ADW: Glossary: A

<!DOCTYPE html> <html xmlns:og="http://ogp.me/ns#" lang="en" xml:lang="en"> <head> <title>ADW: Glossary: A</title> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <link rel="canonical" href="https://animaldiversity.org/glossary/a/" /> <script type="text/javascript" src="//code.jquery.com/jquery-3.6.0.min.js"></script> <script type="text/javascript" src="//code.jquery.com/jquery-migrate-3.3.2.min.js"></script> <script type="text/javascript" src="/static/js/compat.js"></script> <link rel="shortcut icon" href="https://animaldiversity.org/favicon.ico" /> <link href="//fonts.googleapis.com/css?family=Gentium+Book+Basic:400,400italic,700,700italic" rel="stylesheet" type="text/css" /> <link href="//fonts.googleapis.com/css?family=PT+Sans:400,700,400italic,700italic" rel="stylesheet" type="text/css" /> <link rel="stylesheet" type="text/css" href="/static/bootstrap/css/bootstrap.css" /> <link rel="stylesheet" href="/static/css/pica.styles.css" /> <link rel="stylesheet" href="/static/css/pica.print.css" media="print" />  <link rel="stylesheet" href="/static/css/pica.node.css" /> <script type="text/javascript" src="/static/js/Hyphenator.js"></script> <link rel="stylesheet" href="/static/social-likes/social-likes_birman.css" /> <style> .social-likes { margin: 0; } .social-likes__widget { margin: 0; } </style>   </head> <body> <div id="outerwrap"> <div id="header" aria-role="header"> <h1> <a id="homelink" href="/">Animal Diversity Web</a> </h1> <div class="umlinks"> <div class="relative"> <a href="https://lsa.umich.edu/ummz/" id="ummzlink">University of Michigan Museum of Zoology</a> <a href="https://www.umich.edu/" id="umlink">University of Michigan</a> </div> </div> </div> <div id="wrap" class="gradient"> <div class="container-fluid"> <div class="row-fluid"> <div class="span2 sidebar left"> <ul class="nav nav-tabs nav-stacked" id="sitemap"> <li> <a href="/">Home</a> </li> <li> <a href="/about/">About Us</a> </li> <li> <a href="/animal_names/">About Animal Names</a> </li> <li> <a href="/teach/">Educational Resources</a> </li> <li> <a href="/collections/">Special Collections</a> </li> <li> <a href="/glossary/">Glossary</a> </li> <li> <a href="/accounts/Animalia/">Browse Animalia</a> </li> </ul> </div> <div class="span7_5 blahblahblah main" aria-role="main"> <h2>Glossary: A</h2> <div class="social-likes" data-counters="no"> <div class="facebook" title="Share link on Facebook">Facebook</div> <div class="twitter" title="Share link on Twitter">Twitter</div> </div> <div class="inner-wrap"> <div class="row-fluid"> <div class="span3"> <div class="tabbable tabs-left"> <ul class="nav nav-tabs"> <li> <a href="/glossary/3/">3</a> </li> <li class="active"> <a href="/glossary/a/">A</a> </li> <li> <a href="/glossary/b/">B</a> </li> <li> <a href="/glossary/c/">C</a> </li> <li> <a href="/glossary/d/">D</a> </li> <li> <a href="/glossary/e/">E</a> </li> <li> <a href="/glossary/f/">F</a> </li> <li> <a href="/glossary/g/">G</a> </li> <li> <a href="/glossary/h/">H</a> </li> <li> <a href="/glossary/i/">I</a> </li> <li> <a href="/glossary/k/">K</a> </li> <li> <a href="/glossary/l/">L</a> </li> <li> <a href="/glossary/m/">M</a> </li> <li> <a href="/glossary/n/">N</a> </li> <li> <a href="/glossary/o/">O</a> </li> <li> <a href="/glossary/p/">P</a> </li> <li> <a href="/glossary/r/">R</a> </li> <li> <a href="/glossary/s/">S</a> </li> <li> <a href="/glossary/t/">T</a> </li> <li> <a href="/glossary/u/">U</a> </li> <li> <a href="/glossary/v/">V</a> </li> <li> <a href="/glossary/w/">W</a> </li> <li> <a href="/glossary/y/">Y</a> </li> <li> <a href="/glossary/z/">Z</a> </li> </ul> </div> </div> <div class="span9"> <section> <dl> <dt id="200304162141">"Arthropod" eyes</dt> <dd> <p>Eye composed of ommatidia (singular, ommatidium). Synapomorphy of the Arthropoda.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145549">Allee effect</dt> <dd> <p>A situation where the density of an animal population is so low as to cause adverse effects on the population. For example, adult animals may have trouble finding other adults to mate with because they are so scarce.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145653">Antarctic convergence</dt> <dd> <p>The region between 50 to 55 degrees south where the Antarctic surface water sinks beneath the less dense and southward flowing subantarctic water.</p> </dd> </dl> </section> <section> <dl> <dt id="20020916135918">Antarctica</dt> <dd> <p>lives on Antarctica, the southernmost continent which sits astride the southern pole.</p> </dd> </dl> </section> <section> <dl> <dt id="20020917113601">Arctic Ocean</dt> <dd> <p>the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.</p> </dd> </dl> </section> <section> <dl> <dt id="20020917114102">Atlantic Ocean</dt> <dd> <p>the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.</p> <p align="center"> <img alt="World Map" src="/images/worldmap.2001.jpg" /> </p> </dd> </dl> </section> <section> <dl> <dt id="20020916135737">Australian</dt> <dd> <p>Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.</p> <p align="center"> <img alt="World Map" src="/images/worldmap.2001.jpg" /> </p> </dd> </dl> </section> <section> <dl> <dt id="20020904145432">abiotic</dt> <dd> <p>something that was never alive, such as water or rocks. This term is often used to refer to the physical environment.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145355">aboral</dt> <dd> <p>On the side of the body opposite the mouth.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145323">abyssal</dt> <dd> <p>on or near the ocean floor in the deep ocean. Abyssal regions are characterized by complete lack of light, extremely high water pressure, low nutrient availability, and continuous cold (3 degrees C).</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145702">acoelomate</dt> <dd> <p>lacking a coelom (body cavity lined with mesoderm)</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145822">acoustic</dt> <dd> <p>uses sound to communicate</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145537">adhesion</dt> <dd> <p>sticking to a surface</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145459">adult</dt> <dd> <p>A fully developed and mature animal, physically capable of breeding, but not necessarily doing so until social and/or ecological conditions allow.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145352">aerobic</dt> <dd> <p>Deriving energy from a process requiring free oxygen (compare anaerobic).</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145750">aestivate</dt> <dd> <p>To enter a state of dormancy in seasonal hot, dry weather, when food is scarce. Sometimes spelled "estivate."</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145647">agonistic</dt> <dd> <p>Referring to behavior between individuals of the same species that may involve aggression, threat, appeasement or avoidance. Agonistic behavior may arise from a conflict between aggression and fear.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145700">agricultural</dt> <dd> <p>living in landscapes dominated by human agriculture.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145312">allele</dt> <dd> <p>One of the forms of a given gene.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145538">alloparent</dt> <dd> <p>An animal behaving parentally towards infants or young that are not its own offspring.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145438">allopatric</dt> <dd> <p>Referring to a situation in which populations of different species are geographically separated (compare Sympatric).</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145529">alluvial</dt> <dd> <p>referring to soil which has been deposited by running water.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145704">alpha diversity</dt> <dd> <p>See diversity - alpha.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145517">alpine</dt> <dd> <p>Referring to conditions similar to those found in the Alps or other higher mountains (usually above 1500 m (4900')) .</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145328">altricial</dt> <dd> <p>young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.</p> </dd> <dd> <strong>See Also: </strong> <a href="/glossary/p#item955067189">precocial</a> </dd> </dl> </section> <section> <dl> <dt id="20020904145635">ambulacral</dt> <dd> <p>those areas of an echinoderms body that bear tube feet</p> </dd> </dl> </section> <section> <dl> <dt id="200304153157">ambulacral grooves</dt> <dd> <p>radial grooves along which tube feet project to the exterior of the organism.</p> </dd> </dl> </section> <section> <dl> <dt id="200304153301">amniotic egg</dt> <dd> <p>An egg protected by a series of membranes: the amnion, which surrounds the embryo with a constant amniotic fluid environment; the allantois, which allows gas diffusion and waste removal; the yolk sac, providing a food source for the embryo; and the chorion, a protective layer around the entire egg. Synapomorphy of the Amniota.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145651">amoebocyte</dt> <dd> <p>an animal cell without a fixed position in the body, they are able to wander throughout the body and feed on foreign particles, such as invading bacteria. Examples are leucocytes in mammalian blood.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145346">amphibious</dt> <dd> <p>Able to live both on land and in the water.</p> </dd> </dl> </section> <section> <dl> <dt id="item845109600">amphidromous</dt> <dd> <p>Referring to fish that migrate between fresh and salt water, but not as part of their life cycle. Migrations usually occur for short periods of feeding, and amphidromy is common among fishes that inhabit islands.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145728">ampullae</dt> <dd> <p>the enlarged end of a tube or canal, used to refer to the enlarged ends of echinoderm tube feet, an enlargement at the end of the semicircular canals of the inner ear of vertebrates, or, more generally, the dilated end of a vessel or duct.</p> </dd> </dl> </section> <section> <dl> <dt id="item845109598">anadromous</dt> <dd> <p>Referring to fish that live primarily in salt water but migrate to fresh water to reproduce. Most of the growth takes place in oceans and no significant feeding occurs when spawning migration commences.</p> </dd> <dd> <strong>See Also: </strong> <a href="/glossary/c#item845109599">catadromous</a> </dd> </dl> </section> <section> <dl> <dt id="20020904145555">anaerobic</dt> <dd> <p>Deriving energy from a process that does not require free oxygen (compare aerobic).</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145829">anterior</dt> <dd> <p>describing the part of an animal, or position of a structure, that is oriented towards the front in normal locomotion.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145514">anti-predator behavior</dt> <dd> <p>actions an organism takes to keep predators from eating it.</p> </dd> </dl> </section> <section> <dl> <dt id="20020916123459">aposematic</dt> <dd> <p>having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145758">appendage</dt> <dd> <p>body part that sticks out, like a leg or toe or antenna</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145736">aquatic</dt> <dd> <p>Living mainly in the water.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145608">arachnid</dt> <dd> <p>a species in a class of arthropods which includes mostly air-breathing invertebrates, including spiders, scorpions, mites and ticks. Arachnids have a body with two segments, with the front segment having four pairs of legs and no antennae.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145634">arboreal</dt> <dd> <p>Referring to an animal that lives in trees; tree-climbing.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145548">archeocyte</dt> <dd> <p>an amoeboid cell type found in sponges which can differentiate into several other, specialized cells, including sclerocytes, which secrete spicules, spongocytes, which secret spongin fibers, and collencytes, which secrete fibrillar collagen. Archeocytes can also ingest particles through phagocytosis.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145821">archipelago</dt> <dd> <p>A group of islands.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145814">arid</dt> <dd> <p>a climate or habitat characterized by little precipitation, by evaporation exceeding precipitation, and by sparse vegetation.</p> </dd> </dl> </section> <section> <dl> <dt id="item881122341">armor</dt> <dd> <p>protective body covering that is used to protect an animal from predation. For example, a snail's shell or an armadillo's protective plates.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145628">arthropod</dt> <dd> <p>Referring to an insect, spider, crab or other member of a species with a hard, jointed exoskeleton and paired, jointed legs.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145632">articulate</dt> <dd> <p>in bones, coming together or touching</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145724">artiodactyl</dt> <dd> <p>Referring to an even-toed ungulate (includes the cattle, pigs and ruminants).</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145314">asexual</dt> <dd> <p>reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145753">attachment stage</dt> <dd> <p>the stage in an animal's lifecycle when they cease being motile and become attached to a substrate.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145423">auricularia larva</dt> <dd> <p>the larvae of members of the class Holothuroidea, sea cucumbers.</p> </dd> </dl> </section> <section> <dl> <dt id="20020904145715">autotomize</dt> <dd> <p>a process whereby an animal sheds a body part, such as the tail in lizards. Autotomy is followed by regeneration of the body part. It often serves as a protective function, losing the body part to escape predation rather than being eaten, but is also a form of asexual reproduction in polychaete worms.</p> </dd> </dl> </section> <section> <dl> <dt id="item881122340">autotomy</dt> <dd> <p>an adaptation that makes it possible for an animal to rapidly lose an appendage, such as a tail or leg, in order to elude a predator's grasp by sacrificing a non-essential body part. 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ADW: Glossary: A