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