1. Calcarea & Silicea
   1. Calcarea and Silicea are basically defined as sponges, still animals that simply lack tissues.
      1. They were previously mistaken as plants.
         1. They live as suspension feeders, so they have to wait for particles to float by to consume them.
            1. They are basal animals, meaning they are very closely related to the original invertebrate ancestor.
            2. They may not have tissues, but they do have layers of cells that classify them as animals.
            3. They are known for producing antibiotics and other medicines.
            4. They are using them to treat Streptococcus, as well as being tested for cancer treatments.
2. Cnidaria
   1. One of the oldest lineages in the clade Eumetazoa, animals with true tissues.
      1. They are known for representing those animals that haven't physically changed in 570 million years.
         1. The basic body plan is a sac that has two functions: as a mouth and an anus.
            1. They are also only found in two forms: in polyp form, face=up, or medusa form, face-down.
            2. They are carnivores that tend to have tentacles around their mouth to catch their prey.
            3. As they do no have a brain, their movements are coordinated by a nerve net instead.
3. Lophotrochozia
   1. Not only are they in the Eumetazoa clade, but also in the Bilateria clase, which shows bilateral symmetry and develpment.
      1. Lophotrochozoa were identified by molecular data.
         1. Its name came from some of the physical features of the group.
            1. They are the most diverse clade in terms of body plan.
            2. The diversity is shown through the number of animal phyla in the group: 18 animal phyla. This is more than twice the number of any other group.
            3. Most members consist of a lophophore, which is a crown of tentacles that help in eating. This is what the group was named for.
4. Ecdysozoa
   1. They were found primarily by molecular evidence.
      1. It includes animals that shed an external coat, a cuticle, as they grow.
         1. The group actually received their name for this shedding process, called molting or ecdysis.
            1. It consists of 8 animal phyla.
            2. It contains more species than all other plant, protist, animal, and fungus groups combined.
            3. Two of the largest and successful phyla it has are the nematodes and arthropods.
5. Deuterostomia
   1. Much of this group consists of the phylum Chordata, which actually includes vertebrates, but we are not going to include them.
      1. Some of the invertebrate Deuterostomia do have similar characteristics to vertebrates, though.
         1. They have radial cleavage and the formation of the mouth opposite of the blastopore.
            1. This group is defined primarily by DNA similarities, not developmental.
            2. This is because molecular evidence indicates that some animal phyla from other groups could technically be classified into this group.
            3. The three groups of invertebrates placed in the Chordata group are lancelets, tunicates, and hagfishes.