Chondrichthyes

  • Created by: phoeberb
  • Created on: 15-05-19 23:40

Key characters of Chondrichthyes

  • Prismatic endoskeleton calcification
  • Pelvic claspers
  • Gill coverings, separate and uncovered
  • Underslung mouth 
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Features of prismatic endoskeleton calcification

  • Tesselate (overlapping)
  • Polygonal (prismatic)
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Where does prismatic calcification occur?

  • Occurs on the cartilage skeleton 
  • Occurs in the placoid scales which cover shark skin
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What part of sharks are calcified?

  • Endoskeleton
  • Placoid Scales- 70% calcified enameloid, 90% calcified dentin 
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Features of the teeth

  • Form whorls 
  • developing teeth line up behind functional teeth
  • Formed from dentin
  • tooth replacement weekly in young sharks 
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Hyostylic jaw features

  • Jaw directly attached to the cranium
  • Upper jaw capable of protruding out
  • Ethmopalatine ligament enables protrusion 
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Features of gill openings

  • Seperate and uncovered
  • Usually 5 pairs
  • breathing via ram ventilation or buccal pumping 
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Ram ventilation Vs Buccal pumping

  • Ram ventilation- Water is drawn in through the mouth is blown out of gills when the mouth is closed
  • Buccal pumping- gill slits are blown open when water passes through the mouth
  • sharks can switch between both
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Filter feeding features

  • Gill rakers- pass food trapped in gill slits to the oesophagus 
  • Rakers made of keratin
  • Three species of filter feeders- megamouth, whale, basking shark
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Features of pelvic claspers

  • Claspers inserted into the female cloaca
  • Sperm travels into cloaca via groove
  • Male can wrap around female or lie parallel 
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Coelomic cavity features

  • Divided into two parts by a transverse septum
  • anterior pericardial cavity- heart and related viscera
  • posterior peritoneal cavity- internal organs and other viscera 
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Heart

  • Single circulatory system
  • Heart chambers in a series- ventricle then atrium.
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