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Invertebrates
InvertebratesInvertebrates are animals without backbones. This simple definition hides the tremendous diversity found within this group which includes protozoa (single-celled animals), corals, sponges, sea urchins, starfish, sand dollars, worms, snails, clams, spiders, crabs, and insects. In fact, more than 98 percent of the nearly two million described species are invertebrates. They range in size from less than one millimeter to several meters long. Invertebrates display a fascinating diversity of body forms, means of locomotion, and feeding habits. Invertebrates are ectotherms (cold-blooded): they warm their bodies by absorbing heat from their surroundings. Most invertebrates live in water or spend at least some part of their life in water. The external layers of aquatic invertebrates are generally thin and permeable to water. This structure allows the ready exchange of gases needed to keep the animal alive. Some aquatic vertebrates do have specialized respiratory (breathing) structures on their body surface. Aquatic invertebrates feed by ingesting their prey directly, by filter feeding, or by actively capturing prey. Some groups of invertebrates live on land. Common examples include the earthworms, insects, and spiders. These invertebrates need to have special structures to deal with life on land. For example, earthworms have strong muscles for crawling and burrowing and, since drying out on land is a problem for them, they secrete mucous to keep their bodies moist. Insects and spiders move by means of several pairs of legs and are waterproof. [See also Arachnids; Arthropods; Butterflies; Cockroaches; Corals; Crustaceans; Insects; Mollusks; Protozoa ] |
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"Invertebrates." UXL Encyclopedia of Science. 2002. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "Invertebrates." UXL Encyclopedia of Science. 2002. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1G2-3438100378.html "Invertebrates." UXL Encyclopedia of Science. 2002. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3438100378.html |
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invertebrates
invertebrates The kingdom Animalia, comprising over a million described species, has traditionally been divided into those animals that have backbones and those that do not; the vertebrates and the invertebrates. This is an artificial distinction and reflects our anthropocentric viewpoint; however, in the past the invertebrates were regarded as a formal taxonomic group of high rank. The artificiality of this arrangement becomes clear once the range of organisms included within the invertebrates is considered. No single character unites the group and the invertebrates range enormously in size, structural diversity, and in adaptations to different modes of existence. Some of the groups have common phylogenetic origins while others are only remotely related. Some are actually more closely related to vertebrates than they are to invertebrates.
Despite the fact that the word ‘invertebrates’ is currently used mainly as a term of convenience in biology and palaeontology, there are advantages in studying invertebrate organisms. Collectively they comprise much of the fossil record, just as they comprise much of the diversity of life now. The evolution of any one group is tied inextricably to that of the other invertebrates around it and to its changing environment. The evolutionary processes and environments of the past will thus be better understood if the invertebrates are studied as a whole. David K. Elliott |
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PAUL HANCOCK and BRIAN J. SKINNER. "invertebrates." The Oxford Companion to the Earth. 2000. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. PAUL HANCOCK and BRIAN J. SKINNER. "invertebrates." The Oxford Companion to the Earth. 2000. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O112-invertebrates.html PAUL HANCOCK and BRIAN J. SKINNER. "invertebrates." The Oxford Companion to the Earth. 2000. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O112-invertebrates.html |
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invertebrate
invertebrate , any animal lacking a backbone. The invertebrates include the tunicates and lancelets of phylum Chordata, as well as all animal phyla other than Chordata. The major invertebrate phyla include: the sponges ( Porifera ), coelenterates ( Cnidaria ), echinoderms ( Echinodermata ), flatworms ( Platyhelminthes ), roundworms ( Nematoda ), segmented worms ( Annelida ), mollusks ( Mollusca ), and arthropods ( Arthropoda ). Invertebrates are tremendously diverse, ranging from microscopic wormlike mezozoans (see Mezozoa ) to very large animals such as the giant squid . Approximately 95% of all the earth's animal species are invertebrates; of these the vast majority are insects and other arthropods. Invertebrates are important as parasites and are essential elements of all ecological communities.
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"invertebrate." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "invertebrate." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-inverteb.html "invertebrate." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-inverteb.html |
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invertebrate
in·ver·te·brate / inˈvərtəbrit; -ˌbrāt/ • n. an animal lacking a backbone, such as an arthropod, mollusk, annelid, coelenterate, etc. The invertebrates constitute an artificial division of the animal kingdom, comprising 95 percent of animal species and about 30 different phyla. Compare with vertebrate. • adj. of, relating to, or belonging to this division of animals. ∎ humorous irresolute; spineless: so invertebrate is today's Congress regarding foreign policy responsibilities. |
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"invertebrate." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "invertebrate." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O999-invertebrate.html "invertebrate." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-invertebrate.html |
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invertebrate
invertebrate Term for an animal without a backbone. There are more than one million species of invertebrates, divided into 30 major groups. One of these is Arthropoda (joint-legged animals), the largest of all animal phyla in terms of numbers of species. Most are insects, but it also includes crustaceans and arachnids. Molluscs make up the second largest group of invertebrates. See also arthropod; crustacean; phylum
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"invertebrate." World Encyclopedia. 2005. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "invertebrate." World Encyclopedia. 2005. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O142-invertebrate.html "invertebrate." World Encyclopedia. 2005. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-invertebrate.html |
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invertebrate
invertebrate Any animal that lacks a vertebral column (backbone). Invertebrates include all nonchordate animals as well as the more primitive chordates (see Chordata).
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"invertebrate." A Dictionary of Biology. 2004. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "invertebrate." A Dictionary of Biology. 2004. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O6-invertebrate.html "invertebrate." A Dictionary of Biology. 2004. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-invertebrate.html |
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invertebrate
invertebrate An animal without a backbone; invertebrates make up about 95% of all animal species and are found in every available habitat on Earth.
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AILSA ALLABY and MICHAEL ALLABY. "invertebrate." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "invertebrate." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O13-invertebrate.html AILSA ALLABY and MICHAEL ALLABY. "invertebrate." A Dictionary of Earth Sciences. 1999. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-invertebrate.html |
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