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