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Phylogeny of Fishes
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What lead to the dominance of vertebrates?
The notochord
Filter feeding
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
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
What is cephalization and what did it arise from?
Well developed sense organs in anterior (head) region
It arose from epidermal placodes
What are placodes?
Cells that are really sensitive to stimuli
Eventually make up new structures
What are neural crest cells?
Cells that migrate outward and make up different structures in the head such as skull bones and cartilage
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
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
What/when did the first vertebrates show up?
The ostracoderms were a jawless, armored fish that showed up in the Cambrian period (500 mya)
What class were all jawless fishes formerly placed in and what are its subclasses?
Class Agnatha
What type of fish belong to vertebrata yet lack any bone?
The hagfish - they lack bone but have the genetic code for the bone
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
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
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
What are the four chordate characteristics?
Notochord
Pharyngeal gill slits
Dorsal hollow nerve cord
Post-anal tail
Why is thyroxine so important to chordates?
Adequate growth
Development
Tissue Differentiation
Metabolic rate
Define immutable
Cannot change
Deuterosomes
Anus first, mouth second
Author
NateS11
ID
294753
Card Set
Phylogeny of Fishes
Description
Vertebrate
Updated
2015-02-03T18:51:55Z
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