Answer: Cephalochordata.
- A Urochordata
- B Cephalochordata
- C Vertebrata only
- D Hemichordata
Correct answer: B. Cephalochordata
Explanation: In Cephalochordata (e.g., Branchiostoma), the notochord extends from head to tail and persists throughout life. In Urochordata, it is present only in the larval tail.
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.