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