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