The ego is a energetic entity or an mental process that is an emanation of consciousness. The ego arises simultaneously as the body is born, though there is a possibility of it being existent in a ecology of souls prior to the birth of the body. That being said, the ego is not the body and the body is not the ego, though the ego very much claims to be the body but life keeps correcting this illusion. It gets corrected by suffering initially and then, when the consciousness is mature it gets corrected through transcendence.
All biological and immaterial organisms have a certain ego energy to them, and in some this energy is quite so prominent while with others not so much. Nature is here only for evolution and transcendence. Transcendence means dissolution of the separate self-identity.