Notochord Structure in Protochordates — NEET Biology
✅ Asked in NEET 2020Which of the following statements are true for Phylum Chordata? A. In Urochordata, notochord extends from head to tail and is present throughout life. B. In Vertebrata, notochord is present only during embryonic period. C. Central nervous system is dorsal and hollow. D. Chordata is divided into three subphyla: Hemichordata, Tunicata and Cephalochordata. NEET Year: NEET 2020
Which of the following statements are true for Phylum Chordata? A. In Urochordata, notochord extends from head to tail and is present throughout life. B. In Vertebrata, notochord is present only during embryonic period. C. Central nervous system is dorsal and hollow. D. Chordata is divided into three subphyla: Hemichordata, Tunicata and Cephalochordata. NEET Year: NEET 2020
Answer & NCERT explanation
Correct answer: D — B and C only
Statements B and C are correct. In vertebrates, notochord is present only during embryonic period and gets replaced by vertebral column. Central nervous system is dorsal and hollow in chordates. Statement A is wrong - in urochordates, notochord is present only in larval tail. Statement D is wrong - Hemichordata is separate phylum.
Read more NCERT concept on the PYQ
Subphyla Urochordata and Cephalochordata are often referred to as protochordates and are exclusively marine. 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.
NTA tests the key difference in notochord persistence between Urochordata and Cephalochordata. In Urochordates, the notochord appears only in the larval stage within the tail and disappears in adults, while in Cephalochordates, it runs continuously from head to tail throughout their entire life cycle. Students often confuse these two groups and incorrectly assume both have temporary or permanent notochords alike. Remember: Urochordata = larval notochord only; Cephalochordata = lifelong notochord from head to tail. This distinction directly relates to their classification as protochordates and their evolutionary position toward true chordates.
What does NCERT say about Subphyla Urochordata and Cephalochordata?
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