The evolution of endothermy

Sisavci i ptice su pravi endotermni organizmi što znači da drže tjelesnu temperaturu konstantnom. Zbog ovoga se fiziološki i anatomski znatno razlikuju od ektotermnih organizama, čija tjelesna temperatura ovisi o temperaturi okoliša. Isto tako, dosta endoterma pomoću torpora ili hibernacije znatno odstupa od endotermije jer torpor dovodi do velikih promjena u tjelesnoj temperaturi. U ovom radu obrađene su anatomske i fiziološke razlike endoterma i ektoterma te je opisan torpor i moguća hipoteza nastanka istog u endoterma. U radu navedene su hipoteze nastanka endotermije i trofazni model. Trofazni model kombinira različite hipoteze i smješta ih u vremenski okvir, te na taj način opisuje evolucijski tijek nastanka endotermije potpomognut paleontološkim nalazimaMammals and birds are true endothermic organisms which means that they maintain constant body temperature. They have physiological and anatomic differences from ectothermic organisms whose body temperature depends on ambient temperature. At the same time a lot of endotherms tend to enter torpor or hibernation which is considered as abandonment of endothermy due to big changes in body temperature. In this paper anatomic and physiological differences between endotherms and ectotherms are reviewed, along with the description of torpor and a hypothesis of its occurrence in endotherms. In this paper, I also presented hypotheses regarding the evolution of endothermy and a triphasic model which combines different hypotheses and puts them in a time frame in order to describe evolution of endothermy supported by current paleontological data