This monograph emphasizes the many facets of bacterial evolution as impacted by bacterial interactions with phages, as well as, to a lesser degree, the evolutionary impact of phages on other organisms, including other phages. The book starts with a general overview of bacteriophages. Topics discussed in detail include but are not limited to mutagenesis, migration, natural selection and genetic drift as the drivers of evolution as well as an extensive discussion from the author's unique perspective on phage ecology. .