| Invertebrates |
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| CATEGORIES ABOUT INVERTEBRATE | |
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Lamarck divided these animals into two groups, the Insect a and the Vermes , but now, they are classified into over 30 Phyla , from simple organisms such as Sponge s and Flatworm s to complex animals such as Arthropod s and Mollusk s. Since invertebrates include all animals except a certain group, invertebrates form a Paraphyletic group, but, despite not forming a "natural group" (that is, Monophyletic ), "invertebrate" is still a widely used term. Invertebrates include 97% of all animal Species . For a full list of animals considered to be invertebrates, see and Cephalochordata . These two, plus all the other known invertebrates, have only one cluster of Hox Genes , while the vertebrates have duplicated their original cluster more than once. EXTERNAL LINKS
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