Algae
Other sea urchins
Small fish
Sea cucumbers
Toothpick
Dome
Pentamerous
Porcupine
Mouth
Feet
Nose
Spine
Purpuratus
Echinoderms
Strongylocentrotus
Animalia
Intertidal area only
On the beach
Both intertidal area and subtidal areas
Subtidal area only
Because sea urchins have large numbers of eggs
Because a sea urchin's egg is relatively big
Because sea urchins have large numbers of relatively big eggs
Because the eggs make great omlettes