Invertebrate

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Invertebrate is a term coined by Jean-Baptiste Lamarck to describe any animal without a spinal column. It therefore includes all animals except vertebrates (fish, reptiles, amphibians, birds and mammals).

Lamarck divided these animals into two groups, the Insecta and the Vermes, but now, they are classified into over 30 phyla, from simple organisms such as sponges and flatworms to complex animals such as arthropods and mollusks.

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 animal. All the listed phyla are invertebrates along with two of the three subphyla in Phylum Chordata: Urochordata 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.

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External links

ca:Invertebrat cy:Infertebrat da:Invertebrat de:Wirbellose et:Selgrootud es:Invertebrado fr:Invertébré id:Invertebrata he:חסרי חוליות lt:Bestuburiai ms:Invertebrat nl:Ongewerveld ja:無脊椎動物 no:Virvelløse dyr pl:Bezkręgowce pt:Invertebrado simple:Invertebrate zh:无脊椎动物

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