Biology · Animal Kingdom · NEET
Phylum Chordata is divided into three subphyla: Urochordata (also called Tunicata), Cephalochordata, and Vertebrata. Note carefully: Hemichordata is NOT a subphylum of Chordata anymore. NCERT places Hemichordata as a separate phylum among the non-chordates. NEET has tested this exact trap (2020), so never write Hemichordata as a chordate subphylum.
This is the whole basis of the classification. In Urochordata the notochord is present ONLY in the larval tail and disappears in the adult. In Cephalochordata the notochord extends from head to tail and stays for the whole life. In Vertebrata the notochord is present only during the embryonic stage and is later replaced by a cartilaginous or bony vertebral column (backbone). Remembering these three locations answers most PYQs on this topic.
Urochordata and Cephalochordata together are called Protochordates. "Proto" means first or primitive. They are chordates but they do NOT have a backbone; their notochord is never replaced by a vertebral column. Vertebrata are the advanced chordates where the notochord is replaced by a vertebral column. So all Protochordates and all Vertebrates are chordates, but only Vertebrates have a backbone.
Every vertebrate has the four basic chordate features (notochord at some stage, dorsal hollow nerve cord, pharyngeal gill slits, post-anal tail), so every vertebrate is a chordate. But Urochordata and Cephalochordata are also chordates and they never form a vertebral column. So having a backbone is extra; being a chordate does not require a backbone. The reason vertebrates are special is that their embryonic notochord is replaced by a vertebral column. This exact Assertion-Reason appeared in NEET 2022 and 2025.
Urochordata: Ascidia, Salpa, Doliolum. Cephalochordata: Branchiostoma (also called Amphioxus or Lancelet). Vertebrata: fishes, amphibians, reptiles, birds and mammals. In NEET, Branchiostoma is a very common example used to test Cephalochordata, so memorise it firmly.
Yes. A tunicate (Urochordata) starts as a free-swimming larva that has a notochord in its tail. During metamorphosis it changes into a fixed adult and loses the tail notochord. NEET 2018 tested this by asking which animal does NOT undergo metamorphosis (answer was earthworm), while tunicate does undergo metamorphosis.
Which of the following statements are true for the phylum Chordata? (a) In Urochordata notochord extends from head to tail and it is present throughout their life. (b) In Vertebrates notochord is present during the embryonic period only. (c) Central nervous system is dorsal and hollow. (d) Chordata is divided into 3 subphyla: Hemichordata, Tunicata and Cephalochordata.
Assertion (A): All vertebrates are chordates but all chordates are not vertebrate. Reason (R): The members of subphylum Vertebrata possess notochord during the embryonic period, the notochord is replaced by a cartilaginous or bony vertebral column in adults.
Which of the following animals does not undergo metamorphosis?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Cephalochordata (example Branchiostoma / Amphioxus). Its notochord runs from head to tail and stays for the whole life. In Urochordata the notochord is only in the larval tail, and in Vertebrata it is replaced by a vertebral column.
No. In NCERT, Hemichordata is a separate phylum among the non-chordates. The three chordate subphyla are only Urochordata, Cephalochordata and Vertebrata. Treating Hemichordata as a chordate subphylum is a common exam trap.
Urochordata is also called Tunicata. Common examples are Ascidia, Salpa and Doliolum. The name Urochordata means the notochord (chorda) is in the tail (uro) region only, and only in the larva.
Protochordates are the primitive chordates without a backbone: the subphyla Urochordata and Cephalochordata. They have a notochord but never a vertebral column, unlike Vertebrata.
Chordate subphyla are directly tested almost every year, usually as statement-based or Assertion-Reason questions (2020, 2022, 2025). Knowing where the notochord sits in each subphylum and that Hemichordata is not a subphylum lets you answer these quickly and score easy marks.
