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