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closed circulatory system

system in which blood moves through the body enclosed entirely in a series of blood vessels; provides an efficient means of gas exchange within the body


thin membrane that surrounds the internal organs of mollusks; in mollusks with shells, it secretes the shell


organs that remove metabolic wastes from an animal's body

open circulatory system

system where blooc moves through vessels into open spaces around the body organs


in some snails and mollusks, the rasping, tonguelike organ used to drill, scrape, grate or cut food


sac with muscular walls and hard particles that grind soil before it passes into the intesting; common in birds and annelids such as earthworms


tiny bristles that help segmented worms move by anchoring their bodies in the soil so each segment can move the animal along


any structure, such as a leg or an antenna, that grows out of an animal's body

book lung

gas exchange system found in some arthropods where air-filled chambers have plates of folded membranes that increase the surface area of tissue exposed to the air


structure in some arthropods formed by the fusion of the head and thorax

compound eye

in arthropods, a visual system composed of multiple lenses; each lens registers light from a small portion of the field of view, creating an image composed of thousands of parts


in most arthropods, mouth parts adapted for holding, chewing, sucking, or biting various foods

malpighian tubule

in arthropods, tubules located in the abdomen that are attached to an empty waste into the intestine


in arthropods, the periodic shedding of an old exoskeleton


type of asexual reproduction in which a new individual develops from an unfertilized egg


chemical signs gived off by animals that signal animals to engage in specific behaviors

simple eye

visual structure in arthropids that uses one lens to detect light and focus


in arthropods, openings on the thorax and abdomen through which air enters and leaves the tracheal tubes

trachael tube

hollow passages in some arthropods that transport air throughout the body


first pair of an arachnid's six pairs of appendages; located near the mouth, they are often modified into pincers or fangs


in insects, the freeliving, wormlike stage of metamorphosis, often called a caterpillar


in insects, series of chemically-controlled changed in body structure from juvenile to adult; may be complete or incomplete


stage of incomplete metamorphosis where an insect hatching from an egg has the same general appearance as the adult insect but is smaller and sexually immature


second pair of an arachnids six pairs of appendages that are often adapted for handling food and sensing


stage of insect metamorphosis where tissues and organs are broken down and replaced by adult tissues; larvae emerges from pupa as a mature adult


silk-producing glands located at the rear of a spider


in echinoderms, the round muscular structure on a tube food that aids in locomotion


in echinoderms, the sieve like, disk-shaped opening through which water flows in and out of the water vascular system; helps filter out large particles from entering the body


pincel like appendages on echinoderms used for protection and cleaning


long tapered arms of some echinoderms that are covered with short, rounded spines

tube feet

in echinoderms, hollow, thin-walled tubes that end in a suction cup; part of the water vascular system, they also aid in locomotion, gas exchange, and excretion

water vascular system

in echinoderms, the hydraulic system that operates under water pressure; aids in locomotion, gas exchange, and excretion

dorsal hollow nerve cord

nerve cord found in all chordates that forms the spinal cord and brain

gill slit

paired openings found behind the mouth of all chordates; in invertebrate chordates, they are used to strain food and water; in some vertebrates they are used for gas exhange and respiration


long, semirigid, rodlike structure found in all chordate embryos that is located between the digestive system and the dorsal hollow nerve cord

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