This chapter examines how biodiversity is partitioned at a global scale, which is the scope of biogeography. It considers the spatial scale in the classification is neither always global, nor does it incorporate all depths of the pelagic realm or substrates or types of ecosystems for the benthic realm. Variables used to establish the partition were chlorophyll concentration, mixed layer depth, nutrients, and the Brunt-Vaisala frequency, the Rossby radius of internal deformation, photic depth, algal biomass and primary product. It explains the pattern as the tendency for the body size or body mass of individuals, species and assemblages to increase with latitude. Early biogeographic partitions remain highly heterogeneous from a biological point of view, and the division of the biosphere has also been undertaken by biome. High nutrient low chlorophyll (HNLC) areas are oceanic regions where phytoplankton standing stock is low despite high concentrations of macronutrients.