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