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Unit 7 Exam Review
1. Chondrichthyes – “cartilage fish,” – Well developed jaws– Cartilaginous skeleton– Highly developed sense organs– Fusiform body– Most have placoid scales– Oil-filled liver for buoyancy
2. Elasmobranchii – sharks, rays, and skates (extant and extinct)
3. Holocephali – chimeras such as ghostfish and ratfish
4. Cladoselache:– “Branched-toothed” shark– Ligamentous band in a whorl-shaped arrangement– Homocercal caudal fin– No rostrum
5. Hybodus:– Heterocercal caudal fin– Rostrum– Heterodont dentition (more than one type of tooth)
6. Neoselachii:– This is a subset of Elasmobranchii that includes only
extant (still living) sharks
7. Galeomorpha:– “Normal” sharks, extant– Galoids
8. Squalomorpha:– The outlying forms of sharks, extant– Small brained– Live in cold waters (Arctic & Antarctic)– Live in deep waters (aphotic)
9. Batoidea:– Extant rays and skates
4. Rays:– Thin, flexible, and barbed tails– Can be extremely large (25 feet across, weighing
several tons)– Serrated spines that are very difficult to remove from
victim– Spines are covered with a thin skin that contains
painful toxins once ruptured– Predominantly live-bearers (viviparity)
5. Skates:– Fleshy, heavy tails– Relatively small (1 to 5 feet)– Elongated nose– Often found in North America– Large thorns for defense, but not poisonous– Lay eggs (mermaid’s purse [oviparity])
6. Chimeras:– Intermittent organs– Single gill slit, no scales– Only have 6 permanent teeth for grinding – As a group found mostly between 80-2,600 meters,
feeding on hard shelled invertebrates
7. Chondrichthyes Buoyancy:– Heterocercal tail– Cartilaginous skeleton– Large, oil-filled liver instead of a swim/gas bladder
8. Heterocercal/Homocercal caudal fins:
9. 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
10.Placoid scales & other tissues generated by these cells:– Sharp, one-way scales that allow for highly efficient
movement through the water– The cells that make these scales are also responsible
for forming the following:• Spine of stingray• dorsal spine of dogfish• defensive spines in the skate• teeth
11.Tapetum Lucidum:– A layer of reflective tissue that covers the back of the
eye
– This allows for light to be amplified in low-light situations
– During the daytime/bright life, melanin dilates to cover the tapetum lucidum & reduce the amount of reflected light
12.Nictitating membrane:– A transparent 3rd eyelid– This is used to protect the eye when a shark attacks its prey– This can also be used to clear debris from the eye
13.Ampullae of Lorenzini:– Electroreceptors from on the most anterior portion
of a shark
14.Lateral line of sharks:– Cells that can detect the movement/changes in
pressure in the water– Sharks can detect changes in water movement up to 100
meters away
15. Oviparity – ovi = egg– lays eggs (little or no embryonic development within
the mother)
16. Viviparity – internal development– Yolk-sac Viviparity– Uterine Viviparity– Cannibal Viviparity– Placental Viviparity
17.Yolk-sac Viviparity (Ovoviviparity)– Eggs are produced and retained inside the mother– Shell disappears and young are retained until fully developed
18. Uterine Viviparity– Mother secretes nutrient rich fluid which is taken up through
the skin of the embryo
19. Cannibalistic viviparity:– Young in each oviduct consume unfertilized eggs or
other siblings
20. Placental viviparity:– Nutrients are supplied to the embryo directly from
the mother via a umbilical cord
21.Time periods connected with chondrichthyes development & prevalence
Figure 24.01
22.Fusiform:– Torpedo-shaped body
23.Rostrum:– Nose-like protrusion that hangs over the mouth of a
shark– This is a highly sensitive area of the shark, covered
in electro receptors and chemo receptors
24.Squaloid Sharks:– smaller brained – mostly live in cold, deep water – include the various species of dogfish, the
megamouth, and cookie-cutter sharks
25.Galeoid sharks:– the dominant carnivores of shallow waters– Live in warm, rich parts of the ocean– include hammerheads, tiger sharks, threshers,
mackeral sharks, and the whale shark
27.Rows of teeth in sharks:– The rows run anterior to posterior, not side-to-side– The teeth fold out from the mouth & are constantly
replaced– Some sharks replace their teeth as often as once
every 8 days
28.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 Jaws– The jaw is not directly attached to the skull– This 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 attacks
– This 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 white– Tiger shark– Bull shark– Mako shark
32. Shark attack deaths relative to other human death rates:
– Compared to other forms of death, death by shark is exceedingly rare
– 1 death/year in USA– 5 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 markers– Tripled since the 1980s– Shark fins = $500/kilo– Sharkfin Soup = $90/bowl– Hong 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 markets– The continued poverty in developing nations that
leave fishermen with little other choice
36. Example decline in shark populations: Whitetip shark in the Gulf of Mexico
– Population 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 don’t live
long enough to grow to their maximum size.– Sharks are long-lived, slow growing, and slow to
reach sexual maturity
