Chapter 34 Vertebrates Copyright 2005 Pearson Education Inc

Overview: • The animals called vertebrates – Get their name from vertebrae, the series of bones that make up the backbone Figure 34. 1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Concept 34. 1: Derived Characters of Chordates • All chordates share a set of derived characters – Although some species possess some of these traits only during embryonic development Dorsal, hollow nerve cord Muscle segments Brain Notochord Mouth Anus Figure 34. 3 Muscular, post-anal tail Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pharyngeal slits or clefts

Notochord • The notochord – Is a longitudinal, flexible rod located between the digestive tube and the nerve cord – Provides skeletal support throughout most of the length of a chordate • In most vertebrates, a more complex, jointed skeleton develops – And the adult retains only remnants of the embryonic notochord Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Dorsal, Hollow Nerve Cord • The nerve cord of a chordate embryo – Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord – Develops into the central nervous system: the brain and the spinal cord Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Pharyngeal Slits or Clefts • In most chordates, grooves in the pharynx called pharyngeal clefts – Develop into slits that open to the outside of the body • These pharyngeal slits – Are modified for gas exchange in aquatic vertebrates – Develop into parts of the ear, head, and neck in terrestrial vertebrates Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Muscular, Post-Anal Tail • Chordates have a tail extending posterior to the anus – Although in many species it is lost during embryonic development • The chordate tail contains skeletal elements and muscles – And it provides much of the propelling force in many aquatic species Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Concept 34. 2: • Craniates are chordates that have a head • The origin of a head – Opened up a completely new way of feeding for chordates: active predation • Craniates share some common characteristics – A skull, brain, eyes, and other sensory organs Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Concept 34. 3: • Vertebrates are craniates that have a backbone • Vertebrates have – Vertebrae enclosing a spinal cord – An elaborate skull – Fin rays, in aquatic forms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Lampreys • Lampreys, class Cephalaspidomorphi – Represent the oldest living lineage of vertebrates – Have cartilaginous segments surrounding the notochord and arching partly over the nerve cord Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Lampreys are jawless vertebrates – Inhabiting various marine and freshwater habitats Figure

Concept 34. 4: • Gnathostomes are vertebrates that have jaws • Today, jawless vertebrates – Are far outnumbered by those with jaws Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Other characters common to gnathostomes include – Enhanced sensory systems, including the lateral line system – An extensively mineralized endoskeleton – Paired appendages Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Chondrichthyans (Sharks, Rays, and Their Relatives) • Members of class Chondrichthyes – Have a skeleton that is composed primarily of cartilage • The cartilaginous skeleton – Evolved secondarily from an ancestral mineralized skeleton Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• The largest and most diverse subclass of Chondrichthyes – Includes the sharks and rays (a) Blacktip reef shark (Carcharhinus melanopterus). Fast swimmers with acute senses, sharks have paired pectoral and pelvic fins. (b) Southern stingray (Dasyatis americana). Most rays are flattened bottom-dwellers that crush molluscs and crustaceans for food. Some rays cruise in open water and scoop food into Figure 34. 15 a, b their gaping mouth. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pectoral fins Pelvic fins

Ray-Finned Fishes and Lobe-Fins • The vast majority of vertebrates – Belong to a

• Nearly all living osteichthyans – Have a bony endoskeleton • Aquatic osteichthyans – Are the vertebrates we informally call fishes – Control their buoyancy with an air sac known as a swim bladder Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Fishes breathe by drawing water over four or five pairs of gills Dorsal fin Nostril Spinal cord Brain Swim bladder Cut edge of operculum Gills Heart Figure 34. 16 Gonad Urinary Anus bladder Liver Kidney Stomach Pelvic fin Intestine Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Adipose fin (characteristic of trout) Caudal fin Anal fin Lateral line

Ray-Finned Fishes • The ray-finned fishes includes nearly all the familiar aquatic osteichthyans (a) Yellowfin tuna (Thunnus albacares), a fast-swimming, schooling fish that is an important commercial fish worldwide (b) Clownfish (Amphiprion ocellaris), a mutualistic symbiont of sea anemones Figure 34. 17 a–d (c) Sea horse (Hippocampus ramulosus), unusual in the animal kingdom in that the male carries the young during their embryonic development Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (d) Fine-spotted moray eel (Gymnothorax dovii), a predator that ambushes prey from crevices in its coral reef habitat

• The fins, supported mainly by long, flexible rays – Are modified for

Lobe-Fins • The lobe-fins – Have muscle covering bones of their pelvic and pectoral fins – Include coelacanths, lungfishes, and tetrapods Figure 34. 18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Concept 34. 5: • Tetrapods are gnathostomes that have limbs and feet • One of the most significant events in vertebrate history – Was when the fins of some lobe-fins evolved into the limbs and feet of tetrapods Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Derived Characters of Tetrapods • Tetrapods have some specific adaptations – Four limbs and feet with digits – Ears for detecting airborne sounds Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Amphibians • Amphibians are represented by about 4, 800 species of organisms • Most amphibians – Have moist skin that complements the lungs in gas exchange Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Amphibians • Includes salamanders, which have tails (a) salamanders retain their tail as adults.

Amphibians • Includes frogs and toads, which lack tails as adults Figure 34. 21

Amphibians • Includes caecilians, which are legless and resemble worms (c) Caecilians, mainly burrowing amphibians. Figure 34. 21 c Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Amphibians • Amphibian means “two lives” – A reference to the metamorphosis of an aquatic larva into a terrestrial adult (b) The tadpole is an aquatic herbivore with a fishlike tail and internal gills. (a) The male grasps the female, stimulating her to release eggs. The eggs are laid and fertilized in water. They have a jelly coat but lack a shell and Figure 34. 22 a–c would desiccate in air. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (c) During metamorphosis, the gills and tail are resorbed, and walking legs develop.

Concept 34. 6: • Amniotes are tetrapods that have a terrestrially adapted egg • Amniotes are a group of tetrapods – Whose living members are the reptiles, including birds, and the mammals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Derived Characters of Amniotes • Amniotes are named for the major derived character of the clade, the amniotic egg – Which contains specialized membranes that protect the embryo Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• The extraembryonic membranes have various functions Extraembryonic membranes Allantois. The allantois is a disposal sac for certain metabolic wastes produced by the embryo. The membrane of the allantois also functions with the chorion as a respiratory organ. Amnion. The amnion protects the embryo in a fluid-filled cavity that cushions against mechanical shock. Chorion. The chorion and the membrane of the allantois exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell. Yolk sac. The yolk sac contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. Other nutrients are stored in the albumen (“egg white”). Embryo Amniotic cavity with amniotic fluid Yolk (nutrients) Albumen Shell Figure 34. 24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Amniotes also have other terrestrial adaptations – Such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Reptiles • The reptile clade includes – The tuatara, lizards, snakes, turtles, crocodilians, birds,

• Reptiles – Have scales that create a waterproof barrier – Lay shelled

• Most reptiles are ectothermic – Absorbing external heat as the main source of body heat • Birds are endothermic – Capable of keeping the body warm through metabolism Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

The Origin and Evolutionary Radiation of Reptiles • One surviving lineage of lepidosaurs – Is represented by two species of lizard-like reptiles called tuatara Figure 34. 27 a (a) Tuatara (Sphenodon punctatus) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• The other major living lineage of lepidosaurs – Are the squamates, the lizards and snakes • Lizards – Are the most numerous and diverse reptiles, apart from birds Figure 34. 27 b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) Australian thorny devil lizard (Moloch horridus)

• Snakes are legless lepidosaurs – That evolved from lizards (c) Wagler’s pit viper (Tropidolaemus wagleri), a snake Figure 34. 27 c Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Turtles • Turtles – Are the most distinctive group of reptiles alive today • Some turtles have adapted to deserts – And others live entirely in ponds and rivers Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• All turtles have a boxlike shell – Made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs Figure 34. 27 d (d) Eastern box turtle (Terrapene carolina) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Alligators and Crocodiles • Crocodilians – Belong to a lineage that dates back about 200 million years Figure 34. 27 e (e) American alligator (Alligator mississipiensis) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Birds • Birds are archosaurs – But almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Derived Characters of Birds • A bird’s most obvious adaptations for flight – Are its wings and feathers Finger 1 (b) Bone structure Palm (a) wing Finger 2 Forearm Wrist Finger 3 Shaft Vane Shaft Figure 34. 28 a–c Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Barbule Hook (c) Feather structure

Living Birds • The ratites, order Struthioniformes – Are all flightless (a) Emu. This ratite lives in Australia. Figure 34. 30 a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• The demands of flight – Have rendered the general body form of many flying birds similar to one another (b) Mallards. Like many bird species, the mallard exhibits pronounced color differences between the sexes. (c) Laysan albatrosses. Like most birds, Laysan albatrosses have specific mating behaviors, such as this courtship ritual. (d) Barn swallows. The barn swallow is a member of the order Passeriformes. Species in this order are called perching birds because the toes of their feet can lock around a branch or wire, enabling the bird Figure 34. 30 b–d to rest in place for long periods. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Foot structure in bird feet – Shows considerable variation Perching bird (such as a cardinal) Grasping bird (such as a woodpecker) Figure 34. 31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Raptor (such as a bald eagle) Swimming bird (such as a duck)

Concept 34. 7: • Mammals are amniotes that have hair and produce milk • Mammals, class Mammalia – Are represented by more than 5, 000 species Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Derived Characters of Mammals • Mammary glands, which produce milk are a distinctively mammalian character • Hair is another mammalian characteristic • Mammals generally have a larger brain than other vertebrates of equivalent size Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Monotremes • Monotremes – Are a small group of egg-laying mammals consisting of echidnas

Marsupials • Marsupials – Include opossums, kangaroos, and koalas Copyright © 2005 Pearson Education,

• A marsupial is born very early in its development – And completes its embryonic development while nursing within a maternal pouch called a marsupium Figure 34. 34 a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (a) A young brushtail possum.

Eutherians (Placental Mammals) • Compared to marsupials – Eutherians have a longer period of pregnancy • Eutherians – Complete their embryonic development within a uterus, joined to the mother by the placenta Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

The major eutherian orders MAIN CHARACTERISTICS ORDERS AND EXAMPLES Lay eggs; no nipples; young suck milk from fur of mother Monotremata Platypuses, echidnas ORDERS AND EXAMPLES Proboscidea Elephants Koala Long, muscular trunk; thick, loose skin; upper incisors elongated as tusks Tubulidentata Aardvark African elephant Hyracoidea Hyraxes Rock hyrax Manatee Xenarthra Sloths, anteaters, armadillos Reduced teeth or no teeth; herbivorous (sloths) or carnivorous (anteaters, armadillos) Rodentia Squirrels, beavers, rats, porcupines, mice Tamandua Lagomorpha Rabbits, hares, picas Chisel-like incisors; hind legs longer than forelegs and adapted for running and jumping Sharp, pointed canine teeth and molars for shearing; carnivorous Figure 34. 36 Hooves with an odd number of toes on each foot; herbivorous Indian rhinoceros Hooves with an even number of toes on each foot; herbivorous Pacific whitesided porpoise Opposable thumbs; forward-facing eyes; well-developed cerebral cortex; omnivorous Perissodactyla Horses, zebras, tapirs, rhinoceroses Chiroptera Bats Frog-eating bat Bighorn sheep Cetaceans Whales, dolphins, porpoises Red squirrel Golden lion tamarin Coyote Cetartiodactyla Artiodactyls Sheep, pigs cattle, deer, giraffes Short legs; stumpy tail; herbivorous; complex, multichambered stomach Chisel-like, continuously growing incisors worn down by gnawing; herbivorous Primates Lemurs, monkeys, apes, humans Jackrabbit Carnivora Dogs, wolves, bears, cats, weasels, otters, seals, walruses Teeth consisting of many thin tubes cemented together; eats and termites Aardvark Aquatic; finlike forelimbs and no hind limbs; herbivorous Sirenia Manatees, dugongs Embryo completes development in pouch on mother Marsupialia Kangaroos, opossums, koalas Echidna MAIN CHARACTERISTICS Aquatic; streamlined body; paddle-like forelimbs and no hind limbs; thick layer of insulating blubber; carnivorous Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eulipotyphla “Core insectivores”: some moles, some shrews Adapted for flight; broad skinfold that extends from elongated fingers to body and legs; carnivorous or herbivorous Diet consists mainly of insects and other small invertebrates Star-nosed mole

Primates • The mammalian order Primates include – Lemurs, tarsiers, monkeys, and apes • Humans are members of the ape group Figure 34. 37 Lemurs Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Derived Characters of Primates • Most primates – Have hands and feet adapted for grasping • Primates also have – A large brain and short jaws – Forward-looking eyes close together on the face, providing depth perception – Well-developed parental care and complex social behavior – A fully opposable thumb Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Hominoids (Apes) (a) Gibbons, such as this Muller's gibbon, are found only in southeastern Asia. Their very long arms and fingers are adaptations for brachiation. (b) Orangutans are shy, solitary apes that live in the rain forests of Sumatra and Borneo. They spend most of their time in trees; note the foot adapted for grasping and the opposable thumb. Figure 34. 40 a–e (d) Chimpanzees live in tropical Africa. They feed and sleep in trees but also spend a great deal of time on the ground. Chimpanzees are intelligent, communicative, and social. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (e) Bonobos are closely related to chimpanzees but are smaller. They survive today only in the African nation of Congo. (c) Gorillas are the largest apes: some males are almost 2 m tall and weigh about 200 kg. Found only in Africa, these herbivores usually live in groups of up to about 20 individuals.

Concept 34. 8: • Humans are bipedal hominoids with a large brain • Homo

Derived Characters of Hominids • A number of characters distinguish humans from other hominoids – Upright posture and bipedal locomotion – Larger brains – Language capabilities – The manufacture and use of complex tools – Shortened jaw Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

The Earliest Humans • The study of human origins – Is known as paleoanthropology

Hominids Paranthropus robustus 0 Paranthropus boisei 0. 5 1. 0 Millions of years ago 2. 5 3. 0 3. 5 Kenyanthropus platyops Australopithecus garhi 5. 0 Homo rudolfensis habilis Ardipithecus ramidus Australopithecus afarensis 5. 5 6. 0 6. 5 Figure 34. 41 7. 0 Homo erectus Australopithecus anamensis 4. 0 4. 5 Homo ? ergaster Australopithecus africanus 1. 5 2. 0 Homo neanderthalensis sapiens Orrorin tugenensis Sahelanthropus tchadensis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Hominids originated in Africa – Approximately 6– 7 million years ago • Early hominids – Had a small brain, but probably walked upright, exhibiting mosaic evolution Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Early Homo • The earliest fossils that paleoanthropologists place in our genus Homo – Are those of the species Homo habilis, ranging in age from about 2. 4 to 1. 6 million years • Stone tools have been found with H. habilis – Giving this species its name, which means “handy man” Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Homo ergaster – Was the first fully bipedal, large-brained hominid – Existed between 1. 9 and 1. 6 million years Figure 34. 43 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Homo erectus – Originated in Africa approximately 1. 8 million years ago

Neanderthals • Neanderthals, Homo neanderthalensis – Lived in Europe and the Near East from 200, 000 to 30, 000 years ago – Were large, thick-browed hominids – Became extinct a few thousand years after the arrival of Homo sapiens in Europe Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings