Biology · Animal Kingdom · NEET
It is a thin, firm, rod-like structure that runs along the back (the dorsal side) of the body. It forms during the embryo stage. It gives support to the body, like a soft internal backbone. NCERT says it is 'a mesodermally derived rod-like structure formed on the dorsal side during embryonic development.' Any animal that has it, even for a short time, is a chordate.
No. This is the most common NEET mix-up. The notochord is a soft rod present in the embryo. In vertebrates it is later replaced by a hard cartilaginous or bony vertebral column (backbone). So the notochord comes first, the backbone comes later. In lower chordates the backbone never forms and the notochord stays.
The mesoderm. NCERT clearly says the notochord is 'mesodermally derived.' It is not from ectoderm or endoderm. NEET has tested this exact word, so remember: notochord = mesoderm origin, dorsal side of the embryo.
No. It depends on the group. In Urochordata (like Ascidia) the notochord is only in the larval tail. In Cephalochordata (like Amphioxus) it runs from head to tail and stays for the whole life. In Vertebrata it is present only in the embryo and is replaced by the vertebral column. In class Chondrichthyes (sharks) the notochord stays persistent throughout life.
They are two different structures, both on the back. The notochord is a solid supporting rod. The nerve cord in chordates is a dorsal, hollow, single tube that carries the nervous system. In non-chordates the nerve cord is ventral, solid and double. Do not confuse the support rod (notochord) with the nerve cord (nervous system).
No, but it looks similar. Hemichordates have a small rudimentary structure in the collar region called the stomochord. NCERT calls it 'a structure similar to notochord,' but it is not a true notochord. That is one reason Hemichordata is placed as a separate phylum (non-chordate), not inside Chordata.
Assertion (A): All vertebrates are chordates but all chordates are not vertebrates. Reason (R): Notochord is replaced by the vertebral column in the adult vertebrates. Choose the most appropriate answer.
Which statements are true for phylum Chordata? (a) In Urochordata notochord extends from head to tail and is present throughout 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.
Select the incorrect statements: A. Digestive system in Platyhelminthes is incomplete. B. Bilateral symmetry is a characteristic feature of adult Echinoderms. C. Pseudocoelom is possessed by Aschelminthes. D. Notochord is persistent throughout life in the class Chondrichthyes. E. Members of class Reptilia maintain a constant body temperature.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A mesodermally derived, rod-like structure formed on the dorsal (back) side of the body during embryonic development. Animals that have it are called chordates.
On the dorsal side, running lengthwise along the back of the embryo, just below the nerve cord.
The mesoderm. NCERT states the notochord is 'mesodermally derived.'
In Cephalochordata (Amphioxus), where it runs head to tail, and in class Chondrichthyes (cartilaginous fishes), where it is persistent throughout life.
It is the single defining feature that separates chordates from non-chordates. Many NEET questions test where and when it is present, so it is high-yield for the Animal Kingdom chapter.
