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Amanda

1.     Which phyla lack organs? What type of symmetry do they have? Poriferans, assymetrical
2.     List all of the phyla that show cephalization? All of the phyla except Poriferans
3.     Do all organisms on the table have 3 germ layers (endoderm, ectoderm and mesoderm)? If not, which Phyla have fewer than three germ layers? Poriferans and Cnidaria
4.     One phylum has more species than all the others. State the name of this phylum and provide several different examples of species found in this phylum. Arthropoda: Crabs, Spiders, Mites, Millipedes, and Centipedes
5.     According to chapter 24, fish do not all have the same skeletal structure? Describe the differences among fish from the most primitive to more advanced types. Fish can either be jawless, cartilaginous fish, or bony fish. Jawless fish have a notochord for a backbone. Cartilaginous fish have a notochord that is surrounded by cartilaginous vertebrae. Bony fish do not have a notochord and there vertebra are fused together and hard.
6.     Describe the three types of mammals based on how their young develop? Monotremes lay eggs, Marsupials are born immature, so mothers have a pouch that the baby stays in until fully formed, and placental mammals give birth to relatively mature young and the fetus receives nutrients from a placenta.