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