The Evolution of Animal Diversity: The Vertebrates Lesson 8 Biology 1112- On-line

Characteristics of Chordates Four features are evident in chordate embryos and some of these may persist into adulthood Dorsal, hollow nerve cord Notochord - a long support rod in the body of the vertebrate that is NOT composed of cartilage or bone Gill slits in pharynx Post-anal tail 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Chordate Classification Phylum – Chordata Invertebrate chordates Tunicates Lancelets Vertebrata These have a real back bone 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Invertebrate Chordates Chordates WITHOUT Backbones

Tunicates A free-swimming tunicate larva (a) and an adult tunicate (b). In the larva, the body is stiffened by a notochord, there is a dorsal nerve cord, and the tail extends beyond the anus. The only defining chordate feature retained in the adult tunicate is the pharynx with gill slits. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Tunicates Another diagram of a free-swimming tunicate larva. In the larva, the body is stiffened by a notochord, there is a dorsal nerve cord, and the tail extends beyond the anus. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Lancelets Body plan of an adult lancelet. Note the defining chordate features: a notochord, a dorsal nerve cord, a pharynx with gill slits, and a tail that extends beyond the anus. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Vertebrate Classification There Are Seven Classes of Vertebrates That Have Living Representatives. Agnatha - jawless fishes Chondrichthyes - cartilaginous fishes Osteichthyes - bony fishes Amphibia - Amphibians (frogs, salamanders) Reptilia - Reptiles (snakes, turtles) Aves - birds Mammalia - mammals 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Existing Jawless Fishes

Phylum - Chordata Subphylum -Vertebrata Class - Agnatha Jawless fishes (class Agnatha). Hagfishes prey on worms and scavenge. They lack jaws but have a rasping tongue. Lampreys are specialized parasite-like predators. They latch onto prey with an oral disk and use horny, toothlike parts to grasp their victims' flesh. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Existing Jawed Fishes

Phylum Chordata - Subphylum Vertebrata Class - Chondrichthyes Representative cartilaginous fishes (class Chondrichthyes). Sharks prey on marine invertebrates, fishes, and mammals. Skates, rays, and chimaeras patrol the sea bottoms, searching for hard-shelled prey. Chimaeras are commonly called ratfishes. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Class - Osteichthyes The typical teleost body plan and anatomy, represented here by a perch. The swim bladder is an adjustable flotation device that allows the fish to regulate its buoyancy. In all fishes, the heart has two chambers—an atrium and a ventricle. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Amphibians

Phylum Chordata - Subphylum Vertebrata Class - Amphibia Two salamanders (amphibian order Caudata). Most salamanders live in the Northern hemisphere. They are carnivorous, preying on small arthropods, worms, and mollusks. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Class - Amphibia A frog and a toad. Both are members of the amphibian order Anura, which means "without a tail." Some are aquatic, some are terrestrial, and some live in trees. The adults are air-breathing carnivores. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Reptiles

Phylum Chordata - Subphylum Vertebrata Class - Reptilia A rattlesnake and a frilled lizard, both in defensive postures. Snakes arose from short-legged, long-bodied lizards. All snakes have highly movable jaws. Some, like this rattlesnake, produce poisonous venom. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Class - Reptilia A Galápagos tortoise and a green sea turtle. All sea turtles are in danger of extinction. The turtles are threatened by human development of beach habitat and by poaching. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Class - Reptilia Body plan of a male crocodile. A reptile’s brain is small compared to the rest of its body mass, but it governs complex forms of behavior unknown among amphibians. The cerebral cortex, the most complex part of the forebrain, evolved first among the reptiles. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Birds

Phylum Chordata - Subphylum Vertebrata Class - Aves Birds range in size from tiny hummingbirds weighing as little as 2.25 grams (0.08 ounce) to ostriches weighing about 150 kilograms (330 pounds). Ostriches cannot fly, but they are excellent sprinters. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Class - Aves Like reptiles, birds lay amniote eggs. However, birds invest far more energy than reptiles in the care of their eggs. Just about all birds build nests and incubate their eggs. The structure of a bird's egg is shown above. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Class - Aves An artist’s reconstruction based on a 150 million-year-old fossil of an extinct bird – Archaeopteryx. Like modern birds, it had wing feathers but like reptiles it had had wing claws, teeth, and a tail composed of vertebrae. Despite its feathers, Archaeopteryx is not considered an ancestor if modern birds. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Mammals

Phylum Chordata - Subphylum Vertebrata Class - Mammalia Of all the vertebrates, only female mammals feed their young with milk, a nutritious fluid produced by the mammary glands. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Class - Mammalia Two distinctively mammalian characteristics are fur and specialized dentition. Only mammals have hair or fur to help them conserve body heat. Mammals have a distinctive arrangement of teeth. The teeth of the upper and lower jaws match up, allowing mammals to cut and chew food instead of simply swallowing it whole, as reptiles must. There are four types of mammalian teeth:molars, premolars, canines, and incisors. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Montremes - egg-laying mammals Class - Mammalia Montremes - egg-laying mammals 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Marsupials - pouched mammals Class – Mammalia Marsupials - pouched mammals 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylum Chordata - Subphylum Vertebrata Eutherians - placental mammals Class - Mammalia Eutherians - placental mammals 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Phylogenetic tree of the Animal Kingdom The phylogenetic tree gives animal diversity an evolutionary perspective. 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002

Tutorial on the Vertebrates The End of Lesson 8 Tutorial on the Vertebrates 3/16/2002 Biology 1112 – Lesson 8 © All Rights Reserved 2002