Answer: Cephalochordata retains the notochord from head to tail throughout life; Urochordata retains it only in the larval tail.
- A Cephalochordata retains the notochord only in the larval tail before resorption at metamorphosis; Urochordata retains it for life
- B Cephalochordata retains the notochord from head to tail throughout life; Urochordata retains it only in the larval tail
- C Both groups retain a fully ossified vertebral column replacing the notochord in adults
- D Neither group develops a notochord at any embryonic or adult stage
Correct answer: B. Cephalochordata retains the notochord from head to tail throughout life; Urochordata retains it only in the larval tail
Explanation: In Cephalochordata (Amphioxus/Branchiostoma), the notochord persists from head to tail throughout life. In Urochordata (Ascidia), the notochord is present only in the larval tail and is lost in the adult.
Moving across the animal phyla, body organisation becomes progressively more complex: from no symmetry and cellular organisation (Porifera) through radial/diploblastic (Cnidaria), bilateral/acoelomate (Platyhelminthes), pseudocoelomate (Nematoda), to a true coelom with full organ systems (Annelida and beyond).
Concept context
Phylum-level classification of the animal kingdom from Porifera to Chordata, based on body symmetry, coelom, and segmentation. One of the most example-heavy chapters for NEET.