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