Biological classification how are organisms grouped, sorted, and classified? why? model 1

In biological classification, the organisms are grouped on the basis of their cellular structure, presence or absence of cell wall, presence or absence of a membrane-bound nucleus, motility, ability to produce food, mode of reproduction, and mode of nutrition. They are classified so as to distinguish the differently related organisms from each other and to study evolution, as well as better understanding of the biological system. 

When a virus infects a host cell, it uses the cell's machinery to make copies of its own genetic material in a process called replication. finally, during the process of self-assembly, that protein shell and the copies of the virus's genetic material are assembled into new viruses.