Acellular and Cellular Organisms
you should be able to characterise living and non- living matter. However, the boundary-line between the two is not very precise. As you have read there are forms such as viruses which do not obey many of the above criteria.
Their structure is also quite different from that of the other living organisms. Thus we say that most organisms are made up of cells, or they have cellular organization. On the other hand, viruses are non-cellular or acellular. This brings us to the concept of cell, and cell theory.