Neither.
No, they aren't they are plankton
Sponge contains no specialized cells. Sponges are considered one of the most primitive multicellular animals and have a relatively simple cellular structure compared to organisms like paramecium, sea anemone, and jellyfish.
one
It is Phylum Porifera. The porifierans are multicellular organisms but don't have tissues or orgrans. Example: Scypha, Leucosolenia, Euplectella etc.,
No. They are insects and no insect has one.
Yes. It's vertebrate, one of our closer cousins.
One has back bone, one doesn't
Mammals are vertebrates and like all vertebrates have only one back bone . Back bone is made up of vertebrae .
Jellyfish were one of the first creatures to exist on the planet.He was stung by a jellyfish on holiday.Some jellyfish are harmless.
One of your individual backbones is known as a vertebra. The plural is vertebrae.
Most jellyfish can lay 500-700 eggs at one time
Because it is made up of a series of bones called vertebrae and is not one continuous bone. The longest bone, at a guess, is probably the femur.