invertebrate (ĭn'vûr`təbrət, –brāt'), any animal lacking a backbone. The invertebrates include the tunicates tunicate , marine animal of the phylum Chordata, which also includes the vertebrates. The adult form of most tunicates (also called urochordates) shows no resemblance to vertebrate animals, but such a resemblance is evident in the larva.
..... Click the link for more information. and lancelets lancelet, name for small, fishlike lower chordate (see Chordata), also called amphioxus; it shows many affinities with the vertebrates. There are about 30 lancelet species, most belonging to the genus Brachiostoma (formerly Amphioxus).
..... Click the link for more information. of phylum Chordata, as well as all animal phyla other than Chordata. The major invertebrate phyla include: the sponges (Porifera Porifera [Lat.,=pore bearer], animal phylum consisting of the organisms commonly called sponges. It is the only phylum of the animal subkingdom Parazoa and represents the least evolutionarily advanced group of the animal kingdom.
..... Click the link for more information. ), coelenterates (Cnidaria Cnidaria or Coelenterata , phylum of invertebrate animals comprising the sea anemones, corals, jellyfish, and hydroids. Cnidarians are radially symmetrical (see symmetry, biological).
..... Click the link for more information. ), echinoderms (Echinodermata Echinodermata [Gr.,=spiny skin], phylum of exclusively marine bottom-dwelling invertebrates having external skeletons of calcareous plates just beneath the skin.
..... Click the link for more information. ), flatworms (Platyhelminthes Platyhelminthes , phylum containing about 20,000 species of soft-bodied, bilaterally symmetrical, invertebrate animals, commonly called flatworms. There are four classes: the free-living, primarily aquatic class, Turbellaria, and Trematoda, Cestoda, and Monogenea,
..... Click the link for more information. ), roundworms (Nematoda Nematoda , phylum consisting of about 12,000 known species, and many more predicted species of worms (commonly known as roundworms or threadworms). Nematodes live in the soil and other terrestrial habitats as well as in freshwater and marine environments.
..... Click the link for more information. ), segmented worms (Annelida Annelida [Lat., anellus=a ring], phylum of soft-bodied, bilaterally symmetrical (see symmetry, biological), segmented animals, known as the segmented, or annelid, worms.
..... Click the link for more information. ), mollusks (Mollusca Mollusca , taxonomic name for the one of the largest phyla of invertebrate animals (Arthropoda is the largest) comprising more than 50,000 living mollusk species and about 35,000 fossil species dating back to the Cambrian period.
..... Click the link for more information. ), and arthropods (Arthropoda Arthropoda [Gr.,=jointed feet], largest and most diverse animal phylum. The arthropods include crustaceans, insects, centipedes, millipedes, symphylans, pauropodans, and the extinct trilobites.
..... Click the link for more information. ). Invertebrates are tremendously diverse, ranging from microscopic wormlike mezozoans (see Mezozoa Mezozoa , name of an animal subkingdom and also of the subkingdom's only phylum. The mezozoans are simple parasitic marine wormlike animals of only 20 to 30 cells, which are differentiated only into reproductive cells and ciliated cells.
..... Click the link for more information. ) to very large animals such as the giant squid squid, carnivorous marine cephalopod mollusk. The squid is one of the most highly developed invertebrates, well adapted to its active, predatory life. The characteristic molluscan shell is reduced to a horny plate shaped like a quill pen and buried under the mantle.
..... Click the link for more information. . Approximately 95% of all the earth's animal species are invertebrates; of these the vast majority are insects insect, invertebrate animal of the class Insecta of the phylum Arthropoda. Like other arthropods, an insect has a hard outer covering, or exoskeleton, a segmented body, and jointed legs. Adult insects typically have wings and are the only flying invertebrates.
..... Click the link for more information. and other arthropods. Invertebrates are important as parasites and are essential elements of all ecological communities.

Bibliography

See A. Kaestner, Invertebrate Zoology (3 vol., 1967–70); R. D. Barnes, Invertebrate Zoology (5th ed. 1987); R. Buchsbaum et al., Animals without Backbones (3d ed. 1987).

invertebrate

Any animal that lacks a vertebral column, or backbone. They include the protozoans, annelids, cnidarians, echinoderms, flatworms, nematodes, mollusks, and arthropods. More than 90% of living animals are invertebrates. Worldwide in distribution, they range in size from minute protozoans to giant squids. Apart from the absence of a vertebral column, invertebrates have little in common. They are generally soft-bodied and have an external skeleton for muscle attachment and protection. See also vertebrate.

invertebrate

any animal lacking a backbone, including all species not classified as vertebrates

invertebrate [in′vərd·ə‚brət]

(invertebrate zoology)

An animal lacking a backbone and internal skeleton.

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No references found			Verslycke has examined the effects of human-made chemicals on invertebrate hormones, including those regulating molting. Something's rotten in the state of lobster shells: what's causing the ... by Pratt, Sara E. / Oceanus			inverse video inverse voltage inverse Zeeman effect inverse-mapping theorem inverse-square law Inversely Proportional Quantities Inversion inversion axis Inversion Curve inversion heterozygote inversion layer inversion ratio inversion spectrum inversion symmetry Inversion System inversion temperature Inversion Transistor invert invert level invert oil mud invert sugar invert-emulsion mud Invertase Invertebrata invertebrate Invertebrate hormones invertebrate pathology invertebrate zoology Invertebrates inverted inverted amplifier inverted arch inverted compass inverted engine inverted file inverted heading and bench method inverted image inverted index inverted joint inverted L antenna inverted micelle inverted microscope inverted plunge inverted pseudoplastic fluid inverted relief inverted repeats inverted roof Inverted Siphon inverted terminal repeats inverted vee Inverter			Inversor institucional Inversor minorista inversus invert invert invert invert invert Invert Level Invert Level invert oil mud invert soap invert sugar invert sugar invert sugar invert-emulsion mud invertase invertase invertase invertebracy Invertebral Invertebral disc Invertebrata Invertebrata Invertebrata invertebrate invertebrate invertebrate Invertebrate Community Index invertebrate foot Invertebrate hormones Invertebrate Iridescent Virus Invertebrate pathology Invertebrate Pest Monitoring Unit Invertebrate photoreceptor Invertebrate photoreceptor Invertebrate Soil Quality Invertebrate zoology Invertebrated Invertebrated Invertebrated Invertebrates Invertebrates Invertebrates inverted inverted inverted inverted inverted amplifier Inverted arch Inverted arch Inverted Bowl Inverted Bowl Inverted Bowl Inverted Bowls Inverted Bowls Inverted Bowls Inverted Box Rib Inverted CCAAT Box 4 Inverted Champagne Bottle Appearance Inverted Coaxial Magnetron

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