||P.2 2nd paragraph: "Why there is a limited diversity and why some groups are missing will be comprehensible
when the physicochemical factors, which are characteristic for extreme environments (see Table 1.1), are examined. These parameters define niches, which allow occupancy by only certain groups of organisms, none can be expected to survive the whole range of conditions. An early ecologist, Victor Shelford, presented already in 1913 the observation that organisms will usually be limited by abiotic factors in his “law of tolerance” (cited in Krebs 2008). Each particular factor that an
organism responds to in an ecological system has what he called limiting effects. The factors function within a range, that is, a maximum and a minimum value for the factors exists, which Shelford designated “limits of tolerance” (see Table 1.1). For an
organism to succeed in a given environment, each of a complex set of conditions must remain within the tolerance range of that organism, and if any condition exceeds the minimum or maximum tolerance of that organism, it will fail to thrive."