Ans: There is only one species on each named as biologically immortal. That is Jellyfish Turritopsis Dohrnii. These are small transparent animals that live in the oceans. It can travel around the world and return back by reverting to an earlier stage of its life cycle. The Jellyfish vary distinctly. It can cause severity to human beings. When it contacts the human skin, it causes immediate pain, reddish irritating marks on the skin. Some jellyfishes may affect the whole body.