Biochemists: Cellular diff between endo- & exotherms

What biochemistry differences are there between, say, reptiles and mammals? Or perhaps phrased another way, what evolutionary change occured to allow endothermic dinosaurs or other endotherms to become exothermic? I think it has to do with more than just the TCA cycle, but I’m not that up on biochemistry to know where the energy would come from.


See Poikilothermic

I think you’ve got the direction reversed. If dinosaurs were reptilian in their metabolic physiology, they would have been “ectotherms” (heat is obtained from external sources). Somewhere along the way to becoming birds, they would have become “endotherms” (heat generated internally). Endothermy in general is a more derived trait than ectothermy.

Of course, it is still unresolved as to whether dinosaurs as a group were truly endo- or ectothermic (with the more correct terms being, as noted by astro, homeothermy and poikilothermy, respectively).

For more information about the distinction between endotherms/ectotherms and homeotherms/poikilotherms, see the Staff Report by myself and Doug:

What makes some animals cold-blooded and others warm-blooded?

Terminology and links noted. Thanks, guys.