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Phylum of 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. |
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| A longitudinal, flexible rod located between the digestive tube and the nerve cord that is composed of large, fluid–filled cells encased in fairly stiff, fibrous tissue. Provides skeletal support. |
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| Dorsal, Hollow Nerve Cord |
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| Develops from a plate of ectoderm that rolls into a tube located dorsal to the notochord. |
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| Pharyngeal Slits or Clefts |
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| Grooves that separate a series of pouches along the sides of the pharynx and may develop into pharyngeal slits; slits that form from the pharyngeal clefts and communicate to the outside, later developing into gill slits in many vertebrates. |
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| A tail extending posterior to the anus containing skeletal elements and muscles (may be lost during embryonic development). |
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| Subphylum containing tunicates (sea squirts); currently the deepest-branching lineage of chordates. |
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| Subphylum containing lancelets; closest branch to true chordates. |
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| Animals that, as embryos, possess a post-anal tail and notochord, which are reabsorbed after settling in substrate during metamorphosis into sessile adults. |
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| Animals that, as larvae, possess all four traits of chordates. As adults, the pharyngeal slits play a minor role in gas exchange, which mainly occurs across the body surface. |
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| Blocks of mesoderm that compose muscle segments found along the sides of the notochord (only in embryos for some species). |
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Chordates that developed a head consisting of a brain at the anterior end of the dorsal nerve cord, eyes and other sensory organs, and a skull. Possess many unique features: two clusters of Hox genes; neural crest; gill slits for aquatic craniates; higher metabolism; extensive muscular system (including muscles along the digestive tract); a multi-chambered heart; red blood cells; hemoglobin; and kidneys. |
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| A band of cells along the border where the neural tube pinches off from the ectoderm. The cells migrate to various parts of the embryo and form the pigment cells in the skin, bones of the skull, the teeth, the adrenal glands, and parts of the peripheral nervous system. Unique to craniates. |
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| Subphylum of Chordata; a branch-off of craniates that possess a backbone. Arose from a gene duplication involving a group of transcription factor genes called the Dlx family |
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| Superclass of vertebrata containing jawless fishes. |
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| Class of agnatha containing hagfishes. Least derived class of craniates, debatable whether or not is true vertebrate. |
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| Animals possessing a skull made of cartilage, brain, eyes, ears, a nasal opening that connects with the pharynx, and tooth–like formations made of the protein keratin in their mouth. They swim in a snakelike fashion by using their segmental muscles to exert force against their notochord, which they retain in adulthood as a strong, flexible rod of cartilage. Can produce several liters of slime in less than a minute to deter predators. |
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| Class of agnatha containing lampreys; though vertebra are not fully developed, represents the oldest lineage of vertebrates. |
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| Mostly parasitic animals that use their jawless mouths to clamp onto prey (fish), bore a hole into their sides with their raspy tongue and consume their blood and tissues. Possess cartilaginous skeleton made of a stiff protein matrix rather than collagen. They keep their notochords as adults surrounded by a cartilaginous pipe with small projections related to vertebrae. |
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| Ancient lineage of soft-bodied, prominent-eyed, jawless vertebrates that arose during the Cambrian period. Unlike lampreys, they had mineralized mouthparts that could be used for consumption of solid food. |
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| Subgroup of vertebrata possessing jaws. Possess four clusters of Hox genes (among other duplications); enlarged forebrain; lateral line system (aquatic life only); and a progressively mineralized endoskeleton. |
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| A mechanoreceptor system consisting of a series of pores and receptor units (neuromasts) along the sides of the body in fishes and aquatic amphibians; detects water movements made by the animal itself and by other moving objects. |
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| Extinct group of gnathostomes that developed paired fins and tail that assisted in speedier locomotion. The earliest lineage in the fossil records; the name means "plate-skinned". |
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| Extinct group of gnathostomes closely related to osteichthyans. |
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| Class of vertebrates containing jawed, cartilaginous fishes; skeletons are made mostly of cartilage often impregnated with calcium. Oldest surviving lineages of true vertebrates. Characteristics include: large liver full of oil for bouyancy; several rows of teeth that are constantly lost and replaced; spiral valve within short digestive system; ampullae of Lorenzini. Common traits also include paired fins; paired nostrils; scales; and two-chambered heart. Oviparous, ovoviviparous and viviparous embryonic development occur in species. Includes sharks, rays and skates and ratfishes. |
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| Sensory organ in the head of chondrichthyes species that detects weak electrical fields, such as those emmited by fish. |
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| A corkscrew-shaped ridge that increases surface area and prolongs the passage of food along the short digestive tract. |
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| Embryonic development where eggs are layed outside the mother's body from which the young hatch out. |
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| Embryonic development where the mother produces eggs that remain inside her body and are nourished by egg yolk. The young hatch inside the mother's body and are "birthed" live. |
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| Embryonic development where the young are attached inside the mother's body by placental connection and receive nutrients directly from her. |
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| A common opening for the digestive, urinary, and reproductive tracts found in many nonmammalian vertebrates but in few mammals. |
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| Superclass of vertebrata containing bony fishes; jaws and skeleton are made of bone composed of a hard matrix of calcium phosphate. Characteristics include: swim bladder and/or lungs for buoyancy; operculum; flattened, bony scales; two-chambered heart; and skin that secretes mucus to reduce drag during swimming. Main mode of embryonic development is oviparous, although viviparous and ovoviviparous development occur in a small percent of species. |
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| Protective bony flap that covers and shields the gills of bony fish. Also works to draw water through gills for respiration. |
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| An air sac found in osteichthyans that controls buoyancy in the water by exhanging gases from the blood. |
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| Class of osteichthyans containing ray-finned fishes; most abundant class of osteichthyes. |
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| Fish with fins supported by long, flexible rays. Includes tuna, bass, perch, trout, etc. |
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| Subclasses of osteichthyans containing lobe-finned fishes; part of the class Sarcopterygii. |
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| Fish with rod–shaped bones surrounded by a thick layer of muscle in their pectoral and pelvic fins. Includes coelacanths and lungfishes. |
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| Part of the class dipnoi; animals that have a primative lung used for buoyancy in three genera of sarcopterygii fish. |
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| Part of the class actinistia; animals that represent the closest evolutionary link between fish and amphibian. Though to have been extinct until 1938 when discovered off the coast of the Comoros Islands in the western Indian Ocean. |
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| Clade of vertebrata with two pairs of limbs that evolved from pectoral and pelvic fins; the bones of the pelvic girdle are attached to the backbone; and pharyngeal clefts evolved into parts of the ears, glands, and other structures rather than gills. |
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| Class of vertebrata containing semi-terrestrial vertebrates; larval stage is strictly aquatic while adult stage may either be terrestrial, aquatic or both. Characteristics include: three-chambered heart and generally external oviparous fertilization. Includes frogs, toads, salamanders, newts, etc. |
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| Features of Amphibian Larvae |
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| Herbavorous; have gills through which they breathe; possess a lateral line similar to fish; and lack four limbs, using a long tail for locomotion instead. |
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| Features of Ambhibian Adults |
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| Legs; lungs; a pair of external eardrums; digestive system adapted to a carnivorous diet; relies on moist skin for the majority of gas exchange; some species lack lungs entirely. |
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| Clade of vertabrata that have an amniotic egg containing specialized membranes that protect the embryo; descended from tetrapoda clade. Includes reptiles, birds and mammals. |
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| Four membranes (yolk sac, amnion, chorion, allantois) that support the developing embryo in amniotic animals. Functions in gas exchange, waste storage, and the transfer of stored nutrients to the embryo. |
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| A disposal sac for certain metabolic wastes produced by the embryo. Also functions with the chorion as a respiratory organ. |
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| Protects the embryo in a fluid-filled cavity that cushions against mechanical shock. |
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| Exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell. |
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| Contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. |
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| Class of vertebrata containing first true terrestrial vertebrates. Characteristics include: dry, scaled skin that contains keratin; imperfect four-chambered heart; amniotic egg; and internal fertilization with oviparous embryonic development. Includes tuatara, lizards, snakes, turtles and crocodilians. |
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| Referring to organisms that do not produce enough metabolic heat to have much effect on body temperature. |
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| Referring to organisms with bodies that are warmed by heat generated by metabolism. This heat is usually used to maintain a relatively stable body temperature higher than that of the external environment. |
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| Class of vertebrata containing birds. Characteristics include: wings; hollow bones; feathers; complete four-chambered heart; endothermy; and internal fertilization with oviparous embryonic development. |
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| Class of vertebrata containing mammals. Characteristics include: fur/hair; four-chambered heart; diaphragm; endothermy; internal fertilization with oviparous embryonic development; post-partum nutrition via mammary glands; may be terrestrial, aquatic or arboreal. |
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