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2006 Clemson Biology
Merit Exam
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Clemson University Biology Merit Exam
31 March 2006
Please choose the best answer for each of the
following questions. Questions marked with an "*" are worth
4 points each; questions marked with a "#" are worth 2
points each; the unmarked questions are worth 1 point
each.
CAUTION: Incomplete erasures and smudges can be read as
marks. To avoid having a choice read incorrectly, make your
marks lightly at first. After you have made all your
changes, blacken in your marks just before you turn in your
answer sheet.
The theme of this exam is the dolphin, one of the most
popular and appealing marine animals:
1. Dolphins are mammals, not fish. This means that
dolphins, in contrast to fish,
a) breathe air with lungs.
b) nurse their young with mammary glands.
c) are endothermic (warm-blooded).
d) All of these.
2. The dolphins in the picture above are mammals, but there
is also a bony fish called a "dolphin":
Both our mammal dolphins and this bony fish dolphin
a) have backbones.
b) have chitin cell walls.
c) have one circular molecule of DNA per cell.
d) have cells with large central vacuoles.
3. Both the mammal dolphin and the bony fish dolphin belong
to the same
a) kingdom. b) kingdom and phylum.
c) kingdom, phylum, and class. d) kingdom, phylum, class,
and order.
All following questions will be about the mammal
dolphin:
#4. Dolphins and whales arose
from a fully terrestrial mammal. By about 45 million years
ago, there was a semi-aquatic form called Ambulocetus.
This animal had functional hind legs with webbed feet,
and probably moved around on land in the same way a seal
does today. Here, Ambulocetus (top picture) is
compared with a dolphin (bottom picture):
Notice that the dolphin has lost its hind legs, but it
still has a tiny trace of a pelvis that now has no function.
In evolution, this kind of feature is called a ...
structure.
a) primitive b) aposematic c) vestigial
d) complementary
*5. Although the dolphin and
the shark, for example, came from completely different
ancestries, they have a very similar body shape because any
animal that needs to move quickly through water has to be
streamlined. That is, the similarity in body shape between
sharks and dolphins is ..., the result of ... evolution.
a) analogous ... convergent b) analogous ... divergent
c) homologous ... convergent d) homologous ... divergent
Interesting fact: Molecular evidence indicates that the
terrestrial mammal most closely related to the beautiful,
graceful dolphin is...the hippo!
6. There are 34 species of dolphin worldwide. A species is a
group of organisms that
a) have the same evolutionary ancestor.
b) can interbreed and produce fertile offspring.
c) share the same habitat.
d) have DNA that is at least 50% the same.
7. The pictures you have seen so far have shown the most
common dolphin off South Carolina, the Atlantic bottlenose
dolphin, Tursiops truncatus. The practice of
identifying organisms with two Latin names originated
with
a) Darwin. b) Aristotle. c) Lamarck. d) Linnaeus.
#8. We don't think of
bottlenose dolphins as remarkably big animals, but the
biggest ones can get 15 feet long and weigh 650 pounds. That
is, they are about ... m long and weigh about ... kg.
a) 3.5 ... 495 b) 4.5 ... 295 c) 2.7 ... 315 d) 5.5 ...
160
9. Bottlenose dolphins eat mostly fish and squid. Squid are
a member of the phylum
a) Mollusca. b) Chordata. c) Arthropoda. d) Annelida.
*10. Dolphins locate their fish
and squid prey by a combination of vision and echolocation.
Dolphins have excellent eyes that contain both rods and
cones. If dolphin eyes are like human eyes, the rods are
mainly responsible for seeing objects ... and the cones are
mainly responsible for seeing objects
a) moving left to right ... moving up and down.
b) reflecting short wavelengths ... reflecting long
wavelengths.
c) in poor illumination ... in good illumination.
d) that are straight ahead ... that must be seen with
peripheral vision.
*11. The dolphin's brain
determines that a prey has been sighted when an action
potential arrives on the optic nerve. When an action
potential starts in a neuron, it will involve the following
steps, starting with the resting neuron:
1. Axon hillock reaches -55 mV.
2. Potassium channels close.
3. Potassium channels open.
4. Sodium channels close.
5. Sodium channels open.
The correct order of these steps is:
a) 1 3 2 5 4 b) 2 3 5 4 1 c) 5 4 3 2 1 d) 1 5 4 3 2
*12. To echolocate, the dolphin
makes a series of clicks that bounce off objects in the
water. These echoes are picked up by the dolphin's ears. Of
course, the closer the object is, the louder the echoes are.
Which graph below shows the expected pattern of action
potentials in one neuron of the dolphin's auditory nerve as
the dolphin gets closer to its target (a fish)? The
horizontal axis represents 0 mV. Assume that the dolphin is
producing clicks at a constant rate as it homes in on the
fish.
13. Dolphins are renowned for their intelligence, which in
both humans and dolphins is based mainly in the brain's
a) cerebrum. b) pons. c) medulla. d) cerebellum.
Interesting fact: When nosing in rough sediments,
dolphins may cover their snouts with a piece of sponge, like
using a workglove. This means they use tools. They can form
general concepts, like being able recognize an object as a
ball no matter what size or color it is. Dolphins can
recognize themselves in a mirror. Chimps can do this, but
most monkeys cannot. Dolphins also play and may even have a
sense of humor. One dolphin repeatedly leaped out of the
water and arched over a floating pelican, seemingly just to
startle the bird.
*14. When a motor neuron
secretes a neurotransmitter onto a muscle, the most direct
effect is to cause the affected muscle cells to
a) spill calcium ions from their sarcoplasmic reticulum.
b) coil actin into a helix.
c) polymerize myosin into a sarcoplasmic process.
d) phosphorylate tropomyosin.
*15. Dolphins normally cruise
at 5-7 mph (faster than the fastest Olympic swimmers), but
can achieve brief spurts of 20 mph. However, a dolphin
swimming that fast will soon tire. If the reason for the
fatigue is the same as in a human doing a sprint, muscle
fatigue will occur because
a) NADH concentration in the muscles rises to toxic
levels.
b) most of the muscle glucose is converted to unusable
glycogen.
c) high CO2 concentrations
make the muscle too alkaline to contract.
d) glycogen is depleted and lactic acid concentrations
rise.
*16. The ATP for muscle
contraction comes from breakdown of glucose. The overall
equation for this reaction under aerobic conditions is
C6H12O6
+ O2 -->
CO2 +
H2O + energy
The role of the
C6H12O6
here is to ...; the role of the
O2 is to
a) provide carbon atoms that can be reduced ... keep
hydrogen ion concentrations in the mitochondria from rising
too high.
b) furnish energetic electrons ... act as a final electron
acceptor.
c) serve as an electron acceptor ... serve as an electron
donor.
d) provide energy ... store energy until it can be used.
#17. Of course, the equation
above is simplified; the aerobic breakdown of glucose has
many steps. The step that yields the majority of the ATP in
aerobic respiration is
a) fermentation. b) glycolysis.
c) electron transport. d) the Krebs cycle.
*18. An early step of the
breakdown of glucose involves a reaction in which
glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone
phosphate (DHAP) transform into one another:
G3P <==> DHAP
Say we put G3P, DHAP, and the enzyme that catalyzes the
reaction above into a test tube. If nothing is added to or
removed from the reaction mixture, this reaction will
continue until G3P and DHAP have reached some characteristic
ratio to one another. At this point, the equilibrium
point,
a) the number of DHAP molecules transforming into G3P is
equal to the number of G3P molecules transforming into
DHAP.
b) the concentrations of G3P and DHAP must be equal.
c) the cell has exactly the ratio of G3P to DHAP that it
needs.
d) All of these.
*19. In the breakdown of
glucose, both G3P and DHAP are formed in equal amounts by
the first steps of the pathway, but only the G3P continues
on to further steps:
We would predict that
a) virtually all the G3P formed will be transformed into
DHAP.
b) virtually all the DHAP formed will be transformed into
G3P.
c) the G3P will be further metabolized, but the DHAP will be
left behind.
#20. The G3P <==> DHAP
reaction is catalyzed by an enzyme. This enzyme speeds up
the reaction by
a) lowering its activation energy. b) acting as a reducing
agent.
c) providing energy to it. d) making it exergonic.
*21. Say we start with a
reaction chamber that contains this enzyme plus various
concentrations of DHAP, but no G3P. How do we expect that
the initial rate of formation of G3P will react to an
increase in the DHAP concentration?
#22. Our dolphin is still
homing in on a fish. It turns out to be a mullet, a fish
that eats phytoplankton that have settled onto the mud.
These phytoplankton are photosynthetic algae. If they are
like higher plants on land, this means that they
a) use sunlight's energy to excite electrons out of
chlorophyll.
b) pass these high-energy electrons to NADPH.
c) use this NADPH (and ATP) to reduce
CO2 to sugar.
d) All of these.
#23. The Calvin-Benson cycle is
described in answer ... in the previous question.
a) b) c)
d) The Calvin-Benson cycle is not described in any
answer of that question.
24. Eventually, the dolphin reaches the mullet and catches
it in its jaws. Dolphins have conical teeth that are all
alike. These teeth can be used to hold food, but not to chew
it.
In contrast, humans have several different kinds of
teeth. The chisel-like human teeth that are used to shear
off pieces of food are the
a) incisors. b) canines. c) premolars. d) molars.
#25. The dolphin swallows the
mullet whole. Dolphin stomachs have three compartments, and
the second one is most similar to our stomach. We would
expect that this compartment would
a) use bile to emulsify fat.
b) secrete HCl and start digestion of proteins.
c) split polysaccharides into maltose subunits.
d) absorb monomers rather than digesting polymers.
#26. After several hours, the
fat and protein in the mullet are starting to be absorbed by
the dolphin's intestine. If these foods are completely
broken down into monomers, we would expect that they would
yield high concentrations of
a) monosaccharides and disaccharides.
b) amino acids and nucleotides.
c) pentose sugars, purines, and pyrimidines.
d) amino acids, fatty acids, and glycerol.
#27. The circulatory system of
dolphins is similar to that of humans. After the monomers
above are absorbed in the intestine, they would be picked up
by intestinal capillaries, then go to veins, and then enter
the heart in the
a) right ventricle. b) left ventricle. c) right atrium. d)
left atrium.
*28. Dolphins in cool water
have a big problem with heat loss. Body heat is lost 40x
faster to water than to air. Most of the dolphin's body is
insulated with a thick layer of fat (blubber) to prevent
heat loss, but the flippers and tail flukes are not.
Instead, these have a "countercurrent heat exchanger."
Arteries entering the cold tissue are placed right next to
veins coming back from it. This means that instead of being
lost to the outside, the heat in the arterial blood is
transferred to the venous blood just as it is reentering the
warm body core:
Which graph below shows the relationship between the
temperature of the arterial blood and the venous blood in
warm water (light line) and cold water (dark line)? In all
cases, the water temperature is cooler than that of the
arterial blood.
Interesting fact: Whales are often encrusted with fouling
organisms like barnacles, but this doesn't happen with
dolphins. One reason may be that the epidermis (outer skin
layer) of dolphins is entirely replaced every two days! Thus
the outer layer is shed so fast that fouling organisms can
never get a foothold.
#29. Another big problem for
dolphins is osmoregulation. They live in a seawater
environment that is about three times as concentrated as
their blood. This means that the environment is ... to their
cells and the cells will tend to
a) hypertonic ... shrivel up. b) hypertonic ... swell and
burst.
c) hypotonic ... shrivel up. d) hypotonic ... swell and
burst.
*30. Dolphin females have
estrous cycles rather than menstrual cycles, but let's talk
about the human menstrual cycle for a moment. In humans, the
hormones that directly build up the uterine lining
are mostly ... before ovulation and ... after ovulation.
a) FSH ... FSH and LH.
b) estrogen ... estrogen and progesterone.
c) inhibin ... human chorionic gonadotropin.
d) estrogen ... LH and human chorionic gonadotropin.
#31. A human female begins her
menstrual period today. If her cycles are normally 28 days
long, her next fertile period will extend from ... days from
now until ... days from now.
a) 5 ... 10 b) 10 ... 21 c) 16 ... 21 d) 10 ... 15
Interesting fact: Dolphin males do not have a scrotum. It
is thought that they can keep the temperature of their
internal testicles low enough for spermatogenesis by piping
cool blood from the heat exchangers directly to the
testicles.
#32. Many bony fish lay
millions of eggs and swim away immediately after laying
them. Dolphins have a 12-month gestation period and then
deliver a single calf who is one-third as long as the
mother. This calf may take milk from the mother for 18
months, and stay with the mother for years, learning to
hunt, echolocate, and interact correctly with other
dolphins. The calf may not be physcially mature until an age
of 10-20 years, and may live to an age of 50. Dolphin
mortality rates in Sarasota Bay, Florida, average only 1-4%
per year. All this implies that dolphins are ... animals,
... humans.
a) r-selected ... like b) K-selected ... like
c) r-selected ... unlike d) K-selected ... unlike
#33. Given the life history
characteristics above, if you could catch random dolphins in
an area with a stable dolphin population, you would expect
to find that
a) the great majority would be young rather than an old or
middle-aged.
b) the great majority would be old rather than a young or
middle-aged.
c) the great majority would be middle-aged rather than young
or old.
d) there would be fairly equal representation of young,
middle-aged, and old dolphins.
#34. There are instances of
high dolphin mortality, however. In 1987-1988, there was a
massive dolphin dieoff on the East Coast due in part to
toxins produced by red tide organisms. Red tides are
produced by
a) dinoflagellates. b) diatoms. c) ciliates. d)
trypanosomes.
35. Dolphin genetics has been studied with mitochondrial
DNA. Mitochondria are cellular organelles that mainly
function in
a) digestion of worn-out organelles. b) structural support
of the cell.
c) heredity. d) aerobic metabolism.
36. A section of mitochondrial DNA reads AGCTTA. The
complementary strand of DNA would read
a) AGCTTA. b) ATTCGA. c) TCGAAT. d) AGCUUA.
#37. Restriction enzymes are
often used to develop "genetic fingerprints." The feature of
restriction enzymes that makes them most useful for this
application is that they
a) can withstand high temperatures without denaturing.
b) cut DNA only at certain base sequences.
c) add nucleotides to a growing chain but stop when they
incoporate a U nucleotide.
d) can separate DNA into its complementary strands.
*38. A major question in
dolphin biology concerns the genetic structure of dolphin
populations. It seems that local bays have their own
populations that tend to stay in that location, and offshore
there is a roving group of dolphins (transients) that may
sometimes mate with the local dolphins. Say that the top
lane in the electrophoretic gel below is a bay dolphin
female and the second lane is a transient dolphin male. The
next three lanes are three newborn calves from the bay. The
boxes on the left are the wells.
Is there any evidence here that any of the calves came
from these two parents?
a) Yes, Calf 1 did. b) Yes, Calf 2 did. c) Yes, Calf 3 did.
d) No, none did.
*39. Consider the leftmost DNA
band from Calf 1. That band is in the leftmost position
because it ... than any other DNA fragment on the gel.
a) is bigger b) has more A and T
c) is more negatively charged d) has less complementary base
pairing
*40. It is noticed that all the dolphins in the bay
have a dorsal fin that is lower and more swept back than
almost all the transient dolphins do. We'll call the
bay-type fin "low" and the transient-type fin "high." A few
known matings between bay and transient dolphins produce the
following phenotypic results:
|
Mother
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Father
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Calf
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Low
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High
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High ( male)
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High
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Low
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High (male)
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Low
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High
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High (female)
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Low
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High
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Low (female)
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A colleague maintains that fin type is controlled at one
autosomal locus and the "high" allele is dominant. Do these
results allow you to reject his hypothesis?
a) Yes. b) No.
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