Hint:Vertebrates make up less than five percent of all animal species described; invertebrates make up the remainder,
An animal with a spinal cord surrounded by cartilage or bone is a vertebrate. The term derives from the vertebrae, the spine-forming bones. Invertebrates are considered organisms that are not vertebrates. Birds, whales, amphibians, reptiles, and rodents are vertebrates. The vertebrate skeleton pieces are:
Braincase: Brains are covered by a braincase or cranium.
Vertebrae: Joints divide a series of small, rigid vertebrae. The spinal cord is safeguarded by this internal backbone. The joints make the backbone bend between the vertebrae.
Bones: Help and secure the soft tissues of the body and provide muscle attachment points.
Gill arches: Gill arches and some amphibians protect the gills in the pharynx of fish. Some of the arches developed into others as well, In the majority of vertebrates, limbs, and jaws.
Mammals, insects, and fish include examples of vertebrates. There were a few tens of thousands of organisms listed. To identify at least four different kinds of vertebrates, the word 'fish' is used.
Between animals in nearly all environments, vertebrates dominate.
In each primary ecosystem, they contain the largest species, but not the largest living beings (because it would contain trees). They are the only species to have an immune system that is adaptive. These two facts could be related.
So the answer is “An internal bone or cartilaginous skeleton”.
Note:It is possible to subdivide vertebrates into five main groups: fish, amphibians , reptiles , birds, and mammals. Groups include amphibians, rodents, birds , and mammals.