Microorganisms Friend and Foe Class 8 Questions Answers Explained

What Are Microorganisms? Understanding the Basics

Microorganisms, also called microbes, are tiny living organisms invisible to the naked eye. They include bacteria, fungi, viruses, and protozoa. These organisms are found everywhere—in air, water, soil, and even inside our bodies.

Key features:

• Microscopic size
• Can be unicellular or multicellular
• Reproduce rapidly

In Class 8 NCERT Science, understanding microorganisms is crucial as they play both helpful and harmful roles in nature and human life.

Useful Microorganisms: Friends in Our Daily Life

Not all microorganisms cause harm; many are beneficial. Here are some important uses:

• Food Production: Bacteria like Lactobacillus help ferment milk to make curd and yogurt. Yeasts are used in baking bread and brewing alcohol.
• Medicine: Penicillin, the first antibiotic, is derived from the fungus Penicillium. Many vaccines use weakened microbes.
• Nitrogen Fixation: Certain bacteria convert atmospheric nitrogen into forms plants can use, enriching soil fertility.
• Decomposition: Microbes break down dead plants and animals, recycling nutrients in ecosystems.

These friendly microbes support health, agriculture, and industries.

Harmful Microorganisms: The Foes That Cause Diseases

Some microorganisms cause diseases in humans, animals, and plants. These harmful microbes are called pathogens.

Common diseases caused by microbes include:

• Bacterial diseases: Tuberculosis, cholera, typhoid
• Viral diseases: Influenza, common cold, chickenpox
• Fungal diseases: Athlete’s foot, ringworm
• Protozoan diseases: Malaria, amoebiasis

Microbes spread through air, water, contaminated food, and contact. Understanding their role helps in prevention and treatment.

Preventive measures:

• Maintain cleanliness
• Use vaccines
• Drink clean water
• Cook food properly

How Microorganisms Reproduce: Key Processes Explained

Microorganisms reproduce quickly, which helps them spread fast.

• Binary Fission: Most bacteria reproduce by splitting into two identical cells. This is a simple and rapid process.

• Spore Formation: Some fungi and bacteria form spores, which are resistant structures that can survive harsh conditions.

• Budding: Yeasts reproduce by budding, where a new cell grows from the parent cell.

Example: If a bacterium divides every 20 minutes, starting with 1 bacterium, after 2 hours (6 divisions), the number of bacteria will be:

$$ N = 2^6 = 64 $$

This rapid reproduction explains how infections can spread quickly.

Comparison Table: Friend vs Foe Microorganisms

Important NCERT Questions and Answers for Class 8

Here are some typical questions from the NCERT textbook with answers:

Q1: Name two microorganisms which are helpful to us.

• Answer: Bacteria (used in curd making) and yeast (used in bread making).

Q2: How do microorganisms cause diseases?

• Answer: They enter the body, multiply rapidly, and release toxins that damage tissues.

Q3: What is fermentation? Give an example.

• Answer: Fermentation is the breakdown of sugar by microbes to produce energy and useful products. Example: Yeast ferments sugar to produce alcohol and carbon dioxide.

Q4: How can we prevent microbial diseases?

• Answer: By maintaining cleanliness, drinking clean water, using vaccines, and proper food hygiene.

Practicing such questions helps Class 8 students prepare well for exams.