Question

1. which animal phylum includes the roundworms?

annelida
cnidaria
nematoda
porifera

Explanation:

To determine the animal phylum of roundworms, we analyze each option:

• Annelida: Includes segmented worms (e.g., earthworms), not roundworms.
• Cnidaria: Includes organisms like jellyfish and corals, characterized by cnidocytes, not roundworms.
• Nematoda: This phylum specifically includes roundworms, which are unsegmented, have a pseudocoelom, and exhibit bilateral symmetry.
• Porifera: Includes sponges, which are simple filter - feeding organisms, not roundworms.

Answer:

C. Nematoda