This chapter reviews factors, theories or hypotheses that have been proposed to explain global biodiversity patterns, and outlines a unifying scheme, showing the hierarchy between factors and mechanisms and their relationships. It refers to the terrestrial realm because the author believes that to understand global scale biodiversity patterns and to go towards a unifying theory. The chapter explores the metabolic theory of ecology (MTE) on copepod biodiversity using three data sets: a global-scale data set, data from the Continuous Plankton Recorder (CPR) survey and the ODATE collection data set. It shows that the species-energy theory has been separated into two theories: the ambient energy theory; and the production theory. Temperature is a good proxy of the energetic level of the atmosphere or the ocean because it integrates the effects of solar, downward and upward long-wave radiations, the atmospheric albedo effect exerted by clouds, the effects of oceanic currents and atmospheric circulation that redistributes heat, sensible and latent heat.