cholera
C) TB
D) Smallpox
✅ Correct Answer: B) Cholera
Explanation:
- A) Typhoid – Salmonella.
- B) Cholera – ✔ Bacterial disease by Vibrio cholerae.
- C) TB – Mycobacterium.
- D) Smallpox – Virus.
Q41. Which microorganism is used in production of antibiotics like tetracycline?
A) Streptomyces
B) Yeast
C) Amoeba
D) Spirogyra
✅ Correct Answer: A) Streptomyces
Explanation:
- A) Streptomyces – ✔ Bacterium producing tetracycline.
- B) Yeast – Fermentation.
- C) Amoeba – Protozoa.
- D) Spirogyra – Algae.
Q42. Which microorganism produces insulin through biotechnology?
A) Yeast
B) Rhizobium
C) Bacteria (E. coli)
D) Amoeba
✅ Correct Answer: C) Bacteria (E. coli)
Explanation:
- A) Yeast – Alcohol, not insulin.
- B) Rhizobium – Nitrogen fixation.
- C) Bacteria (E. coli) – ✔ Engineered to produce insulin.
- D) Amoeba – Not used in biotechnology.
Q43. Which disease is spread by Aedes mosquito?
A) Cholera
B) Dengue
C) Malaria
D) Tuberculosis
✅ Correct Answer: B) Dengue
Explanation:
- A) Cholera – Water-borne.
- B) Dengue – ✔ Spread by Aedes aegypti mosquito.
- C) Malaria – Spread by Anopheles mosquito.
- D) Tuberculosis – Air-borne.
Q44. Which of the following is NOT a food preservation method?
A) Pasteurization
B) Salting
C) Fermentation
D) Infection
✅ Correct Answer: D) Infection
Explanation:
- A) Pasteurization – Preservation.
- B) Salting – Preservation.
- C) Fermentation – Preservation.
- D) Infection – ✔ Spoils food, not preservation.
Q45. Which microorganism is used in nitrogen fixation other than bacteria?
A) Blue-green algae
B) Amoeba
C) Yeast
D) Paramecium
✅ Correct Answer: A) Blue-green algae
Explanation:
- A) BGA – ✔ Fix nitrogen in soil.
- B) Amoeba – Protozoa.
- C) Yeast – Fermentation.
- D) Paramecium – Protozoa.
Q46. Which disease is caused by virus?
A) Polio
B) Typhoid
C) Tuberculosis
D) Ringworm
✅ Correct Answer: A) Polio
Explanation:
- A) Polio – ✔ Viral disease.
- B) Typhoid – Bacterial.
- C) Tuberculosis – Bacterial.
- D) Ringworm – Fungal.
Q47. Which microorganism spoils bread by growing on it?
A) Rhizobium
B) Yeast
C) Moulds
D) Algae
✅ Correct Answer: C) Moulds
Explanation:
- A) Rhizobium – Nitrogen fixer.
- B) Yeast – Fermentation.
- C) Moulds – ✔ Fungal growth on bread.
- D) Algae – Grow in water.
Q48. Which disease is caused by HIV?
A) Malaria
B) AIDS
C) Dengue
D) Cholera
✅ Correct Answer: B) AIDS
Explanation:
- A) Malaria – Protozoa.
- B) AIDS – ✔ Caused by HIV virus.
- C) Dengue – Virus but not HIV.
- D) Cholera – Bacteria.
Q49. Which of these is NOT an industrial product of microorganisms?
A) Antibiotics
B) Alcohol
C) Cotton
D) Citric acid
✅ Correct Answer: C) Cotton
Explanation:
- A) Antibiotics – Made by microbes.
- B) Alcohol – Made by yeast.
- C) Cotton – ✔ Plant product, not microbial.
- D) Citric acid – Made by fungi.
Q50. Which scientist discovered penicillin?
A) Pasteur
B) Leeuwenhoek
C) Fleming
D) Koch
✅ Correct Answer: C) Fleming
Explanation:
- A) Pasteur – Pasteurization.
- B) Leeuwenhoek – First observed microbes.
- C) Fleming – ✔ Discovered penicillin (1928).
- D) Koch – Discovered anthrax bacteria.
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