Question

All vertebrates are chordates but all chordates are not vertebrates. Justify the statement.

Answer 1

A Chordate is an animal of the phylum Chordata. They possess a notochord, a dorsal nerve cord, pharyngeal slits and a post-anal tail. All these for anatomical sites define the characters of phylum Chordata.

Complete answer:
Vertebrates consists of all species of animals within the subphylum Vertebrata (chordates with backbones). They represent the immense majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates include certain groups of organisms that are as follows:
1. Jawless fishes.
2. Jawed vertebrates mainly include the cartilaginous fishes such as sharks, rays, and ratfish.
3. Tetrapods also include amphibians, reptiles, birds and mammals.
4. Bony fishes.
In subphylum Vertebrata, the notochord present in embryos gets replaced by a cartilaginous or bony vertebral column when turned into adults. In cephalochordates, the notochord continues throughout life as such and in urochordates, the notochord is present only in larval stages and becomes absent in adults.
Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.

Note: Amphioxus also known as lancelet is a fish-like marine chordate. Unlike vertebrates, the dorsal nerve cord is not protected by bone but by a simpler notochord made up of a cylinder of cells that are closely packed to form a toughened rod. In some chordates, the notochord is only available in the larvae tail region. The notochord is present in some other chordates throughout the length of the body. In some chordates, the vertebral column replaces the notochord.