How do you get a backbone?

tuna,sponges and all invertabrates

a backbone has a backbone and a no backbone doesnt but most of the backbone are full bone .e.g mamamls no backbone has no bones .e.g worm

your back bone is a bone that runs down your back .It has a pattern of bone ,plate ,bone ,plate .....so you can move and bend your back.And if i recall correctly the ribs are connected to it.

It's a bone. In your back.Actualy, it is a bone that holds the central nervus system. A long strand of nerves that goes directly to your brain connecting to the other parts of your body.

well insects don't have backbones.they have exoskeletons thats. Cockroaches for example dont have back bones.Thats why when you squish them there is a crunch sound