Class 8 Science – Chapter 2
Microorganisms: Friend and Foe
Page 2: Types of Microorganisms

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1️⃣ Bacteria

Bacteria are very small microorganisms that can be seen only under a microscope. They are found everywhere – in air, water, soil, and inside our bodies.

• Some bacteria are useful (making curd, fixing nitrogen).
• Some bacteria cause diseases like cholera and tuberculosis.

2️⃣ Fungi

Fungi are microorganisms that grow in warm and moist places. Examples include yeast, mould, and mushroom.

• Yeast is used in making bread and alcohol.
• Some fungi spoil food and cause skin diseases.

3️⃣ Protozoa

Protozoa are single-celled microorganisms found in water and soil.

• Example: Amoeba, Plasmodium.
• Some protozoa cause diseases like malaria.

4️⃣ Algae

Algae are plant-like microorganisms found mostly in water. They prepare their own food by photosynthesis.

• They release oxygen into the atmosphere.
• Some algae are used as food.

5️⃣ Viruses

Viruses are the smallest microorganisms. They can reproduce only inside the body of a living organism.

• They cause diseases like common cold, flu, COVID-19.
• Viruses are inactive outside a host.

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📌 Next Page: Useful Microorganisms