Notochord: Defining Chordates — NEET Biology
📚 Practice ConceptNotochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates and those animals which do not form this structure are called non-chordates, e.g., porifera to echinoderms.
Which of the following statements concerning the notochord and its presence in animals are correct? S1: Notochord is a mesodermally derived, rod-like structure formed on the dorsal side during the embryonic development of all Chordates. S2: In Urochordata, the notochord is present throughout their life, extending from the head to the tail region. S3: All vertebrates possess a notochord during their embryonic period, which is later replaced by a cartilaginous or bony vertebral column in adults. S4: Organisms belonging to phyla from Porifera to Echinodermata are classified as non-chordates, explicitly lacking a notochord. S5: Hemichordates possess a rudimentary structure called stomochord in the collar region, which is considered similar to a notochord.
View solution & NCERT explanation
Correct answer: B — S1, S3, S4, and S5
The question asks to identify the correct statements about the notochord. S1: This statement is correct. Notochord is a mesodermally derived, rod-like structure formed on the dorsal side during embryonic development in all chordates. (NCERT, Section 4.1.6 and 4.2.11) S2: This statement is incorrect. In Urochordata, the notochord is present only in the larval tail, not throughout their life extending from head to tail. This persistent, head-to-tail notochord is characteristic of Cephalochordata. (NCERT, Section 4.2.11) S3: This statement is correct. Vertebrates possess a notochord during the embryonic period, which is subsequently replaced by a vertebral column in the adult. (NCERT, Section 4.2.11) S4: This statement is correct. Phyla from Porifera to Echinodermata are categorized as non-chordates, and they do not form a notochord. (NCERT, Section 4.1.6) S5: This statement is correct. Hemichordates have a rudimentary structure in the collar region called stomochord, which is similar to a notochord. (NCERT, Section 4.2.10) Therefore, S1, S3, S4, and S5 are correct statements.
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