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