Final answer:
Barbara Hurd uses the comparison to highlight the regenerative abilities of sea stars, contrasting them with humans who cannot regenerate limbs. This ability is a form of asexual reproduction called fragmentation, signifying a stark difference in healing and reproductive capacities.
Step-by-step explanation:
Barbara Hurd is making a point by comparing a sea star missing an arm to a human missing a limb to emphasize the regenerative ability of sea stars compared to humans. While humans can experience significant trauma and long-term disability after losing a limb, sea stars are capable of regenerating lost limbs, often complete with new individuals arising from these limbs due to fragmentation. This is a fascinating aspect of asexual reproduction in echinoderms and highlights the significant differences between human and sea star physiology and their capacities for healing and reproduction.