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