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