Microorganisms: Friend and Foe 8 Science — Revision Notes
Microorganisms are tiny living organisms visible only under microscopes including bacteria, viruses, fungi, and protozoa. They play crucial roles in nature
TL;DR: Microorganisms are tiny living organisms visible only under microscopes including bacteria, viruses, fungi, and protozoa. They play crucial roles in n…
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Microorganisms are tiny living organisms visible only under microscopes including bacteria, viruses, fungi, and protozoa. They play crucial roles in nature
Types of Microorganisms
- Bacteria are single-celled prokaryotes found everywhere on Earth
- Fungi include yeasts and molds that decompose organic matter
- Viruses are non-living infectious agents that require host cells to reproduce
- Protozoa are single-celled eukaryotes many of which are parasitic
Beneficial Microorganisms
- Bacteria in soil fix nitrogen making it available to plants
- Lactobacillus bacteria ferment milk to produce yogurt and cheese
- Fungi decompose dead organic matter returning nutrients to soil
- Yeast ferments sugars to produce bread and alcoholic beverages
Harmful Microorganisms
- Pathogenic bacteria cause diseases like cholera, typhoid, and tuberculosis
- Viruses cause diseases like influenza, measles, and HIV infection
- Fungi cause diseases like ringworm and athlete's foot in humans
- Spoilage organisms damage food causing putrefaction and fermentation
Preservation of Food
- Refrigeration slows microbial growth by reducing metabolic rate
- Heat treatment kills microorganisms preventing food spoilage
- Salting and pickling create hostile environment for microbial growth
- Drying removes water which microorganisms need to survive
Key Terms
- Microorganism: Tiny organism visible only under microscope including bacteria, virus, fungus, and protozoan
- Pathogenic: Capable of causing disease in host organism
- Decomposition: Process of breaking down dead organic matter by microorganisms
- Fermentation: Process where microorganisms break down organic compounds in absence of oxygen
Frequently Asked Questions
Why are some microorganisms beneficial and others harmful?
Beneficial microorganisms help in nitrogen fixation, food production, and decomposition. Harmful ones cause diseases or spoil food and materials.
How does refrigeration preserve food?
Refrigeration slows the reproduction of microorganisms by lowering temperature, extending shelf life of food without using chemical preservatives.
More 8 Science Revision Notes
- Crop Production and Management
- Cell: Structure and Functions
- Reproduction in Animals
- Force and Pressure
- Sound
- Chemical Effects of Electric Current
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