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