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