UCMP Glossary: Zoology
abdomen -- Region of the body furthest from the mouth. In insects, the third body region behind the head and thorax.
ambulacra -- Row of tube feet of an echinoderm.
amniotic egg -- n. An egg that can be laid on land due to the presence of a fluid-filled amniotic sac (amnion) that cushions and protects the developing embryo; amniote- n. Any of a group of land-dwelling vertebrates that have an amnion during embryonic development, including reptiles, birds, and mammals.
biramous -- Arthropod appendages that are biramous have two branches, an outer branch and an inner branch. These branches may have separate functions; in crustaceans, for instance, the inner branch of a leg is used for walking, while the outer branch may be paddle-shaped or feathery and often functions as a gill. Contrast with uniramous.
book lung -- A set of soft overlapping flaps, covered up by a plate on the abdomen, through which oxygen is taken up and carbon dioxide given off. Characteristic of many terrestrial arachnids such as scorpions and spiders.
brain -- Collection of nerve cells usually located at the anterior end of an animal, when present at all. The nerves coordinate information gathered by sense organs, locomotion, and most internal body activities.
chaetae -- Stiff bristles characteristic of annelids.
chela -- The claw of an arthropod.
chelicera -- The first pair of appendages of a chelicerate arthropod. Originally a short clawed appendage, the chelicerae of many arachnids are highly modified for feeding; in spiders, for instance, they are modified into poisonous fangs.
chordate -- n. An animal with a notochord (a cartilaginous rod that extends the length of the body), dorsal hollow nerve cord (a fluid-filled tube that runs the length of the body), gill slits or pouches, and a tail at some stage in its life cycle.
clitellum -- In annelids, a swelling of the body towards the head of the animal, where the gonads are located. Both oligochaetes and leeches have a clitellum.
cnidocyst -- The "stinging cell" of a cnidarian.
coelom -- Fluid-filled cavity within the body of an animal; usually refers to a cavity lined with specialized tissue peritoneum in which the gut is suspended. The structure and development of the coelom is an important character for recognizing major groups of animals.
compound eye -- Found in many but not all arthropods, a compound eye is composed of a large number of small, closely packed simple eyes (ommatidia), each with its own lens and nerve receptors.
cuticle -- 1) In animals, a multilayered, extracellular, external body covering, usually composed of fibrous molecules such as chitin or collagen, and sometimes strengthened by the deposition of minerals such as calcium carbonate. 2) A waxy layer which seals the outer surface of land plants, helping to retain moisture.
epithelium -- Layer of cells which lines a body cavity; cells may be ciliated or unciliated, and may be squamous (flat, scale-shaped), cuboidal (cube-shaped), or columnar (column-shaped). Your stomach and cheeks are lined with epithelium.
gastrodermis -- In cnidarians, the endodermis which lines the gut cavity. The term is often used instead of endodermis since cnidarians only have two tissue layers instead of three.
gill -- In aquatic animals, highly vascularized tissues with large surface area; these are extended out of the body and into the surrounding water for gas exchange.
gill arches -- Stiffenings which support the flesh between the gill slits of chordates. In most vertebrates, the first gill arches have been modified to form the jaw, and in tetrapods, the inner ear bones.
gill slit -- A slitlike or porelike opening connecting the pharynx of a chordate with the outside of the body. Gill slits may contain the gills and be used for gas exchange, as in most fish, but may also be used for filter-feeding, or may be highly modified in land-dwelling vertebrates.
gut (enteron) -- Body cavity formed between the mouth and anus in which food is digested and nutrients absorbed; it consists of the mouth, pharynx, esophagus, stomach, intestine, and anus, though some animals do not have all these regions.
librigenae -- The "free cheeks"; separate, detachable portions of the trilobite cephalon. More info?
lophophore -- Complex ring of hollow tentacles used as a feeding organ. The tentacles are covered by cilia, which generate a current to bring food particles into the mouth. The structure is only found in the brachiopods, phoronids, and bryozoans. More info?
mesoderm -- In animals with three tissue layers (i.e. all except sponges and cnidarians), the middle layer of tissue, between the ectoderm and the endoderm. In vertebrates, for instance, the mesoderm forms the skeleton, muscles, heart, spleen, and many other internal organs.
mesogloea -- Jellylike material between the outer ectoderm and the inner endoderm of cnidarians. May be very thin or may form a thick layer (as in many jellyfish).
mouth -- Front opening of the digestive tract, into which food is taken for digestion. In flatworms, the mouth is the only opening into the digestive cavity, and is located on the "belly" of the worm.
muscle -- Bundle of contractile cells which allow animals to move. Muscles must act against a skeleton to effect movement.
myotome -- Segment of the body formed by a region of muscle. The myotomes are an important feature for recognizing early chordates.
nematocyst -- Older name for a cnidocyst.
neuron -- A specialized cell that can react to stimuli and transmit impulses. A neuron consists of a body which contains the nucleus; dendrites, which are short branches off the body that receive incoming impulses; and a long axon which carries impulses away from the body and to the next neuron.
notochord -- Characteristic of chordates, the notochord is a stiff rod of tissue along the back of the body. In vertebrates, the backbone is deposited around the notochord and nerve cord.
organ -- Collection of tissues which performs a particular function or set of functions in an animal or plant's body. The heart, brain, and skin are three organs found in most animals. The leaf, stem, and root are three organs found in most plants. Organs are composed of tissues, and may be organized into larger organ systems.
osculum -- The main opening through which filtered water is discharged. Found in sponges.
pedipalps -- The second pair of appendages of cheliceromorphs. In many arachnids, such as spiders, the pedipalps are enlarged in the male and used for copulation.
pharyngeal slits -- Characteristic of chordates, pharyngeal slits are openings through which water is taken into the pharynx, or throat. In primitive chordates the pharyngeal slits are used to strain water and filter out food particles; in fishes they are modified for respiration. Most terrestrial vertebrates have pharyngeal slits only in the embryonic stage.
placenta -- n. In mammals, a tissue formed within the uterus through which nutrients are passed from the mother to the embryo (and later the fetus) and its wastes are removed; placental- n. (adj.) A mammal whose young form a placenta as they develop in the motherís uterus.
proboscis -- Elongated organ, usually associated with the mouth. The proboscis is an important feeding appendage in echiurans.
segmentation -- In many animals, the body is divided into repeated subunits called segments, such as those in centipedes, insects, and annelids. Segmentation is the state of having or developing a body plan in this way.
skeleton -- Support structure in animals, against which the force of muscles acts. Vertebrates have a skeleton of bone or cartilage; arthropods have one made of chitin; while many other invertebrates use a hydrostatic skeleton, which is merely an incompressible fluid-filled region of their body.
spicule -- Crystalline or mineral deposits found in sponges, sea cucumbers, or urochordates. They are structural components in many sponges, and may serve a protective function in other organisms.
spongocoel -- Central body cavity of sponges. More Info?
telson -- The last segment of the abdomen in many arthropods. May be flat and paddlelike, buttonlike, or long and spiny, as in the horseshoe crabs.
tissue -- A group of cells with a specific function in the body of an organism. Lung tissue, vascular tissues, and muscle tissue are all kinds of tissues found in some animals. Tissues are usually composed of nearly identical cells, and are often organized into larger units called organs.
tracheae -- Internal tubes through which air is taken for respiration. Vertebrates with lungs have a single trachea carrying air to the lungs, while insects and some other land-living arthropods have a complex network of tracheae carrying air from the spiracles to all parts of the body.
tube feet -- Extensions of the water-vascular system of echinoderms, protruding from the body and often ending in suckers. May be used for locomotion and/or for maintaining a tight grip on prey or on the bottom.
uniramious -- Among arthropods, uniramous refers to appendages that have only one branch. Insects, centipedes and millipedes, and their relatives are uniramous arthropods; land-living chelicerates such as scorpions, spiders,and mites are also uniramous but probably descended from ancestors with biramous appendages. Contrast with biramous.
vascular -- Refers to a network of tubes which distribute nutrients and remove wates from the tissues of the body. Large multicellular animals must rely on a vascular system to keep their cells nourished and alive.
vertebra -- A component of the vertebral column, or backbone, found in vertebrates.
zooxanthellae -- Symbiotic dinoflagellates in the genus Symbiodinium that live in the tissues of a number of marine invertebrates and protists, notably in many foraminiferans, cnidarians, and some mollusks.