Why is having a hydrostatic skeleton rather than an internal skeleton advantageous to an earthworm?

• A. Having an internal skeleton would not allow the fine movements an earthworm uses when it moves.
• B. Having an internal skeleton would prevent an earthworm from being able to burrow underground tunnels.
• C. Having a hydrostatic skeleton means that having muscles is not a requirement for movement.
• D. None of the listed responses is correct.
• E. Having a hydrostatic skeleton allows the earthworm to use peristaltic motion to move over the substrate.

Answer: (E)

Verified step by step guidance

1. Understand the concept of a hydrostatic skeleton: A hydrostatic skeleton is a structure found in many soft-bodied animals, including earthworms, where fluid-filled compartments provide support and facilitate movement.
2. Recognize the role of a hydrostatic skeleton in movement: In earthworms, the hydrostatic skeleton allows for peristaltic motion, which is a wave-like muscle contraction that enables the worm to move efficiently through soil.
3. Compare hydrostatic and internal skeletons: An internal skeleton, like those found in vertebrates, provides rigid support but may limit flexibility and fine movements necessary for burrowing, which are crucial for an earthworm's lifestyle.
4. Identify the advantages of peristaltic motion: Peristaltic motion allows earthworms to extend and contract their bodies, pushing against the substrate to move forward, which is essential for burrowing and navigating through soil.
5. Conclude why a hydrostatic skeleton is advantageous: The flexibility and adaptability of a hydrostatic skeleton enable earthworms to perform complex movements and efficiently burrow, which would be challenging with a rigid internal skeleton.