Well, Lavos doesn't seem so much as an animal, but more as a Cell to me.
He has a Nucleus inside of it, which holds all of it's genetic material. It's main goal is to reproduce. It uses means to defend itself (Cell Membranes, the Robotic part of him may have been added in it's desgin while it's evolution). His outer shell can be compared to a Membrane, allowing only certain materials (DNA and energy) to pass. The Humanoid and other bit could be considered organelles for this example. It manipulates elements to further itself (Construction of the Shell), and there can be many more examples, really...