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