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Unit 7 Exam Review. 1.Chondrichthyes – “cartilage fish,” – Well developed jaws – Cartilaginous skeleton – Highly developed sense organs – Fusiform body

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Text of Unit 7 Exam Review. 1.Chondrichthyes – “cartilage fish,” – Well developed...

  • Unit 7 Exam Review

  • Chondrichthyes cartilage fish, Well developed jawsCartilaginous skeletonHighly developed sense organsFusiform bodyMost have placoid scalesOil-filled liver for buoyancyElasmobranchii sharks, rays, and skates (extant and extinct)

    Holocephali chimeras such as ghostfish and ratfish

  • 4. Cladoselache:Branched-toothed sharkLigamentous band in a whorl-shaped arrangementHomocercal caudal finNo rostrum

    5. Hybodus:Heterocercal caudal finRostrumHeterodont dentition (more than one type of tooth)

  • 6. Neoselachii:This is a subset of Elasmobranchii that includes only extant (still living) sharks7. Galeomorpha:Normal sharks, extantGaloids8. Squalomorpha:The outlying forms of sharks, extantSmall brainedLive in cold waters (Arctic & Antarctic)Live in deep waters (aphotic)

  • 9. Batoidea:Extant rays and skates

  • Rays:Thin, flexible, and barbed tailsCan be extremely large (25 feet across, weighing several tons)Serrated spines that are very difficult to remove from victimSpines are covered with a thin skin that contains painful toxins once rupturedPredominantly live-bearers (viviparity)

  • Skates:Fleshy, heavy tailsRelatively small (1 to 5 feet)Elongated noseOften found in North AmericaLarge thorns for defense, but not poisonousLay eggs (mermaids purse [oviparity])

  • Chimeras:Intermittent organsSingle gill slit, no scalesOnly have 6 permanent teeth for grinding As a group found mostly between 80-2,600 meters, feeding on hard shelled invertebrates

  • Chondrichthyes Buoyancy:Heterocercal tailCartilaginous skeletonLarge, oil-filled liver instead of a swim/gas bladder

  • Heterocercal/Homocercal caudal fins:

  • Three methods of respiration in chondrichthyes: Ram ventilation: species swims with mouth open

    Two Pump: buccal pumping (diaphragm-like muscles) that allow a chondrichthyes to stay in one place & draw water in & push it out over the gills

    Spiracles: small holes behind each eye that opens to the mouth in chondrichthyes

  • Placoid scales & other tissues generated by these cells:Sharp, one-way scales that allow for highly efficient movement through the waterThe cells that make these scales are also responsible for forming the following:Spine of stingraydorsal spine of dogfishdefensive spines in the skateteeth

  • Tapetum Lucidum:A layer of reflective tissue that covers the back of the eyeThis allows for light to be amplified in low-light situationsDuring the daytime/bright life, melanin dilates to cover the tapetum lucidum & reduce the amount of reflected light

  • Nictitating membrane:A transparent 3rd eyelidThis is used to protect the eye when a shark attacks its preyThis can also be used to clear debris from the eye

  • Ampullae of Lorenzini:Electroreceptors from on the most anterior portion of a shark

  • Lateral line of sharks:Cells that can detect the movement/changes in pressure in the waterSharks can detect changes in water movement up to 100 meters away Oviparity ovi = egglays eggs (little or no embryonic development within the mother)

  • Viviparity internal developmentYolk-sac ViviparityUterine ViviparityCannibal ViviparityPlacental Viviparity Yolk-sac Viviparity (Ovoviviparity)Eggs are produced and retained inside the motherShell disappears and young are retained until fully developedUterine ViviparityMother secretes nutrient rich fluid which is taken up through the skin of the embryo

  • Cannibalistic viviparity:Young in each oviduct consume unfertilized eggs or other siblings Placental viviparity:Nutrients are supplied to the embryo directly from the mother via a umbilical cord

  • Time periods connected with chondrichthyes development & prevalence

  • Figure 24.01

  • Fusiform:Torpedo-shaped bodyRostrum:Nose-like protrusion that hangs over the mouth of a sharkThis is a highly sensitive area of the shark, covered in electro receptors and chemo receptors Squaloid Sharks:smaller brained mostly live in cold, deep water include the various species of dogfish, the megamouth, and cookie-cutter sharks

  • Galeoid sharks:the dominant carnivores of shallow watersLive in warm, rich parts of the oceaninclude hammerheads, tiger sharks, threshers, mackeral sharks, and the whale shark Rows of teeth in sharks:The rows run anterior to posterior, not side-to-sideThe teeth fold out from the mouth & are constantly replacedSome sharks replace their teeth as often as once every 8 days

  • Be able to recognize variation in tooth structure & food types:

  • Flat grinders to eat shelled organisms

  • Flat grinders to eat shelled organisms

  • Needle-like teeth for eating relatively small fish & other smaller prey

  • Reduced teeth & gill rakers for filter-feeding fish such as basking sharks & whale sharks

  • Reduced teeth & gill rakers for filter-feeding fish such as basking sharks & whale sharks

  • Broad, serrated teeth to tear & exsanguinate prey:

  • 29. Hyostylic JawsThe jaw is not directly attached to the skullThis allows the entire jaw to move forward when attacking prey

  • 30. Spear fishing & its connection to shark attacks on humans:Spear fishermen are the most common victims of shark attacksThis method does not kill the hunted fish quickly, allowing a large amount of blood to escape into the water & the electric signal from the thrashing fish to dissipate through the water

  • 31. 4 most dangerous types of sharks:Great whiteTiger sharkBull sharkMako shark32. Shark attack deaths relative to other human death rates:Compared to other forms of death, death by shark is exceedingly rare1 death/year in USA5 death/year globally

  • 33. Gill nets & bycatch:Prior to the 1980s, this was the most-common cause of shark death (accidental; bycatch)

  • 33. Gill nets & bycatch:The number of deaths has not decreased since the 1980s, but instead has been beat out by the intentional catching of sharks on long lines for finning

  • 34. Shark finning & sharkfin soup:Driven by the economic success of Asian markersTripled since the 1980sShark fins = $500/kiloSharkfin Soup = $90/bowlHong Kong is the largest global importer of shark fins

  • 35. What has caused the rise in shark finning?The rise in economic success of Asian marketsThe continued poverty in developing nations that leave fishermen with little other choice36. Example decline in shark populations: Whitetip shark in the Gulf of MexicoPopulation numbers are down 150 times their numbers in the 1970s

  • 37. Example size (individual) decline in:Whitetip: 33%Mako: 50%Blue: 50%Dusky: 60%Silky: 83%

  • 38. Why are these populations suffering such a rapid decline?Fishing often preferentially removes older animals, Fishing pressure is so intense that animals dont live long enough to grow to their maximum size.Sharks are long-lived, slow growing, and slow to reach sexual maturity