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