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