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Invertebrate
An '''invertebrate''' is an animal lacking a vertebral column. The group includes 98% of all animal species[Encarta Reference Library Premium 2005 DVD. Article - Invertebrate.] — all animals except those in the Chordate subphylum vertebrate|Vertebrata (fish, reptiles, amphibians, birds, and mammals).
Carolus Linnaeus' ''Systema Naturae'' divided these animals into only two groups, the Insecta and the now-obsolete vermes (worms). Jean-Baptiste Lamarck, who was appointed to the position of "Curator of Insecta and Vermes" at the Muséum National d'Histoire Naturelle in 1793, both coined the term "invertebrate" to describe such and divided the original two groups into ten, by splitting off Arachnida and Crustacea from the Linnean Insecta, and Mollusca, Annelida, Cirripedia, Radiata, Coelenterata and Infusoria from the Linnean Vermes. They are now classified into over 30 phylum (biology)|phyla, from simple organisms such as sea sponges and flatworms to complex animals such as arthropods and Mollusca|molluscs.
Invertebrates form a paraphyletic group. (For a full list of animals considered to be invertebrates, see animal.) All the listed phyla are invertebrates along with two of the three subphylum|subphyla in Phylum chordate|Chordata: Tunicata|Urochordata and Lancelets|Cephalochordata. These two, plus all the other known invertebrates, have only one cluster of Homeobox|Hox genes, while the vertebrates have duplicated their original cluster more than once.
Within paleozoology and paleobiology, invertebrates big and small are often studied within the fossil discipline called invertebrate paleontology.
Phyla and common examples
- Annelida — segmented worms (earthworms, leeches, polychaetes)
- Arthropoda — insects, arachnids, crustaceans
- Cnidaria — jellyfishes, corals, sea anemones, Hydra (genus)|hydras
- Echinodermata — sea stars, sea urchins, sea cucumbers
- Mollusca — squid, snails, bivalves
- Nematode|Nematoda — round worms
- Nematomorpha — horsehair worms or gordian worms
- Platyhelminthes — flat worms
- Porifera — sponges
See also
- Marine invertebrates
References
Further reading
- Libbie Hyman|Hyman, L. H. 1940. ''The Invertebrates'' (6 volumes) New York : McGraw-Hill. A classic work.
- Anderson, D. T. (Ed.). (2001). ''Invertebrate zoology'' (2nd ed.). Oxford: Oxford University Press.
- Brusca, R. C., & Brusca, G. J. (2003). ''Invertebrates'' (2nd ed.). Sunderland, Mass. : Sinauer Associates.
- Miller, S.A., & Harley, J.P. (1996). ''Zoology'' (4th ed.). Boston: WCB/McGraw-Hill.
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- Ruppert, E. E., Fox, R. S., & Barnes, R. D. (2004). ''Invertebrate zoology: a functional evolutionary approach''. Belmont, CA: Thomas-Brooks/Cole.
External links
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- Support for endangered invertebrates
- ''African Invertebrates''
- Life Cycle of Macroinvertebrates. Macroinvertebrates go through a life cycle in usually one season or less. They go through complete or incomplete metamorphosis.
Category:Animals
Category:Paleontology
Category:Zoology
simple:Invertebrate
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