Answer :
Their powerful, sharp spines help urchins survive. With the exception of a few species, which are capable of venom, adult sea urchins are often well protected from the majority of predators.
Hundreds of razor-sharp spines cover it, acting as an adaption to deter many possible predators. The sea urchin, a herbivore, has evolved five incredibly sharp, hard teeth to scrape tiny algae plants off the rocks in rocky tidepools where it lives.
The spines shield an urchin from predators and serve as feeding spears. A water stream is produced by the tiny hairs (cilia) surrounding the spines, which delivers food to the urchin and removes waste. On the ocean floor, mainly on hard surfaces, sea urchins can move around by using their tube feet or spines.
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