Phylum Chordata
It includes animals with notochord, dorsal tubular nerve cord, and pharyngeal gill slits.
Notochord is a flexible rod located in the mid-dorsal line between the alimentary canal and the nerve cord in the embryo.
Differences between Chordata and Non-Chordata
| Chordata | Non-Chordata |
|---|---|
| Notochord is found in the embryonic stage. | Absent |
| Central nervous system is dorsal, hollow, and single. | Ventral, solid, and double |
| Pharyngeal gill slits present. | Absent |
| Ventral heart. | Dorsal heart (if present) |
| Post-anal part (tail) is present. | Absent |
Phylum Chordata is classified into 3 subphyla: Urochordata, Cephalochordata, and Vertebrata.
Protochordata (Acraniata)
Urochordata (Tunicata)
- Notochord is present only in larval tail.
- Exclusively marine.
- Hermaphrodite.
- E.g., Ascidia, Salpa, Doliolum
Cephalochordata
- Notochord from head to tail region and is persistent throughout the life.
- Fish-like body.
- Exclusively marine.
- Sexes are separate.
- E.g., Branchiostoma (Amphioxus or Lancelet)
Ascidia
Vertebrata (Craniata)
- Possess notochord during the embryonic period.
- Notochord is replaced by a cartilaginous or bony vertebral column in the adult.
- Ventral muscular heart.
- Kidneys for excretion and osmoregulation.
- Paired appendages (fins or limbs).
Classification of Vertebrata
