Microorganisms and Disease (Class 8 Science)

Learn about microscopic life forms, bacteria, viruses, and their role in disease and fermentation. Understand how disease spreads and prevention methods.

Microorganisms and Disease (Class 8 Science)

Learn about microscopic life forms, bacteria, viruses, and their role in disease and fermentation. Understand how disease spreads and prevention methods.

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TL;DR: Learn about microscopic life forms, bacteria, viruses, and their role in disease and fermentation. Understand how disease spreads and prevention metho…

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Learn about microscopic life forms, bacteria, viruses, and their role in disease and fermentation. Understand how disease spreads and prevention methods.

Microorganisms and Disease MCQs with Answers & Explanations

Q1. What are microorganisms?

  1. Large organisms
  2. Organisms visible only under a microscope ✓ (correct)
  3. Dead organisms
  4. Visible to naked eye

Explanation: Microorganisms are organisms so small they are visible only under a microscope. They include bacteria, viruses, fungi, and protozoans.

Q2. What are bacteria?

  1. Viruses
  2. Eukaryotic cells
  3. Prokaryotic cells without a nucleus ✓ (correct)
  4. Multicellular organisms

Explanation: Bacteria are prokaryotic microorganisms without a nucleus. They are single-celled and can be beneficial or harmful to humans.

Q3. What are viruses made of?

  1. Only protein
  2. DNA and cell wall
  3. Cell membrane only
  4. DNA or RNA surrounded by protein coat ✓ (correct)

Explanation: Viruses consist of genetic material (DNA or RNA) surrounded by a protein coat called a capsid. They cannot reproduce on their own.

Q4. How do viruses reproduce?

  1. By infecting host cells and using host machinery ✓ (correct)
  2. Viruses do not reproduce
  3. By photosynthesis
  4. By binary fission

Explanation: Viruses cannot reproduce independently. They must infect host cells and use the host cells machinery to replicate their genetic material.

Q5. What are fungi?

  1. Viruses
  2. Eukaryotic organisms that feed on dead organic matter ✓ (correct)
  3. Prokaryotes
  4. Bacteria

Explanation: Fungi are eukaryotic organisms including mushrooms, molds, and yeasts. They absorb nutrients by secreting enzymes on food and absorbing digested matter.

Q6. How do infectious diseases spread?

  1. Only through water
  2. Through air only
  3. Through air, water, food, and direct contact ✓ (correct)
  4. Only through touch

Explanation: Infectious diseases spread through multiple routes: airborne (sneezing, coughing), water, contaminated food, direct contact, and vectors like insects.

Q7. What is immunization?

  1. Treatment of disease
  2. Complete cure
  3. Isolation of patients
  4. Prevention of disease through vaccines ✓ (correct)

Explanation: Immunization is a preventive measure using vaccines that stimulate the immune system to recognize and fight specific pathogens without causing the disease.

Q8. What is fermentation?

  1. Microbial breakdown of food producing useful products ✓ (correct)
  2. Viral replication
  3. A harmful process
  4. Growth of mold

Explanation: Fermentation is microbial decomposition of organic matter. Bacteria and yeasts ferment sugars to produce useful products like yogurt, cheese, and bread.

Q9. What is antibiotic resistance?

  1. Weakness of immune system
  2. Ability of bacteria to survive antibiotic drugs ✓ (correct)
  3. Viral infection
  4. Allergy to antibiotics

Explanation: Antibiotic resistance occurs when bacteria mutate and survive antibiotic treatment. Overuse of antibiotics accelerates this process.

Q10. How can we prevent the spread of microorganisms?

  1. Never wash hands
  2. Avoid all contact
  3. Practice good hygiene, vaccination, proper food storage ✓ (correct)
  4. Ignore hygiene

Explanation: Prevention involves: good personal hygiene, vaccination, proper food storage and cooking, safe water, sanitation, and avoiding contact with infected persons.

Frequently Asked Questions

Are all microorganisms harmful?

No, many microorganisms are beneficial. Bacteria in soil help plants grow, in digestive system they aid digestion, in fermentation they create useful products, and some produce antibiotics.

What is the difference between bacteria and viruses?

Bacteria are living cells that can reproduce independently and grow in culture. Viruses are non-living and need host cells to reproduce. Antibiotics kill bacteria but not viruses.

More Class 8 Science MCQs

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