Answer: Nematoda.
- A Platyhelminthes
- B Nematoda
- C Annelida
- D Mollusca
Correct answer: B. Nematoda
Explanation: Ascaris is a parasitic roundworm of phylum Nematoda, characterized by a pseudocoelom and a circular cross section.
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.