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Chapter 17 – Invertebrate Animal Vocabulary
Invertebrate – an animal that does not have a backbone.
Symmetry – arrangement of individual body parts; can be radial or bilateral.
Cnidarians – radially symmetrical, hollow-bodied animal with two cell layers
organized into tissue
Polyp – vase shaped, usually sessile body form of cnidarians
Medusa – free swimming, bell – shaped body form of cnidarians
Mollusk - soft-bodied, bilaterally symmetrical invertebrate with a large, muscular
foot, a mantle, and an open circulatory system; usually have a shell
Mantle – thin layer of tissue that covers a mollusk’s body that can secrete a shell.
Radula – scratchy, tonguelike organ in many mollusks that has rows of teethlike
projects used to scrape and grate food.
Gill – organ that allows a water-dwelling animal to exchange carbon dioxide for
dissolving oxygen in the water
Closed Circulatory System – a type of blood circulation system in which blood is
transported through blood vessels rather than washing over organs.
Open Circulatory System – a type of blood circulation system that lacks blood
vessels and in which blood washes over the organs.
Arthropods – bilaterally symmetrical animal with jointed appendages, a protective
endoskeleton, and a segmented body.
Appendage – structure such as a claw, leg, or antenna that grows from the body.
Exoskeleton – rigid, protective body covering of an arthropod that supports the
body and reduces water loss.
Metamorphosis – a change in body form that can be complete or incomplete