The range of transdisciplinarity becomes clear when the four central questions of biological research ((1) causation, (2) ontogeny, (3) adaptation, (4) phylogeny [after Niko Tinbergen 1963, see also Tinbergen's four questions, cf. Aristotle: Causality / Four Major Causes]) are graphed against distinct levels of analysis (e.g. cell, organ, individual, group; [cf. "Laws about the Levels of Complexity" of Nicolai Hartmann 1940/1964, see also Rupert Riedl 1984]):[14]