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Discussion Questions for Week 1
Readings from HWA pgs. 3-28 and Bennett
1. Consider Hill’s time frames of physiology (Table 1.2 HWA). Into what time
frame(s) would each of Bennett’s 9 definitions of adaptation fit? Note that some
of the definitions could potentially fit into multiple time frames.
2. How do you explain the adaptive significance of vestigial structures in animals?
For example, the human appendix.
3. When studying physiological traits such as metabolism, scientists often correct for
an animal’s body size. Why might they do this?
4. What is a size-corrected residual (Pg. 9 of Bennett)? Refer to Fig. 1.8 of HWA.
Using the regression line to estimate size-corrected residuals, is the gestation
period of the Plains zebra unusual? What about the Bushbuck?
5. Wood ducks do not nest on the ground, like most ducks, but instead nest in tree
cavities. When the ducklings hatch, they must follow their mother to the nearest
wetland. The ducklings cannot fly, so they must jump out of the nest and fall to
the ground. Often, they fall several feet. Luckily, the ducklings are light, thus the
fall does not cause them injury. Can the light weight of the ducklings be
considered an adaptation? How would you test this? What is the likely
explanation that Bennett would give?
6. Suppose that you are asked on a test why male birds are so brightly colored. You
answer that many males are brightly colored because bright colors advertise their
health to a potential mate, and that more brightly colored males are more
successful in mating. From the perspective of an evolutionary physiologist, what
is lacking with this explanation? Suppose your friend answers that birds are
brightly colored because of carotenoids in their feathers. Why would an
evolutionary physiologist be dissatisfied with your friend’s explanation?
7. Convergent evolution is the process by which unrelated organisms develop
similar traits. For example, birds, bats, and insects have all developed wings.
Although the function of these wings is similar, the structures are quite different.
How does this example of convergent evolution support Francois Jacob’s
statement that evolution is best compared to tinkering (Pg. 7 HWA)?
8. Discuss the principal advantages and disadvantages of regulation and conformity.
9. Physiologists may measure the metabolic rate of wild animals using the doubly
labeled water method. In this method, a known volume of water that includes
isotopes of hydrogen and oxygen is injected into an animal’s body. After several
days, physiologists recapture the animal and take a blood sample. The amount of
doubly labeled water remaining in the animal’s blood is used to calculate how
rapidly the animal eliminated the labeled water from its body, providing an index
of its metabolic rate. What property of animals allows physiologists to use this
method (Pgs 10,11 HWA)?
10. Norms of Reaction (Box 1.2 HWA) plot an organism’s phenotypic response to
changes in its environment. The Norm of Reaction can be plotted graphically like
the one below:
16
14
Genotype 1
Genotype 2
Evaporative Water Loss
Genotype 3
12
10
8
6
4
2
0
Cool
Hot
Temperature
This reaction norm shows the evaporative water loss of 3 different genotypes in a
population across 2 different environments. The symbols represent the water loss for
each genotype in a cool and a hot environment. The steepness of the slope of the line
connecting the two points represent the degree of phenotypic plasticity shown by each
genotype. Thus, genotype 3 is the most plastic, and genotype 1 is the least plastic.
Considering that evaporative water loss is an important avenue of heat loss in animals,
which genotype might respond most favorably to being placed in a warm climate? What
about a cool climate? Which genotype would be the most common in an area with cold
winters and hot summers? Why?
11. Refering to the reaction norm above, what change might we see in the genetic
structure of the population as we moved away from the equator, toward the poles?
Would we observe the same trend if genotype 2 were the only genotype? Why?
12. The ability of fish to utilize oxygen from the air is an adaptation more common in
tropical regions than temperate or arctic regions. Why do we see this
biogeographical trend?
13. Leopard Frogs lack specialized skin to prevent desiccation. They lose water at
roughly the same rate per surface area as a dish of water. Yet Leopard Frogs are
largely terrestrial, inhabiting open meadows. Describe how a Leopard Frog might
use the habitat of an open meadow to prevent desiccation (Pgs. 21-23 HWA).
14. People with sickle cell anemia experience problems with blood circulation, which
can lead to acute attacks of pain and organ damage. The lifespan of people with
this disease is significantly reduced, thus decreasing their reproductive potential.
Yet among people of Sub-Saharan African descent, the allele for sickle cell is
quite common. Why might this be so? You might have to do a bit of quick
research if you aren’t familiar with the disease (Wikipedia is acceptable in this
case).
15. Consider the wings of birds, bats, and insects as discussed in question 7. Can we
consider wings as an adaptation for an aerial lifestyle? What method for inferring
adaptation justifies your answer?
16. How is natural selection in the laboratory different from the artificial selection of
domestic organisms (Pg. 13 of Bennett)?
17. In the polar seas, temperatures remain at -1.9oC, the lowest temperature at which
seawater remains in liquid form. The organisms in these seas do not freeze. Polar
fish employ special protections against freezing, such as natural antifreeze in their
bodies. However, marine invertebrates in the polar seas do not require these same
protections to prevent freezing. Why? Refer to pages 12,13,17,18 of HWA for
help.
18. When you go outside on a cold day without adequate clothing, your body begins
to cool below the customary 98.6oF. Your physiological response is to begin
shivering to maintain your internal temperature at a set point. What physiological
control causes you to oppose deviations from your internal temperature by
shivering?