Microorganisms Friend and Foe — Class 8 Science NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 8 Science chapter "Microorganisms Friend and Foe" — 8 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 8 Science chapter "Microorganisms Friend and Foe" — 8 important questions with detailed answers for CBSE b…

By Syllab.in · Updated Jun 14, 2026

Key Questions Covered:

What are microorganisms?
Define bacterium and mention its shape.
Name five beneficial uses of microorganisms.
What are diseases caused by harmful bacteria? Give two examples.
What are viruses? Name three viral diseases in humans.
Explain fermentation. Name two products made by fermentation.
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
What are microorganisms?	✓ Solved
Define bacterium and mention its shape.	✓ Solved
Name five beneficial uses of microorganisms.	✓ Solved
What are diseases caused by harmful bacteria? Give two ex…	✓ Solved
What are viruses? Name three viral diseases in humans.	✓ Solved
Explain fermentation. Name two products made by fermentat…	✓ Solved

Showing 6 of 8 questions

Q1: What are microorganisms?

Microorganisms are living organisms too small to be seen with naked eye, visible only under a microscope. They include bacteria, viruses, fungi, algae, and protozoa.

Q2: Define bacterium and mention its shape.

Bacteria are single-celled, prokaryotic microorganisms lacking a membrane-bound nucleus. Shapes: cocci (spherical), bacilli (rod-shaped), spirilla (spiral-shaped), and vibrio (comma-shaped).

Q3: Name five beneficial uses of microorganisms.

1) Yogurt and cheese production (lactic acid bacteria), 2) Bread and beer fermentation (yeast), 3) Vaccine production, 4) Antibiotic synthesis (penicillin from mold), 5) Decomposition of dead matter and nutrient cycling in ecosystems.

Q4: What are diseases caused by harmful bacteria? Give two examples.

Bacterial diseases: tuberculosis (Mycobacterium tuberculosis), typhoid (Salmonella), cholera (Vibrio cholerae), pneumonia, food poisoning. Examples: tuberculosis damages lungs; typhoid causes intestinal fever.

Q5: What are viruses? Name three viral diseases in humans.

Viruses are non-cellular obligate parasites containing nucleic acid (DNA/RNA) surrounded by protein coat. Cannot reproduce independently; require host cells. Three viral diseases: measles, mumps, influenza (flu).

Q6: Explain fermentation. Name two products made by fermentation.

Fermentation is anaerobic respiration carried out by microorganisms converting sugars into alcohol or acid without using oxygen. Products: wine (yeast fermentation of grapes), vinegar (acetic acid fermentation), yogurt (lactic acid fermentation).

Showing 6 of 8 questions. Visit the full page for complete solutions.