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Chordate Test Review Key All Chordates share four major characteristics. At some time during their development, they will have a _______notochord___________, which becomes the spine in vertebrate animals. They will also have ______pharyngeal pouches_______, which become the gill slits of aquatic chordates. They have a __dorsal hollow nerve cord___ which becomes the spinal cord and brain, and they will have a postanal tail. There are only two types of ____invertebrate chordates_______. These are the tunicates and lancelets. All other chordates have a backbone, and belong to the subphylum ____Vertebrata_________. Fishes make up 4 classes of vertebrate. Two of the classes, Myxini and Cephalaspidomorphi, are jawless fishes. They belong to the superclass ___Agnatha____. The only members of this superclass of jawless fishes are the hagfish and _____lamprey_____. Sharks, skates and rays are in the class _____Chondrichthyes_________. These fishes have a skeleton composed of _____cartilage__________ rather than bone. There are more bony fishes, from the class _________Osteichtyes_________, than any other type of fish. All fishes are characterized by a ____2____ chambered heart, a closed circulatory system and respiration through gills. Gills function by allowing ___oxygen_______ to diffuse from the water into the capillaries of the gill filaments, and _______carbon dioxide____ diffuses from the blood, into the water. Fishes also have a ________lateral line system___________ that allows them to detect movement in the water. The other 4 classes; _____amphibians______, ______reptiles________, ______birds (Aves) ___________, and _________mammals___________ can be recognized as being either endothermic or ectothermic. The _________amphibians _____________ and _________reptiles____________ are ectotherms. The _______birds_________ and ______mammals_______ are endotherms. Endothermic animals produce their own body heat. Their temperature remains fairly constant, regardless of their surroundings. Because of this, they must have a way to insulate their bodies to conserve heat. All _____birds (Aves) _____, have a covering of feathers, and in _____mammals____ this covering will be in the form of hair or fur. All endothermic animals have a __4______chambered heart. In addition to the feathers of birds, they are also characterized by having 2 legs and 2 ____wings_____. And they have a ___beak______ with no teeth. Mammals can be subdivided by the way they bear their young. ___Placental_______ mammals are the most common. Their young develop inside a membrane sac known as a _________placenta_________. __________Marsupial__________ mammals, such as kangaroos, complete their development inside a pouch. There are only two egg laying mammals, known as ______monotremes________. They are the _____platypus______ and the ___echidna (spiny anteater) ______. The class Mammalia gets its name from the ___mammary_____ glands of the females, which serve to supply _____milk______ for the young. Mammals can be found on the land, in the water ( _____whales__________ and _____dolphins_____) and some are even capable of flight (____bats______). Ectotherms include the classes _____Amphibia__________ and ______Reptilia________. Ectothermic animals do not produce or store a lot of heat. Their body temperatures will change to match their surroundings. Ectothermic animals have ___3____ heart chambers. In most ____reptiles_______, the heart is partly divided. The exceptions to this are the _____ crocodilians______, who have a heart with four chambers. Members of the class _______Amphibia____________ start off in a larval form in the water. They have characteristics of fish, such as gills and fins. They will eventually undergo a change, called a ________metamorphosis_____________ in which they loose their gills and gain a set of ____lungs_____ for respiration. Most will also gain legs. Even though they have legs to move about on the land, most have to remain fairly close to water. They have a very sensitive skin that must be kept moist. In fact, most of them carry out _________respiration_____ through their skin and can suffocate if it dries out. Members of the class _____Reptilia_________ do not have this problem, because they have a scaly skin that helps them retain moisture. _______Reptiles____________ do not undergo metamorphosis either. They develop in an ____amniotic_________ egg with a ______leathery____________ shell. Once they hatch, respiration is only through _____lungs________. Most reptiles have the ability to pick up scent molecules with their tongue. They flick their tongue, and then insert it into the _____Jacobson’s ______ organ, which is located on the roof of the mouth. The hearts of mammals and birds are much more efficient than those of reptiles and amphibians. The reason for this is ________the oxygenated blood is separated from the deoxygenated which allows the cells to make more energy to keep the body warm_________________ Some mammals, known as ____bats_____ are unique because they are capable of flight. Humans are classified as mammals because we are _____endothermic_____, meaning we maintain a constant body temperature, we have a ______4_____ chambered heart, our bodies have a sparse covering of _____hair______, and females have _______mammary glands_________ which produce milk for our young.