Phylogeny of Fishes

  1. What lead to the dominance of vertebrates?
    • The notochord
    • Filter feeding
  2. What are some characteristics of the notochord?
    • Lead to the dominance of vertebrates
    • Allows a one way digestive system
    • Its development induces the development of other structures
    • Good in small animals but is not enough in bigger ones
    • Vertebrae rings protect it and eventually turn it into the vertebrae we know today
  3. What led to the development of vertebrae and what do the vertebrae do?
    • The notochord
    • They act as a axis of support for the body
    • Provide protection for the spinal cord and early blood supply to core structures
  4. What is cephalization and what did it arise from?
    • Well developed sense organs in anterior (head) region
    • It arose from epidermal placodes
  5. What are placodes?
    • Cells that are really sensitive to stimuli
    • Eventually make up new structures
  6. What are neural crest cells?
    Cells that migrate outward and make up different structures in the head such as skull bones and cartilage
  7. Describe filter feeding and give examples.
    • Pre-vertebrates were likely filter feeders such as amphixious 
    • They were abundant in the past but today consist of lamprey and hagfish
    • Possible because of pharyngeal gill slits
  8. Where did Jaws derive from and what do they allow?
    • Its not for certain whether jaws started in the placoderms or the ostracoderms 
    • It allowed for animals to eat virtually anything; doesn't have to wait for food to come by
    • Could become more predaceous 
    • Could get better food, safer food, and live longer
  9. What/when did the first vertebrates show up?
    The ostracoderms were a jawless, armored  fish that showed up in the Cambrian period (500 mya)
  10. What class were all jawless fishes formerly placed in and what are its subclasses?
    Class Agnatha
  11. What type of fish belong to vertebrata yet lack any bone?
    The hagfish - they lack bone but have the genetic code for the bone
  12. Class Myxini
    • A class of jawless fish
    • Include hagfishes
    • Entirely marine
    • Cartilaginous skeleton w/o body armor, no hint of vertebral development
    • Feed by boring into dead or dying fish with raspy tongue
    • Evidence suggests that hagfish are the most primitive living vertebrate
  13. Class Pteraspidomorphi - Diplorhina
    • A class of jawless fish
    • Oldest documented vertebrate fossils
    • Appear in late Cambrian-Devonian (500-400mya)
    • Paired nasal openings (two nostrils)
    • Most have bony heads (meaning cephalization was important early on
  14. Class Cephalaspidomorpha - Monorhina
    • A class of jawless fish
    • Varied lifestyles and body shapes
    • Single nasal opening (mono-)
    • Fossil forms heavily armored (silurian - late Devonian)(425-400 mya)
    • Bony plates down body suggests these guys were more active and got into more danger leading to these bony adaptions
  15. What are the four chordate characteristics?
    • Notochord
    • Pharyngeal gill slits
    • Dorsal hollow nerve cord
    • Post-anal tail
  16. Why is thyroxine so important to chordates?
    • Adequate growth
    • Development
    • Tissue Differentiation 
    • Metabolic rate
  17. Define immutable
    Cannot change
  18. Deuterosomes
    Anus first, mouth second
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Phylogeny of Fishes