Review evidence that the El Niño Southern Oscillation significantly influences populations around the globe. Much of our discussion in chapter 23 focused on the effects of the El Niño Southern Oscillation on populations. Considering our discussions in chapters 18 and 19 of physical controls on rates of terrestrial primary production and decomposition, how does the El Niño Southern Oscillation likely affect these ecosystem processes in Australia or the American Southwest? How would you test your ideas?
> Ecologists often ask questions about observed frequencies of individuals in a population relative to some theoretical or expected frequencies. For example, an ecologist studying the nesting habits of Darwin’s finches may be interested i
> In chapter 1, we reviewed the roles of questions and hypotheses in the process of science. Briefly, we considered how scientists use information to formulate questions about the natural world and convert their questions to hypotheses. A hypothesis, we sa
> Imagine sampling a population of plants or animals to determine the distribution of individuals across the habitat. One of the most basic questions that you could ask is, “How are individuals in the population distributed across the stu
> As we have seen, the extent to which phenotypic variation in a trait is determined by genetic variation affects its potential to evolve by natural selection. In other words, the potential for a trait to evolve is affected by the trait’s
> What advantage does advertising give to noxious prey? How would convergence in aposematic coloration among several species of Müllerian mimics contribute to the fitness of individuals in each species? In the case of Batesian mimicry, what are the costs a
> Ecologists are often interested in the relationship between two variables, which we might call X and Y. For example, in chapter 7 we reviewed a study of how the size of pumas, variable X, is related to the size of prey that they take, variable Y (see fig
> The number of observations included in a sample, that is, sample size, has an important influence on the level of confidence we place on conclusions based on that sample. Let’s examine a simple example of how sample size affects our est
> One of the most powerful ways to test a hypothesis is through an experiment. Experiments used by ecologists generally fall into one of two categories—field experiments and laboratory experiments. Field and laboratory experiments generally provide complem
> In chapter 2 we calculated the sample mean and in chapter 3 we determined the sample median. The mean and median are different ways of representing the middle, or typical, within a sample of a population. Another important question we can ask is, how muc
> Throughout this series of discussions of investigating the evidence, we have emphasized one main source of evidence— original research. While original research is the foundation on which science rests, our emphasis has neglected one of
> What conclusion can we draw from the parallel between photosynthetic response curves in plants and functional response curves of animals?
> Why are plants such as mosses living in the understory of a dense forest, which show higher rates of photosynthesis at low irradiance, unable to live in environments where they are exposed to full sun for long periods of time?
> In type 3 functional response, what mechanisms may be responsible for low rates of food intake—compared to type 1 and type 2 functional response—at low food densities?
> Why are all the endothermic fish relatively large?
> Can behavioral thermoregulation be precise? What evidence supports your answer?
> What are the relative advantages and disadvantages of being an herbivore, a detritivore, or a carnivore? What kinds of organisms were left out of our discussions of herbivores, detritivores, and carnivores? Where do parasites fit? Where does Homo sapiens
> Why would it be a disadvantage for Encelia farinose (p. 110) to produce highly reflective, pubescent leaves in both hot and cool seasons?
> There is genetic evidence that mating between G. magnirostris and G. fortis (see fig. 13.8) may have helped establish sufficient genetic variation in the population of G. fortis at El Garrapatero for the distribution of beak sizes at that site (see fig.
> Why is rapid, human-induced environmental change a threat to natural populations?
> Why may the history of CFCs in the atmosphere in the years following the Montreal Protocol offer encouragement as humanity strives to reverse the modern buildup of atmospheric CO 2?
> Are there uncertainties remaining regarding global warming?
> What aspects of global warming are widely supported by available evidence?
> What can we conclude from the evidence summarized by figures 23.20 to 23.23? Figures 23.20: Figures 23.23: Continue to next pages………. The concentration of "C in the atm
> What component of species diversity (see chapter 16, p. 360) did Tilman’s research group manipulate in their studies? What other components of species diversity could influence rates of primary production? Continue to next pages
> How can we explain the results of Lubchenco’s manipulation of Littorina populations summarized in figure 17.8? Figure 17.8:
> What was the major limitation of Paine’s first removal experiment involving Pisaster?
> In chapter 7, we emphasized how the C 4 photosynthetic pathway saves water, but some researchers suggest that the greatest advantage of C 4 over C 3 plants occurs when CO2 concentrations are low. What is the advantage of the C 4 pathway when CO2 concentr
> Paine discovered that intertidal invertebrate communities of higher diversity include a higher proportion of predator species. Did this pattern confirm Paine’s predation hypothesis?
> Why is rapid, human-induced environmental change a threat to natural populations?
> Suppose you discover that the fish species inhabiting small, isolated patches of coral reef use different vertical zones on the reef face—some species live down near the sand, some live a bit higher on the reef, and some higher still. Based on this patte
> Can we link increased nutrient availability during the Park Grass Experiment with decreased environmental complexity?
> Does Tilman’s finding that Asterionella and Cyclotella exclude each other under certain conditions but coexist under other conditions violate the competitive e xclusion principle (see chapter 13, p. 286)?
> Both mathematical and laboratory models offer valuable insights into the dynamics of predator-prey systems. What are some advantages and limitations of each approach?
> According to Keller’s theory, under what general conditions would the mutant Helianthella quinquenervis, lacking extrafloral nectaries, increase in frequency in a population and displace the typical plants that produce extrafloral nectaries?
> Suppose you discover a mutant form of Helianthella quinquenervis that does not produce extrafloral nectaries. What does Keller’s theory predict concerning the relative fitness of these mutant plants and the typical ones that produce extrafloral nectaries
> Why is it not surprising that snowshoe hare populations are controlled by a combination of factors, food and predators (see fig. 14.15), and not by a single environmental factor? Figure 14.15:
> When the coupled cycling of lynx and snowshoe hare populations (see fig. 14.14) was first described, many concluded that lynx control snowshoe hare populations. Why are lynx not the primary factor controlling snowshoe hare populations even th
> In what kinds of environments would you expect to find the greatest predominance of C 3 , C 4 , or CAM plants? How can you explain the co-occurrence of two, or even all three, of these types of plants in one area?
> Is there any way that predators could alter the outcome of competition as shown in figure 13.14 a, where species 1 excludes species 2, and in figure 13.14 b, where species 2 excludes species 1? Figure 13.14:
> Can we conclude that interspecific competition commonly restricts species to realized niches in nature, based on the results of mathematical models and laboratory experiments?
> Paramecium aurelia and P. caudatum coexisted for a long period when fed full-strength food compared to when they were fed half that amount. What does this contrast in the time to competitive exclusion suggest about the role of food supply on competition
> Why might medium ground finch population responses to short-term, episodic increases in rainfall (see fig. 11.17) differ from their responses to increases in rainfall lasting for years or decades? Figure 11.17:
> Where would you place the following plant species, in Grime’s and in Winemiller and Rose’s classifications of life histories (see figs. 12.20 and 12.21)? The plant species lives in an environment where it has access to
> If a concept, such as r and K selection, does not fully represent the richness of life history variation among species, can it still be valuable to science?
> What appears to set the carrying capacity for medium ground finches on Daphne Major Island?
> Why can we be sure that all animal and plant populations are under some form of environmental control?
> How would human mortality patterns have to change for our species to shift from type I to type II survivorship?
> Female cottonwood trees (Populus species) produce millions of seeds each year. Does this information give you a sound basis for predicting their survivorship pattern?
> Why don’t plants use highly energetic ultraviolet light for photosynthesis? Would it be impossible to evolve a photosynthetic system that uses ultraviolet light? Does the fact that many insects see ultraviolet light change your mind? Would it be possible
> How would substantial emigration and immigration affect estimates of survivorship within a population, where estimates are based on age distributions?
> What does the position of pines along moisture gradients in both the Santa Catalina Mountains of Arizona (see fig. 9.17) and the Great Smoky Mountains of Tennessee (see fig. 9.18) suggest about pine water relations? FigureÂ
> Why might the winter aggregations of crows occur mainly along river valleys?
> What factors might be responsible for the aggregation of American crows in winter (see fig. 9.15)? Figure 9.15: High The American crow, which is very widely distributed, is most abundant in a limited number of "hot spots." Low (a) Withi
> Explain how a Batesian mimic, such as the hoverfly in figure 7.15 b, could evolve, through natural selection, from a nonaposematic ancestor. Figure 7.15b: (b)
> What would you expect to see in figure 8.15 if performance were equal across pollen donors?
> What roles did greenhouse and field studies play in the investigation of mating patterns by wild radish?
> Compare the dietary challenges associated with being a detritivore versus an herbivore. Consider figure 7.14, p. 160. Figure 7.14: Live leaves contain twice the nitrogen as dead leaves. 3 Live Dead Figure 7.14 Nit
> Why do pumas face fewer challenges from the perspective of stoichiometry compared to herbivores, such as deer, on which they prey?
> If you observe no changes in gene frequencies in a population over several generations, can you conclude that the population is not subject to natural selection?
> Ronald Neilson and his colleagues (1992, 1995) used the environmental requirements of plants to predict the responses of vegetation to climate change. In chapter 1, we briefly discussed the studies of Margaret Davis (1983, 1989) that reconstructed the mo
> The body fluids of many freshwater invertebrate species have very low internal salt concentrations. What is the benefit of such dilute internal fluids?
> Why do isosmotic marine invertebrates expend less energy for osmoregulation compared to hypo osmotic marine fish?
> How can we be sure that the two distinctive responses to temperature shown by Atriplex lentiformis were due to acclimation and not the result of genetic differences (see fig. 5.12)? Figure 5.12: Photosynthetic rate of shrubs
> Signs of thermal stress in fish include swimming on their sides and swimming in spirals. Using what you know about temperature and acetylcholinesterase, explain.
> Why does grazing by Littorina on emergent substrata reduce algal diversity?
> Why is the ecological impact of deforestation always greater than the area of forest removed?
> What major pattern do patterns of island diversity and continental diversity have in common?
> Why is reducing forest area through deforestation a fundamental threat to biodiversity?
> Why does the annual rainy season in regions near 23 8 N latitude begin in June?
> How would seasonality in temperature and precipitation be affected if earth’s rotation on its axis were perpendicular to its plane of orbit about the sun?
> Review water and salt regulation by marine and fresh water bony fish. Which of the two is hypoosmotic relative to its environment? Which of the two is hyperosmotic relative to its environment? Some sharks live in freshwater. How should the kidneys of mar
> How does the construction of dams for storing water affect the turnover time for water in rivers?
> The organic horizon is generally absent from agricultural soils because tilling, e.g., plowing, buries organic matter. Why is an organic horizon generally absent from desert soils?
> Why do physiologically tolerant rather than sensitive species inhabit estuaries and salt marshes?
> Why is the prospect of global warming considered a serious threat to coral reefs?
> After years of successful reductions in phytoplankton populations, phytoplankton blooms are on the increase in parts of Lake Erie following the introduction of zebra mussels. Why?
> Are there any potential risks associated with increasing the exchange of individuals between habitat patches through the creation of habitat corridors?
> Habitat corridors are widely recommended for conservation of species whose populations are restricted to isolated patches of habitat. Why?
> What do the patterns shown in figure 21.11 suggest about the relative impact of fragmentation of prairie habitat on populations of Sigmodon, Microtus, and Peromyscus Figure 21.11: During succession, nitrogen, moisture, and organic matter content inc
> How are the biomass accumulation model of Bormann and Likens (see fig. 20.16) and Grimm’s observations of changes in nitrogen retention during succession in Sycamore Creek similar? Figure 20.16: According to
> What would equal levels of nitrogen input and output in the stream reaches (sections) studied by Nancy Grimm indicate?
> While we have concentrated in chapter 6 on regulation of water and salts, most marine invertebrates are isosmotic with their external environment. What is a potential benefit of being isosmotic?
> Why are the changes in soil properties during the course of succession documented by Stuart Chapin and his colleagues ecologically significant?
> How are the results of Suberkropp and Chauvet (see fig. 19.12) and Rosemond (see fig. 19.13) similar? How do their results differ? Figure 19.12: Figure 19.13: Yellow poplar leaves decompose
> Suppose you fertilize a lake with nitrogen only, phosphorus only, and nitrogen plus phosphorus and observe no change in phytoplankton biomass. What is the most likely explanation of your results?
> During the past 30 years, thousands of papers have been published on decomposition within ecosystems. Why have ecologists spent so much time studying decomposition?
> How would the results of the experiment shown in figure 17.7 change if the effect of Brassica nigra on Nassella pulchra were the result of direct competition, with small herbivorous mammals playing no significant role? Figure 1
> Suppose that when you add nitrogen to one-half of a lake, you observe no change in phytoplankton biomass, but when you add phosphorus to the other half of the lake, phytoplankton biomass more than doubles. What is the most likely explanation of your resu
> What distinguishes competition and apparent competition?
> How are competition and apparent competition the same?
> Why did Bertschy and Fox restrict their study to lakes without major inflows or outflows?
> Suppose you sample an area and find the five species of forest trees listed in table 16.1 in the following proportions: 0.35, 0.25, 0.15, 0.15, and 0.10. What is the S hannon-Wiener diversity of this community, c, compared to communities a an
> Many desert species are well waterproofed. Evolution cannot, however, eliminate all evaporative water loss. Why not? (Hint: Think of the kinds of exchanges that an organism must maintain with its environment.)
> Pollution of streams generally reduces the diversity of Trichoptera (see fig. 16.7), and several other groups of stream insects, by reducing both species richness and species evenness. Why? Figure 16.7: These rank
> In terms of costs and benefits, why might corals expel their zooxanthellae when placed in the dark?
> If reef-building corals are placed in the dark, they will expel the zooxanthellae in their tissues. What does this suggest concerning controls on the relationship between corals and zooxanthellae?
> How could you test experimentally for the combined influence of bats and birds on numbers of arthropods on foliage, as well as their individual contributions?
> The patterns shown in figure 14.7 suggest that Helicopsyche depletes its algal food supply. However, Lamberti and Resh were not certain and so conducted their second set of experiments. Why could they not reach a firm conclusion regarding the
> Do resources have to be present in limited supplies for competition to shape species niches?
> The competitive exclusion principle states that two species cannot occupy the same niche indefinitely. What is a fundamental assumption of this principle?
