An Endotherm is any organism that can gain heat through itself. Another term used to describe this is a warm-blooded animal. The complete opposite of this is a cold-blooded animal such as a Lizard. The picture Is one of a human because humans produce their own heat. Cold blooded animals must lay in the sun in order to gain their heat. An endothermic organism must constantly be at work in order to be producing heat. A human body is usually kept around 97.5 degrees. Vital organs along with the blood system work at ensuring that the body stays at hemostasis. If the temperature drops then the body will do a process called negative feed back in order to return to homeostasis.