The brothers Eugene and Howard Odum are among the most famous ecologists of the second half of the 20th century. Their popularity is lanrgely owing to one work, Eugene Odum’s Fundamentals of Ecology (1953). It is considered one of the standard textbooks on ecology and has made ecology popular to a large audience beyond the field. Along with the book, one concept became especially famous: that of the ecosystems. Eugene himself did not contribute much to the progress of the theory of ecosystems because his book is mainly a summary of theoretical concepts that were developed by others. Moreover, it is exceedingly problematic to talk about the Odumian theory because the brothers’ views differ fundamentally (in spite of all their commonalities). While Eugene Odum views ecosystems as “organisms,” his brother Howard, in contrast, understands them as (physically describable) “machines” (Hagan 1992,Chapter 7). Beyond ecology, both concepts, meaning the so-called (holistic) organicism and the so-called (reductionistic) physicalism, play decisive roles as cores of certain antagonistic ideologies that are very influential in the debates on environmentalism and nature conservation. Within ecology, both concept were heavily criticized and rejected. I will focus on this point in the following. That is, I will show why Eugene Odum’s organicism is insupportable, and I will focus on the limits of Howard Odum’s Physical theory of ecosystems, especially the concept of information he uses.