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