1. Introduction to Virus Origins and Their Role in Biological Evolution2. Molecular Basis of Genetic Variation of Viruses 3. Darwinian Principles Acting on Highly Mutable Viruses4. Dynamics of Virus Populations and Their Hosts5. Viral Fitness as a Measure of Adaptation 6. Virus Population Dynamics Examined with Experimental Model Systems 7. Long-term Virus Evolution in Nature8. Quasispecies Dynamics in Disease Prevention and Control9. Trends in Antiviral Strategies10. Collective Population Effects in Non-Viral Systems