I believe they are round so they can have the most surface area for spines, thus protecting more of their bodies.
The structural deference between them is that Sea urchins are more globular whereas sand dollars are flattened. Unlike sea urchins, the sand dollars burrow themselves when threatened. Sand dollars have anus opening at their back side whereas the sea urchins have it at the top.
Yes, they are animals. Sea urchins, specifically, are round and prickly like hedgehogs.
No. Sea urchins live in the sea.
More sea urchins.
The classification of a Sea Urchin is Echinoidea
there are excatly 3million purple sea urchins
sea urchins eat kelp.
Echinoderms.
No. Sea urchins are primary consumers and only eat sea weed, algae and kelp.
in the sea
Yes, sea urchins are herbivores because they mainly feed on algae.
Sea urchins reproduce by releasing eggs and sperm into the water, where external fertilization takes place. Once fertilized, the eggs develop into larvae that eventually settle and grow into adult sea urchins. Some species of sea urchins can also reproduce by asexual means, such as splitting or budding.