Chordata & Vertebrata

• Chordates are higher animals that have characteristics features like - Dorsal tubular nerve cord,  dorsal  Notochord and pharyngeal gill slit.

• In addition to this , they have closed circulatory system and a specific post anal tail.

• Chordates are Triploblastic, Coelomate, bilateral symmetrical with organ system level of organisation.

General Comparison between Non chordates and Chordates 

• In Non chordates, Notochord and pharyngeal gill slit are absent whereas these are present in Chordates.

• In some  Non chordates, nerve cord is ventrally located but all chordates have nerve cord located dorsally.

• In  Non chordates, central nervous system  is ventral solid and double whereas  In  chordates, Central nervous system is dorsal hollow and single.

• Post anal tail is absent in Non chordates but present in Chordates.

• Heart is dorsal in Non chordates whereas Heart is in  ventral side in Chordates.

Division of  Chordates 

• Chordates are divided into Protochordata and Vertebrata

• Protochordates include Urochordates and  cephalochordates.

• Vertebrata is divided into Agnatha and Gnathostomata.

• Term Agnatha refer to absence of jaws and it include the member of Cyclostomata.

• Gnathostomata is further divided into  Pisces 🐟 and Tetrapods.

• Tetrapods include Amphibian, Reptiles, Birds and Mammals.

• Term Vertebrates is used for such chordates in which Notochord is replaced by the vertebral column that can be cartilaginous or Bony. 

• But, all chordates do not have vertebral column that is notochord is not replaced into vertebral column.

• Therefore, all vertebrates are chordates but all chordates are not vertebrates.

• For example: In urochordates and cephalochordates, notochord is not replaced by vertebral column hence they are chordates but not vertebrates.

• Beside chordates characters, vertebrates has kidney for excretion and osmoregulation. Three and four chambered of muscular heart and fin or limb 🦵 for locomotion.