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Chapter 34

Chapter 34. Vertebrates. Chordates. Craniates. Vertebrates. Gnathostomes. Osteichthyans. Lobe-fins. Tetrapods. Amniotes. Echinodermata (sister group to chordates). Chondrichthyes (sharks, rays, chimaeras). Cephalaspidomorphi (lampreys). Amphibia (frogs, salamanders).

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Chapter 34

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  1. Chapter 34 Vertebrates

  2. 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 Hypothetical Phylogeny of Chordates

  3. Vertebrates • 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 • There are approximately 52,000 species of vertebrates • Which include the largest organisms ever to live on the Earth

  4. Figure 34.1 Vertebrates • The animals called vertebrates • Get their name from vertebrae, the series of bones that make up the backbone

  5. Chordates • Chordates have a notochord and a dorsal, hollow nerve cord, post-anal tail, and pharyngeal slits during some part of their development • Vertebrates are a subphylum of the phylum Chordata • Chordates are bilaterian animals that belong to the clade of animals known as Deuterostomia • Two groups of invertebrate deuterostomes, the urochordates and cephalochordates, are more closely related to vertebrates than to invertebrates

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. Notochord Dorsal, hollownerve cord Tail Excurrent siphon Musclesegments Incurrentsiphon Intestine Stomach Atrium Pharynx with slits (c) A tunicate larva is a free-swimming butnonfeeding “tadpole” in which all fourchief characters of chordates are evident. Tunicates – Invertebrate Chrodates • Tunicates, subphylum Urochordata belong to the deepest-branching lineage of chordates are marine suspension feeders commonly called sea squirts • Tunicates most resemble chordates during their larval stage which may be as brief as a few minutes Figure 34.4c

  12. Incurrentsiphonto mouth Excurrentsiphon Excurrent siphon Atrium Pharynxwith numerousslits Anus Intestine Tunic Esophagus Stomach (b) In the adult, prominent pharyngeal slits function in suspension feeding, but other chordate characters are not obvious. (a) An adult tunicate, or sea squirt, is a sessile animal (photo is approximately life-sized). Figure 34.4a, b Tunicates – Invertebrate Chrodates • As an adult a tunicate draws in water through an incurrent siphon, filtering food particles

  13. Tentacle 2 cm Mouth Pharyngeal slits Atrium Notochord Digestive tract Atriopore Dorsal, hollownerve cord Segmentalmuscles Anus Tail Figure 34.5 Lancelets – Invertebrate Chrodates • Lancelets, subphylum Cephalochordata are named for their bladelike shape. Lancelets are marine suspension feeders that retain the characteristics of the chordate body plan as adults.

  14. Craniates • 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

  15. 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

  16. (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 • Neural crest cells give rise to a variety of structures, including some of the bones and cartilage of the skull

  17. Slime glands Figure 34.9 Hagfishes • The least derived craniate lineage that still survives is class Myxini, the hagfishes • Hagfishes are jawless marine craniates that have a cartilaginous skull and axial rod of cartilage derived from the notochord but lack vertebrae

  18. Derived Characteristics of Vertebrates • Vertebrates are craniates that have a backbone • During the Cambrian period • A lineage of craniates evolved into vertebrates • Vertebrates have • Vertebrae enclosing a spinal cord • An elaborate skull • Fin rays, in aquatic forms

  19. Lampreys • Lampreys • Represent the oldest living lineage of vertebrates • Have cartilaginous segments surrounding the notochord and arching partly over the nerve cord

  20. Figure 34.10 Lampreys • Lampreys are jawless vertebrates inhabiting various marine and freshwater habitats

  21. Origins of Bone and Teeth • Mineralization • Appears to have originated with vertebrate mouthparts • The vertebrate endoskeleton • Became fully mineralized much later

  22. Gill slits Cranium Mouth Skeletal rods Figure 34.13 Gnathostomes • Gnathostomes are vertebrates that have jaws • Today, jawless vertebrates • Are far outnumbered by those with jaws • Gnathostomes have jaws • That evolved from skeletal supports of the pharyngeal slits

  23. Gnathostomes • Other characters common to gnathostomes include • Enhanced sensory systems, including the lateral line system • An extensively mineralized endoskeleton • Paired appendages

  24. 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

  25. (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 Sharks & Rays • The largest and most diverse subclass of Chondrichthyes includes the sharks and rays – having streamlined bodies and acute senses

  26. Ray-Finned Fishes and Lobe-Fins • The vast majority of vertebrates • Belong to a clade of gnathostomes called Osteichthyes (BONY FISHES) • 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

  27. 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 • Fishes breathe by drawing water over four or five pairs of gills located in chambers covered by a protective bony flap called the operculum

  28. (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 (c) Sea horse (Hippocampus ramulosus), unusual in the animal kingdom in that the male carries the young during their embryonic development (d) Fine-spotted moray eel (Gymnothorax dovii), a predator that ambushes prey from crevices in its coral reef habitat Figure 34.17a–d Ray-Finned Fishes • Class Actinopterygii, the ray-finned fishes includes nearly all the familiar aquatic osteichthyans

  29. Figure 34.18 Lobe-Fins • The lobe-fins, class Sarcopterygii • Have muscular and pectoral fins • Include coelacanths, lungfishes, and tetrapods

  30. Tetrapods • 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 • Tetrapods have some specific adaptations • Four limbs and feet with digits • Ears for detecting airborne sounds

  31. 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

  32. Amphibians • Class Amphibia • Is represented by about 4,800 species of organisms • Most amphibians • Have moist skin that complements the lungs in gas exchange

  33. (a) Order Urodela. Urodeles (salamanders) retain their tail as adults. Figure 34.21a Urodela • Order Urodela • Includes salamanders, which have tails

  34. (b) Order Anura. Anurans, such as this poison arrow frog, lack a tail as adults. Figure 34.21b Anura • Order Anura • Includes frogs and toads, which lack tails

  35. (c) Order Apoda. Apodans, or caecilians, are legless, mainly burrowing amphibians. Figure 34.21c Apoda • Order Apoda • Includes caecilians, which are legless and resemble worms

  36. (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 Amphibians • Amphibian means “two lives” • A reference to the metamorphosis of an aquatic larva into a terrestrial adult

  37. Amniotes • 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

  38. dinosaurs other Saurischian than birds Ornithischiandinosaurs Crocodilians Ichthyosaurs Plesiosaurs Squamates Mammals Pterosaurs Parareptiles Tuatara Turtles Birds Saurischians Dinosaurs Lepidosaurs Archosaurs Synapsids Diapsids Reptiles Ancestralamniote Figure 34.23 A Phylogeny of Amniotes

  39. Derived Characters of Amniotes • Amniotes are named for the major derived character of the clade, the amniotic egg • Amniotic eggs contain specialized membranes that protect the embryo (leathery shell) – the shell prevents desiccation of the embryo • The amniotic egg removes the need to return to water for reproduction – the embryonic membrane allows for gas and waste exchange; food supplies are stored in yolk; and the amnion protects the embryo in a fluid filled cavity from mechanical shock • In amniotes, there is more efficient reproduction with internal fertilization – fewer gametes required • New hatchlings are more fully developed in amniotes

  40. 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 Amniotes • The extraembryonic membranes have various functions

  41. Adaptations in Amniotes • Amniotes also have other terrestrial adaptations • Such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs

  42. Figure 34.25 Reptiles • The reptile clade includes the tuatara, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs. • Reptiles have scales that create a waterproof barrier and lay shelled eggs on land

  43. Reptiles • 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

  44. Figure 34.27b (b) Australian thorny devil lizard (Moloch horridus) Evolution of Reptiles • 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

  45. (c) Wagler’s pit viper (Tropidolaemus wagleri), a snake Figure 34.27c Snakes • Snakes are legless lepidosaurs • That evolved from lizards

  46. 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

  47. Figure 34.27d (d) Eastern box turtle (Terrapene carolina carolina) Turtles • All turtles have a boxlike shell • Made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs

  48. Figure 34.27e (e) American alligator (Alligator mississipiensis) Alligators and Crocodiles • Crocodilians • Belong to an archosaur lineage that dates back to the late Triassic

  49. Reptiles Have Waterproofed Skin • Reptiles have several adaptations for terrestrial living not generally found in amphibians: • Scales containing keratin waterproof the skin – helping prevent dehydration in dry air. • This adaptation permits life on terrestrial habitats and provides mechanical and chemical protection of the body • They have well-developed lungs so they are better able to exchange gases with their atmosphere (air instead of water)

  50. Birds • Birds are archosaurs • But almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight • Many of the characters of birds • Are adaptations that facilitate flight

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