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