Biology 5370 –(Mammalogy) --Exam 3
11 Nov. 2003
Name: _______________________
1. (7 pts) Define and describe the basic differences between plantigrade, digitigrade and
unguligrade limbs. How do these differences affect the physical principles of locomotion
and what forms of locomotion are favored by each?
Plantigrade - on heel and sole of foot, favors walking
digitigrade -on digits, favor running.
unguligrade -on hoofs, favor running – high speed.
These changes involve proportional lengthening of limb, particularly distal limb elements with
reduction, loss, or fusion of some elements.
2. (12 pts) a) Snowshoe hares replace their brown summer fur with a white coat of fur for the
winter.
In what tissue layer of the skin is hair formed? _____epidermis_____.
What molecule gives hair its strength? _______keratin_____.
What molecule gives hair its color? _______melanin_______.
b) The feathers of birds are homologous with the scales of reptiles. What is the relationship
between the feathers of birds and the hair of mammals? _______analogous_______.
c) The hairs of the fur of the snowshoe hare are longer in the winter coat than in the summer
coat. On the figure below, indicate how the longer fur coat would change the energy use of
the animal over the range of ambient temperatures, i.e., redraw the profile for the longer coat:
Metabolic
rate
Ambient temperature
d) What is the flat portion of the curve called? Thermal Neutral Zone
e) In a sentence or two explain why it is called this term and give an example of a behavior
that could influence the magnitude of this section of the curve.
TNZ – ambient temperature range in which no energy is necessary to maintain body temperature.
Behaviors that could influence the magnitude of this section of the curve include huddling,
burrowing, spreading out, fluffing/retracting fur…..etc.
Name:__________________________
3. (12pts) a) Shrews are the smallest mammals with some species as small as 2 grams. No
species of shrews consume plants. Why? Use the graph to support your answer.
No shrews consume plants because they need high
energy food in order to satisfy high metabolic
demands (large SA:V). Plants are too hard to digest
and assimilate energy from – they couldn’t possibly
consume enough food.
shrew
Metabolic rate
(mls O2/g/hr)
Though the linear
line was correct,
both answers were
accepted
Log body size
b) In what section of the shrew’s gut does the majority of nutrient absorption take place?
__________small intestine________.
c) One species of shrew, Sorex palustris, is semi-aquatic and is active throughout the year. It
even swims under the ice. Its hairs are unusually shaped to provide increased surface area
for air to adhere to each hair. So many air bubbles are trapped that the swimming shrew
appears silvery under water. What is the function of trapping air?
The air serves as thermal insulation for the shrew
d) What are the physiological consequences of not trapping air?
The shrew would suffer heat loss because it would be completely soaked with water,
which is a better conductor of heat than air.
4. (7pts) List five morphological or behavioral differences between Odontocetes and
Mysticetes. Use these characteristics to speculate why Odontocetes evolved sonar but
Mysticetes did not.
Odontocetes
Smaller
Teeth
Piscivorous or carnivorous
Sonar
Larger males
Assym. Skulls
Social
Mostly non-migratory
Mysticetes
larger
no teeth
filter feeders
no sonar
larger females
symm. skulls
less social
migratory
Mysticetes do not use
sonar because their food is
to small to be detected
with decreased
frequencies
5. (7pts) a) Which is thought to have evolved first, fur or endothermy?
Endothermy
Name:__________________________
b) Give two pieces of paleontological evidence from class to support your answer.
1. Haderian gland in Morganonucodonts
2. Fossilized hair and Multituberculates fossils in coprolites.
c) Based on this evidence, date the origin of fur.
The Haderian gland of Morganonucodont demonstrates that they had hair as well. The
most recent common ancestor of Mults And Morgs was 210 million years ago, so hair
must be a least that old.
6. (10) The Rat kangaroo (Potorous tridactylus) inhabits the deserts of Australia. It utilizes
cooling strategies depending on temperature. As temperatures rise, it first pants. As
temperatures continue to rise, it stops panting and starts sweating profusely from its naked
tail. It also wags its tail while sweating.
a). In this case, how is sweating similar to panting? Both sweating and panting cool using
evaporative cooling.
b). Give one advantage of panting over sweating: The animal doesn’t suffer salt loss when
panting.
c) Give one advantage of sweating over panting. Panting causes a build-up of CO2 in the
lungs, which contributes to Alkenosis.
d) What specialization do you expect to find in the kidney of such desert animals?
You expect to see very long loops of Henle
e) Where in the nephron does the urine become concentrated?
In the collecting duct
7. (7pts) Draw a cladogram that illustrates the evolutionary relationships of : elephant, pig,
manatee, whale, bison (include each of these on a separate branch of the tree).
Name:__________________________
8. (12pts) a) Blue duikers (a type of antelope) are 4 kg ruminants that occur in Africa. In a
sentence, explain the difference between rumination and other foregut fermentation
strategies:
Ruminants regurgitate and re-chew their food, and they have a sieve-like structure which
keeps large particles from entering the small intestine.
b) Based on this small body size, what type of fermentation would you have expected for this
herbivore?
I would expect any type of hindgut fermentation.
c) Nursing duikers have a tubular fold in their gut through which milk travels bypassing the
fermentation chamber to the acidic stomach. What is the purpose of this fold?
The fold keeps the milk from entering the fermentation chamber where the high nutrient
load of the milk would be lost to the microbes instead of benefiting the baby duiker.
d) Duikers have limbs built for running from predators. Duikers co-occur with aardvarks,
which have powerful limbs to excavate termite mounds. For the levers, given below,
indicate which is most likely the aardvark and which is most likely the duiker. Using the
information in the table and on the diagrams, generate a ratio to support your answer.
B
A
Effort (Power) arm
Fulcrum radius
Muscle Length
Load (Resistance)
arm
A
1
1
0.25
0.28
5
5.6
10
2
B
Figures are not available
A = Duiker, the ratio is 1/10
B = Aardvark; the ration is 1/2
Smaller ratios mean a larger distance is traveled for a given exertion. Larger ratios represent
limbs that create force rather than large movements.
9. (6pts) List 2 major trends in horse evolution. What change in habitat was occurring to drive
these trends?
1. Lengthening of limbs and loss of digits
2. increased body size
3. development of high crown teeth
These trends were driven by the change in habitat from woodlands to open grasslands.
Name:__________________________
10. (8pts) a) There are small (less than 30 g) flying mammals and small terrestrial mammal
but there are no truly aquatic mammals in that size range. What limits the exclusive use of
the aquatic habitat for small mammals?
There are no very small truly aquatic mammals because in the water they suffer increased heat
loss because of the high conductance of water. They have such a large S:V ratio and such a high
metabolism that an increase in conductance of heat is deadly.
b) If there were a small aquatic mammal in that size range, which animal (swimmer,
flier, or runner) would have the highest cost of transport (energy use/distance traveled).
Give 2 reasons why this is the most expensive form of transport.
Runners have the highest cost of transport because they have four oscillating limbs; they
experience the largest change in their center of gravity, and they are accelerating and
decelerating with every step, all of which are energetically costly.
11. (12pts) Weddell seals routinely dives to depths of 400m where they encounter pressures on
the order of 600 lbs/in2!!! (Wow.) These dives can last for 15 minutes (double wow!), yet
they completely exhale before diving. Where do these seals store their oxygen?
They store their oxygen in their hemoglobin and myoglobin.
b) Give two reasons seals exhale before diving.
a. To avoid needing a structure that would keep their lungs from being crushed
b. To minimize the gas that could be forced into solution and then come back out
upon surfacing (the bends).
c) List two other physiological responses to diving found in mammals:
a. They decrease their heart rate
c. They glide when possible
b. They shunt blood from unused visceral organs (liver, gut) to brain.
d) Would these specializations of the Weddell seal make it good at snorkeling? Why or
why not?
The Weddell seal would not be a good snorkeler. Its adaptations are for diving deeply
and not breathing. In order to be a snorkeler, it would face similar problems to the
elephant and would need to change the lining of its pleural cavity so the difference in
pressure between the air it breathes and the pressure on its body would not cause
hemorrhaging of the lining.