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