Question

some chordate animals are called vertebrates and some are called invertebrates? why ?

Answer 1

Chordates are the members of Phylum Chordata. The organisms having notochord and nerve cord are known as Chordates. Most of the chordates are vertebrates like mammal, reptile, fish etc. in which the notochord has been replaced by the spinal cord (vertebrae). Some organisms like hagfish, lamprey etc. is chordates but as they do not have vertebrae, they are invertebrates.