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Chapter 34- A Survey of Vertebrates - TeacherWeb

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					    A Survey of Vertebrates


*Adapted from PowerPoint Lecture Presentations from Biology (8th
                 Ed.) by Campbell and Reece
        Evolution of Vertebrates
• Vertebrates arise ~530 mya during the
  Cambrian explosion
  – Have vertebrae, repeating bones in the spine


• There are now 52,000 vertebrate species
  • Great disparity


• A subphylum of Chordata
Fig. 34-2
                                                                            Echinodermata
                                                                            (sister group to chordates)

 ANCESTRAL                                                                  Cephalochordata
 DEUTERO-                                                                   (lancelets)
 STOME
                                                                            Urochordata
            Notochord                                                       (tunicates)

             Common                                                         Myxini
             ancestor of                                                    (hagfishes)
             chordates
                                                                            Petromyzontida
                            Head                                            (lampreys)

                                                                            Chondrichthyes
                   Vertebral column                                         (sharks, rays, chimaeras)

                                                                            Actinopterygii
              Jaws, mineralized skeleton                                    (ray-finned fishes)

                                                                            Actinistia
                    Lungs or lung derivatives                               (coelacanths)

                                                                            Dipnoi
                                           Lobed fins                       (lungfishes)

                                                                            Amphibia (frogs,
                                                                            salamanders)

                                                                            Reptilia
                                                            Legs            (turtles, snakes,
                                                                            crocodiles, birds)
                                                        Amniotic egg
                                                                            Mammalia
                                                                       Milk (mammals)
Fig. 34-UN10
                Derived Characteristics
• Some derived traits are only preset in embryos
• “Four key characters of chordates:
   – Notochord
      • Flexible rod between digestive tube and nerve cord
      • Provide support, only remnants are present in adults

   – Dorsal, hollow nerve cord
      • Tube develops from the ectoderm
      • Becomes central nervous system

   – Pharyngeal slits or clefts
      • For suspension feeding, gas exchange
      • Become parts of ears, head and neck of tetrapods

   – Muscular, post-anal tail”
      Lancelets (Cephalochordata)
• Marine suspension
  feeders

• Retain chordate
  traits as adults

• Not true vertebrates
           Tunicates (Urochordata)
• More closely related to other chordates than lancelets
• Marine suspension feeders (sea squirts)
• Resemble chordates during embryonic phase
   – May last only a few minutes
            Early Vertebrates
• May have resembled lancelets

• Share genes with tunicates
                    Craniates
• Skull, brain, eyes, and other senses
  – Allows for active predation
• Derived Characteristics:
  1. Two clusters of Hox genes
  2. Neural Crest- gives rise to some of the bones and
     cartilage of the spine and skull
  3. Pharyngeal clefts become gills in aquatic organisms
  4. Higher metabolism, more muscles
  5. Heart with 2 chambers, blood with hemoglobin
  6. Kidneys
              Hagfishes (Myxini)
• Least derived of the craniates

• Cartilaginous skull

• No jaw or vertebrae
 Derived Characters of Vertebrates
• “Vertebrates underwent a second gene
  duplication involving the Dlx family of
  transcription factors

• Vertebrates have the following derived
  characters:
  – Vertebrae enclosing a spinal cord
  – An elaborate skull
  – Fin rays, in the aquatic forms”
         Early Vertebrate Fossils
• Conodonts
  – Mineralized teeth
    and pharynx
  – Some had bones
    over skin, for
    defense

• Mineralization
  occurred first in
  teeth
      Lampreys (Petromyzontida)
• Oldest vertebrate lineage
   – Jawless
   – Marine or freshwater

• Cartilagenous segments cover the notochord and part
  of the nerve cord
                   Gnathostomes
• Jawed vertebrates              • “Other characters
   – May have evolved from         common to
     support elements of           gnathostomes:
     pharyngeal slits
                                   – An additional duplication
                                     of Hox genes
                    First          – An enlarged forebrain 
                    fossils=         enhanced smell and vision
                    placoderms
                                   – In aquatic gnathostomes,
                    (plated)         the lateral line system,
                                     which is sensitive to
                                     vibrations”
                Chondrichthyans
• Skeleton of cartilage
   – Evolved secondarily from mineralized skeleton

• The biggest class includes:
   1. Sharks- streamlined carnivores with acute senses.
     •   Internal fertilization
     •   Can be Oviparous, Ovovivparous or Vivparous
     •   Have a cloaca
   2. Rays
   3. Skates
               Ray-Finned Fishes
• Part of the clade Osteichthyes, also including tetrapods

• Bony skeleton
• Swim Bladder
• Operculum protects the gills
   Ray-Finned Fishes
        Cont’d
• Most of the common fish
  of today

• Fins
  – Flexible
  – Supported by rays
  – Used for maneuvering,
    defense and other
    functions
   Tetrapods
• Lobe-finned
  gnathostomes

• “Specific
  Adaptations:
  – Four limbs, with
    feet and digits
  – Ears for detecting
    airborne sounds”
                   Amphibians
• “Both ways of life”
   – Aquatic larva  terrestrial adult

• Have both skin and lungs are for gas exchange

• Fertilization is mostly external, and eggs require
  moist environments (lack shells)

• Three classes:
   1. Urodela- salamanders
   2. Anura- frogs and toads
   3. Apoda- caeclilians (legless, resemble worms)
                  Amniotes
• Includes reptiles, birds and mammals
• Amniotic Egg:
Fig. 34-24
              Parareptiles

              Turtles

              Crocodilians


              Pterosaurs

              Ornithischian
              dinosaurs
              Saurischian
              dinosaurs other
              than birds
              Birds

  ANCESTRAL   Plesiosaurs
  AMNIOTE
              Ichthyosaurs

              Tuataras

              Squamates

              Mammals
                            Reptiles
• Derived Traits:
  1. Scales act a waterproof barrier
  2. Lay eggs on land
  3. Mostly ectothermic, except birds

• Originated ~310 mya
  – Parareptiles dwindled, and diapsids succeeded
     • Diapsids are split into:
         1.   Lepidosaurs
         2.   Archosaurs
      Lepidosaurs                 Archosaurs
• Tuataras, lizards, and    • Pterosaurs and dinosaurs
  snakes
                            • Theropods- bipedal
• “Lizards are the most       carnivores
  diverse and numerous
  reptiles, except for
  birds”                    • Agile and fast-moving

• Turtles- “boxlike shell   • First signs of parental care
  made of upper and
  lower shields that are    • Birds are the only
  fused to the vertebrae,     surviving lineage
  clavicles, and ribs”         – Probably descended from
                                 small theropods ~150 mya
                           Birds
• Derived traits, mostly      • Advantages of flight:
  for flight:                      1. Escape predators
   1. Keratin feathers             2. Migration
   2. Lack bladder                 3. Enhances hunting and
   3. Small gonads and only           scavenging
      one ovary
   4. Lack teeth              • Some birds are flightless
   5. Hollow bones
   6. Acute vision
   7. Fine muscle control     • High degree of variation
   8. High metabolism
                                in foot form
                    Mammals

• 5,300 species              • Three reproductive
                               strategies:
  – From synapsids in
    late Triassic
                             1. Marsupials
                               –   Unterus with placenta
• Derived characters:              develops the embryo
  1. Hair                      –   Offspring born into pouch
                                   (marsupium)
  2. Mammary Glands
     (Milk)                  2. Monotremes
  3. Differentiated Teeth      –   Egg-laying
  4. Larger brain for size
                             3. Eutherians (Placental)
                               –   Longer pregnancy
                       Primates
• Derived Characteristics:   • Oldest known anthropoid
   1. Grasping feet and        fossils ~45 mya
      hands                     – Evidence that they are
      •   Opposable thumb         more closely related to
                                  tarsiers than lemurs
   2. Large brain
   3. Short jaws             • “The first monkeys
   4. Forward-looking          evolved in the Old
      eyes (depth              World (Africa and Asia)”
      perception)               – Then in the New World
   5. Complex social              ~25 mya
      behavior                  – Apes diverged from Old
                                  World monkeys ~20
   6. Parental Care               mya
Fig. 34-37




                                                                    Lemurs, lorises,
                                                                    and pottos

  ANCESTRAL                                                         Tarsiers
  PRIMATE
                                                                    New World monkeys

                                                                    Old World monkeys

                                                                    Gibbons

                                                                    Orangutans

                                                                    Gorillas

                                                                    Chimpanzees
                                                                    and bonobos
                                                                    Humans


             60   50       40           30            20   10   0
                       Time (millions of years ago)
                      Humans
• Derived Traits:             • Paleoanthropology- study of
                                human origins
   1. “Upright posture and
      bipedal locomotion      • Hominins are more related to
                                humans than chimps
   2. Larger brains              – ~20 species
   3. Language capabilities      – Originated 6-7 mya
      and symbolic
      thought                 • “Two common
                                misconceptions about early
   4. The manufacture and       hominins:
      use of complex tools       – Thinking of them as
                                   chimpanzees
   5. Shortened jaw              – Imagining human evolution as a
   6. Shorter digestive            ladder leading directly to Homo
                                   sapiens”
      tract”
Fig. 34-40

                                                                  Paranthropus               Homo               Homo
                                                                  robustus                   neanderthalensis   sapiens
        0
                                            Paranthropus                          Homo       ?
                                            boisei                                ergaster
      0.5

      1.0

      1.5                Australopithecus
                         africanus
      2.0
                Kenyanthropus
                platyops
      2.5
          Australo-                            Australopithecus
      3.0 pithecus                             garhi                                         Homo
          anamensis                                                                          erectus
      3.5                                                                         Homo
                                                                                  habilis
      4.0                                                           Homo
                                                                    rudolfensis
      4.5
                      Ardipithecus          Australopithecus
                      ramidus               afarensis
      5.0

      5.5

      6.0         Orrorin tugenensis

      6.5
                              Sahelanthropus
                              tchadensis
      7.0
                                            Fig. 34-41a




        Australopiths
• Paraphyletic

• Originated ~2-4 mya

• Some walk completely upright
  (bipedalism)

• First tool-use ~2.5 mya

• 2 types:
   – Robust- sturdy skulls, powerful jaws
   – Gracile- more slender, light jaws
                                            (a) Australopithecus
                                            afarensis skeleton
                 Genus Homo
• Homo habilis (~2.4-1.6 mya) evolved first
• 1st stone tools (“handy man”)

• Homo ergaster (~1.9-1.5 mya)
• 1st fully bipedal, large brained hominin
• Decreased Sexual Dimorphism

• Homo erectus (~1.8 mya)
• 1st to leave Africa
                Neanderthals
• Homo
  neanderthalensis
• ~200,000 – 28,000
  years ago

•   Thick bones
•   Larger brain
•   Buried Deceased
•   Hunting tools
                 Homo sapiens
• ~195,000 (Africa)
• ~115,000 (Middle East)
• ~15,000 (New World)

• Rapid expansion thought to arise from changes in
  brain
   – “For example, the FOXP2 gene is essential for
      human language, and underwent intense natural
     selection during the last 200,000 years

• Homo sapiens were the first group to show evidence
  of symbolic and sophisticated thought”
          “You should now be able to
1.   List the derived traits for:   6.   Describe an amniotic egg
     chordates, craniates,              and explain its significance
     vertebrates, gnathostomes,         in the evolution of reptiles
     tetrapods, amniotes, birds,        and mammals
     mammals, primates, humans      7. Explain why the reptile
2.   Explain craniate evolution         clade includes birds
3.   Describe the trends in         8. Distinguish among
     mineralized structures in
                                        monotreme, marsupial, and
                                        eutherian mammals
     early vertebrates
                                    9.   Define the term hominin
4.   Describe and distinguish       10. Describe the evolution of
     between Chondrichthyes and           Homo sapiens from
     Osteichthyes, noting the             australopith ancestors,
     main traits of each group            and clarify the order in
5.   Define and distinguish               which distinctive human
                                          traits arose
     among gnathostomes,
     tetrapods, and amniotes
                                    11. Explain the significance of
                                          the FOXP2 gene

				
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