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