invertebrate (ĭn'vûr`təbrət, –brāt'), any animal lacking a backbone. The invertebrates include the tunicates tunicate (t
..... 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 (pōrĭf`ərə) [Lat.,=pore bearer], animal phylum consisting of the organisms commonly called sponges .
..... Click the link for more information. ), coelenterates (Cnidaria Cnidaria (nīdâr`ēə) or Coelenterata
..... Click the link for more information. ), echinoderms (Echinodermata Echinodermata (əkī'nōdûr`mətə) [Gr.
..... Click the link for more information. ), flatworms (Platyhelminthes Platyhelminthes (plăt'ēhĕlmĭn`thēz)
..... Click the link for more information. ), roundworms (Nematoda Nematoda (nĕm'ətōd`ə)
..... Click the link for more information. ), segmented worms (Annelida Annelida (ənĕl`ĭdə) [Lat.
..... Click the link for more information. ), mollusks (Mollusca Mollusca (məlŭs`kə)
..... Click the link for more information. ), and arthropods (Arthropoda Arthropoda (ärthrŏp`ədə) [Gr.,=jointed feet], largest and most diverse animal phylum.
..... Click the link for more information. ). Invertebrates are tremendously diverse, ranging from microscopic wormlike mezozoans (see Mezozoa Mezozoa (mĕz`əzō'ə, mē`zə–), name of an animal subkingdom and also of the subkingdom's only phylum.
..... 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.

invertebrate (redirected from Invertebrate hormones)

Bibliography

invertebrate

invertebrate
(redirected from Invertebrate hormones)