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