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