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Chapter 34. Vertebrates. Overview: Half a Billion Years of Backbones By the end of the Cambrian period, some 540 million years ago An astonishing variety of animals inhabited Earth’s oceans One of these types of animals Gave rise to vertebrates, one of the most successful groups of animals.

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chapter 34

Chapter 34

Vertebrates

slide2
Overview: Half a Billion Years of Backbones
  • By the end of the Cambrian period, some 540 million years ago
    • An astonishing variety of animals inhabited Earth’s oceans
  • One of these types of animals
    • Gave rise to vertebrates, one of the most successful groups of animals
slide3

Figure 34.1

  • The animals called vertebrates
    • Get their name from vertebrae, the series of bones that make up the backbone
slide4
There are approximately 52,000 species of vertebrates
    • Which include the largest organisms ever to live on the Earth
slide5
Concept 34.1: Chordates have a notochord and a dorsal, hollow nerve cord
  • Vertebrates are a subphylum of the phylum Chordata
  • Chordates are bilaterian animals
    • That belong to the clade of animals known as Deuterostomia
slide6

Chordates

Craniates

Vertebrates

Gnathostomes

Osteichthyans

Lobe-fins

Tetrapods

Amniotes

Echinodermata(sister group to chordates)

Chondrichthyes(sharks, rays, chimaeras)

Cephalaspidomorphi(lampreys)

Amphibia(frogs, salamanders)

Cephalochordata(lancelets)

Reptilia(turtles, snakes,crocodiles, birds)

Actinopterygii(ray-finned fishes)

Urochordata(tunicates)

Actinistia(coelacanths)

Dipnoi(lungfishes)

Myxini(hagfishes)

Mammalia(mammals)

Milk

Amniotic egg

Legs

Lobed fins

Lungs or lung derivatives

Jaws, mineralized skeleton

Vertebral column

Head

Brain

Notochord

Ancestral deuterostome

Figure 34.2

  • A hypothetical phylogeny of chordates
derived characters of chordates

Dorsal,hollownerve cord

Brain

Notochord

Musclesegments

Mouth

Anus

Pharyngealslits or clefts

Muscular,post-anal tail

Figure 34.3

Derived Characters of Chordates
  • All chordates share a set of derived characters
    • Although some species possess some of these traits only during embryonic development
notochord
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
dorsal hollow nerve cord
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
pharyngeal slits or clefts
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
    • Function as suspension-feeding structures in many invertebrate chordates
    • Are modified for gas exchange in aquatic vertebrates
    • Develop into parts of the ear, head, and neck in terrestrial vertebrates
muscular post anal tail
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
slide12
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
derived characters of craniates

Neuraltube

Neuralcrest

Dorsal edgesof neural plate

Ectoderm

Ectoderm

(a) The neural crest consists of bilateral bands of cells near the margins of the embryonic folds that form the neural tube.

(b) Neural crest cells migrate todistant sites in the embryo.

Migrating neuralcrest cells

Notochord

Figure 34.7a, b

Derived Characters of Craniates
  • One feature unique to craniates
    • Is the neural crest, a collection of cells that appears near the dorsal margins of the closing neural tube in an embryo
slide14

(c) The cells give rise to some of the anatomical structuresunique to vertebrates, including some of the bones and cartilage of the skull.

Figure 34.7c

  • Neural crest cells
    • Give rise to a variety of structures, including some of the bones and cartilage of the skull
hagfishes

Slime glands

Figure 34.9

Hagfishes
  • The least derived craniate lineage that still survives
    • Is class Myxini, the hagfishes
slide16
Concept 34.3: Vertebrates are craniates that have a backbone
  • During the Cambrian period
    • A lineage of craniates evolved into vertebrates
derived characters of vertebrates
Derived Characters of Vertebrates
  • Vertebrates have
    • Vertebrae enclosing a spinal cord
    • An elaborate skull
    • Fin rays, in aquatic forms
origins of bone and teeth
Origins of Bone and Teeth
  • Mineralization
    • Appears to have originated with vertebrate mouthparts
  • The vertebrate endoskeleton
    • Became fully mineralized much later
slide19
Concept 34.4: Gnathostomes are vertebrates that have jaws
  • Today, jawless vertebrates
    • Are far outnumbered by those with jaws
derived characters of gnathostomes

Gill slits

Cranium

Mouth

Skeletal rods

Figure 34.13

Derived Characters of Gnathostomes
  • Gnathostomes have jaws
    • That evolved from skeletal supports of the pharyngeal slits
slide21
Other characters common to gnathostomes include
    • Enhanced sensory systems, including the lateral line system
    • An extensively mineralized endoskeleton
    • Paired appendages (fins for swimming)
chondrichthyans sharks rays and their relatives
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
slide23

(a) Blacktip reef shark (Carcharhinus melanopterus).Fast swimmers with acute senses, sharks have paired pectoral and pelvic fins.

Pelvic fins

Pectoral fins

(b) Southern stingray (Dasyatis americana).Most rays are flattened bottom-dwellers thatcrush molluscs and crustaceans for food. Some rays cruise in open water and scoop food into their gaping mouth.

Figure 34.15a, b

  • The largest and most diverse subclass of Chondrichthyes
    • Includes the sharks and rays
slide24

(c) Spotted ratfish(Hydrolagus colliei). Ratfishes, or chimaeras, typically live at depths greaterthan 80 m and feed on shrimps, molluscs, and sea urchins. Some species have a poisonous spine at the front of their dorsal fin.

Figure 34.15c

  • A second subclass
    • Is composed of a few dozen species of ratfishes
slide25
Most sharks
    • Have a streamlined body and are swift swimmers
    • Have acute senses
ray finned fishes and lobe fins
Ray-Finned Fishes and Lobe-Fins
  • The vast majority of vertebrates
    • Belong to a clade of gnathostomes called Osteichthyes
slide27
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
slide28

Adipose fin(characteristic oftrout)

Dorsal fin

Caudal fin

Swim bladder

Spinal cord

Brain

Nostril

Cut edge of operculum

Anal fin

Gills

Anus

Gonad

Liver

Heart

Lateral line

Stomach

Urinary bladder

Kidney

Intestine

Pelvic fin

Figure 34.16

  • Fishes breathe by drawing water over four or five pairs of gills
    • Located in chambers covered by a protective bony flap called the operculum
slide29
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
derived characters of tetrapods
Derived Characters of Tetrapods
  • Tetrapods have some specific adaptations
    • Four limbs and feet with digits
    • Ears for detecting airborne sounds
the origin of tetrapods

Bonessupportinggills

Tetrapodlimbskeleton

Figure 34.19

The Origin of Tetrapods
  • In one lineage of lobe-fins
    • The fins became progressively more limb-like while the rest of the body retained adaptations for aquatic life
slide32

Millions of years ago

420

370

340

310

295

280

265

415

400

385

355

325

Silurian

Devonian

Carboniferous

Permian

To present

Paleozoic

Ray-finned fishes

Coelacanths

Lungfishes

Eusthenopteron

Panderichthys

Elginerpeton

Metaxygnathus

Acanthostega

lchthyostega

Hynerpeton

Greerpeton

Amphibians

Amniotes

Figure 34.20

  • Extraordinary fossil discoveries over the past 20 years
    • Have allowed paleontologists to reconstruct the origin of tetrapods
amphibians
Amphibians
  • Class Amphibia
    • Is represented by about 4,800 species of organisms
  • Most amphibians
    • Have moist skin that complements the lungs in gas exchange
slide34

(a) Order Urodela. Urodeles (salamanders) retain their tail as adults.

Figure 34.21a

  • Order Urodela
    • Includes salamanders, which have tails
slide35

(b) Order Anura. Anurans, such as this poison arrow frog, lack a tail as adults.

Figure 34.21b

  • Order Anura
    • Includes frogs and toads, which lack tails
slide36

(c) Order Apoda. Apodans, or caecilians, are legless, mainly burrowing amphibians.

Figure 34.21c

  • Order Apoda
    • Includes caecilians, which are legless and resemble worms
slide37

(b) The tadpole is an aquatic herbivore witha fishlike tail and internal gills.

(c) During metamorphosis, the gills and tail are resorbed, andwalking legs develop.

(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 would desiccate in air.

Figure 34.22a–c

  • Amphibian means “two lives”
    • A reference to the metamorphosis of an aquatic larva into a terrestrial adult
slide38
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
derived characters of amniotes
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
slide40

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.

Allantois. The allantois is a disposal

sac for certain metabolic wastes pro-

duced by the embryo. The membrane

of the allantois also functions with

the chorion as a respiratory organ.

Extraembryonic membranes

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”).

Amnion. The amnion protectsthe embryo in a fluid-filled cavity that cushions againstmechanical shock.

Embryo

Amniotic cavitywith amniotic fluid

Yolk (nutrients)

Albumen

Shell

Figure 34.24

  • The extraembryonic membranes
    • Have various functions
slide41
Amniotes also have other terrestrial adaptations
    • Such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs
early amniotes
Early Amniotes
  • Early amniotes
    • Appeared in the Carboniferous period
    • Included large herbivores and predators
reptiles
Reptiles
  • The reptile clade includes
    • The tuatara, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs
slide44

Figure 34.25

  • Reptiles
    • Have scales that create a waterproof barrier
    • Lay shelled eggs on land
slide45
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
the origin and evolutionary radiation of reptiles
The Origin and Evolutionary Radiation of Reptiles
  • The oldest reptilian fossils
    • Date to about 300 million years ago
  • The first major group of reptiles to emerge
    • Were the parareptiles, which were mostly large, stocky herbivores
slide47
The dinosaurs
    • Diversified into a vast range of shapes and sizes
    • Included the long-necked giants called the theropods
slide48

Figure 34.26

  • Traditionally, dinosaurs were considered slow, sluggish creatures
    • But fossil discoveries and research have led to the conclusion that dinosaurs were agile and fast moving
  • Paleontologists have also discovered signs of parental care among dinosaurs
lepidosaurs

(a) Tuatara (Sphenodon punctatus)

Figure 34.27a

Lepidosaurs
  • One surviving lineage of lepidosaurs
    • Is represented by two species of lizard-like reptiles called tuatara
slide50

Figure 34.27b

(b) Australian thorny devil lizard (Moloch horridus)

  • 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
slide51

(c) Wagler’s pit viper (Tropidolaemus wagleri), a snake

Figure 34.27c

  • Snakes are legless lepidosaurs
    • That evolved from lizards
turtles
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
slide53

Figure 34.27d

(d) Eastern box turtle (Terrapene carolina carolina)

  • All turtles have a boxlike shell
    • Made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs
alligators and crocodiles

Figure 34.27e

(e) American alligator (Alligator mississipiensis)

Alligators and Crocodiles
  • Crocodilians
    • Belong to an archosaur lineage that dates back to the late Triassic
birds
Birds
  • Birds are archosaurs
    • But almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight
derived characters of birds
Derived Characters of Birds
  • Many of the characters of birds
    • Are adaptations that facilitate flight
slide57

Finger 1

(b) Bone structure

Palm

(a) wing

Finger 2

Forearm

Wrist

Finger 3

Shaft

Vane

Barb

Shaft

Barbule

Hook

Figure 34.28a–c

(c) Feather structure

  • A bird’s most obvious adaptations for flight
    • Are its wings and feathers
the origin of birds
The Origin of Birds
  • Birds probably descended from theropods
    • A group of small, carnivorous dinosaurs
slide59

Wing claw

Toothed beak

Airfoil wing with contour feathers

Long tail with many vertebrae

Figure 34.29

  • By 150 million years ago
    • Feathered theropods had evolved into birds
  • Archaeopteryx
    • Remains the oldest bird known
living birds

(a) Emu. This ratite lives in Australia.

Figure 34.30a

Living Birds
  • The ratites, order Struthioniformes
    • Are all flightless
slide61

(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 to rest in place for long periods.

Figure 34.30b–d

  • The demands of flight
    • Have rendered the general body form of many flying birds similar to one another
slide62

Raptor(such as a bald eagle)

Grasping bird (such as a woodpecker)

Swimming bird(such as a duck)

Perching bird (such as a cardinal)

Figure 34.31

  • Foot structure in bird feet
    • Shows considerable variation
slide63
Concept 34.7: Mammals are amniotes that have hair and produce milk
  • Mammals, class Mammalia
    • Are represented by more than 5,000 species
derived characters of mammals
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
slide65

Jaw joint

Jaw joint

Dimetrodon

Morganucodon

Key

Dentary

Angular

Squamosal

Eardrum

Middle ear

Inner ear

Articular

Quadrate

Inner ear

Eardrum

Stapes

(a) The lower jaw of Dimetrodon is composed of several fused bones; two small bones, the quadrate and articular, form part of the jaw joint. In Morganucodon, the lower jaw is reduced to a single bone, the dentary, and the location of the jaw joint has shifted.

Middle ear

Stapes

Incus (evolvedfrom quadrate)

Sound

Sound

Malleus (evolvedfrom articular)

Morganucodon

Dimetrodon

(b) During the evolutionary remodeling of the mammalian skull, the quadrate and articular bones became incorporated into the middle ear as two of the three bones that transmit sound from the eardrum to the inner ear. The steps in this evolutionary remodeling are evident in a succession of fossils.

Figure 34.32a, b

  • The jaw was remodeled during the evolution of mammals from nonmammalian synapsids
    • And two of the bones that formerly made of the jaw joint were incorporated into the mammalian middle ear
slide66
Living lineages of mammals originated in the Jurassic
    • But did not undergo a significant adaptive radiation until after the Cretaceous
monotremes

Figure 34.33

Monotremes
  • Monotremes
    • Are a small group of egg-laying mammals consisting of echidnas and the platypus
marsupials
Marsupials
  • Marsupials
    • Include opossums, kangaroos, and koalas
slide69

(a) A young brushtail possum. The young of marsupials are born very early in their development. They finish their growth while nursing from a nipple (in their mother’s pouch in most species).

Figure 34.34a

  • A marsupial is born very early in its development
    • And completes its embryonic development while nursing within a maternal pouch called a marsupium
primates
Primates
  • The mammalian order Primates include
    • Lemurs, tarsiers, monkeys, and apes
  • Humans are members of the ape group
derived characters of primates
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
slide72
Concept 34.8: Humans are bipedal hominoids with a large brain
  • Homo sapiens is about 160,000 years old
    • Which is very young considering that life has existed on Earth for at least 3.5 billion years
derived characters of hominids
Derived Characters of Hominids
  • A number of characters distinguish humans from other hominoids
    • Upright posture and bipedal locomotion
    • Larger brains
    • Language capabilities
    • Symbolic thought
    • The manufacture and use of complex tools
    • Shortened jaw
the earliest humans
The Earliest Humans
  • The study of human origins
    • Is known as paleoanthropology
slide75
Hominids originated in Africa
    • Approximately 6–7 million years ago
  • Early hominids
    • Had a small brain, but probably walked upright, exhibiting mosaic evolution
slide76
Two common misconceptions of early hominids include
    • Thinking of them as chimpanzees
    • Imagining human evolution as a ladder leading directly to Homo sapiens
early homo
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”
slide78

Figure 34.43

  • Homo ergaster
    • Was the first fully bipedal, large-brained hominid
    • Existed between 1.9 and 1.6 million years
slide79
Homo erectus
    • Originated in Africa approximately 1.8 million years ago
    • Was the first hominid to leave Africa
homo sapiens

Figure 34.44

Homo sapiens
  • Homo sapiens
    • Appeared in Africa at least 160,000 years ago
slide82

Figure 34.45

  • The rapid expansion of our species
    • May have been preceded by changes to the brain that made symbolic thought and other cognitive innovations possible