What feature allows earthworms, members of the Annelida phylum, to be classified by external rings?
Answer
Obvious external rings corresponding to internal divisions
The classification of earthworms under the phylum Annelida is directly linked to their segmented structure. The term 'annelid' itself translates to 'little rings.' This characteristic is seen as obvious external rings, or annulations, which correspond precisely to the internal divisions along the worm's body length. This segmentation is not merely superficial; it allows for specialized functions within each section and provides the precise, flexible articulation necessary for their complex, undulating burrowing locomotion, contrasting sharply with the smooth bodies of groups like nematodes.
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