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