The correct answer is option (4): D and E Only.

Segmented Body Phyla

Animals with true metameric segmentation (body divided into repeating similar segments, internally and externally) belong to phylum Annelida (D: earthworms, leeches with ring-like metameres) and Arthropoda (E: insects, spiders, crustaceans with tagmata like head-thorax-abdomen).

Option Analysis

• Option (1) A, B and C Only: Incorrect—Protozoa (A: unicellular, no body segmentation), Cnidaria (B: radial symmetry, polyps/medusae), Ctenophora (C: biradial, comb rows ≠ segments).

• Option (2) C and D Only: Misses Arthropoda; Ctenophora lacks true segments.

• Option (3) B and D Only: Excludes Arthropoda; Cnidaria has no metamerism.

• Option (4) D and E Only: Correct—both exhibit segmentation (Annelida: homonomous; Arthropoda: heteronomous/fused).

Introduction: Animals Having Segmented Body Belong to the Phylum

NEET zoology tests phyla with segmentation, asking which contain “animals having segmented body.” Correctly identifying Annelida (worms) and Arthropoda (insects) as option (4) D and E nails classification. This details metamerism, eliminates distractors, and preps exam success.

True Segmentation: Annelida and Arthropoda

Metamerism repeats body segments with similar organs (coelom, nerves, nephridia):

• Annelida (D): Earthworms show ~100-150 identical ring segments (metameres) separated by septa; enables peristaltic locomotion.

• Arthropoda (E): Insects/crustaceans have fused segments into tagmata (head, thorax, abdomen); chitin exoskeleton per segment.

Evolved independently but homologous in protostome lineage.

Why Not A, B, C?

• Protozoa (A): Single-celled; no tissues.

• Cnidaria (B): Gastrovascular cavity, no segmentation (e.g., jellyfish).

• Ctenophora (C): Comb plates in rows, superficial division ≠ true metamerism.

NEET Winner: Option (4) D and E Only

Both phyla dominate animal diversity (Arthropoda: 80% species). Trap: Forgetting arthropod tagmata counts as segmentation.

Phyla Segmentation Quick Table

NEET Tip: Mnemonic—”AnnArth Segmented: Worms + Jointed legs.” Link to coelomate protostomes.