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?
> 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
> 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 ch
> 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?
> 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?
> What is a main difference between the study by Bertschy and Fox (1999) and that of Gunderson (1997)?
> What do the GSI values for rougheye rockfish, 0.02, and northern anchovy, 0.65, mean in terms of the body weights of these two fish species?
> Why might a manager of an exploited population, such as a commercially important fish, want to keep fish population size near one-half K and not much lower?
> In the Sonoran Desert, the only insects known to evaporatively cool are cicadas. Explain how cicadas can employ evaporative cooling while hundreds of other insect species in the same environment cannot.
> How could you test the hypothesis that carrying capacity for the Paramecium population shown in figure 11.10 was set by the availability of their main food—yeast cells? Figure 11.10: Growth leveled off afte
> Interpret the pattern of population growth shown by figure 11.11 in terms of the information given in figure 11.14, and discuss the relationship between population size and r (realized per capita rate of increase). Figure 11.11:
> Contrast human influences on metapopulations of the Rocky Mountain Parnassian butterfly versus those of the lesser kestrels of the Ebro River valley.
> The Rocky Mountain Parnassian butterfly tends to disperse from small to large meadows. Why is this direction of movement more advantageous than the reverse?
> Figure 10.11 and the upper portion of figure 21.13 show the relationship between meadow size and population size in two butterfly species. How are the patterns shown by the two graphs similar? How do they differ? (Note 1Â&nb
> In the study of the distribution of stingless bee colonies (see pp. 205–206), why were measurements of the number and distribution of potential nest trees necessary? An individual has an equal probability of occurring anywhere in a
> How could you test the hypothesis that low overlap in root systems in creosote bush populations (see fig. 9.14) is the result of ongoing competition? Figure 9.14: The actual root systems were not circular and If excavated sh
> Are the concepts of “small” versus “large” scale the same for all organisms?
> Which results clearly show the influence of intrasexual selection on male scorpionfly mating success?
> What led Thornhill to conclude that mating success by male scorpionflies is tied to the quality of nuptial offerings presented by males?
> In this chapter, we discussed water relations of tenebrionid beetles from the Namib Desert. However, members of this family also occur in moist temperate environments. How should water loss rates vary among species of tenebrionids from different environm
> What evidence is there that the availability of dead insects for scorpionfly feeding is limited in nature?
> How are water and temperature regulation related in many terrestrial organisms?
> During severe droughts, some of the branches of shrubs and trees die, while others survive. How might losing some branches increase the probability that an individual plant will survive a drought?
> In general, what must be true of the chemical energy of the products of chemosynthesis compared to that of the reactants, for instance, the chemical energy of the product S0 (elemental sulfur) versus that of the reactant H 2 S shown in figureÂ&nbs
> The tiger beetle Cicindela oregona (see figs. 6.15 and 6.16) has a distribution that extends from Arizona through the temperate rain forests of Alaska. Why should the amounts of cuticular hydrocarbons vary geographically among populations of
> How might immigration oppose the effects of genetic drift on genetic diversity in a small population?
> If your research team obtained the hypothetical results described in question 1, what could you conclude about the principle of allocation?
> If growing lines of Escherichia coli at 20 8 C for 2,000 generations increased their fitness at 20 8 C without reducing their fitness at 40 8 C, how would the distribution of points in figure 5.7 change? Figure 5.7:
> How does highly selective mating by females (for example, see fig. 8.10) affect the potential for Hardy-Weinberg equilibrium? Figure 8.10:
> Why is genetic drift more probable in small populations than in large populations?
> Compare the water budgets of the tenebrionid beetle, Onymacris, and the kangaroo rat, Dipodomys, shown in figures 6.9 and 6.10. Which of these two species obtains most of its water from metabolic water? Which relies most on condensation of fo
> In the course of studies by Simberloff and Wilson (1969) and Simberloff (1976), several mangrove islands were defaunated and several were partially destroyed to reduce island area. Do such experiments raise ethical issues?
> What result would have been grounds for Diamond to reject the equilibrium model of island biogeography based on his studies of the California Channel Islands (see fig. 22.10)? Figure 22.10:
> Why are virtually all estimates of immigration and extinction rates on islands underestimates of the true rates?
> How will global warming affect the proportion of the earth’s water that resides in the oceans?
> What are two ways in which the cutting of tropical forests and replacing them with lower productivity cattle pastures affect the global carbon balance?
> In figure 22.7, the number of mammal species on the isolated mountain ranges varies greatly for a given distance from large montane areas, for instance, at a distance of 150 km. What is the likely source of much of this variation? Fig
> In chapter 21 we discussed the influences of habitat fragmentation from the perspective of populations (see figs. 21.11 and 21.12). Drawing from the information in this section, how do you think fragmentation will affect species richnessâ€
