Which characteristic is essential for identifying segmented worms?

The segmentation of the body is a fundamental characteristic that is essential for identifying segmented worms, which belong to the phylum Annelida. This feature distinguishes segmented worms from other groups of invertebrates. The body is divided into a series of repeating segments, which allows for increased mobility and flexibility. Each segment may contain components of the circulatory, nervous, and excretory systems, contributing to the organism's overall complexity.

This segmentation allows for specialized movement and the development of more complex organ systems, which are traits that segmented worms possess compared to non-segmented worms or other invertebrates. Hence, the presence of segmentation is a defining characteristic, making it vital in identifying these organisms.