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Case History: Heads Up in the Mesozoic Seas
Featured Organisms
(p. 106):
Ctenochasma
(pterosaur,
Jurassic
Period, 180 Mya)
Plesiosaurs
RQ 5.1: Could
you distinguish between some possible versus
unlikely modes
of feeding in Ctenochasma or a plesiosaur?
I. Buoyancy, Streamlining, and Drag: Coping with Water
Density and Viscosity
a) The Control of Buoyancy
1) Many organisms
neutralize their buoyancy by maintaining
lightweight body fluids.
terms: neutrally buoyant
Featured
organisms (p. 108, Fig. 5.1):
Siphonophores (colonial
jellyfishes)
Chambered nautilus
(Nautilus)
Cuttlefish (Sepia)
Ray-finned
fishes (teleosts
and relatives)
RQ 5.2: How does
each of the above featured organisms solve
the problem
of maintaining neutral buoyancy?
2) Bubbles,
swim bladders, and other gas-filled spaces provide
lots of lift, a few hazards.
terms: swim
bladder, gas gland,
rete
mirabile [link dead? 3/13/01], oval organ
RQ 5.3: What
is at least one advantage and one disadvantage of
the gas-filled
space solution to maintaining
buoyancy?
RQ 5.4: Describe
the alternative use of a gas gland versus an
oval organ in
a teleost
fish.
3) Risk-management
strategies by fishes
include no swim
bladders, oil-filled
swim bladders, and other options.
RQ 5.5: Contrast buoyancy-control
in a fish like a shark, whose
ancestors never
had a swim bladder, with that of a skipjack tuna,
whose more ancient
ancestors had a swim bladder? Why would
a tuna benefit
from "giving up" a functional swim bladder?
4) Giant living
hot-oil balloon?
terms: spermaceti (whalers
made into candles), spermaceti organ
Featured organism (p. 111): sperm whale
RQ 5.6: Explain
how a sperm whale uses its circulation system
in contact with
its spermaceti oil to either help it sink to deep
"hunting" depths
or rise back up to the surface for air.
b) Movement,
Streamlining, and Speed
1) Large streamlined
animals create little turbulence and
can swim rapidly.
2) Water viscosity
prevents small swimmers from going
fast - and retards their sinking.
terms: surface-to-volume (S/V) ratio, surface area, body volume
Featured
Organisms (p. 113, Fig. 5.5):
Arrowworm
(chaetognath,
6mm length)
Saury
(predatory fish, 30cm or 300mm length)
RQ 5.7: Briefly
contrast the problems faced by a tiny chaetognath
(high S/V ratio)
with a much larger saury (low S/V ratio).
II. Pressure and the Depth of the Oceans
terms: atmospheric pressure, lb. of force, 1 atmosphere (atm),
1 pascal
a) The Effect of Pressure on Enzymes and Metabolic Rates
1) Pressure changes the rates at which enzymes operate.
2) Some enzymes
of deep-living animals are not affected
by pressure change.
3) Are most deep-sea bacteria inhibited by high pressure?
RQ
5.8: When the submersible, Alvin,
accidentally sunk in
1968, why were the crews’ lunches still edible after being
submerged for 10 months?
4) To avoid death by pressure, stay at one depth.
b) The Distortion of Organisms with
Gas-Filled Spaces in their
Bodies
Featured
organism (p. 118): Tuffy-the-dolphin
RQ
5.9: What happens if a scuba diver in a swimming pool
blows up a balloon, ties it off, and then lets go? Why?
What happened to a container of eggs that Jacques
Piccard
had attached to the outside of his submersible, Trieste,
during
his deep dive? Why?
c) Bends - the Result of Rapid
Release of Pressure
terms: bends
Featured
organisms (deep divers, p. 119):
Weddell seal
or links: 1 - 2
Elephant
seal
Sperm
whales
Emperor
penguins
d) The Difficulty of Studying Pressure Effects
III. Life on Land and Life in the Sea
RQ 5.10 (Fig. 5.8): What are five ways that sea and land
animals differ?
a) Liberation from the Force of Gravity
Featured
organism (p. 120): crab, Cancer
productus
b) Life in Three Dimensions
c) Suspension Feeding: Common in the Sea, Absent on Land
d) Ectothermy in Cold Water
e) Bioluminescence in Dark Water
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This page created 2/16/01 © D.J. Eernisse, Last Modified 2/28/01,
Last Completely Checked 5/7/01