Eurytherm

[4][5][6] Eurythermy can be an evolutionary advantage: adaptations to cold temperatures, called cold-eurythemy, are seen as essential for the survival of species during ice ages.

It is in contrast with the idea of stenothermic organisms, which can only operate within a relatively narrow range of ambient temperatures.

[8] Through a wide variety of thermal coping mechanisms, eurythermic organisms can either provide or expel heat for themselves in order to survive in cold or hot, respectively, or otherwise prepare themselves for extreme temperatures.

Although invasive species are typically considered to be detrimental to the environment in which they are introduced, and even considered to be a leading cause of animal extinctions,[15] the ability of an animal to thrive in various environmental conditions is a form of evolutionary fitness, and therefore is typically a characteristic of successful species.

[16] The worldwide increase in oceanic temperatures has caused many coral reefs to begin bleaching and dying because the coral have begun to expel the zooxanthellae algae that live in their tissues and provide them with their food and color.

It is important to note that endotherms do not solely rely on internal thermogenesis for all parts of homeostasis or comfort; in fact, in many ways, they are equally as reliant upon behavior to regulate body temperature as ectotherms are.

[22] Reptiles are ectotherms, and therefore rely upon positive thermotaxis, basking (heliothermy), burrowing, and crowding with members of their species in order to regulate their body temperature within a narrow range and even to produce fevers to fight infection.

Tardigrades are able to enter an anhydrobiotic state, often called a tun, in order to both prevent desiccation and endure extreme temperatures.

This displayed extremotolerance has led scientists to speculate that tardigrades could theoretically survive on Mars, where temperatures regularly fluctuate between –123° and 25 °C, as well as even possibly the near absolute zero of interplanetary space.

The tardigrade's ability to withstand extremely cold temperatures as a tun is a form of cryptobiosis called cryobiosis.

[29][30] Tardigrades are able to withstand such cold temperatures not by avoiding freezing using antifreeze proteins as a freeze avoidance organism would, but rather by tolerating ice formation in the extracellular body water, activated by ice nucleating proteins.

Rainbow trout (Salmo gairdneri) have shown constant protein synthesis rates

This may mean that the aforementioned compounds aid in antioxidant defense, osmoregulatory processes, or energetic purposes at these temperatures.