Describe the three types of mammals based on how their young develop.

Answer the following questions as they relate to the nine phyla in the assignment table. (Porifera, Cnidaria, Nematoda, Athropoda, Platyhelminthes, Annelida, Mollusca, Echinodermata, and Chordata.)
Which phyla lack organs? What type of symmetry do they have?
List all of the phyla that show cephalization.
Do all organisms on the table have 3 germ layers (endoderm, ectoderm, and mesoderm)? If not, which phyla have fewer than three germ layers?
One phylum on the table has more species than all the others. State the name of this phylum, and provide several different examples of species found in this phylum.
Fish do not all have the same skeletal structure. Describe the differences among fish skeletal structures from the most primitive to more advanced types of fish.
Describe the three types of mammals based on how their young develop.