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