These are multicellular leafy organisms. They are predominantly marine, with cellulose cell walls. These are abundant reef-building algae, and some species produce large amounts of agar and carrageenan. They often have intricate external structures called 'lorica', and resemble the individual cells of sponges. These organims probably resemble the ancestral protists from which animals arose.
Animals are colonial or multicellular organisms with chondroitin cell walls.
Morphological classification is fairly consistant with the molecular phylogenetic data - probably because of their morphological complexity. Most of the animals are microscopic. The most abundant groups by far are microscopic nemotodes and arthropods. Eukaryotic evolution Eukarya are morphologically complex, but biochemically simple compared to either Bacteria or Archaea. Eukaryal evolution is predominated by increased genetic complexity.