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