- Animals belonging to phylum Chordata are fundamentally characterized by the presence of a notochord, a dorsalhollow nerve cord and paired pharyngeal gill slits.
- These are bilaterally symmetrical, triploblastic, and coelomate with organ-system level of organization.
- They possess a post anal tail and a closed circulatory system.
- Phylum Chordata is divided into three subphyla, which are Urochordata or Tunicata, Cephalochordata and Vertebrata.
- Subphyla Urochordata and Cephalochordata are often referred to as protochordates.
- In Urochordata, notochord is present only in larval tail, while in Cephalochordata, it extends from head to tail region and is persistent throughout their life.
Examples- Urochordata – Ascidia
Cephalochordata – Branchiostoma
- The members of Vertebrata possess notochord during the embryonic period, which is replaced by a cartilaginous or bony vertebral column in the adult and hence all vertebrates are chordates but all chordates are not vertebrates.
Comparison of chordates and non-chordates
- Notochord is present in chordates, on the other hand, absent in non-chordates.
- Central nervous system is dorsal, hollow and single in chordates, whereas ventral, solid, and double in non-chordates.
- In chordates, pharynx perforated by gill slits, whereas gill slits are absent in non-chordates.
- Heart is ventral in chordates, whereas heart is dorsal in non-chordates.
- A post-anal part (tail) is present in chordates but Post-anal tail is absent in non-chordates.