Prime purpose of this lecture is to present on Viruses. Here briefly present on is Virus a Living Organism. This lecture also describe on Viruses: Cellular Respiration, Reproduction, Metabolism, Homeostasis, Heredity, Responsiveness, Growth and development. Finally focus on how do viruses replicate. Two methods of replication: Lytic Cycle – the virus enters the cell, replicates itself hundreds of times, and then bursts out of the cell, destroying it. Lysogenic Cycle – the virus DNA integrates with the host DNA and the host’s cell helps create more virus DNA. An environmental change may cause the virus to enter the Lytic Cycle.