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Exploring Higher Chordates: The Fascinating World of Fishes and Their Adaptations

Delve into the diverse classifications within higher chordates, specifically focusing on fishes. From jawless species like lampreys in the class Petromyzontida to cartilaginous chondrichthyans like sharks and rays, and bony fishes in the clade Osteichthyes. Discover key adaptations such as the development of jaws, a closed circulatory system, and specialized fins, which enhance their ability to capture food and avoid predators. Learn about differences among ray-finned and lobe-finned fish, their unique anatomical structures, and fascinating reproductive strategies.

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Exploring Higher Chordates: The Fascinating World of Fishes and Their Adaptations

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  1. Higher Chordates: “Fishes” Petromyzontida - Sarcopterygii

  2. Subphyla Vertebrata

  3. Subphyla: vertebrata • Key adaptations allowed them to be more efficient @ capturing food and avoiding being eaten • Endoskeleton • Vertebrae:bone or cartilage • Took over role of notochord & encloses spinal cord in most verts. • Closed circulatory system • Single well developed heart • Skull with a brain • Anterior to the spinal cord • Extinct vertebrate: • Conodont (jawless w/ “cone teeth”)

  4. Class: Petromyzontida • ~35 species • Lamprey • Agnatha: Jawless • More pronounced Cartilage Skull • Keratin Teeth (not bony) http://www.youtube.com/watch?v=3K0ZrWWpqio

  5. Clade: Gnathostomes • ~470mya • Jaws “jaw mouth” • Hinged structure • Derived from skeletal supports of the gill slits • Teeth • Rip apart food • Lateral line system • Organs run along the side of the body • Detect vibrations in the water • Extinct: placoderms/acanthodians

  6. Class Chondricthyes • ~750 species • “Cartilage Fish” (bone in teeth & scales) • Cartilaginous “backbone” may have derived from bony skeleton ancestor • Sharks, Skates, Rays, Ratfish & Chimeras

  7. Chondricthyes characteristics • Premier Predators • Streamlined body (power, not grace) • Oil bladder (helps buoyancy, sinks if it doesn’t swim) • Acute Vision (but colorblind) • Detect electric fields—lateral line system • For shark fins • Dorsal for stability • Pectoral & Pelvic for lift • Caudal for propulsion

  8. Chondricthyes characteristics • Gills • Gas exchange (O2) • Short digestive tract • Nostrils of sharks used for smelling only

  9. Chondricthyes characteristics • Reproduction (variety) • Oviparous • lay eggs & hatch externally • Ovoviviparous • keep eggs in uterus until hatching • Egg membrane sometimes breaks during delivery • Viviparous • Placenta – true live birth

  10. Clade Osteichthyes • “Bony fish” • Ossification of the skeleton (Bone) • w/ Calcium Phosphate • Draw H2O across gills • Operculum protective bony covering • Swim bladder (buoyancy) • Gases moving between swim bladder & blood • Sound like any organ that humans have??? • Lateral line system • Mostly oviparous • Fish (Actinopterygii, Actinistia, & Dipnoi) http://www.youtube.com/watch?v=zvrigHi3pS0 http://www.scienceisart.com/B_SwimBladder/SwimBladder.html

  11. 1 http://www.kscience.co.uk/animations/anim_3.htm

  12. Class Actinopterygii • Ray finned fish • Fins supported by bony rays http://www.howjsay.com/index.php?word=actinopterygii&submit=Submit

  13. Each fin on a fish is designed to perform a specific function: • Dorsal fin. Lends stability in swimming. • Ventral (pelvic) fin. Serves to provide stability in swimming. • Caudal fin. In most fish, the Caudal or tail fin is the main propelling fin. • Anal fin. Also lends stability in swimming. • Pectoral fins. Locomotion and side to side movement. • Adipose fin. Stability.

  14. Actinistia (coelacanth) Dipnoi (lungfish) Surface to gulp air into lungs Class SarcopterygiiLineages Actinistia & Dipnoi • Rod shaped bones surrounded by thick layer of muscle in pectoral & pelvic fins…hence “Lobe finned fish”. http://www.ucmp.berkeley.edu/vertebrates/sarco/dipnoi.html

  15. What’s the difference? • Lobe-finned • Ray-finned

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