Pentamerous
Porcupine
Toothpick
Dome
Other sea urchins
Sea cucumbers
Algae
Small fish
Mouth
Spine
Feet
Nose
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
Animalia
Strongylocentrotus
Echinoderms
Purpuratus
Intertidal area only
On the beach
Subtidal area only
Both intertidal area and subtidal areas