8th Class Science Microorganisms : Friend and Foe Notes - Microorganism-Friend and Foe

Microorganisms - Friend and Foe

·                     Some organisms are too small to be visible by the naked eyes. These are called microorganisms. They may be unicellular or multicellular.

·                     Microorganisms are found everywhere and in almost all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands.

·                     Microorganisms are also found inside human beings and other animals.

·                     Microorganisms are classified mainly into five categories ?

Viruses, though different from the living microorganisms, are considered microbes. They can reproduce only inside the host organism like bacterium, plant or animal cell. Because of this viruses are also called at the borderline of living and non-living organisms.

·                     Some microorganisms are harmful for human beings while some others are useful in various aspects.

·                     Some microorganisms are used in making medicines. Some microorganisms decompose the organic waste and dead plants and animals into simple substances and help in cleaning up of the environment.

·                     The diseases like typhoid, cholera, tuberculosis are caused by the microorganisms. Protozoa also cause diseases like dysentery and malaria.

·                     Some microorganisms can also cause food poisoning.

·                     Some microorganisms like rhizobium reside in the root nodules of leguminous plants. They help in fixing nitrogen from air into the soil and increase the soil fertility.

·                     Blue green algae present in the soil also helps in fixing nitrogen from the atmosphere and convert into nitrogenous compounds.