Which phylum does the organism Ascaris belong to?
Ascaris (roundworm) belongs to phylum Nematoda, characterized by pseudocoelomate, unsegmented bodies (NCERT, Chapter 4, page 51). Annelida includes segmented worms, Platyhelminthes includes flatworms, and Echinodermata includes starfish.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Aschelminthes and Annelida