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