A brain.
Jellyfish have no ears.Jellyfish lack basic sensory organs and brain, but their nervous systems generally allow them to perceive stimuli such as light and odor.
Despite neither jellies nor sponges having central nervous systems, jellies have true tissues. The cells in jellyfish are also bound together, unlike in sponges.
hydraMany lower invertebrates lack a brain but do possess a central nervous system. These include jellyfish, starfish, and sponges.
a backbone
Bones
Yes they do, invertebrates have small nervous systems, which consist of many small brains. Because of the anatomy of their nervous systems and the lack of neurons, they are thought to have limited cognitive capacity, and this means that they are likely to not be capable of emotions like we feel. This is why scientists are unsure whether or not or to what degree they feel pain.
Plants lack nervous system.
No, jellyfish are neither of these. The gastropods and bivalves belong to the phylum Mollusca, whilst jellyfish are Cnideria. Jellyfish are in many ways more primitive than molluscs, and lack many of their structural features.
Yes; jellyfishes have no head.
No, they lack the body parts needed to preform that function.
spine
No. They lack a nervous system