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