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