Critique the research article by answering the questions contained in the "Critique Form" in Unit 3 of the Course Units. When you submit your answers, be sure to label each answer with the corresponding question label on the "Critique Form" (thus, the answer to question "1a" will be labelled "1a"). Since a critique is based on opinion, most of the questions require you to "justify" or "explain" your answers. Thus, there are often several acceptable answers to a particular question, and most of the marks for a question will be assigned to your justification or explanation.
Before you begin your critique, review the following guidelines:
x The "Critique Instructions" at the end of Unit 3 in your Course Units
x The following article in your printed Course Readings:
Fitzgibbon, C. D., & Fanshawe, J. H. (1988.) Stotting in Thomson's gazelles: An honest signal of condition. Behavioral Ecology and Sociobiology, 23, 69-74.
x The sample critique of the above article (end of Unit 3 in your Course Units)
These three readings will remind you of what is expected in your critique.
Part B: Short Answer Questions
1. A badger living in Oklahoma could hunt for either scorpions or ground squirrels (or both). Scorpions provide only 10 calories each, but require only 2 minutes to find, on average, with an additional 3 minutes to remove the stinger; ground squirrels offer 1000 calories, but take an average of 3 hours to find and an additional 90 minutes to capture, kill, and consume. If the badger's ultimate goal is to maximize its rate of caloric gain, should it forage for squirrels, scorpions, or both? Show your math.
2. A hummingbird species feeds almost exclusively on the nectar of Heliconia flowers. Each hummer has a circuit that takes it from one plant to another, with the bird showing up regularly at a given flower after a set period. It could be 30 minutes more or less to do the roundtrip.
a. In one sentence, explain why this statement could be wrong:
"The bird is behaving optimally because it is getting more energy than it is expending on the foraging trips."
b. I want to collect information in order to determine if the bird is really foraging optimally in an energy gathering sense. What aspects of its foraging behaviour would I need to know and measure in order to calculate the net caloric gain for the foraging hummer?
c. Hummingbirds have been observed to hesitate before inserting their beaks into heliconia flowers to feed. How might this hesitation still be consistent with an optimal foraging hypothesis?
3. If I were to say that pelicans do not fly in V formation because of the energy savings it provides but because solitary birds are attracted to flying groups where they can sense the updrafts created by the birds in front of them, you would tell me that I:
a. Had provided a true alternative to the energy savings hypothesis.
b. Had provided an example of an illegitimate use of the comparative method.
c. Was mistaken in thinking that a proximate hypothesis could replace an ultimate one.
d. Did not need the attraction hypothesis because the energy savings hypothesis was correct.
4. "The activity of N2RB gene declines in older mice and causes a decline in learning ability." Some have suggested that this is beneficial because it means older mice cannot forage as efficiently as they once did, which frees up resources for the next generation. This hypothesis is based on group selection because:
a. It deals with two populations, older and younger mice, rather than one species as a whole.
b. The trait of interest is said to have features that reduce the reproductive success of some individuals.
c. The trait of interest is said to cause individuals to sacrifice some reproductive opportunities in order to help another generation of mice to grow and reproduce.
d. Individuals with this kind of gene have already reproduced.
5. "An alternative explanation for the decline in gene activity and poorer foraging success of older mice is that as they get older, their brains begin to deteriorate. They are not foraging poorly and dying in order to let the next generation have a chance to reproduce; these features are simply side effects of old age." The two hypotheses in this paragraph are:
a. True alternatives.
b. Probably both false.
c. Examples of two different levels of analysis.
d. Based on two different theories, group selection and natural selection.
6. If I were to say that the decline in learning ability was due to the benefits of improved reproduction early in life for individuals with one copy of the N2RB gene, this would be an example of a:
a. Group selectionist hypothesis
b. By?product of an adaptation hypothesis
c. Maladaptation hypothesis
d. Sexual selectionist hypothesis
7. "If a mutation were to occur in which the N2RB gene doubled, so that individuals carried two copies of the gene instead of one, these individuals would be guaranteed to live longer and reproduce more because they could learn better into the later part of life."
a. This statement is probably false because it considers only the benefits of the extra copy of the gene, not the fitness costs.
b. This statement is probably false because these individuals would interfere with turnover in the population, a necessity for evolution by natural selection.
c. This statement is surely true because better learners would remember where to find food better, and so could survive better.
d. This statement is probably true because the gene product of N2RB has an effect on the functioning of brain cells.
Part C:
Questions
1. In Belding's ground squirrels and many other mammals, young males disperse while young females remain on or near their natal territory,
but this pattern is exactly reversed in most birds. Why might this be so? In producing your hypotheses, consider the fitness value of a territory to a typical male and female mammal and a typical male and female bird.
2. Todd Shelly did an experiment with the Mediterranean fruit fly, a lekking species, in which he placed two cups with wire mesh tops containing different numbers of males in a coffee bush [1092]. After the cups were in position, he released 400 females in another coffee bush about 10 meters away. He then counted, at 10?minute intervals, the number of males in each cup releasing pheromones (signalling males evert an abdominal pheromone gland) and the number of females perched on or near each cup. Each trial lasted 80 minutes, and he did 30 trials in all. The data he collected are presented in Figure 11.39 in the textbook. Reconstruct the science underlying this research, working from the graphs in whatever direction makes sense until you have the causal question, hypothesis, prediction, test, and scientific conclusion. You should be able to relate the work to one of the hypotheses described in this section on why males aggregate at leks.
3. In their classic paper on mating systems, Steve Emlen and Lew Oring suggested that two ecological factors could promote the evolution of monogamy: a high degree of synchrony in reproductive cycling within a population and a highly dispersed distribution of receptive females.
Try to reconstruct the logic of these predictions and then make counterarguments to the effect that synchronized breeding could facilitate acquisition of multiple mates while a relatively dense population of receptive females might actually promote monogamy.