Q1
The bacteria that helps make curd is:
ALactobacillus
BSalmonella
CVibrio
DStreptococcus
CBSEClass 8 (CBSE)ScienceCh 2 · Topic 2
Useful and Harmful Microorganisms
Learning about the beneficial and harmful roles microorganisms play.
Core concept
Diseases caused by harmful microorganisms include the common cold and typhoid (bacteria/viruses), while food spoilage occurs when microorganisms grow on food, sometimes producing toxins dangerous to eat. Preservation methods like refrigeration, drying, salting, and pasteurisation work by slowing or stopping microorganism growth, keeping food safe for longer. Antibiotics, discovered by Alexander Fleming (penicillin), are medicines that specifically target and kill harmful bacteria without harming human cells.
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CBSE class 8 useful and harmful microorganisms
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• Useful microorganisms: Lactobacillus (curd), yeast (bread/brewing), antibiotic-producing bacteria.
• Harmful microorganisms cause diseases and spoil food.
• Food preservation methods (refrigeration, drying, salting) slow microorganism growth.
• Antibiotics, discovered by Alexander Fleming, target and kill harmful bacteria.