Every organism is an animal, fungus, human-being, micro-organism, or plant.
Every animal is a vertebrate or invertebrate.
Every vertebrate is an amphibian, bird, fish, mammal, or reptile.
Every invertebrate is an annelid, arthropod, echinoderm, mollusk, or protozoan.
# To continue, click button «Clear your mind.» or «Restart.».