Vertebrate and Germ Layers

Topics: Vertebrate, Chordate, Fish Pages: 2 (494 words) Published: March 27, 2011
1. Which phyla lack organs? What type of symmetry do they have? Flatworms, Roundworms and Segmented Worms lack organs. They all are Bilateral in symmetry. 2. List all of the phyla that show cephalization.

Platyhelmnthes, Annelida, Molluscu, Arhropodia and Chordata
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? No, they all do not. Scyphozoa (Cnidaria) 2 layers, Insecta (Athropoda) 2 layers, Porifera (Hexactinella), Asteroidea (Echinodermata) 1 layer, Aves (Chordata) 1 layer and Platyhelminthe (Cestoda) 1 Layer ( 4. 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. Insecta. Over 925,000 species described. Insects represent more than half of all identified animal species, and some authorities estimate that less than 10 percent of living insect species actually have been described and named. The beetles are the most numerous insects, with over 400,000 species. 170, 000 butterfly and moth, 120,000 fly, 82,000 true bug, 110,000 bee and ant, 5,000 dragonfly, 2,000 praying mantis and 20,000 grasshopper species ( 5. Fish do not all have the same skeletal structure. Describe the differences among fish from the most primitive to more advanced types of fish. Jawless fish (Agnatha)- Often considered a super class within the subphylum Vertebrata. The two extant groups of jawless fish are the lampreys and the hagfish. They both lack scales and plates and have slimy skin. They are cold blooded, do not have to warm themselves through eating, have a slow metabolism and have to eat relatively small quantities of food ( Cartilagnous fish (Chondrichthyes)- Major class of jawed fish that includes the shards, rays and skates, and whose skeleton is...
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