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