Pre-AP Invertebrates

16619539	invertebrate	animal that does not have a backbone
16619540	radial symmetry	body plan in which body parts repeat around the center of the body
16619541	bilateral symmetry	body plan in which only a single, imaginary line can divide the body into 2 equal halves
16619542	cephalization	concentration of sense organs & nerve cells at the front of an animal's body
16619543	spicule	spike-shaped structure that makes up the skeletons of harder sponges
16619544	larva	immature stage of an organism that looks different from the adult form
16619545	gemmule	group of archaeocytes surrounded by a tough layer of spicules; produced by some sponges
16619546	polyp	sessile stage of the life cycle of a cnidarian; cylindrical body with armlike tentacles
16619547	medusa	mobile stage of the life cycle of a cnidarian, has a bell-shaped body
16619548	hydrostatic skeleton	layers of circular & longitudinal muscles, together with the water in the gastrovascular cavity, that enable movement
16619549	coelom	fluid-filled body cavity lined with mesoderm
16619550	hermaphrodite	individual that has both male & female reproductive organs
16619551	septum	internal wall between the segments of an annelid's body
16619552	seta	bristle attached to the segments of many annelids
16619553	crop	part of the digestive system in which food can be stored
16619554	gizzard	part of the digestive system in which food is ground into smaller pieces
16619555	mantle	thin layer of tissue that covers most of a mollusk's body
16619556	shell	structure in mollusks made by glands in the mantle that secrete calcium carbonate
16619557	radula	tongue-shaped structure used for feeding by snails & slugs
16619558	siphon	tubelike structure through which water enters & leaves a mollusk's body
16619559	exoskeleton	external skeleton; tough external covering that protects & supports the body of many invertebrates
16619560	chitin	complex carbohydrate found in the exoskeletons of arthropods
16619561	appendage	structure, such as a leg or antenna, extending from the body wall
16619562	spiracle	small opening located along the side of the body through which air enters & leaves
16619563	book lung	organ with layers of respiratory tissue for exchange of gases
16619564	molting	process of shedding an exoskeleton & manufacturing a larger one to take its place
16619565	incomplete metamorphosis	type of insect development; all stages of life cycle look similar
16619566	complete metamorphosis	type of insect deveropment; larvae look & act completely different from parents
16619567	nymph	immature form that lacks functional sex organs & other adult structures
16619568	pupa	stage of metamorphosis in which an insect changes from larva to adult
16619569	society	group of closely related animals of the same species that work together for the benefit of the group
16619570	caste	group of individual insects specialized to perform particular tasks, or roles
16619571	pheromone	specific chemical messenger; affects behavior or development of other individuals of same species
16619572	endoskeleton	structural support located inside the body of an organism
16619573	tube foot	suction-cuplike structure attached attached to radial canals of echinoderms, used to walk & to open shells