INSTRUCTIONS: homework answers must be typed in complete sentences in standard grammatically correct English in the concise, informative, straightforward style recommended for scientific writing. Be sure to read the questions carefully and answer all parts to each question. Do not re-state the question in what you hand in, just give your answer. Remember that you must keep one copy of your answer for yourself (and it is a good idea include the question on that one if you want to have the question and answer together for future reference.)
This page will contain all homework questions for the semester. You are expected to do one each week (or, rarely, two; see the syllabus.) Do the question number that is assigned on the syllabus for the week.
HOMEWORK QUESTIONS:
Homework Question #1. (Due 28 August) You sample the proportion of songbird nests that have been parasitized by the brood parasite the brown-headed cowbird in a large number of replicates of three kinds of habitat: dense forest, edge habitat, and open grassland. State an ecological hypothesis that can be tested with these data. State a prediction of this hypothesis that can be tested with these data. Now suppose that you observe what you predicted. Assuming that your data have been taken without any errors, does observing what you predicted mean that your hypothesis is true? Fully explain why or why not.
Homework Question #2. (Due 04 September). In your study (from last week's homework) of cowbirds, you used the following methods: you sampled from six dense forests, six edge areas, and six grasslands. In each location from which you sampled, you searched for bird nests within 30 large quadrats, the locations of which were chosen randomly from within the location. Clearly explain the importance of each of the described methods (sampling from six of each habitat type, sampling from 30 sites within each location, and randomly selecting sites to sample) by explaining what potential errors each method avoids and why they avoid those errors.
Homework Question #3. (Due 11 September). You are interested in studying the food niche axis of several species that occur together in a community. These are: a weasel species and a squirrel species which have the same mass (but the weasel has a more elongate shape), a mouse species which is much smaller than the weasel and squirrel and a frog which has the same mass as the mouse. Rank these species with regard to how much energy they are expected to need to take in for the purpose of thermoregulation. Fully explain, applying geometry as needed, why you have ranked them in this order.
Homework Question #4. (Due 25 September). Eight gypsy moths are inadvertently introduced to a western forest. They grow with a constant per capita growth rate of 0.73 individuals/individual/year. Since the per capita growth rate is constant, what is the appropriate population growth model to use to model this situation? After five years, how many gypsy moths are in the forest? SHOW THE FORMULA YOU USE AND INTERMEDIATE STEPS SO I CAN TELL WHAT YOU DID.
NOTE: The following TWO homework questions (5&6) are BOTH DUE on 02 October
Homework Question #5. (Due 2 October) A small number of house mice are introduced to an island where no house mice previously occurred. The island has many resources and the population begins to grow in a pattern that appears to be exponential growth. Could this really be logistic growth? Justify your answer with a mathematical demonstration of whether or not population growth according to the logistic model shows the same pattern as exponential growth for small populations.
Homework Question #6. (Due 2 October): Base your answer to this question on the assigned reading by Barrett and Odum (2000). (on reserve in the library; also available on line through the ProQuest database available by way of the library's electronic databases web page.) Distinguish between the maximum carrying capacity and the optimum carrying capacity for humans as defined by Barrett and Odum. Upon what is the maximum carrying capacity for humans predicted to depend? Upon what is the optimum carrying capacity for humans predicted to depend? Explain what economic measures Barrett and Odum use to identify the optimum carrying capacity; why do they think this determines the optimum carrying capacity for humans?
Homework Question #7 (Due 9 October): You mark all individuals in a cohort of newly hatched song sparrows in an isolated population with no movement of new individuals into the population or dispersal out of the population so that you know that all individuals who disappear have died and obtain the following information on numbers of these individuals at each of age classes shown: 525 newly hatched individuals, 170 one-year olds, 97 two-year olds, 42 three-year olds, 17 four year olds, zero five-year olds. Use this information to make a life table in which you calculate lx, dx, qx, and kx. SHOW ENOUGH WORK so I can follow what you did.
Homework Question #8 (Due 23 October): In tree swallows, a species of bird that nests in holes, you find that the number of eggs produced per nest (the clutch size) varies. What clutch size (small, intermediate, or large) do you predict will lead to the largest number of surviving offspring per nest? Why? Suppose you find that the average clutch size for the population is slightly smaller than the clutch size that leads to the largest number of surviving offspring per nest. State two hypotheses that would explain why it would be adaptive for individuals to produce clutches that are slightly smaller than the size that leads to the largest number of surviving offspring per nest.
NOTE: The following TWO homework questions (9&10) are BOTH DUE on 30 October
Homework Question #9 (Due 30 October): ANSWER THE FOLLOWING BASED ON THE ASSIGNED PAPER BY Thomas and Hanski (1997; on reserve in the library.) To study metapopulations, it is necessary to be able to describe potential habitat patches even if they are not currently identified by populations. Use the studies of the skipper butteryfly (Hesperia comma) and checkerspot butterfly (Euphydrias editha bayensis) mentioned in Thomas and Hanski (1997; bottom of p. 361) to illustrate the care with which this must be done and the kinds of factors that must be considered. There is bound to be some error in identifying habitat patches when they are empty, but Thomas and Hanski argue (bottom of p. 363) that it is a minor issue for butterfly studies. What evidence from ecological experiments do they present to support the hypothesis that there are empty habitat patches for butterflies?
Homework Question #10 (Due 30 October): You want to know whether a turtle species occurs in discrete demes or not. Explain how to address this question using genetic information and describe predicted results about genetic variation within populations and similarity/difference among populations if the turtles DO occur in discrete demes. Explain why these results are predicted based on the forms of evolution affecting the genetics of populations.
Homework Question #11 (Due 06 November): You are studying the impact of interspecific competition on your favorite species of salamander, Newtus cutus. You suspect it is affected by a potentially competing salamander species Newtus brutus. You are interested in acb, (c stands for N. cutus and b stands for N. brutus). Define acb. Describe an ecologically reasonable way in which they could be interacting that would make acb>1 and an ecologically reasonable way in which they could be interacting that would make acb<1; for each of your proposed ways that they interact, be sure to explain what would make the acb value greater or less than 1.
Homework Question #12 (Due 13 November): You find that in areas where they coexist, Newtus cutus and Newtus brutus use different microhabitats, with N. cutus occurring in areas with more leaf litter and N. brutus occurring in areas with less leaf litter. In areas outside the geographic range of Newtus brutus,where only N. cutus occurs, N. cutus occurs both in areas with high leaf litter and in areas with low leaf litter. You want to test they hypothesis that it is competition with N. brutus that causes N. cutus to use only high leaf litter areas in the regions where they coexist. Describe an exclosure experiment to test this. Describe the appropriate controls and explain why they are needed. Describe the predicted results if your hypothesis is correct. Finally, describe the results predicted by a hypothesis of "the ghost of competition past."
Homework Question #13 (Due 26 November): You hypothesize that a species of weasel is a keystone predator maintaining species diversity in a rodent community. Explain what a keystone predator is and why it would maintain species diversity among prey species. Explain how you could test this hypothesis through a field experiment; include appropriate experimental and control treatments.
Homework Question #14 (Due 4 December): Within an archipelago (group of islands), you find more small mammal species on large islands than on small islands. Explain this based on the MacArthur-Wilson model of island biogeography (make this a complete explanation; you are welcome to include a graph to illustrate the model but need to explain it in words, too.) Then give one alternate explanation for the pattern (based on something not considered in the MacArthur-Wilson island biogeography model)
Homework Question #15. There is no homework question 15 but you can each have one whole point, free of charge, since I said the homeworks were going to add up to 15 points. Don't say I never gave you anything.