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