> Eudora
> Our Universe
> Galaxies
> Individual Galaxies
> Milky Way
> Spiral Arms of the Milky Way
> Orion–Cygnus Arm
> Individual Planetary & Star Systems in the Orion-Cygnus Arm
> Solar System
> Objects in the Solar System
> Planets of the Solar System
> Individual Planets in the Solar System
> Earth
> Chronology of Earth
> History of the Earth
> Evolution of Life
> Tree of Life on Earth
> Domains, Species Kingdoms etc.
> Node
> Eukaryota
> Unikonta
> Opisthokonta
> Holozoa
> Filozoa
> Node
> Animalia (syn. Metazoa)
> Eumetazoa
Platyzoa
Nephrozoa. Bilateria. Except for a few phyla (i.e. flatworms and gnathostomulids), bilaterians have complete digestive tracts with a separate mouth and anus.
Some bilaterians lack body cavities (acoelomates, i.e. Platyhelminthes, Gastrotricha and Gnathostomulida), while others display primary body cavities (deriving from the blastocoel, as pseudocoel) and/or secondary cavities (that appear de novo, for example the coelom). Evolution[edit]
