The maximum body temperature that can be tolerated by an organism. When body temperature exceeds the upper critical point, cellular components and process become disrupted, and the organism eventually dies. For most animals the upper critical temperature lies in the range 30–45°C, while few plants can survive leaf temperatures in excess of 50°C, exceptions being desert plants such as agaves and cacti, which can tolerate temperatures of 60°C or more. Some specialized bacteria, notably certain archaebacteria (see Archaea), live near deep-sea vents at temperatures exceeding 100°C (see thermophilic). Compare lower critical temperature.
Subjects: Biological Sciences.