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