Class 8 Chapter 2 Microorganisms

A microorganism, or microbe, is a microscopic organism, which may exist in its single-celled form or a colony of cells. Microorganisms include all unicellular organisms and so are extremely diverse. Of the three domains of life identified by Carl Woese, all of the Archaea and Bacteria are microorganisms.

Edited at 2023-10-02 06:52:02

Sunita Meena

Recent works View more works>>

Class 8 Chapter 2 Microorganisms
A microorganism, or microbe, is a microscopic organism, which may exist in its single-celled form or a colony of cells. Microorganisms include all unicellular organisms and so are extremely diverse. Of the three domains of life identified by Carl Woese, all of the Archaea and Bacteria are microorganisms.

Class 8 Chapter 2 Microorganisms

Sunita Meena

Recent works View more works>>

Class 8 Chapter 2 Microorganisms
A microorganism, or microbe, is a microscopic organism, which may exist in its single-celled form or a colony of cells. Microorganisms include all unicellular organisms and so are extremely diverse. Of the three domains of life identified by Carl Woese, all of the Archaea and Bacteria are microorganisms.

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Microorganisms

Definition

Organisms not visible to naked eyes, Only visible under microscope.

Places to be found

Everywhere

Either live on host's body or Live freely

Types

Alga/Algae

They have chlorophyll

They can be unicellular or multicellular

Eg-> Chlamydomonas, Spirogyra

Bacterium/Bacteria

They don't have organelles

They are unicellular

Eg->Vibriocholerae, Lactobacillus, Cyanobacteria

Fungi/Fungus

They are Saprophytes

They can be unicellular or multicellular

Eg-> Bread mould, Aspergillus, Penicillium

Protozoan/Protozoa

They are parasites

They are unicellular

Eg-> Amoeba, Paramecium, Plasmodium

Harmful Microorganisms

Pathogens are disease-causing microorganisms

In humans

In plants

In animals

Some microorganisms spoil food, clothing and leather

Food Poisoning

Advantages of Microorganisms

Making of Curd, Bread

Curd is made by Lactobacillus which promotes conversion of milk into curd

Bacteria and Yeast are used for fermentation in rice idlis and dosa batter as when they respire, they release CO2 which bubbles the dough and increase its volume

Yeast is used in baking industry to make breads, pastries and cakes fluffy and soft

Commericial Usage

Microorganisms are used for making alcohol, wine and acetic acid or vinegar

Yeast is used for alcohol and wine production as if we feed them on natural sugars, they do fermentation(process of conversion of sugar into alcohol)

Medicinal Usage

Antibiotics are medicines obtained from microorganisms which stop the growth of disease-causing microorganisms in our body

Eg-> Streptomycin, Tetracycline, Erythromycin, Azithromycin

They are mixed in fodder of livestock and poultry to check microbial infection in animals

• Antibiotics should be taken by prescription of qualified doctor • We should complete the course of medicines given by doctor • If taken in no need or wrong doses, it will be less effective when needed • Unnecessary doses may kill beneficial bacteria in body • They are not effective against viral diseases

Vaccine

Antibodies (Immunoglobulin Protiens or Clycoprotiens) are produced when invader enters the body

Antibodies learn how to fight a particular microorganisms by experiencing it

Vaccines are dead/weakened microorganisms which teach body how to release suitable antibodies for a particular disease

Children are given vaccines in different ages to prevent diseases and are encouraged to be given in programmes like Pulse Polio Programme

Increasing the soil fertility

Some Microorganisms convert atmospheric nitrogen into soluble nitrogen and increase soil fertility for plants

Cleaning the environment

Animal and plant wastes are decomposed by microorganisms

They also release the nutrients back into the soil

Facts

Louis Pasteur discovered Fermentation in 1857

In 1929, Alexander Fleming was working on a culture of disease causing bacteria. Suddenly he found the spores of a little green mould in one of his culture plates. He observed that the presence of mould prevented the growth of bacteria. In fact, it also killed many of these bacteria. From this the mould penicillin was prepared.

Edward Jenner discovered the first vaccine of smallpox in 1798

Robert Köch (1876) discovered the bacterium (Bacillus anthracis) which causes anthrax disease

Food Preservation

Spoiled food emits bad smell and changed colour and has a bad taste while also being dangerous to us so we should preserve food

Chemical Method

Salt or acid preservatives prevent attack

Eg-> Sodium Metabisulphate, Sodium Benzoate in Jams and Squashes

Sugar

Sugar reduces moisture which prevents attacks

Eg-> Sugar in Jams, Jellies. Squashes

Common Salt

It is used since ancient times for prevention of bacteria

Eg-> Sodium Chloride in Amla, Raw mangoes, Tamarind

Oil and Vinegar

Bacteria cannot live in such environment

Eg-> Oil and Vinegar in Pickles, Vegetables, Fish, Meat

Heat and Cold Treatments

Low and high temperature can kill microorganisms

Pasteurisation is the process of heating milk to 70 degrees for 15 to 30 seconds and suddenly chilling and storing

Storage and Packing

Frutis and vegetables can be stored in sealed air tight packs to prevent attack

Nitrogen Fixation

Nitrogen is essential for plants to make protiens, amino acid etc. which are building blocks of life but plants can't take it directly from atmosphere so they have to be synthesized by bacteria first.

1st. Nitrogen Fixation-> The Atmospheric Nitrogen is turned into soluble nitrogen by either nitrogen fixing bacteria or energy of a lightning.

2nd. Nitrification-> The soluble nitrogen is released into the soil.

3rd. Assimilation-> The soluble nitrogen is taken up by the plants for utilisation.

4th. Ammonification-> When animals take up the plants and later on die, their dead body releases nitrogen back into the soil.

5th. Denitrification-> When the nitrogen returns back in soil, denitrifying bacteria turn it back into atmospheric nitrogen and release it.