Viruses are host specific.i.e viruses shows the characteristics of living as well as non living.They are said to be on the threshold of life.viruses are acellular,ultramicroscopy, disease causing entities.there size ranges from 10nm to 2000nm.viruses do not grow ,do not eat food or respire.viruses are obligate parasites and only can multiply within the living host cell . They have the capacity to transmit the disease from diseased to healthy organism.viruses show very simple structure i.e a nucleic acid core surrounded by a protein coat (capsid) to form nucleocapsid. They genetic material like DNA or RNA.
