GENERAL HISTOLOGY

Detailed explanation-1: -Chordates include Urochordates, Cephalochordates (both are called protochordate), and vertebrates. In vertebrates notochord is replaced by the vertebral column (backbone), however, the vertebral column is not present in a protochordate. Therefore, all vertebrates are chordates but all chordates are not vertebrates. Q.

Detailed explanation-2: -Of the approximately 50, 000 living chordates, 97% are vertebrates-animals whose skeletons include a backbone. Three features are present in all chordates. These include a stiffening rod, called a notochord that in many members (e.g., the vertebrates) is replaced during development by a bony, vertebral column.

Detailed explanation-3: -Non-vertebrate chordates: Cephalochordata (lancelets), Urochordata (Tunicates), and Myxini (hagfishes) These groups are the chordates which do not possess vertebrae. Many are hermaphroditic, sessile or buried within the sand of aquatic environments, and hatch from eggs within the parent’s body.

Detailed explanation-4: -The members of Vertebrata possess notochord during embryonic development. Thus, all vertebrates are chordates. However, the notochord gets replaced by a cartilaginous or bony vertebral column in the adult. Thus, all chordates are not vertebrates.

Detailed explanation-5: -Both chordates and vertebrates contain a nerve cord, pharyngeal gill slits, and post-anal tail at some points of their life. The main difference between chordates and vertebrates is that some chordates do not have a vertebral column whereas all vertebrates have a vertebral column.