lesson notes of micro-organisms. class 8

MICRO-ORGANISMS (FRIENDS OR FOE)

Organisms that are so small that they can only be seen through a microscope are called microorganisms or microbes.
The study of microorganisms is known as microbiology.
Most organisms are hardy and can be found in almost any kind of environment – hot desert, polar ice caps, salt water, marsh lands and inside other organisms.

Types of microorganisms:

There are five major groups of microorganism. These are as follows:

1. Bacteria
2. Algae
3. Protozoa
4. Fungi
5. Virus

Bacteria

1. They are simple living organisms which are found all around us. They are mostly single- celled tiny organisms, but they live together in colonies of millions.
2. Bacteria are found in three different shapes:

1. Rod shaped, called bacilli.
2. Spherical shaped, called cocci.
3. Spiral called spirilla.
4. comma shaped called vibrio.

Algae:

• Algae are simple plant- like organisms which are usually aquatic in nature.
• They contain a cell wall and chlorophyll and can make their own food by photosynthesis.
• Algae can be unicellular or multicellular.
• Some of the common examples are diatoms, chlamydomonas, and seaweed.

Protozoa:

• These are unicellular microscopic organisms similar to animals that can move about to capture food and are heterotrophic in nature.
• They are mostly aquatic in nature.
• Amoeba, paramecium are some examples of protozoa.

• Fungi:

• Plant -like organisms that do not contain chlorophyll are called Fungi.
• Fungi may be unicellular (Yeast) or multicellular (Bread mould) and are found in warm and moist places.
• Fungi can be heterotrophic, saprophytic or parasitic in nutrition.
• Examples: Yeast, Rhizopus (Bread mould), mushrooms, puffballs.

Viruses:

• Viruses are smaller than any known cell.
• Viruses can only be seen with electron microscope.
• Viruses can reproduce only inside the bodies of other organisms, which mean they need a host.
• A virus is like a non- living thing outside the body of other organisms. Therefore, it is a borderline between a living and a non- living thing.

USEFUL MICROORGANISMS

Microorganisms are useful in the following ways:

• In food and beverage industry
• In making medicines and vaccines
• In agriculture
• In cleaning the environment

• HARMFUL MICROORGANISMS

• Microorganisms that cause diseases in human, animals and plants are called pathogens or germs.
• Diseases that can spread from an infected person to a healthy individual through air, water or direct contact are called communicable diseases. Examples: Common cold, chicken pox, AIDS etc.
• Micro organisms also cause diseases in animals and plants. For examples-
• Anthrax is a disease caused by bacterium and affects human and cattle.
• A virus causes the dangerous foot and mouth disease in cattle.
• Citrus canker is a bacterial disease that affects trees of citrus fruits and is spread by air.
• Rust of wheat is a viral disease that affects vegetable like bhindi & spread by insects.
• Malaria is actually caused by pathogen called plasmodium (protozoa) which is transmitted by female Anopheles mosquito.
• Dengue is caused by dengue virus and spread by female Aedes mosquito.

• Food spoilage:

  Many bacteria and fungi grow on food items and produce certain toxic substances. This makes the food unfit for consumption. Consuming such food can cause a serious illness called food poisoning.
  

  Food preservation:

• Processing of food to prevent their spoilage and to retain their nutritive value for period is called food preservation.
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