Chapter 24 Animal Diversity II Vertebrates Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc 24 1 What Are the Key Features of Chordates All chordates have four distinctive structures A notochord a stiff flexible rod extending the length of the body A dorsal hollow nerve chord lies above the digestive tract and expands anteriorly to form the brain Pharyngeal gill slits located in the pharynx that may form respiratory organs or may appear as grooves A post anal tail the chordate tail extends past the anus Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 1 What Are the Key Features of Chordates Humans are members of the phylum Chordata In humans the chordate features are best seen during embryonic development but later we lose our notochord gill slits and tails Only the dorsal nerve cord is retained in post embryonic human development Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 3 What Are the Major Groups of Vertebrates Today vertebrates include the following groups Lampreys Cartilaginous fishes Ray finned fishes Coelacanths Lungfishes Amphibians Reptiles Mammals Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Amphibians live a double life This group includes frogs toads salamanders and caecilians The double life of amphibians Amphibians begin life adapted to an aquatic environment e g tadpoles have gills They later mature into semi terrestrial adults with lungs Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Amphibians Amphibians have a three chambered heart Most adults respire through lungs and moist skin Most have four limbs They reproduce sexually using external fertilization Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Most amphibians are confined to moist habitats Their skin must be kept moist to avoid desiccation when out of water Their breeding behavior and use of external fertilization requires water The male sperm swim to the female eggs The eggs protected only by a jelly like coating are vulnerable to water loss The larvae such as the tadpoles of some frogs and toads develop in water Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Amphibians are represented by the frogs toads salamanders and caecilians Frogs and toads undergo a metamorphosis during their life cycle starting out as aquatic tadpoles and developing into terrestrial hopping adults Salamanders have lizard like bodies with four legs and a long tail They begin life as aquatic larvae with gills that are retained in adulthood by some species while others metamorphose into terrestrial adults Caecilians are limbless burrowing amphibians that resemble an earthworm and can be up to 5 feet long they have small eyes and limited vision Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Reptiles belong to the class Reptilia and are adapted for life on land These animals evolved from an amphibian ancestor about 250 million years ago Reptiles include lizards snakes turtles birds crocs alligators They respire exclusively through lungs Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Reptiles are adapted for life on land continued There are three notable adaptations that allowed the reptiles freedom from their aquatic origins They have tough scaly skin that protects the body and resists water loss They have internal fertilization where the male deposits sperm in the female s body They have evolved a shelled amniotic egg which encapsulates the embryo in a liquid filled membrane the amnion which prevents the embryo from drying out on land Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Reptiles are adapted for life on land continued All reptiles have modified three or four chambered hearts which separate oxygenated and deoxygenated blood more effectively than do amphibian hearts All reptiles have more efficient lungs than do amphibians and do not use their skin as a respiratory organ The reptile skeleton provides better support and more efficient movement on land than do those of amphibians Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Reptiles are represented by lizards snakes alligators crocodiles turtles and birds Lizards and snakes form a common lineage whose ancestors had limbs and whose representatives are mostly predators Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Snakes have a number of adaptations that help them acquire food Many snakes have special sense organs that help track prey by sensing body temperature Some snakes immobilize prey with venom that is delivered through hollow teeth Snakes have a distinctive jaw joint that allows the jaws to distend so that the snake can swallow prey much larger than its head Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Crocodilians include the alligators and crocodiles and are found in the warmer waters of Earth Crocodilians have nostrils located high on their heads so that they are able to remain submerged for long periods with only the uppermost portion of the head above the water surface They have strong jaws and conical teeth to crush and kill the fish birds mammals turtles and amphibians that they eat Parental care is extensive in crocodilians they bury their eggs in mud nests and later the parents guard the hatched young moving them safely to water in their mouths Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 24 2 What Are the Major Groups of Vertebrates Turtles occupy a variety of habitats including deserts streams ponds and the ocean All turtles are protected by a boxlike shell that is fused to the vertebrae ribs and collarbone Turtles have no teeth but have a horny beak instead which is used to eat a variety of foods including both plant and animal matter The largest turtle is the leatherback which lives in the ocean and can grow to 6 feet in length and feeds largely on jellyfish Turtles can migrate long distances to reach beaches where they bury their eggs Biology Life
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