NAME: _______________________________________________________
LAB INSTRUCTOR:____________________________________________
ECOL 302 – First midterm examination – Fall 2006
Put your name at the top of each page NOW. All questions are worth 10 points each. ANSWER IN THE
SPACE ALLOTTED OR LESS. Use graphs or equations in your answers wherever you want or need to.
1. We found that adaptation is the key to understanding the success of organisms in their particular
environment. Please describe one adaptation of an organism to its environment that we discussed
in class. Please include both a description of how the adaptation works, and what environmental
condition or constraint it is an adaptation for in your answer.
A list of possibilities:
• Enzyme activity shifts with salt concentrations in bacteria
• Rainbow trout – 2 forms of AChE enzymes at 2 temperature ranges
• Counter current exchange and shunt in bird legs for freezing temperatures
• Counter current exchange in fish for efficient gas exchange
• C4 Photosynthesis/CAM Photosynthesis for hot, dry conditions
• Kangaroo rat to conserve water – behaviors: nocturnal, burrow microclimate,
coprophagy; physiological: impermeable skin, nasal cooling, dry feces,
concentrated urine
• The ability to acclimate (fish and temperatures; photosynthetic rates and
temperatures)
2. Tropical songbirds tend to have nests with fewer eggs than birds nesting at higher latitudes.
David Lack, of Oxford University, first placed this observation in a life-history context. First, what
do we mean by ‘life-history strategy”. Second, what were the key concepts elaborated by David
Lack in this regard?
Life history refers to the schedule of an individuals life – age at maturity, # of offspring,
life span, etc. Lack recognized that life-history traits are shaped by natural selection. He
also proposed that life history traits contribute to reproductive success and thus to
evolutionary fitness. They vary in predictable ways with environmental factors and
constraints. Finally, he hypothesized that clutch size was related to availability of
resources (food, in this case) and that experimental increase of clutch size would result
in poor reproductive success.
3. The Pacific swingtail is a colonial-nesting seabird found only on an isolated coral island in the
central Pacific Ocean. The swingtail feeds exclusively on adults of a large species of flying fish that
it scoops from just above the ocean's surface. The ocean immediately surrounding the island is
unproductive and essentially devoid of fish. However, there are small areas of upwelling at several
different distances from the island that provides a source of flying fish for the swingtail. Below is
an optimal foraging model for the Pacific swingtails. (a) Please label the axes.
(b) What is labeled at point a. optimum search time and at point b. maximum rate of prey
capture?
(c) What do you predict the results of increasing travel time would be on search time and trip
frequency for the Pacific swingtails.
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Increased travel time will lead to longer search time and less frequent trips
(d)What would you predict would happen to line X if the swingtails were foraging in an
environment where they encountered predatory raptors? Please draw your prediction on the
figure. What kind of foraging is this called, and what is the effect on the number of prey captured in
your prediction?
Risk-sensitive foraging. The number of prey captured will decrease because the
swingtails will reduce the time spent foraging in an environment with predators.
new X
X
# of prey
caught
b.
travel time
a.
search time
4. Describe global patterns in temperature and precipitation with respect to latitude. What is the
cause of these global patterns?
It is warmer at the equator with temperature decreasing with increased latitude. This is
because sunlight is more direct at the equator – at the poles, sunlight is less direct and
passes through more atmosphere than at the equator. Precipitation is higher in the
tropics, and decreases at higher latitudes. This is because cold air can hold less
moisture.
5. A VERY wealthy friend of yours has decided to construct a massive indoor "biome garden,"
containing representative ecosystems from many parts of the world (something like Biosphere II).
You have been hired you as an ecological consultant. The biome garden is to be developed in
Asheville, North Carolina, where warm summers alternate with mild winters to create conditions
naturally suitable for the temperate deciduous forest biome. The site chosen for development of the
biome garden is a pine plantation that was established approximately 70 years ago. The soils are
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clayey, acidic, relatively infertile, and have low organic matter content. For the biomes listed
below, make recommendations for environmental conditions in the greenhouse modules with
respect to temperature and precipitation, including seasonality of these factors where appropriate.
Also, what plant forms would you need to establish in each biome (don’t worry about specific
species)? Bonus points - describe the new soil conditions you would need.
a) Grassland Biome
Climate control would include hot summer temperatures (again avoiding excessive
heating) with reduced annual rainfall than the temperate forest (& less in the summer
than the rest of the year), alternating with cold winter temperatures.
Plants: prairie grasses with more shrubs if it is drier.
Bonus: Grassland soils tend to be non-acidic and rich in organic matter and nutrients.
Amendment of the existing soil with lime (to raise the pH), organic matter, and
appropriate fertilizers would probably suffice.
b) Tropical Rain Forest Biome
Tight climate control would be essential, with air-conditioning (in summer), heating (in
winter), and humidity (year-round) regulation important. Continually warm and moist
conditions, with some seasonality of precipitation.
Plants: Import tall evergreen trees, understory of small trees, shrubs and herbs, climbing
vines, epiphytes
Bonus: It might be possible to utilize the existing soil of the site with little amendment.
However, rain forest plants would be used to growing on soils with lower clay content
and higher content of iron and aluminum oxides.
c) Arctic Tundra Biome
Climate control would include keeping temperatures at or below freezing most of the
year, some warming in the summer. Much less precipitation annually, with most coming
in the summer.
Plants: import dwarf prostrate woody shrubs, lichens too (but they aren’t plants)
Bonus: Organic soils that are permanently frozen except during a brief growing season
(permafrost)
6. You are an ecologist interested in energetics of ecological systems. You begin collecting data on
energy flux in a population of kangaroo rats in the Sonoran Desert of Arizona. You determine that
these animals feed exclusively on the seeds of various desert plants. In your study area, the net
production of these seeds (expressed in units of energy) is 10 Kcal/m2/yr. You discover that
kangaroo rats are quite effective at finding and consuming these seeds, ingesting 8 Kcal/m2/yr.
Thus exploitation efficiency for these animals is 80%. Through further study, you learn that
kangaroo rats assimilate 6 Kcal/m2/yr and that their net production is 0.3 Kcal/m2/yr.
(a) Account for the difference (how much is it, how is it referred to?) between the rates of
ingestion and assimilation for this population of kangaroo rats.
This difference (2 Kcal/m2/yr) must be energy lost through egestion. For the
kangaroo rat, this would represent energy loss associated with seed components that
are not readily digested and thus passed as feces.
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(b) What is the assimilation efficiency for this population of kangaroo rats?
The assimilation efficiency is the ratio of assimilation to ingestion, expressed as a
percentage. For the kangaroo rats, this is 6 Kcal/m2/yr divided by 8 Kcal/m2/yr times 100,
or 75%.
(c) Account for the difference (how much is it, how is it referred to?) between the rates of net
production and assimilation for this population of kangaroo rats.
This difference (5.7 Kcal/m2/yr) must represent energy losses resulting from respiration
and excretion.
(d) What is the net production efficiency for this population of kangaroo rats?
The net production efficiency is the ratio of net production to assimilation, expressed as
a percentage. For the kangaroo rats, this is 0.3 Kcal/m2/yr divided by 6 Kcal/m2/yr times
100 or 5%.
(e) What is the ecological efficiency (food chain efficiency) of this population of kangaroo rats,
considering only the net production of its food?
The net production of seeds in the desert ecosystem is 10 Kcal/m2/yr. Kangaroo rats
have a net production of 0.3 Kcal/m2/yr. This represents an ecological efficiency of only
3% (0.3 / 10).
7. Compare and contrast the carbon and nitrogen cycles. Include in your answer discussion of
assimilatory and dissimilatory processes, as well as the dominant pools and fluxes of each cycle.
Carbon Cycle:
• Sun is the driving force
• assimilatory = photosynthesis, dissimilatory = respiration
• Dominant Pool: limestone, dolomite – a slow turnover pool
(dominant biological pool is dead organic matter)
• Dominant flux – exchange between atmosphere and oceans, and assimilation thru
photosynthesis are about the same
Nitrogen Cycle
• Driven by biotic fixation
• Assimilatory = N fixation, dissimilation = ammonification
• Dominant pool: Atmospheric N2
• Dominant flux: fixation/denitrification, there is a lot more cycling within an
ecosystem than these inputs however
The nitrogen cycle pathways in the biotic compartment are more complicated because
there are more forms of oxidized and reduced N than there are for C. The organisms
responsible for assimilation into the biotic compartment of the N cycle are heterotrophic
microorganisms, while they are autotrophs in the C cycle. However, microorganisms are
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important to both cycles. Most C is stored in a slow turnover pool, while most N is stored
in a faster turning over pool. In an organism, assimilation of N is linked to dissimilation
processes (usually of C) that release energy.
8. Briefly describe the difference between the usage of the word “theory” in common and scientific
language. Give an example of a scientific theory used in this course, and provide one example of its
conceptual and one example of its empirical content.
A common theory is a speculation, hypothesis or guess. A scientific theory is a formal
deductive structure or a system of conceptual constructs.
Some examples:
Optimal Foraging Theory
Ecosystem energetic approach
Global Nutrient/Biogeochemical Cycles
Evolution by Natural Selection
Conceptual Content – assumptions, definitions, concepts
Empirical Content - data, facts, generalizations
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Curved As
Raw
Curved
Percent
Raw
Curved
Curved as Percent
66
67.15
95.92
41
48.57
69.38
64
65.60
93.72
40
47.80
68.28
63
64.84
92.62
39
47.02
67.18
62
64.06
91.52
38
46.49
66.41
61
63.29
90.42
37
45.71
65.31
60
62.52
89.31
36
44.94
64.20
59
61.98
88.55
33
42.63
60.90
58
61.21
87.44
31
41.34
59.06
57
60.44
86.34
30
40.55
57.93
56
59.67
85.24
28
39.01
55.72
55
58.90
84.15
26
37.25
53.22
54
58.13
83.04
25
36.54
52.20
53
57.36
81.94
23
35.58
50.83
52
56.81
81.16
19
32.30
46.14
51
56.05
80.07
17
30.99
44.27
50
55.28
78.97
49
54.50
77.86
48
53.73
76.76
47
52.96
75.66
46
52.19
74.56
45
51.65
73.79
44
50.88
72.68
43
50.11
71.59
42
49.34
70.49
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