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