Animal Kingdom: Vertebrates

Vertebrates are animals with backbones and a subphyla of Phylum: Chordata. All chordates have a strong, flexible, rodlike notochord at some stage in their lives. They also have pharyngeal slits and a hollow dorsal nerve chord. Vertebrates are part of subphylum: Vertebrata. A vertebral column replaces the notochord in most vertebrates. The vertebral column encloses and protects the nerve chord. There are seven classes of vertebrates.

Class: Agnatha (Jawless Fishes) includes the hagfishes and lampreys. Jawless fishes have a cartilaginous skeleton, a notochord that is present throughout the animal's life, and a rasping mouth that is used to bore a hole in the side of prey.

Class: Chondrichthyes (Cartilaginous Fishes) are jawed, and include sharks, rays and skates. These fish have a notochord at birth that is replaced by vertebrae in adults, are cold-blooded (typically), have a tail fin that is usually asymmetrical, pectoral and pelvic fins, and respire through gills.

Class: Osteichthyes (Bony Fishes) include catfish, eels, founder, trout, and tuna. These fish have a bony jaw and skeleton, paired pectoral and pelvic fins, a tail that is usually symmetrical, are cold-blooded (typically), respire through gills, are oviparous (egg laying). Some have live birth reproduction.

Class: Amphibia (Amphibians) live part of their lives in water and part on land, mostly. Most amphibians hatch and begin life in water, and most return to the water as adults to mate and reproduce. Two orders are included in this class: Anura (frogs and toads) and Urodela (salamanders). Amphibians lay eggs without shells, grow from larva to adult through metamorphosis, are cold-blooded hibernate during harsh winters and estivate in warm, dry climates, have smooth skin, respire in the larval stage through gills, respire in most land-dwelling adults through lungs and through gills for water-dwelling adults, and absorb oxygen through the skin and through the lining of the mouth and throat.

Class: Reptilia (Reptiles) belong to three main orders: Chelonia (turtles and tortoises), Crocodilia (alligators and crocodiles), and Squamata (lizards and snakes). Reptiles have scales which prevent drying out of the body, respire through lungs, are cold-blooded, have a venomous bite (in some cases), grow by the shedding of skin, have leathery-shelled eggs, usually, and hibernate during the winder and estivate in tropical climates.

Class: Aves (Birds) are the only animals that have feathers. All birds have two wings and two legs and feet. Not all birds and fly and/or walk. Birds are divided into three groups: non-flying, non-walking, and those that can walk and fly. Birds have the ability to travel faster than any other group of animals, have oviparous reproductions, migrate to warmer or moister regions, lose moisture through droppings and exhalation, have the highest body temperature of all animals, are warm-blooded, and have a beak or a bill.

Class: Mammalia (Mammals) can be divided into three main groups: Monotremata (egg-laying), Marsupalia (pouched), and the remaining placental mammals. Mammals nourish their young with mother's milk, have hair at some point, are warm-blooded and have a high body temperature, have a diaphragm, a four-chambered heart, double circulation, a highly developed brain, both axial and appendicular skeletons, a diet that is varied, and viviparous reproduction.

Notebook Science Fact Book