Answer: Invertebrates

Skeleton refers to the body part which supports the body structure of a living organism. It is the internal as well as an external system of bones, muscles, cartilage that is utmost essential for the body structure support of a living organism on the planet Earth.

Invertebrates refer to the group of those organism species which lack a backbone or bony skeleton. This is by the percentage aspect,  the largest animal group in the animal kingdom. They account for 97 percent of the total animals living on the Earth.

1.25 million species have been noticed and a large portion of which are creepy insects and there are millions more to be found. The all outnumber of invertebrate species could be 10 or even 30 million, compared to only 60,000 vertebrates.

One explanation behind the accomplishment of these spineless creatures (invertebrates) is the manner by which rapidly they reproduce. corals, for instance, produce the two eggs and sperm. For another example, ants and honey bees lay eggs that can produce without fertilization process.