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