Animal Evolution

I. To be on the Animal family tree A. must be multicellular B. must be heterotrophs C. can not have cell wall D. must be Eukaryotes

II. All Phyla more advanced than Porifera A. Have tissues 1. groups of cells that work together 2. attached by a membrane

B. Have symmetry 1. radial symmetry a. circular body plan b. can cut in half many ways

2. Bilateral Symmetry a. can only cut in ½ one way b. left and right sides c. have developed a head end (cephalization) c. all animals more advanced than Phylum Cnidaria d. all are triploblastic (3 tissue layers)

III. To be more advanced than flatworms A. animals need an empty space inside body for organs to form B. Empty space is called a coelom C. Acoelomate = no coelom having D. Porifera, Cnidaria, & flatworms are acoelomates

D.Simple animals like Nematodes have a pseudocoelom = fake body cavity 1. Not very well developed 2. Just a space between tissue layers

E. More advanced organisms have a Coelom (true body cavity) 1. called eucoelomates 2. complex cavity in mesoderm 3. provides space & attachment site for organs to grow

IV. Embryo Development A. Used to divide up advanced animals C. looks at formation of digestive tube 1. alimentary canal 2. one way tube mouth to anus B. Mollusks, Annelids & Arthropods 1. protostomes first mouth 2. mouth forms first

C. Echinoderms & Chordates 1. Deuterostomes second mouth 2. mouth forms second 3. anus forms first