Download Chapters 28-30 sample exam

Integrating Concepts in Biology II
Answer Key for Sample Exam covering Chs 28-30 on Homeostasis of populations/ecological systems
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guide to grading. You might be looking for something more specific and because some of the
questions are open-ended, other answers not provided here might also be correct. See the ICB
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1. (CH28) Describe seasonal changes observed in arctic fox used to help them maintain body
temperature homeostasis. Use data and evidence from Data Gallery #1 to support your answer.
It appears foxes grow thicker fur insulation over most of their bodies, except where they need to
maintain good sensory perception (nose, mouth, and ears) and in areas that can radiate heat centrally
when they curl up for sleeping (inner legs) (FIGURE 28.3). Overall hair length has a positive correlation
with the temperature measurement.
2. (CH28) Hypothesize a homeostatic mechanism to explain how the arctic fox’s body responds by
growing longer hair. Use data from Data Gallery #1 to support your answer.
Fur length lags behind the change in ambient temperature, which could indicate the lag time between
foxes sensing the temperature change, their cells processing that information, and the amount of time it
takes for hair to grow noticeably longer. However, the length of day is also changing as indicated in the
yellow/black color gradient at the bottom of FIGURE 28.3. It is impossible to know from these data
whether light and/or temperature is the environmental factor that stimulates hair growth in the fox.
3. (CH28) Explain why the fur on an arctic fox does not get uniformly long on all parts of its body.
Use data from Data Gallery #1 to support your answer.
Fur length does not grow long in areas where they need to maintain good sensory perception (nose,
mouth, and ears) and in areas that can radiate heat when they curl up for sleeping (inner legs) (FIGURE
28.3).
4. (CH28) Do the camels maintain a consistent body temperature like other mammals? Explain the
difference between the hydrated and dehydrated states for camel temperature homeostasis. Use
data from Data Gallery #1 to support your answer.
No, it fluctuates greatly on a daily basis. They have an overall average temperature like all mammals.
Hydrated camels experience less fluctuation than dehydrated camels, which reflects the larger mass of
hydrated animals and water’s chemical property of changing temperatures slowly. Although camels
appear to have an average body temperature near 37° C like humans, a camel’s core body temperature
can reach 40° C. But camels maintain brain temperatures within tighter limits than the rest of the body.
A camel is better able to keep their brains cool than most mammals, even when their body temperature
is very high.
5. (CH28) Present data that supports the hypothesis that the hypothalamus is involved in body
temperature homeostasis in mammals. Use data from Data Gallery #1 to support your answer.
Figure 28.6 demonstrates what happens when a small area of the hypothalamus is damaged; body
temperatures were no longer linked to the animals’ surroundings. The data indicate that mammals
without functional temperature regulation can generate more heat despite being in a warm room, and
vice versa. Figure 28.7 indicates that individual neurons can sense their local temperature and respond
to changes by altering the rate of their action potentials and thus cell-to-cell communication. After the
brain begins information processing, the anesthetized animal altered its breathing rate, which helped
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maintain the normal body temperature. It appears that an increase in hypothalamus temperature leads
to a slightly delayed organismal response of increased breathing and perhaps other physiological
responses. Finally, FIGURE 28.8C shows that under natural conditions, the horse maintains a cooler
cavernous sinus compared to the other three areas measured. The hypothalamus does not get as hot as
the core temperature because the cavernous sinus protects the brain from overheating. If the horse is
going to process its core body temperature, neurons in the hypothalamus must detect an increase in
temperature so that they can increase their rate of action potentials and initiate physiological responses
to cool the animal. When air is prevented from entering the horse’s nasal cavity, the cavernous sinus
heats up much faster, which makes the hypothalamus to get nearly as hot as the core body temperature
until the experiment is stopped. The experimental animal in Figure 28.8D experiences a rise of about 3°
C in the cavernous sinus compared to the control animal.
6. (CH28) Explain the data that shows hypothalamic regulation of body temperature in the horse.
Use data from Data Gallery #1 to support your answer.
Figure 28.8C shows that under natural conditions, the horse maintains a cooler cavernous sinus
compared to the other three areas measured. The hypothalamus does not get as hot as the core
temperature. As the hypothalamus temperature rises, the temperature of the cavernous sinus
decreases, which protects the brain region from overheating. Neurons in the hypothalamus detect an
increase in core body temperature, increase their rate of action potentials and initiate physiological
responses. One response is increased breathing, which brings in more air that can reduce the
temperature of the cavernous sinus located at the far end of the nasal cavity. The core body
temperature cools faster than the hypothalamus until the two regions approach their original 38° C.
When air is prevented from entering the horse’s nasal cavity, the cavernous sinus heats up much faster,
which makes the hypothalamus to get nearly as hot as the core body temperature until the experiment
is stopped out of concern for the animal. The experimental animal in Figure 28.8D experiences a rise of
about 3° C in the cavernous sinus compared to the control animal. Rapid breathing is one cooling
response that brings in cool air and maintains the cavernous sinus to remain cooler than many other
parts of the body. Endotherms sense body temperature and ambient temperature, integrate this
information, and use neuronal responses to maintain organismal thermal homeostasis.
7. (CH28) When the route of air is surgically diverted in a horses nasal cavity, what happens to the
temperature in the hypothalamus and the cavernous sinus? What do you conclude about body
temperature regulation from this result? Use data from Data Gallery #1 to support your answer.
Limit your answer to 3 sentences.
When air is prevented from entering the horse’s nasal cavity, the cavernous sinus heats up much faster,
which makes the hypothalamus to get nearly as hot as the core body temperature until the experiment
is stopped out of concern for the animal. The experimental animal in Figure 28.8D experiences a rise of
about 3° C in the cavernous sinus compared to the control animal. From these data and those of
previous figures, it appears mammals allow the hypothalamus to warm a little bit, which stimulates
neurons to increase their depolarization rate. The subsequent release of neurotransmitter initiates
cooling responses to maintain thermal homeostasis (see Figure 28.7). Rapid breathing is one cooling
response that brings in cool air and maintains the cavernous sinus to remain cooler than many other
parts of the body. The cooler temperature in the cavernous sinus protects the hypothalamus from
getting too warm, which could lead to brain damage. If the hypothalamus were damaged, then the
organism’s ability to regulate body temperature would be disconnected from its ability to increase or
decrease body temperature, as you saw in Figure 28.6 when the cats lost hypothalamus function. In
short, endotherms sense their current body temperature and the ambient temperature, integrate this
information, and use neuronal responses to maintain organismal thermal homeostasis.
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8. (CH28) Why does a human begin to sweat if his skin is never heated beyond 31° C? What cranial
temperature appears to be the “sweat point” for this man? Use data from Data Gallery #1 to
support your answer. Limit your answer to 1 sentence.
As the skin approached average human body temperature of 37° C, even though it never exceeded 31° C
(FIGURE 28.9), the man generated less heat, because he was not as cold. Once the core temperature
exceeded this man’s specific set point of 37.1° C, he began to sweat and lose heat through water
evaporation on various parts of his body. Even though skin temperature was never that high, as outside
temperatures rise, the ability to lose heat produced through basal metabolism is reduced, leading to a
buildup of heat inside the body, increasing core temperature and initiating cooling mechanisms. The
man continued to sweat as long as his core body temperature exceeded his specific set temperature of
37.1° C.
9. (CH28) Describe how a horse’s skull morphology plays a critical role in an individual’s core body
temperature homeostasis. Use data from Data Gallery #1 to support your answer. Limit your
answer to 2 sentences.
The cavernous sinus is adjacent to the hypothalamus, which protects the brain region from overheating
(FIGURE 28.8). When air is prevented from entering the horse’s nasal cavity, the cavernous sinus heats
up faster, which makes the hypothalamus to get nearly as hot as the core body temperature until the
experiment is stopped. The experimental animal in Figure 28.8D experiences a rise of about 3° C in the
cavernous sinus compared to the control animal.
DATA GALLERY #1
Figure 28.1
Figure 28.2
Figure 28.3
Figure 28.5
Figure 28.4
Figure 28.9
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Figure 28.6
Figure 28.7
Figure 28.10
Figure 28.12
Figure 28.8
Figure 28.11
Figure 28.13
Table 28.1
Figure 29.1
Figure 29.2
Figure 29.5
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Figure 29.3
Figure 29.4
Table 29.1
10. (CH28) Describe how and why two related species may allocate resources, such as nutrients or
food, differently. Use data from Data Gallery #1 to support your answer. Limit your answer to 3
sentences.
They may have different reproductive strategies that cause them to allocate resources differently. For
instance, plants may allocate resources differently if they use sexual vs. vegetative reproduction (FIGURE
28.11), or two animal species may allocate resources differently if one grows to a larger size and puts
more resources into growth earlier on and the other puts more resources into reproduction early on
(TABLE 28.1 and FIGURES 28.13 and 28.14).
11. (CH28) What is the difference between sorghum and Johnson grass in how they allocate nutrient
resources and what explains that difference? Use data from Data Gallery #1 to support your
answer. Limit your answer to 2 sentences.
In terms of allocation of limited resources, Johnson grass and sorghum have priorities for vegetative
reproduction and sexual reproduction, respectively (FIGURE 28.11). The proportion of biomass Johnson
grass allocated to seeds was about 0.05 to 0.07 and was much higher (from 0.30 to 0.37) for rhizomes.
That proportion remained fairly constant across nutrient levels, so Johnson grass allocated five to seven
times more biomass to rhizomes than to seeds. Sorghum allocated 0.30 to 0.40 of total biomass to
seeds, much higher than Johnson grass, but sorghum reproduces only by seed. Seed reproduction in
Johnson grass might be an alternative means of reproduction to increase genetic diversity and allow for
long-distance dispersal, but only when sufficient resources are available.
12. (CH28) Describe how changes in protein content of food or consumption affect the allocation of
resources. Use data from Data Gallery #1 to support your answer. Limit your answer to 2
sentences.
Individuals respond to changes in the diet, allocating their resources differently. For instance, number of
egg clutches in pond snails varies with protein content of food (FIGURE 28.13). Species respond
differently; one species has their growth rate much more reduced as protein content in the diet declines
than the other species (TABLE 28.1). When protein is high more is allocated to reproduction and growth,
but consumption is not as high as when protein is lower. Snails are compensating by eating more total
food when the protein content of their food is low (FIGURE 28.14).
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13. (CH28) Describe two examples of homeostasis at the population level. Homeostatic processes
lead to what kinds of changes in populations? Use data from Data Gallery #1 to support your
answer. Limit your answer to 2 sentences.
Number of egg clutches in pond snails varies with protein content of food (FIGURE 28.13). This is an
example of homeostasis because the environmental conditions change and individuals respond to the
change in the diet, allocating their resources differently. This then affects the population of pond snails,
mostly in terms of the size of the population in this case, perhaps through feedback mechanisms, and
perhaps leading to a new average population size, analogous to a “set point.”
Another example also related to food is found in FIGURE 29.4. Here, fish exposed to different
environments have different reproductive strategies that have evolved, related to food levels and
predation risk. Fish descended from populations living without predators are larger, mature later, and
allocate less of their resources to reproduction than fish descended from populations living in the
presence of predation. Each population achieves homeostasis, but their responses are different
dependent upon the environmental context.
One more example is the peppered moth (FIGURES 29.1-29.3), where different populations have
different proportions of dark and light colored morphs related to the level of carbon soot pollution or
dark tree bark in their habitat. Each population has achieved homeostasis, which in this case is the
proportion of each morph, and this proportion is relatively stable over time if the environment does not
change (FIGURE 29.3B).
14. (CH28) Describe the principle of resource allocation and how it relates to homeostasis of
populations. Use data from Data Gallery #1 to support your answer. Limit your answer to 2
sentences.
The principle of allocation states that evolution will lead to organisms that optimize partitioning of
resources to maximize fitness. What this means is that in environmental where some resource, such as
protein, or food, or some nutrient, is limiting that resource may be allocated differently than in an
environment where the resource is abundant. For instance, number of egg clutches in pond snails varies
with protein content of food (FIGURE 28.13). This is an example of homeostasis because the
environmental conditions change and individuals respond to the change in the diet, allocating their
resources differently. This then affects the population of pond snails, mostly in terms of the size of the
population in this case, perhaps through feedback mechanisms, and perhaps leading to a new average
population size. Other examples can be used, e.g., from question #13.
15. (CH28) How would you test the hypothesis that sex of experimental subjects has an effect on a
physiological trait?
Many studies do not report whether their test subjects are male or female. For any experiment that
tests the physiological response to some factor, whether it’s internal (e.g., hormonal) or external (e.g.,
drug) to the organism, we may test both males and females and then account for the factor of sex in
statistical analysis.
16. (CH29) What do you conclude about the composition of phenotypes in populations of peppered
moths in the United Kingdom and how that composition relates to the conditions in the
environment? Use data from Data Gallery #1 to support your answer. Limit your answer to 3
sentences.
The composition of phenotypes in populations of peppered moth varies geographically depending upon
the level of carbon soot pollution in the UK (FIGURE 29.1). More dark carbonaria morphs are present in
populations closer to and downwind from major industrial centers where coal was being burned to
produced electricity and heat. Natural populations that exist in soot-covered forests or forests with
trees that have dark bark have high proportions of carbonaria individuals, whereas high proportions of
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typica light colored individuals are found in forests where trees are not exposed to soot pollution and
have light or lichen-covered bark (FIGURE 29.3B).
17. (CH29) Describe data that show how long-term exposure to predation or a particular food level
affects the evolution of reproductive traits. What differences do you observe in population of
origin (predator-free versus high predation)? Use data from Data Gallery #1 to support your
answer. Limit your answer to 3 sentences.
In FIGURE 29.4 fish exposed to different environments have different reproductive strategies that have
evolved, related to food levels and predation risk. Fish descended from populations living without
predators are larger, mature later, and allocate less of their resources to reproduction than fish
descended from populations living in the presence of predation. Each population achieves homeostasis,
but their responses are different dependent upon the environmental context.
18. (CH29) Are humans, when acting as predators, driving evolutionary change more rapidly than
other selective factors? Use data from Data Gallery #1 to support your answer. Limit your answer
to 2 sentences.
The mean changes are greater in populations of organisms hunted or collected by humans, thus over a
certain period of time, changes are occurring more rapidly when compared to changes in populations
either not affected by humans or affected by humans in other ways than hunting/collecting (FIGURE
29.5). TABLE 29.1 shows that 95% or more of variables measured in these populations hunted by
humans have changed significantly over time.
19. (CH29) What are the implications for homeostasis of populations when environments change very
rapidly? Use data from Data Gallery #1 to support your answer. Limit your answer to 3 sentences.
The introduction of a predator (FIGURE 29.4), hunting by humans (TABLE 29.1 and FIGURE 29.5), a
change in diet (FIGURE 28.13), or increase in soot pollution (FIGURE 29.1-3) can all lead to rapid changes
in populations that upset homeostasis, and initiate feedback mechanisms that then alter the population
and bring it to a new homeostasis (either a new population size, or a new distribution of phenotypes,
e.g.).
20. (CH28) For TWO of the following three figures, explain both the animal’s response to changing
temperature and the adaptation that helps maintain body temperature. Be specific.
It appears foxes grow thicker fur insulation over most of their bodies, except where they need to
maintain good sensory perception (nose, mouth, and ears) and in areas that can radiate heat centrally
when they curl up for sleeping (inner legs) (FIGURE 28.3). Fur length lags behind the change in ambient
temperature, which could indicate the lag time between foxes sensing the temperature change, their
cells processing that information, and the amount of time it takes for hair to grow noticeably longer.
Overall hair length has a positive correlation with the temperature measurement. Thicker, longer fur in
the colder weather is an adaptation to maintain constant body temperature.
The camel’s body temperature it fluctuates on a daily basis. They have an overall average
temperature but because of adaptations that prevent the brain from heating up, they can allow their
core body temperature to rise to pretty high levels. FIGURE 28.5 shows that if they are hydrated, camels
experience less fluctuation than dehydrated camels, which reflects the larger mass of hydrated animals
and water’s chemical property of changing temperatures slowly.
FIGURE 28.7 indicates that individual neurons can sense their local temperature and respond to
changes by altering the rate of their action potentials and thus cell-to-cell communication. After the
brain begins information processing, the anesthetized animal altered its breathing rate, which helped
maintain the normal body temperature. It appears that an increase in hypothalamus temperature leads
8
to a slightly delayed organismal response of increased breathing and perhaps other physiological
responses.
Figure 28.3
Figure 28.5
Figure 28.7
21. (CH28) The yellow-billed magpie (Pica nuttalli) lives along the northern California coast, in a very
well-defined climate regime. Researchers examined the response of these birds to variation in
temperature to understand their adaptations to their climate. They measured the
thermoregulatory responses by measuring their body temperature and oxygen consumption at air
temperatures between -10 and 45°C. The figures show body temperature (Tb) and metabolism
(Hm; a measure estimated from oxygen consumption) during rest of birds exposed to various
ambient temperatures. The line in the body temperature graph shows the line where body
temperature equals ambient temperature. Solid lines in the lower graph are best fit regression
lines for each portion of points through which the lines extend. The dashed line shows extension
of one best fit line to the x-axis.
a. Why does metabolism increase when ambient temperatures are above 38 oC? What effect
does this have on body temperature?
Metabolism increases when ambient temperatures are high because cooling actions are initiated, such
as sweating, shallow and more rapid breathing, increased blood flow to the skin, but also because
chemical reactions are temperature-dependent and as body temperature rises above the set point,
reactions speed up and consume more oxygen. Ideally, the cooling mechanisms will compensate for the
increase in temperature to bring the core body temperature back down to its set point, however, that
doesn’t always happen especially in this case where the birds are trapped in a cage.
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b. In what temperature regime (or range of temperatures) would you expect to find populations
of these birds thriving, given the data in the figure, and why?
Between about 15 and 35oC, because that is where metabolism and energy costs are lowest – only basal
metabolic processes are in play, hence the straight horizontal line that fits the data in that region.
22. (CH28) What were the differences and similarities between the two species of grass in the figures
below in how they allocated resources in response to nutrient level? Explain in no more than 3
sentences, using data from the figures.
Figure 28.10
Figure 28.12
Figure 28.11
In terms of allocation of limited resources, Johnson grass and sorghum have priorities for vegetative
reproduction and sexual reproduction, respectively (FIGURES 28.10 and 11). The proportion of biomass
Johnson grass allocated to seeds was about 0.05 to 0.07 and was much higher (from 0.30 to 0.37) for
rhizomes. That proportion remained fairly constant across nutrient levels, so Johnson grass allocated
five to seven times more biomass to rhizomes than to seeds. Sorghum allocated 0.30 to 0.40 of total
biomass to seeds, much higher than Johnson grass, but sorghum reproduces only by seed. Seed
reproduction in Johnson grass might be an alternative means of reproduction to increase genetic
diversity and allow for long-distance dispersal, but only when sufficient resources are available.
Nitrogen and phosphorus were preferentially allocated to seeds and rhizomes and not shoot unless the
nutrient levels were high (FIGURE 28.12).
23. (CH29) Answer both of the following questions. Answers should be brief and concise.
a. What do the data in Figures 29.2 and 29.3 indicate about homeostasis at the population level?
Different populations have different proportions of dark and light colored morphs related to the level of
carbon soot pollution or dark tree bark in their habitat. Each population has achieved homeostasis,
which in this case is the proportion of each morph, and this proportion is relatively stable over time if
the environment does not change (FIGURE 29.3B). More dark carbonaria morphs are present in
populations closer to and downwind from major industrial centers where coal was being burned to
produced electricity and heat. Natural populations that exist in soot-covered forests or forests with
trees that have dark bark have high proportions of carbonaria individuals, whereas high proportions of
typica light colored individuals are found in forests where trees are not exposed to soot pollution and
have light or lichen-covered bark (FIGURE 29.3B).
b. What is the feedback mechanism at work here, and how do the data support your answer?
The feedback mechanism is predation on conspicuous moths that are not camouflaged well against the
common background in their habitat. FIGURE 29.2 shows conspicuousness of different morphs against
different backgrounds.
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Figure 29.2(l) Percentages of peppered moths deemed conspicuous by researchers in one of two
forests.
Figure 29.3(r) Results of studies of peppered moths in two forests.
24. (CH29) Explain the mechanism(s) behind density-dependent population regulation in two
different species we examined. Use data from Data Gallery #2 to support your answers. Limit
your answers to 2 sentences per example.
There were four examples in this section.
Damselfish competed for safe space above a coral or anemone at night (FIGURE 29.8) in order to
avoid density-dependent predation (FIGURES 29.6-8). Predation caused density-dependent mortality,
which affects population sizes, all else being equal.
European rabbit females competed for nesting sites in their warrens. This limiting resource led to
density-dependent effects on births, with females producing fewer litters per year when densities were
high (FIGURE 29.10). Also, because young and old females were not as good competitors for nesting
sites, age-dependent reproduction also occurred (FIGURE 29.11).
When jack pines grow in a very dense forest, mortality occurs as the trees age and density declines.
Again, competition for light and soil nutrients among trees that are close together occurs with the losers
dying and resulting in a uniformly distributed forest of trees (TABLE 29.2).
White wallrocket plants have higher reproduction when they are closer together, leading to a
density-dependent effect (FIGURE 29.12). The mechanism here is pollinator interactions – the plants
have more reproductive success when they are close together because more pollinators are attracted
and more cross-pollination occurs.
25. (CH29) What differences do you observe regarding the mortality effects of small and large
predators as damselfish density varies? What do these results suggest about regulation of
damselfish populations? Use data from Data Gallery #2 to support your answer. Answer in no
more than 2 sentences.
FIGURE 29.6D shows that there is density-dependent mortality from both small and large predators, but
that at high densities larger predators add an additional component of mortality.
26. (CH29) What are the effects of age and population density on rabbit reproduction? Does either of
these factors act as a feedback mechanism involved in maintaining population homeostasis for
European rabbits? If so, explain how the feedback works. Use data from Data Gallery #2 to
support your answer. Answer in no more than two sentences.
Both age and population density lead to feedback mechanisms that maintain population homeostasis in
European rabbits. The feedback mechanism works through competition for nesting sites in warrens. This
limiting resource of sites led to density-dependent effects on births, with females producing fewer litters
per year when densities were high (FIGURE 29.10). Also, because young and old females were not as
good competitors for nesting sites, age-dependent reproduction also occurred (FIGURE 29.11).
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27. (CH29) How does the lower social rank of 1 year old rabbits relate to their fecundity as compared
with older females, which are generally higher in the social hierarchy? Does this help explain how
density affects population size, and if so, how? Use data from Data Gallery #2 to support your
answer. Answer in no more than 3 sentences.
European rabbit females competed for nesting sites in their warrens. This limiting resource led to
density-dependent effects on births, with females producing fewer litters per year when densities were
high (FIGURE 29.10). Because young females are not good competitors for nesting sites and because
they are not experienced mothers, age-dependent reproduction also occurred where 1 year olds
produced fewer offspring than older females (FIGURE 29.11).
28. (CH29) Describe a mechanism that could produce inverse density-dependence, that is, as density
increases, population size increases, which is opposite to what is normally observed in densitydependent population regulation. Use data from Data Gallery #2 to support your answer. Answer
in no more than 2 sentences.
White wallrocket plants have higher reproduction when they are closer together, leading to a densitydependent effect (FIGURE 29.12) that is not what we might normally expect in that reproduction
actually increases in plants that are in densely populated clusters. The mechanism here is pollinator
interactions – the plants have more reproductive success when they are close together because more
pollinators are attracted and more cross-pollination occurs.
29. (CH29) Is there unequivocal evidence that DDE causes eggshell thinning, and if so, what is it? If
not, what else would you need to know to rule out other causes? Use data from Data Gallery #2
to support your answer. Answer in no more than 2 sentences.
The research study that actually manipulated DDE in the diet of kestrels allowed the scientist to make a
cause-and-effect conclusion that DDE was causing eggshell thinning (FIGURE 29.15). Further, the dosedependent relationship between DDE in the diet and DDE in eggs and eggshell thinning is quite
convincing. However, the one potential flaw in this study is that we don’t know what the birds had been
exposed to prior to capture, so it can be argued that these data are not unequivocal.
DATA GALLERY #2
Figure 29.6
Figure 29.7
Figure 29.8
Figure 29.9
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Figure 29.11
Figure 29.10
Figure 29.12
Table 29.2
Figure 29.14
Table 29.3
Figure 29.15
Figure 29.16
Figure 30.1
Figure 30.2
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Figure 30.3
Figure 30.5
Figure 30.4
Figure 30.9
Table 30.1
Table 30.2
Figure 30.6
Figure 30.8
Figure 30.10
Figure 30.11
14
Figure 30.12
Figure 30.12
Figure 30.13
Table 30.3
Table 30.4
Table 30.5
Table 30.6
Figure ELSI 30.2
30. (CH30) Explain how fish can affect the phosphorus cycle, how the data from fish effects can be
used to understand the phosphorus cycle, and how this illustrates the Big Idea of homeostasis.
Use data from Data Gallery #2 to support your answer. Answer in no more than 4 sentences.
Fish increased phosphorus in the water column (FIGURE 30.1). The proportion of total phosphorus
present as particulates also tended to be higher in fish presence. At the end of the second year
experiment, zooplankton constituted a smaller part of the particulate phosphorus in the low and high
fish treatments than in the no fish treatment. The smaller particles separated from zooplankton
constituted a greater fraction of particulate phosphorus when fish were present than when fish were
absent. This may be caused by fish reducing total zooplankton numbers and preferentially consuming
larger organisms in the plankton, leaving the smaller zooplankton to dominate. The researchers
concluded that fish consuming zooplankton increase total phosphorus in both the water column and
particulate matter. In addition, phosphorus lost from the water to assimilation by organisms growing on
walls and through sedimentation both increased with increasing fish biomass (FIGURE 30.2).
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31. (CH30) How can individual organisms help maintain ecological system homeostasis when
confronted by pollutants or contaminants? Use data from Data Gallery #2 to support your
answer. Answer in no more than 2 sentences.
Contaminants in the soil can disrupt homeostasis of ecological systems or populations, but organisms
that are adapted to uptake, detoxify, or sequester these pollutants or contaminants with little harm to
themselves allow other species to exist in what is otherwise a toxic habitat (FIGURE 30.6).
32. (CH30) What is the effect of clearcutting a forest on export of organic and inorganic particulate
matter? What effects do you observe over time in the two watersheds? How do you explain the
decrease in particulate matter export in the clearcut watershed during year 5? Use data from
Data Gallery #2 to support your answer. Answer in no more than two sentences.
Clearcutting the forest had a dramatic effect on particulate matter export relative to undisturbed,
forested watersheds (FIGURES 30.4 and 30.5). Total particulate matter export from the clearcut
watershed averaged 156 kg × hectare-1 × year-1, which was six times higher than the output of the
undisturbed watershed. Export increased each year following deforestation up to year 4.
33. (CH29) Interpret the two graphs below. Then explain how one of the graphs leads to a stronger
conclusion than the other about the effects of DDE on birds-of-prey. Be brief but thorough.
In 29.14, a correlation is made between eggshell thickness and DDE concentration in eggs. In 29.15,
researchers fed kestrels a diet of meat laced with varying doses of DDE and showed a resulting effect on
eggshell thickness and DDE in eggs. The latter study actually manipulated DDE in the diet of kestrels and
allowed the scientist to make a cause-and-effect conclusion that DDE was causing eggshell thinning,
which is much stronger than the correlative data in FIGURE 29.14.
Figure 29.14 (l) Eggshell thickness in natural populations (circles) and captive populations (xes).
Figure 29.15 (r) Relationship between dietary DDE fed to kestrels and DDE in eggs and eggshell
thickness.
34. (CH30) How is climate change acting or predicted to act as a disruption to ecological systems?
Name two ways, using data from Data Gallery #2. Limit yourself to one sentence per example.
Climate change and associated increases in atmospheric carbon dioxide can lead to changes in net
primary production (FIGURE 30.8), arrival time of migrants or blooming time of spring annuals (FIGURE
30.10), and survival or longevity of tropical cloud forest epiphytes (FIGURE 30.12).
35. (CH30) Explain how the data to the right relate to each of the following three Big Ideas. Answer in
no more than 1 sentence per Big Idea.
a. Homeostasis
Contaminants in the soil can disrupt homeostasis of ecological systems or populations, or can lead to
adaptations allowing species to tolerate such contaminants that may also be toxic.
b. Evolution
Contaminants in the soil can lead to adaptations that help species to tolerate,
translocate, or detoxify contaminants.
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c. Emergent Properties
The ability of a plant to decontaminate soil or uptake a heavy metal leads to an emergent property
where the presence of the plant allows many other species to live in an otherwise uninhabitable soil.
36. (CH30) What is the purpose of the control plots set up with a FACE (free-air carbon exchange)
array and no elevated CO2? What about the plots set up with no FACE array?
The array that is set up but pumps out only ambient air, not elevated CO2, allows researchers to
determine whether there is an effect of the array itself on the growth of the forest by comparing FACEambient air to no-FACE-ambient air plots. One could hypothesize that the array adversely affects trees,
especially ones that are growing very close to the structure itself. Plots set up with no FACE array are
another type of control, as mentioned. These plots allow researchers to compare the ambient air plots
with elevated CO2 plots without the additional cost of the FACE arrays, assuming the FACE-ambient
control plot shows no effect of the array itself.
37. (CH30) What does it suggest to you to have a lot of scatter in a plot of ordinal day of first
blooming over a 60-year time span? What do the data suggest to you if the day of first blooming
of a flower species changes from year to year vs. another species that always begins blooming
around the same day every year? Use data from Data Gallery #2 to support your answer. Answer
in no more than 3 sentences.
If there is a lot of scatter then the first bloom occurs on a different day of the year, and along with any
trend over decades where the average first bloom is occurring earlier, the scatter would suggest that the
species is using environmental cues, such as harshness of the winter or spring temperatures, to trigger
blooming (FIGURE 30.10). Even if there is no change over decades, but there is year to year variation,
cues other than fixed cues or variation within the population are likely at work in those species. If the
first day of blooming is strongly fixed, then the species might be using a cue that does not change over
time, such as the daylength, which at any latitude is always the same on a particular day of the year.
38. (CH30) Is there an effect of elevation on longevity and reproduction of epiphytic plants in tropical
cloud forests, and if so, what is it? Do all species respond the same way to the elevation
differences? Use data from Data Gallery #2 to support your answer. Answer in no more than 3
sentences.
Longevity and reproduction of most tropical cloud forest epiphytes declined as elevation declined
(FIGURE 30.12). Elevation simulated drying conditions that are predicted with global climate change. Not
all species responded the same way or as strongly as others, and the effect was stronger if the plants
were transplanted during the dry season.
39. Homeostasis is best defined as (highlight, underline or circle the best answer)
a) a positive feedback control that enables the body to respond to changes in the environment.
b) a control system that causes body systems to change if the external environment remains constant.
c) a feedback system to maintain body systems within an optimal range while responding to internal or
external changes.
d) a feedback system that prevents a body system from changing.
e) a control system designed to regulate the external environment by making subtle changes to the
internal environment.
f) None of the above.