1. Viruses are much smaller than bacteria, lack cellular structures, and can only replicate inside living cells. Bacteria are larger, have cellular structures, and can replicate through binary fission inside or outside of host cells. 2. Typical viruses contain either DNA or RNA surrounded by a protein coat that uses the host cell's machinery to replicate, producing structures to transfer the viral nucleic acid to other cells. 3. Viral classification is based on nucleic acid type, morphology, and host species, with Herpesviridae and human herpesvirus 2 given as examples.