Which animals are segmented worms?

Which animals are segmented worms?

• A. Jellyfish
• B. Octopus
• C. Earthworms
• D. Coral

Answer: (C)

Segmentation, or metamerism, means the body is built from repeated units along its length. This trait is characteristic of annelids, the group that includes earthworms. Earthworms show many body segments, and these segments each contain portions of nerves, muscles, and organs. That repeating plan lets the worm move efficiently by locally contracting muscles in each segment and using tiny bristles called setae to grip soil, while still keeping the digestive and circulatory systems continuous along its length. The arrangement also allows some specialization of structures in different segments without changing the overall body plan.

Jellyfish and coral are cnidarians with radial symmetry and no repeating body segments, so they don’t fit the idea of segmented worms. An octopus is a mollusk (a cephalopod) with a centralized body and many arms, but it does not have the true, repeated body segments seen in earthworms.