Our article debates the issues at stake in the Heideggerian examination of the Umwelt theory in his Fundamental Concepts of Metaphysics. This discussion sheds light on the links and differences between the lifeworld that is constituted as a set of meanings and interactions, and the world that opens up to Being, by providing a definition of the world as what is experienced through “the accessibility of beings” (Heidegger, 1983/1995, p. 196, §47), i.e. the lived relationship to the subjective world itself. (...) As Heidegger (1983/1995, p. 192, §46) theorizes the idea of the animal “poor in world” (based on the Uexküllian (1934/2010, p. 51) concept of “poverty”), he implies that both humans and animals perceive the fundamental nature of the world, albeit in different ways. Therefore, the article contends that the distinct treatment of human beings helps avoid confusion between the ontology of beings and their ontic biological structure. As Uexküll also makes the human being the exception in the harmonics of nature, we demonstrate that Uexküll’s statement of the human imperfection in fact prevents a biological reductionism. This article thus highlights the challenge, for biosemiotics, to provide a clear distinction between the ontology of living beings and their biological disposition. (shrink)