Virus can be defined as an ultramicroscopic acellular parasitic living particles made up of nucleic acid and protein. They can reproduce in the host body only. It remains inert like a non-living particle outside the host.
In the year 1898, a scientist named Beijerink discovered and coined the term virus. The term virus is derived from Latin word "viruses" means position .
Viruses can be found in water, soil and air, almost every place. It can live in plants, animals, bacteria and fungi. Virus may be round, rod-shaped, tafpole-shaped or bread like shaped. It cannot be see without election microscope. Generally their size 10-300 nm.
Characteristics of Viruses :
Their body is made up of only nucleic acid and protein .
They do not have any nucleus and cytoplasm.
They do not show any activists outside the host.
They contain a protein coat callec the capsid.
They are enclosed in a protective envelop.
Ribosomes and enzymes are absent.
They are considered both as living and non living things.
Either DNA or RNA is present in the virus.
There are some kind of viruses :
T2 Bacteriophage
Human Adino Virus
Human Pollo Virus
Tibaco Mosaic Virus
Measles Virus
Influenza Virus
Vaccinia Virus
Virus is very dangerous. It causes many deases. Also virus help us . It is very important for human life. It has both useful and hearmful effect. The vaccins of pox, polio,rabis, viral heoatitis etc are discovered froam these viruses.