Yuri Lotman, a semiotician at Tartu University, Estonia, was inspired by Vladimir Vernadsky's terms biosphere and noosphere to propose that a semiosphere comes into being when any two Umwelten are communicating.[clarification needed] Later, Jesper Hoffmeyer suggested a variation to the effect that the community of organisms occupying the semiosphere will inhabit a "semiotic niche". This implies that the semiosphere may be partially independent of the Umwelten. Kalevi Kull argues that this suggestion is not consistent with the nature of semiosis which can only be a product of the behaviour of the organisms in the environment.