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Early Vertebrates PART II

VERTEBRATE ZOOLOGY (VZ Lecture05 – Spring 2012 Althoff - reference PJH Chapter 3). Early Vertebrates PART II. Radiation of Paleozoic Jawless Vertebrates: __________________. Cover several distinct lineages This “line” is extinct ( see Figs. 3-3, p46 & 3-4, p48 )

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Early Vertebrates PART II

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  1. VERTEBRATE ZOOLOGY (VZ Lecture05 – Spring 2012 Althoff - reference PJH Chapter 3) Early VertebratesPART II

  2. Radiation of Paleozoic Jawless Vertebrates:__________________ • Cover several distinct lineages • This “line” is extinct (see Figs. 3-3, p46 & 3-4, p48) • Characterized by presence of covering of dermal bone carapace and/or smaller plates & scales (see Fig. 3.7, p55) • Jawless, probably feed on soft-bodied prey • Early demise probably linked to lowering of global sea levels during early Devonian that resulted in loss of coastal marine habitats • Extinction occurred in late Devonian

  3. Pteraspids Cephalaspids

  4. Fig. 3-3 p46 PJH

  5. Transition from Jawless  _______ Vertebrates Transition from Agnathous “condition”  Gnathostome “condition” • Originally thought Gnathostomes radiated separately from the Agnathans….. • Now, recognized that Gnathostomes derived from Agnathans both in jaw development and other ways

  6. AGNATHOUS CONDITON 1st gill slit 1st gill arch GNATHOSTOME CONDITON 1st gill slit 1st gill arch 1st gill arch

  7. Jawed “condition” –greatest of all advances in vertebrates????Jaws permitted ____________________________ • Ability to grasp objects (food, mates, young, nesting materials, etc.) • Combined with teeth, ability to ___________, and/or ___________ • ______________ diet now possible

  8. Transition from Jawless  Jawed Vertebrates Transition from Agnathous “condition”  Gnathostome “condition” •  Jaws that bear teeth •  Two sets of _________________ in the pectoral and pelvic regions

  9. 2 GENERALIZED “JAWED” VERTEBRATE 1 2.5 Fig. 3-9 p58 PJH

  10. Generalized JAWED vertebrate – ____advancements(numbering matches previous slide) • Jaws containing teeth • Pectoral and pelvic fins -- paired • Jointed, brachial arches with internal gill rakers • Hypobrachial musculature: strong suction • Two distinct olfactory bulbstwo distinct nostrils • Original gill slit squeezed to form spiracle • Three semicircular canals in inner ear • Conus arteriosus: elastic reservoir in front of ventricle (i.e., heart) • Lateral line & spetumdorsal from ventral portion • “elements” around the notochord & ribs .5

  11. Generalized JAWED vertebrate –other important developments • Presence of cerebellum & olfactory tract • Nervous system: insulating sheaths of myelin (increased speed of nerve impulses), thicker spinal cord, nerves exiting the spinal column • Eyes have intrinsic musculatureaccomodation of the lens • Sensory elements of lateral line covered by special scales • Distinct spleen, pancreas, and spiral valve within intestine • Gonads have distinct ducts to cloaca • Separate contractile proteins for muscles

  12. Fins: Origin & Function • Probably originated from pre-jawed fishes that had ______________________ (that were immobile)—served same purpose (see below) • Function: ________ in 3-dimensional space….water that is virtually incompressible. Force applied by one fin in one direction produces thrust in the opposite direction. Tail fins—increased area—gives more thrust during propulsion • Advantages: _______________________________

  13. Pitch Pitch Yaw Roll Yaw Fig. 3-12 p62 PJH

  14. Gnathosomes CHONDRICHTHYANS (cartilaginous fishes) OSTEICTHYANS (bony vertebrates) Fig. 3-15p66 PJH

  15. ___________ Jawed Fishes (Paleozoic) • Placoderms – the armored fishes • Acanthodians – the stout-spined fishes

  16. In summary: Jawless to Jawed Vertebrates • Jaws: a) improved gill ventilation & bite prey • Fins: improved locomotion/maneuverability • True vertebrae • Ribs • Step up in __________________ design • Step up in __________________ design • Nerves: enclosed in myelinated shields • Large, distinct cerebellum in hindbrain • Two olfactory tracts • Thicker spinal cord (with “gray matter”) • Lateral line sensory system • Third semicircular canal in inner ear

  17. Gnathosomes CHONDRICHTHYANS (cartilaginous fishes) OSTEICTHYANS (bony vertebrates) _____________

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