Micro-organisms: friend and foe · सूक्ष्मजीव: मित्र और शत्रु
A free Biology lesson for Class 8 children.
Micro-organisms are too small to see without a microscope. They are bacteria, fungi, protozoa, algae and viruses.
Friendly microbes make curd from milk, make bread and cake rise, make medicines called antibiotics, and fix nitrogen in the soil.
Harmful microbes cause diseases: bacteria cause typhoid and tuberculosis, viruses cause the common cold, polio and chickenpox, protozoa cause malaria.
Diseases that spread from one person to another are communicable. Mosquitoes and flies carry some of them.
Vaccines protect us by helping the body make antibodies. Edward Jenner made the first vaccine, against smallpox.
Food is preserved with salt, sugar, oil, vinegar, cold storage, and by pasteurising milk.