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Microorganisms: Their Roles Explained
Aug 28, 2024
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Microorganisms: Friend or Foe
Introduction
Overview of the chapter for Class 8 Science.
Topic: Microorganisms and their classification.
What are Microorganisms?
Definition: Very small living organisms that cannot be seen with the naked eye.
Visible only through a microscope or magnifying glass.
Classification: Microorganisms are divided into four main types:
Bacteria
Fungi
Protozoa
Algae
Characteristics of Microorganisms
Size
: Microorganisms are very small ("micro" means small).
Visibility
: Cannot be seen with the naked eye, only under a microscope.
Types of Microorganisms
1. Bacteria
Examples of diseases caused by bacteria include Typhoid and Tuberculosis.
2. Fungi
Can spoil food, e.g., bread mold (fungus).
Examples include Penicillium and Aspergillus.
3. Protozoa
Examples include Amoeba and Paramecium, which can cause diseases like Malaria and Dysentery.
4. Algae
Examples include Spirogyra and Chlamydomonas.
5. Viruses
Cannot reproduce outside a host's body.
Examples of diseases include Cold, Influenza, Polio, and Chickenpox.
Microorganisms as Friends
Uses in Daily Life
:
Yeast is used in baking (e.g., making bread fluffy) and in alcohol production (fermentation).
Antibiotics derived from microorganisms help cure diseases.
Vaccines prepare the immune system to combat certain diseases.
Rhizobium bacteria improve soil fertility by fixing nitrogen.
Decomposers play a vital role in recycling nutrients in the ecosystem.
Microorganisms as Foes
Harmful Effects
:
Spoilage of food (e.g., mold on bread).
Disease-causing pathogens spread through air, water, and food.
Common communicable diseases include cold, malaria, and anthrax.
Food Preservation Techniques
Importance: To protect food from microbial spoilage.
Methods
:
Chemical Methods
: Use of preservatives like sodium benzoate, sugar, and salt.
Refrigeration
: Low temperature inhibits microbial growth.
Heating
: Boiling kills microorganisms.
Storage and Packing
: Airtight containers prevent contamination.
The Nitrogen Cycle
Importance of nitrogen for plant growth.
Nitrogen Fixation
: Rhizobium bacteria in leguminous plants convert atmospheric nitrogen into usable forms.
Cycle involves conversion of nitrogen compounds back into the atmosphere through decomposition by microorganisms.
Summary
Microorganisms play dual roles as beneficial (friends) and harmful (foes).
Awareness of both aspects is crucial for health and environmental sustainability.
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