Class 8 Science – Chapter 2
Microorganisms: Friend and Foe
Page 4: Harmful Microorganisms & Diseases

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⚠️ What are Harmful Microorganisms?

Some microorganisms cause diseases in humans, animals, and plants. These disease-causing microorganisms are called pathogens.

🧍 Diseases Caused in Humans

Pathogens enter our body through air, water, food, or contact.

• Bacteria: Cholera, Typhoid, Tuberculosis
• Viruses: Cold, Flu, COVID-19, Measles
• Protozoa: Malaria, Amoebic dysentery
• Fungi: Ringworm

🐄 Diseases in Animals

Animals also suffer from diseases caused by microorganisms.

• Anthrax affects cattle and sheep.
• Foot-and-mouth disease affects cows and goats.

🌾 Diseases in Plants

Microorganisms cause diseases in plants which reduce crop yield.

• Citrus canker – caused by bacteria
• Rust of wheat – caused by fungi
• Yellow vein mosaic of bhindi – caused by virus

🦟 How Do Diseases Spread?

• Through air (coughing, sneezing)
• Through contaminated food and water
• By direct contact
• By insects like mosquitoes and houseflies

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📌 Next Page: Food Preservation Methods