What fundamental physical characteristics do worms generally lack, defining their body type?
Answer
Jointed limbs or a backbone
The term 'worm' encompasses a broad category of soft-bodied animals distinguished by a fundamental lack of complexity in their vertebrate features. Specifically, they are defined by the absence of jointed limbs, which are characteristic of arthropods and vertebrates, and they completely lack a backbone, meaning they are invertebrates. This anatomical simplicity—a soft, elongated body without rigid skeletal support or complex appendages—is what allows them to maintain a tubular shape suitable for burrowing across diverse environments.
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