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