Tuesday, 1 December 2015

zoology - Are 'homeothermic' and 'endothermic' synonymous?


I got this question from the comments below this answer. So, do homeothermic and poikilothermic have the same meaning as endothermic and ectothermic, respectively? A user also suggested that the terms such as poikilothermic and homeothermic have become obsolete. What is the reason for them being obsolete?




Answer




[D]o homeothermic and poikilothermic have the same meaning as endothermic and ectothermic respectively[?]



No. Once you are referring to the source of the heat, while the other time you are referring to whether the internal temperature varies through time.


Source of heat



  • endo = inside

  • exo = outside



Variance in internal temperature



  • Poikilo = varies

  • homeo = does not vary


Combinations


Any combination of these two axes exist. For example: If the temperature in the environment never varies you can be homeotherm without needing to be endotherm. You, for example, are a homeo-endo-therm.


A fun common example are the large dinosaurs that are thought to be homeotherms (but see @John's and @Gerardo's comments) because their metabolism produce some heat as by-product (just like any organism) and they are so large that they remain warm thanks to this heat source. However, they were probably not able to regulate actively their temperature. Therefore, I would tend to qualify dinosaurs as homeo-exo-therm but I wouldn't be surprised if someone prefers to call large dinosaurs homeo-endo-therm.


Note that the terminology might be a bit more complicated in reality as the diversity of mechanisms of body temperature regulation is important.


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