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