Notochord 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.
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