Unit 7 Exam Review
1. Chondrichthyes – “cartilage fish,”
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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
10. 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)
11. 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])
12. 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
13. Chondrichthyes Buoyancy:
– Heterocercal tail
– Cartilaginous skeleton
– Large, oil-filled liver instead of a swim/gas bladder
14. Heterocercal/Homocercal caudal fins:
15. 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
16. 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:
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Spine of stingray
dorsal spine of dogfish
defensive spines in the skate
teeth
17. Tapetum Lucidum:
– A layer of reflective tissue that covers the back of the
eye
– This allows for light to be amplified in lowlight situations
– During the daytime/bright life, melanin dilates
to cover the tapetum lucidum & reduce the
amount of reflected light
18. 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
19. Ampullae of Lorenzini:
– Electroreceptors from on the most anterior portion
of a shark
20. 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
21. Oviparity – ovi = egg
– lays eggs (little or no embryonic development
within the mother)
22. Viviparity – internal development
– Yolk-sac Viviparity
– Uterine Viviparity
– Cannibal Viviparity
– Placental Viviparity
23. Yolk-sac Viviparity (Ovoviviparity)
– Eggs are produced and retained inside the mother
– Shell disappears and young are retained until fully developed
24. Uterine Viviparity
– Mother secretes nutrient rich fluid which is taken up through
the skin of the embryo
25. Cannibalistic viviparity:
– Young in each oviduct consume unfertilized eggs or
other siblings
26. Placental viviparity:
– Nutrients are supplied to the embryo directly from
the mother via a umbilical cord
27. Time periods connected with chondrichthyes
development & prevalence
Figure 24.01
28. Fusiform:
– Torpedo-shaped body
29. 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
30. Squaloid Sharks:
– smaller brained
– mostly live in cold, deep water
– include the various species of dogfish, the
megamouth, and cookie-cutter sharks
31. 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
32. 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
33. 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:
34. Hyostylic Jaws
– The jaw is not directly attached to the skull
– This allows the entire jaw to move forward when
attacking prey
35. 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
36. 4 “most dangerous” types of sharks:
– Great white
– Tiger shark
– Bull shark
– Mako shark
37. 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
38. Gill nets & bycatch:
– Prior to the 1980s, this was the most-common cause
of shark death (accidental; “bycatch”)
39. 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
40. 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
41. 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
42. Example decline in shark populations:
Whitetip shark in the Gulf of Mexico
– Population numbers are down 150 times their
numbers in the 1970s
43. Example size (individual) decline in:
– Whitetip: 33%
– Mako: 50%
– Blue: 50%
– Dusky: 60%
– Silky: 83%
44. 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