Figure 2. This diagram is a pie chart showing the contribution of each animal phylum to the total number of animal species. Beginning at the top of the key and indicating the smallest slice of the pie is the Bryozoa shown in dark blue. The next slice is the porifera shown in red. The third slice represents 14 minor phyla and is shown in an olive green. The next and slightly larger piece is the echinodermata shown in purple. Continuing clockwise around the pie chart is the cnidaria shown in bright blue. Next come the annelida shown in orange. The next slightly larger slice is the nematoda shown in bluish-grey. Again moving clockwise, the next section is the platyhelminthes shown in a pink. The next increasingly larger slice is the chordata shown in pale green. The second largest slice is the mollusca shown in light purple. Finally the largest group taking up most of the pie chart is the arthropoda shown in blue.
"Animals Relative Numbers" by Nick Beeson, Wikimedia Commons is in the Public Domain
Animals are generally considered to have a common ancestor, evolving from a flagellated eukaryote. Their closest known living relatives are the choanoflagellates, which are collared flagellates that are morphologically similar to the choanocytes of certain sponges. Animals form the kingdoms Animalia orMetazoa.
Eumetazoa is a clade comprising all major animal groups except sponges and placozoa. Characteristics of eumetazoans include true tissues that are organized into germ layers and an embryo that undergoes a gastrula stage. The clade contains Ctenophora, Cnidaria, and Bilateria.
The Bilateria include all animals with bilateral symmetry, i.e., they have two planes of symmetry. The Bilateria comprise a major group of animals and includes the majority of phyla. The most notable exceptions are the sponges, which belong to Parazoa, and cnidarians, which belong to Radiata. The parazoa group is now considered paraphyletic. It is not included in most modern cladistic analyses. For the most part, bilaterians have bodies that develop from three different germ layers. Nearly all are bilaterally symmetrical. The most notable exception is echinoderms, which achieve near-radial symmetry as adults, but are bilaterally symmetrical as larvae.
Figure 3. The diagram shows the phylogenetic tree of animals. On the left side you have metazoa (animals) this then branches into parazoa (no tissue) and eumetazoa (specialized tissues). The only member of the parazoa group is the sponges. The eumetazoa then divides into the radiata (radial symmetry, diploblastic) and bilateria (bilateral symmetry, triploblastic). The radiata group divides once more into the cnidarians and comb jellies. Bilateria splits in to the protostomia and dueterostomia, the later further divides into chordates and echinoderms. Protostomia divides into ecdysozoa and lophotrochozoa. The ecdysozoa splits into arthropods and roundworms. The lophotrochozoa then divides into five categories: flatworms, rotifers, ribbon worms, annelids, and mollusks.
"Phylogenetic Tree of Animals" by OpenStax College is licensed under CC BY 3.0