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Exam 2 - 2008-Spring-key.pdf

9 Pages
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Department
Agronomy
Course Code
PCB 4043C
Professor
Christou

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Name: KEY
Page 1 of 9
Instructions:
--Write your name on all the pages
--Make sure that all 9 pages are attached.
--You may not use calculators or other electronic aids. The math needed to solve a problem
should be relatively simple. If you can't do the math, just show what needs to be
calculated (e.g., "answer = .5 x .3")
--If you get hung up on a problem, skip it; return to it after you’ve answered the “easy”
problems.
GENERAL ECOLOGY
PCB 3034/4044
Spring 2008
EXAM 2
PAGE POINTS POSSIBLE SCORE
1 2 _____
2 12 _____
3 15 _____
4 8 _____
5 11 _____
6 13 _____
7 10 _____
8 17 _____
9 12 _____
_____ _________
TOTAL 100 _____
(2 points):
1) Are you interested in being an undergraduate TA for this course next year? ( YES, NO )
2) From where/whom did you take Intro Bio (Ecology): e.g., “UF, Dr. Palmer”: ________
Name: KEY
Page 2 of 9
2-1. a. (4 points) Rank the following animals in order of lowest to highest production
efficiency. Also indicate lowest and highest with words.
__4___worm that eats decomposing plant material (Highest)
__3___fish that eats other fish
__1___goose that grazes on wetland grasses (Lowest)
___2__chicken that eats grain
b. (4 points) Explain your ranking for each organism in relation to its (1) activity
level, (2) assimilation efficiency of food resources and (3) thermoregulation.
Goose: Lowest production efficiency because it has a high activity level (grazing, flying, escaping
predators, migrating in search of food resources),a high cost of homeostasis since it is an
endotherm/homeotherm, and it is consuming grasses, a food resource that has relatively low
assimilation efficiency (60-70%).
Chicken: Like the goose, it has a high activity level (finding grain, flying, escaping predators, “the
pecking order”) and is an endotherm. Unlike the goose, it is consuming a food resource with a
relatively high assimilation efficiency (80%). As a result, it has higher production efficiency than the
goose.
Fish: lower activity level than birds and low cost of homeostasis due to
ectotherm/poikilotherm/heterotherm thermoregulation. High assimilation efficiency of meat (60-
90%).
Worm: Highest production efficiency because of low activity (surrounded by food resources) and
medium-high assimilation efficiency since it is consuming a rich mix of plant material and microbes.
It is an ectotherm so the energetic costs of homeostasis are relatively low.
2-2. (4 points) Explain why there are no wood eating hummingbirds.
High energetic cost of activity and homeostasis, low assimilation efficiency of wood.
Name: KEY
Page 3 of 9
3-1. Assume that trophic efficiency for phytoplankton-animal energy transfer is 10%,
animal-animal energy transfer is 50%.
a) (5 points) How many kg of phytoplankton would it take to produce 70 kg of
human biomass if that phytoplankton is first eaten by sardines, the sardines
are eaten by tuna, and the tuna is eaten by humans?
70 g human / 0.5 = 140 g tuna, 140 g tuna / 0.5 = 280 g sardines, 280 g sardines/ 0.1 = 2,800
g phytoplankton
b) (5 points) How many kg of sardines would it take to produce 70 kg of human
biomass if the humans ate the sardines directly? How many kg of
phytoplankton if the humans ate the phytoplankton directly?
70 g human / 0.5 = 140 g sardines
70 g human / 0.1 = 700 g phytoplankton
3-2. (5 points) On a recent trip to the north, you are startled by a rat scurrying across the
snowy surface of a parking lot; you do not see it at first because its creamy white fur
blends almost perfectly with the snow. How would you determine if the rat’s white
fur is an acclimation to the snowy conditions?
An acclimation is a reversible physiological change that helps to maintain the functioning of
the organism in changed environmental conditions. Watch the rat over time and see if its coat
color changes as the snow melts and the dark tarmac is revealed or some other activity that
determines whether coat color is a reversible change that is related to the environment.

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Description
Name: KEY Page 1 of 9 Instructions: --Write your name on all the pages --Make sure that all 9 pages are attached. --You may not use calculators or other electronic aids. The math needed to solve a problem should be relatively simple. If you can't do the math, just show what needs to be calculated (e.g., "answer = .5 x .3") --If you get hung up on a problem, skip it; return to it after you’ve answered the “easy” problems. GENERAL ECOLOGY PCB 3034/4044 Spring 2008 EXAM 2 PAGE POOSNIBLE SCORE 1 2 _____ 2 12 _____ 3 15 _____ 4 8 _____ 5 11 _____ 6 13 _____ 7 10 _____ 8 17 _____ 9 12 _____ _____ _________ TOTAL 100 _____ (2 points): 1) Are you interested in being an undergraduate TA for this course next year? ( YES, NO ) 2) From where/whom did you take Intro Bio (Ecology): e.g., “UF, Dr. Palmer”: ________ Name: KEY Page 2 of 9 2-1. a. (4 points) Rank the following animals in order of lowest to highest production efficiency. Also indicate lowest and highest with words. __4___worm that eats decomposing plant material (Highest) __3___fish that eats other fish __1___goose that grazes on wetland grasses (Lowest) ___2__chicken that eats grain b. (4 points) Explain your ranking for each organism in relation to its (1) activity level, (2) assimilation efficiency of food resources and (3) thermoregulation. Goose: Lowest production efficiency because it has a high activity level (grazing, flying, escaping predators, migrating in search of food resources),a high cost of homeostasis since it is an endotherm/homeotherm, and it is consuming grasses, a food resource that has relatively low assimilation efficiency (60-70%). Chicken: Like the goose, it has a high activity level (finding grain, flying, escaping predators, “the pecking order”) and is an endotherm. Unlike the goose, it is consuming a food resource with a relatively high assimilation efficiency (80%). As a result, it has higher production efficiency than the goose. Fish: lower activity level than birds and low cost of homeostasis due to ectotherm/poikilotherm/heterotherm thermoregulation. High assimilation efficiency of meat (60- 90%). Worm: Highest production efficiency because of low activity (surrounded by food resources) and medium-high assimilation efficiency since it is consuming a rich mix of plant material and microbes. It is an ectotherm so the energetic costs of homeostasis are relatively low. 2-2. (4 points) Explain why there are no wood eating hummingbirds. High energetic cost of activity and homeostasis, low assimilation efficiency of wood. Name: KEY Page 3 of 9 3-1. Assume that trophic efficiency for phytoplankton-animal energy transfer is 10%, animal-animal energy transfer is 50%. a) (5 points) How many kg of phytoplankton would it take to produce 70 kg of human biomass if that phytoplankton is first eaten by sardines, the sardines are eaten by tuna, and the tuna is eaten by humans? 70 g human / 0.5 = 140 g tuna, 140 g tuna / 0.5 = 280 g sardines, 280 g sardines/ 0.1 = 2,800 g phytoplankton b) (5 points) How many kg of sardines would it take to produce 70 kg of human biomass if the humans ate the sardines directly? How many kg of phytoplankton if the humans ate the phytoplankton directly? 70 g human / 0.5 = 140 g sardines 70 g human / 0.1 = 700 g phytoplankton 3-2. (5 points) On a recent trip to the north, you are startled by a rat scurrying acr oss the snowy surface of a parking lot; you do not see it at first because its c reamy white fur blends almost perfectly with the snow. How would you determine if the rat’s white fur is an acclimation to the snowy conditions? An acclimation is a reversible physiological change that helps to maintain the functioning of the organism in changed environmental conditions. Watch the rat over time and see if its coat color changes as the snow melts and the dark tarmac is revealed or some other activity that determines whether coat color is a reversible change that is related to the environment. Name: KEY Page 4 of 9 4-1. A student doing an independent project (Zoo 4905) monitored Daphnia growth in a lake, and based on their performance was able to describe how the per capita growth rate varied as a function of density. Her data are shown below. 0.4 0.2 0 (per week)464 11 -0.2 -0.4 Per Capita Growth Rate, dN/Ndt Daphnia Density (no. / 10 ml) a) (4 points) Given enough time, to what density will the population converge if initiated at the following densities: Final Density N 0= 1 0 N 0= 3 11 N 0= 7 11 N 0= 14 11 b) (4 points) Give a biologically plausible explanation for this hump-shaped function. Possible answers: The increase arises from a positively density-dependent factor, such as social facilitation of reproduction, feeding facilitation (Daphnia increase food quality by feeding), or predator satiation (or handling time). The decrease arises from a negatively density-dependent factor, such as competition for food (it also could represent the increase incidence of dis ease or an increase in predation caused by a habitat or diet shift in predato rs that target Daphnia as their density increases). Name: KEY Page 5 of 9 5-1. (3 points) Dr. I.M. Green followed a cohort of plants through time, and at each point in time, recorded the number of survivors. (note the logarithmic scale). 100 10 Number still alive 0123456789 01 age (or time) Which of the following statements is correct (circle the correct one)? i. Younger plants have a higher annual survival probability than older plants ii. Older plants have a higher annual survival probability than younger plants iii. Young and old pl
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