On Rheostasis: The Hierarchical Organization of Physiological Stability - Hardcoverby Tyler John Stevenson (Author) All our inner organs and tissues require a constant environment to work effectively. Warm blooded animals keep a core body temperature around 98 F as the cells function at an optimal capacity at this temperature. The core body temperature of cold blooded animals is the same as the surrounding environment and animals need to move into warmer or colder environments so that the internal state becomes ideal for