Geiser, Fritz; Stawski, Clare; Wacker, Chris B; Nowack, Julia

Author(s)

Geiser, Fritz

Stawski, Clare

Wacker, Chris B

Nowack, Julia

Publication Date

2017-11-02

Abstract

The evolution of endothermy in mammals and birds has been widely debated. Endothermy is characterized by high endogenous heat production via combustion of metabolic fuels. This differs from ectothermy in most living organisms, which generally do not produce substantial amounts of internal heat for thermoregulation (Tattersall et al., 2012; Withers et al., 2016). Endogenous heat production is energetically very costly. In comparison to ectothermic terrestrial vertebrates, namely the amphibians and reptiles, the minimum metabolic rate (MR) of normothermic or homeothermic (high constant body temperature, Tb) animals at rest is about 4–8-fold higher in the endotherms. This difference is even more pronounced at low ambient temperatures (Ta) at which the Tb of ectotherms follows Ta, and the MR decreases to even lower levels. In contrast, the Tb of homeothermic endotherms remains high and constant over a wide range of Ta. Therefore, to compensate for increased heat loss at low Ta, MR of especially small mammals and birds must increase substantially and can be 100-fold or more of that in ectotherms (Bartholomew, 1982). Of course this high MR requires a substantial uptake of food and in endotherms much of this chemical energy is simply converted into heat for thermoregulation rather than growth or reproduction as in ectotherms.

Citation

Frontiers in Physiology, v.8, p. 1-7

ISSN

1664-042X

Pubmed ID

29163191

Link

https://hdl.handle.net/1959.11/51768

Publisher

Frontiers Research Foundation

Rights

Attribution 4.0 International

Title

Phoenix from the Ashes: Fire, Torpor, and the Evolution of Mammalian Endothermy

Type of document

Journal Article

Entity Type

Publication

Author(s)	Geiser, Fritz Stawski, Clare Wacker, Chris B Nowack, Julia
Publication Date	2017-11-02
Abstract	The evolution of endothermy in mammals and birds has been widely debated. Endothermy is characterized by high endogenous heat production via combustion of metabolic fuels. This differs from ectothermy in most living organisms, which generally do not produce substantial amounts of internal heat for thermoregulation (Tattersall et al., 2012; Withers et al., 2016). Endogenous heat production is energetically very costly. In comparison to ectothermic terrestrial vertebrates, namely the amphibians and reptiles, the minimum metabolic rate (MR) of normothermic or homeothermic (high constant body temperature, T<sub>b</sub>) animals at rest is about 4–8-fold higher in the endotherms. This difference is even more pronounced at low ambient temperatures (T<sub>a</sub>) at which the T<sub>b</sub> of ectotherms follows T<sub>a</sub>, and the MR decreases to even lower levels. In contrast, the T<sub>b</sub> of homeothermic endotherms remains high and constant over a wide range of T<sub>a</sub>. Therefore, to compensate for increased heat loss at low T<sub>a</sub>, MR of especially small mammals and birds must increase substantially and can be 100-fold or more of that in ectotherms (Bartholomew, 1982). Of course this high MR requires a substantial uptake of food and in endotherms much of this chemical energy is simply converted into heat for thermoregulation rather than growth or reproduction as in ectotherms.
Citation	Frontiers in Physiology, v.8, p. 1-7
ISSN	1664-042X
Pubmed ID	29163191
Link	https://hdl.handle.net/1959.11/51768
Publisher	Frontiers Research Foundation
Rights	Attribution 4.0 International
Title	Phoenix from the Ashes: Fire, Torpor, and the Evolution of Mammalian Endothermy
Type of document	Journal Article
Entity Type	Publication

Phoenix from the Ashes: Fire, Torpor, and the Evolution of Mammalian Endothermy

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