Evolution lies at the heart of all modern biology. Genetics, development and ecology interact to create phenotypic variation within species and differences among species. The results are almost incomprehensibly diverse. How has evolution worked, over several billion years of earth history, to yield this richness of form and function? Most of modern biological science explores this central question, at least implicitly. But many SBS researchers confront it more explicitly by focusing on particular taxonomic groups, or ecological contexts, or evolutionary mechanisms, or threats to biodiversity posed by human activities.