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