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