Definition: number of currently described and taxonomically accepted marine species in this clade (Appeltans et al. 2012. The Magnitude of Global Marine Species Diversity. Current Biology 22, 2189–2202. http://dx.doi.org/10.1016/j.cub.2012.09.036)
Definition: position of an organism in a food web. May be described verbally with descriptors including primary producer, herbivore or carnivore. If described numerically, 1 indicates a primary producer, 2 a herbivore, and so on up the food web.