Intertidal area only
Both intertidal area and subtidal areas
Subtidal area only
On the beach
Toothpick
Porcupine
Dome
Pentamerous
Nose
Mouth
Feet
Spine
Purpuratus
Echinoderms
Animalia
Strongylocentrotus
Other sea urchins
Algae
Small fish
Sea cucumbers
Because sea urchins have large numbers of eggs
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