Answer: Echinodermata adults, radial symmetry.
- A Porifera, exhibiting bilateral body symmetry overall
- B Echinodermata adults, radial symmetry
- C Annelida, exhibiting radial body symmetry overall
- D Platyhelminthes, lacking any defined body symmetry
Correct answer: B. Echinodermata adults, radial symmetry
Explanation: Echinodermata show radial symmetry as adults but bilateral symmetry as larvae. Porifera is generally asymmetrical, and Annelida and Platyhelminthes show bilateral symmetry.
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.