L36 (Animal Diversity III: Echinoderms and Chordates) Key Terms

echinoderms

a slow-moving or sessile marine deuterostome with a water vascular system and, in larvae, bilateral symmetry. Echinoderms include sea stars, brittle stars, sea urchins, feather stars, and sea cucumbers

water vascular system

a network of hydraulic canals unique to echinoderms that branches into extensions called tube feet, which function in locomotion and feeding

vertebrates

a chordate animal with vertebrae, the series of bones that make up the backbone

chordates

a member of the phylum Chordata, animals that at some point during their development have a notochord; a dorsal, hollow nerve cord; pharyngeal slits or clefts; and a muscular, post-anal tail

notochord

a longitudinal, flexible rod made of tightly packed mesodermal cells that runs along the anterior-posterior axis of a chordate in the dorsal part of the body

pharyngeal slits

in chordate embryos, one of the slits that form from the pharyngeal clefts and open into the pharynx, later developing into gill slits in many vertebrates

lancelets

a member of the clade Cephalochordata, small blade-shaped marine chordates that lack a backbone

tunicates

a member of the clade Urochordata, sessile marine chordates that lack a backbone

neural crest

in vertebrates, a region located along the sides of the neural tube where it pinches off from the ectoderm. Neural crest cells migrate to various parts of the embryo and form pigment cells in the skin and parts of the skull, teeth, adrenal glands, and peripheral nervous system

cyclostomes

member of one of the two main clades of vertebrates; cyclostomes lack jaws and include lampreys and hagfishes

hagfish

marine jawless vertebrates that have highly reduced vertebrae and a skull made of cartilage; most hagfishes are bottom-dwelling scavengers

lamprey

any of the jawless vertebrates with highly reduced vertebrae that live in freshwater and marine environments. Almost half of extant lamprey species are parasites that feed by clamping their round, jawless mouth onto the flank of a live fish; nonparasitic lampreys are suspension feeders that feed only as larvae

gnathostomes

member of one of the two main clades of vertebrates; gnathostomes have jaws and include sharks and rays, ray-finned fishes, coelacanths, lungfishes, amphibians, reptiles, and mammals;

chondrichthyans

a member of the clade Chondrichthyes, vertebrates with skeletons made mostly of cartilage, such as sharks and rays

oviparous

referring to a type of development in which young hatch from eggs laid outside the female’s body

ovoviviparous

referring to a type of development in which young hatch from eggs that are retained in the uterus

viviparous

referring to a type of development in which the young are born alive after having been nourished in the uterus by blood from the placenta

osteichthyans

a member of a vertebrate clade with jaws and mostly bony skeletons

operculum

in aquatic osteichthyans, a protective bony flap that covers and protects the gills

swim bladder

in aquatic osteichthyans, an air sac that enables the animal to control its buoyancy in the water

ray-finned fishes

a member of the clade Actinopterygii, aquatic osteichthyans with fins supported by long, flexible rays, including tuna, bass, and herring

lobe-fins

member of a clade of osteichthyans having rod-shaped muscular fins. The group includes coelacanths, lungfishes, and tetrapods

tetrapods

a vertebrate clade whose members have limbs with digits. Tetrapods include mammals, amphibians, and birds and other reptile