Zoo/Bot/FWE 460: General Ecology Exam 1

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Zoo/Bot/FWE 460: General Ecology

Exam 1

Jun 8, 2023

Please read the instructions below carefully.

This exam is open book, and you may collaborate with your classmates. However, I expect that all the answers you turn in will be your own, and I will be reviewing exams for evidence of plagiarism. All exams are due via Canvas on Jun 8 by 11:59pm. The course late policy will be applied to exams turned in late.  

● Download the Answer Sheet and use it to type in your answers to all questions below.

● You must submit your completed Answer Sheet as a word document (.doc, .docx) or pdf. 

● Write concisely and briefly. Points will be deducted from correct answers that include irrelevant information or incorrect parts. 

● For calculations, round to 4 decimal places for all intermediate calculations. Your final answer should be rounded to the nearest two decimal places.

● You must show all work for full credit on calculations.

PART I – Instructions: Circle the letter that is the best answer.

Multiple Choice Questions (3 points each – 45 points total): 

 

1. The figure above shows tree height at different elevations from a mountain range from an observational study. Using just the information presented, which of the following statements is true?

a. Both panels depict the same strength of relationship between elevation and tree height because their slopes are the same.

b. Both panels show that tree height is higher at lower elevations.

c. Panel 1 shows a stronger relationship between elevation and tree height.

d. These panels show a causative relationship between elevation and tree height.

e. Both b. and d.

2. You spend a field season observing a colony of Meerkats in Botswana and record their behaviors. You observe that some Meerkats will stand guard and give a warning call to others in the group. As a result of the warning calls, the other Meerkats in the group have higher survival and reproduction because they are less likely to be preyed upon. The guarding Meerkats are the last to take cover when a predator appears while giving their warning call, making them more likely to be preyed upon than others in the group. Which of the following describes the behavioral interaction between the guarding Meerkats and those in the rest of the group?

a. Cooperation

b. Altruism

c. Spitefulness

d. Selfishness

e. None of the above

3. Which of the following management programs would you expect to have greatest impact on sea turtle population dynamics given the findings of Crouse et al. 1987?

a. Capturing and relocating raccoons that eat turtle eggs on nesting beaches.

b. Higher fines for catching juvenile turtles while shrimp trawling.

c. Harsher criminal punishment for poachers killing mature turtles for shells.

d. Stopping human development on and near nesting beaches.

e. A captive breeding program that releases newly hatched turtles to the wild.

4. The difference between the fundamental niche of a given species and its realized niche can be explained by:

a. Biotic interactions that limit the species’ distribution.

b. The species’ physiological tolerance to abiotic factors.

c. The ability of the species to disperse.

d. Both a. and c.

e. All of the above.

5. You find the following population growth rates for different species of treefrogs across the world, some of which breed discretely and others of which breed continuously:

Treefrog Species 1 λ = 0.75

Treefrog Species 2 r = 0.5

Treefrog Species 3 λ = 1.64872

Treefrog Species 4 r = -0.05

Using this information, which of the following is true?

a. Treefrog Species 1 is growing faster than Treefrog Species 3.

b. Treefrog Species 4 is changing faster than Treefrog Species 1.

c. Treefrog Species 1 and 3 have the same population growth rate.

d. Treefrog Species 4 is the only population that is declining.

e. Treefrog Species 2 and 3 have the same population growth rate.

6. According to the exponential growth model, which would increase a population’s doubling time?

a. A decrease in the initial population size.

b. An increase in the initial population size.

c. An increase in the intrinsic growth rate.

d. A decrease in the intrinsic growth rate.

e. A decrease in both the initial population size and the intrinsic growth rate.

7. For a given population, if r remains constant over time

a. the population will increase exponentially.

b. the population will increase logistically.

c. the population will remain at its current size.

d. the population will display discrete exponential growth.

e. There is not enough information to predict population growth.

8. Consider a situation in which overharvesting causes the number of fish in a population to become drastically smaller, which causes genetic variation in that fish to decrease over a few generations. This is an example of

a. directional selection.

b. recombination.

c. isolation by distance.

d. the bottleneck effect.

e. the founder effect.

9. Human populations in nations that have not undergone the demographic transition are characterized by

a. a greater percentage of women than men.

b. low birth rates and low death rates.

c. high birth rates and low death rates.

d. a greater percentage of individuals in younger age classes.

e. None of the above

10. A wildlife biologist measured song sparrow size in before and after an intense storm in Rhode Island in 1898. He found that the sparrows that survived the storm were more likely to be of intermediate size than sparrows that had perished from the storm. This is most likely an example of:

a. Disruptive selection.

b. Directional selection.

c. Stabilizing selection.

d. Both a. and b.

e. None of the above.

11. Imagine the sparrows from the question above experienced the introduction of a new predator. This predator prefers to catch the largest sparrow possible but is unable to catch the largest sparrows. Over many generations of sparrows, this would likely result in:

a. Directional selection.

b. Disruptive selection.

c. Stabilizing selection.

d. Both a. and b.

e. None of the above.

12. Which of the following examples are LEAST likely to show some form of “Universal Law”, or generalizable pattern, as described in Lawton 1999?

a. a single species of bacteria growing in new media

b. the number of reptile species observed in habitats of increasing size

c. the position of global biomes in relation to annual precipitation and temperature

d. the community structure of fish species in lakes across Wisconsin

e. All of the above are equally likely to show a “Universal Law”

13. If a population of butterflies is under strong natural selection favoring large wings but there is no genetic variation for wing size, what do we expect to occur in the next generation?

a. Wings will evolve to be smaller.

b. There will be no evolutionary change in wing size.

c. Wings will evolve to be larger.

d. Wings will evolve to be more variable.

e. We can’t be sure how the wing size will evolve.

14. A sink habitat patch in a metapopulation is best characterized by

a. local birth rates less than local death rates

b. a net loss of individuals from the population

c. high connectivity with neighboring habitat patches

d. emigration rates greater than immigration rates

e. logistic population growth within the patch

15. Which of the following best defines survivorship (l_x)?

a. the likelihood that an individual survives from birth to a particular age or stage class

b. the likelihood that an individual survives between two consecutive age or stage classes

c. the likelihood that an individual dies within a particular age or stage class

d. the likelihood that an individual gives birth during a particular age or stage class

e. the average number of offspring an individual produces over the course of their lifetime

PART II -

True/False. (3 points each – 15 points total)

Instructions:  For each underlined prompt, circle T for True statements and F for false statements. Include a short sentence explaining why you picked T or F.

16. The field of microevolution studies genetic differences within a single species. T or F

17. A cohort life table, like that used by Peter and Rosemary Grant in their study of Darwin’s finches, is based on counting the number of individuals in a population in various age or stage groups at a single point in time. T or F

18. The behavior of organisms is subject to natural selection. T or F

19. Evolution by natural selection requires genetic variation, heritability of traits, and non-random mortality or fecundity between traits. T or F

20. If a population with an age-structure with a high proportion of young were to instantly reduce its growth rate to the replacement rate (2 children per woman), the population would eventually stabilize at its current size. T or F

PART III – SHORT ANSWER AND PROBLEM SETS

(See Instructions on page 1 – 40 points total)

21. (6 points) Many subpopulations of the Glanville fritillary butterfly are found on islands in the Baltic Sea. The butterflies are present on 20 of 25 islands in an archipelago, where all islands are suitable habitats with identical resources. The local colonization and extinction rates of the population are 60% and 15%, respectively. Is the population of Glanville fritillaries growing, stable, or declining? Explain your answer and show all your work for full credit. 

Use the metapopulation equation dp/dt = c(1-p) – ep , where p = 20/25 = 0.8, c=0.6, e=0.15

dp/dt = 0.6*(1-0.8) – (0.15*0.8) = 0

The population is stable bc dp/dt = 0, there are the same number of occupied patches

1 pt for model, 1 point for correct values for p, c, & e, 2 pts for correct value of dp/dt, 2 pts for interpretation with reason.

22. As discussed in lecture, testicle size relative to body weight varies greatly among species of primates

a. (2 points) Which mating system would be most likely to favor the evolution of large testicles (one word, be specific!)? ____promiscuity/ (1 pt for polyandry)____

b. (2 points) Explain your answer to part a.

In situations where females mate with multiple males, there is a strong likelihood of sperm competition between males. To increase fitness, selection would increase sperm output (and hence testicle size) relative to other males to increase chances of being the father of offspring following mating.  

c. (2 points) Which mating system would be least likely to favor the evolution of large testicles (one word, be specific!)? ___polygamy/monogamy_________________

d. (2 points) Explain your answers to part c. 

In a monogamous (or polygamous) mating system, where females only mate with one male, there will be no selection for increased sperm output since males do not compete with each other after access to mates has been established.

23. Killer whale females experience a long, slow physiological decline, and continue to live long after their last reproductive event.

a. (2 points) What is this long, slow physiological decline called? ___ Senescence _____

b. (3 points) In 1-2 sentences, describe which aspects of the killer whale’s life history that likely cause this extended decline? 

Post-reproductive killer whale females often lead their pods to food resources, especially in years where resources are lacking; this leadership shows that these elder females possess ecological knowledge that can be shared with her pod.  This leadership is especially important for male whales, which have higher reproductive output than females, and have increased mortality in years after their mothers pass away. Thus, by helping sons, the mother orcas are increasing their lifetime fitness.   Points were taken off if you did not specify what the female orca’s had knowledge of (food resources) or how their overall fitness was improved (by assisting with male offspring).

24. The eastern gray treefrog lives in Wisconsin forests, while the related Cope’s gray treefrog lives in prairies. These species are our most common treefrogs, and are reproductively isolated from each other by calls and chromosome numbers. Each breeds in ponds; tadpoles feed on algae and metamorphose into adults that live and feed on small insects in the adjacent uplands, clinging to vegetation via suction pads on their toes. Outline two qualitatively different hypotheses (relying on different mechanisms that constrain species distributions) that might account for the different distributions of these species. Describe a simple experiment/(s) or observational study that would allow you to test each hypothesis. 

Hypothesis 1 (2 pts): Hypotheses can vary, but they should deal with one of the 4 mechanisms constraining species distributions that we discussed in class: dispersal limitation, habitat selection, physiological tolerance, and biotic interactions.  As practiced in the homework assignments, the hypothesis should be clear, concise, and testable.  3 points lost if the second hypothesis addresses the same mechanism as the first. 

Experiment 1 (3 pts): The experiment should clearly address the proposed hypothesis, and be able to distinguish between the different factors that can limit species distributions. Many answers accepted. Points lost if the experiment did not address the hypothesis, or if it was not explained well.

25. You are interested in comparing per capita population growth rates for White-tailed Deer populations in Dane vs. Vilas Counties in Wisconsin. This species breeds once a year, and for simplicity’s sake you can assume that resources are unlimited. The Department of Natural Resources estimates that Dane County’s deer population was approximately 22,300 in 2018 and 26,200 in 2020. You also have data from the population of deer in Vilas County, which shows that the population size in 2017 was 14,700 and 18,300 in 2020.

a. (8 points) Use the correct population model to calculate the geometric rates of increase for the populations of White-tailed Deer in Dane County and Vilas County. You must calculate the yearly geometric rate of increase, as the populations were sampled over different timespans. Which population is growing faster? Show your work, including the correct equation.

The correct population model to use in both cases is the discrete exponential model:

N_t = N₀ λ^t N_t = N₀ λ^t

For Dane County: For Vilas County:

N_t = 26,200; N₀ =22,300;  t=2 N_t = 18,300; N₀ =14,700;  t=3

26,200 = 22,300 * λ² 18,300 = 14,700 * λ³

sqrt(26,200/22,300) = λ 3rt(18,300/14,700) = λ

λ_Dane = 1.084 λ_Vilas = 1.075

Dane is growing faster bc λ_Dane = 1.084 > λ_Vilas = 1.075, would also accept they are approximately equal as an answer if numerical values correct

2 points for correct model, 2 pts for work, 1 point for each correct lambda value. Up to 4 points total if the incorrect population model is used (e.g. r used instead of lambda), but calculations are accurate. 2 pt for stating which population is growing faster.  

b. (3 points) Calculate the doubling time for the population of White-tailed Deer in Dane County.