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