In the Gefen laboratory, at the Department of Biology, University of Haifa- Oranim, we study animal ecophysiology. We use both comparative and experimental evolution approaches to study water relations, respiratory physiology and energy metabolism of terrestrial arthropods in the context of evolution of environmental-stress tolerance. Temperature and water availability regimes are fundamental in determining the geographic distribution of terrestrial arthropods. Their often small body size, and thus their relatively high body surface area to volume ratio, compounds the challenge they face in conserving body water in a predominantly dry environment. Nevertheless, arthropods are the most successful terrestrial animals in both biomass and diversity, many of which occupy some of the hottest and driest habitats on earth. In our laboratory we study various aspects of the physiological mechanisms underlying resistance to these environmental extremes.