Karl August Möbius's conception and studies of “biocenosis ”, or living community, and thus his contributions in founding both, ecology and marine biology is not very widely known or acknowledged today. The same is true for his influence as one of the most eminent museum reformers, having implemented an innovative museum and exhibition concept first in the Zoological Museum in Kiel (since 1880) and later in the Natural History Museum in Berlin (since 1887). Moreover, his other scientific achievements have rarely found any mentioning or even remained unstudied. In a biographical outline I will first review Möbius's role in zoology, pointing out his concurrent scientific and popular writings and his mutually reinforcing research and civic activities that have helped his conceptual contributions to emerge. Second, I will analyse particularly two of Möbius's papers in 1874 and 1886 on the importance of the concepts of species (his “Artbegriffe ”) in context with Darwin's then new theory of evolution. These papers provided the theoretical background for Möbius's understanding of the underestimated but overwhelming diversity of organisms living on earth (that, on the other hand, should be represented in museum collections). Actually, Möbius was one of the few zoologists at his time realizing the implications of sharpening the concepts of species and the magnitude of what we today call biodiversity. I further argue that Möbius attempted and envisioned an early synthesis of systematics, evolutionary theory and ecology, justifying to regard Karl August Möbius as an albeit underrated but extraordinary zoologist of the second half of the 19th century. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)