Question: In chapter 21 we discussed the influences
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 richness—for instance, the number of bird species living in forest fragments? Figure 21.11: 
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> 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
> What are the primary mechanisms producing the great differences in succession rates in forests, rocky intertidal, and stream communities?
> In the landscapes shown in figure 21.4, what is patch and what is matrix? Figure 21.4:
> Why do primary forest succession at Glacier Bay and secondary forest succession in the Southeastern United States occur at such different rates (compare figs. 20.2 and 20.4)? Figure 20.2: Figure 20.4: Continue
> Leaf water potential is typically highest just before dawn and then decreases progressively through midday. Should lower leaf water potentials at midday increase or decrease the rate of water movement from soil to a plant? Assume soil water potential is
> What are the relative fluxes of nitrogen through fixation and denitrification on land and in the oceans (see fig. 19.3)? Figure 19.3: Annual N fixation slightly exceeds denitrification. Annual N fixation by lightning is smal
> Do the oceans act as a source or a sink for phosphorus (refer to fig. 19.2)? Figure 19.2: Pmoving from land to atmosphere Human movement of P from terestrial to fresh- water ecosystems Atmospheric deposition of P onto land Au
> How would actual evapotranspiration and net primary production in the desert dune ecosystem, which is a hot desert, and the arctic and alpine tundra ecosystems likely respond to a significant increase in precipitation?
> How are the desert dune ecosystem and the arctic and alpine tundra ecosystems indicated in figure 18.2 the same? Figure 18.2: Terrestrial primary production increases with actual evapotranspiration. 3,200- Tropical forest 1,6
> Why was precipitation alone, without temperature, sufficient to account for most of the variation in grassland net primary production across central North America (see fig. 18.3)? Figure 18.3: Primary production in grassland
> In what other main way did Tscharntke simplify his study of trophic interactions in the wetland along the Elbe River?
> What was the primary way by which Tscharntke simplified the food web representing the interactions of blue tits and feeding on insects living on the wetland reed Phragmites australis (see fig. 17.5)? Figure 17.5: Identifying the stro
> What are the main advantages of including only strong linkages in a food web?
> In Inouye and Taylor’s study, why wasn’t the comparison of seed predation on plants naturally with and without ants sufficient to demonstrate the influence of ants on rates of seed predation?
> Why did the massive sampling efforts associated with the moth collections shown in figure 16.4 reveal only a portion of the lognormal distribution, while the studies of birds and plants produced the nearly complete lognormal distributions sho
> Distinguish among vapor pressure deficit, osmotic pressure, and water potential. How can all three phenomena be expressed in the same units of measure: pascals?
> Why do smaller samples result in only part of the bellshaped curve that is characteristic of the lognormal distribution?
> Why did Johnson’s control consist of a sterilized mixture of soils from the fertilized and unfertilized study areas?
> Why did Johnson create her inocula by mixing sterilized and unsterilized soils from the fertilized and unfertilized study areas?
> Large darter species produce larger numbers of smaller eggs compared to smaller darter species (see figs. 12.3 and 12.4). Consequently, would you expect to find more genetic differences along the length of a river system among small darters or large dart
> How did Moore’s laboratory and field experiments complement each other?
> Why did Moore conduct “blind” behavioral observations— that is, without knowing whether individual Armadillidium was infected or not?
> How might using other indicators of competition, such as growth rate, reproductive rate, and size at maturity, have affected Grosholz’s conclusions regarding lack of food limitation in his study populations?
> Do you think that Grosholz might have observed food limitation if he had used higher densities of Porcellio scaber in his experiments?
> Why did Jakobsson and Eriksson (2000) conduct their study of the relationship between seed size and seedling size in a greenhouse?
> Why did Westoby, Leishman, and Lord (1996) include five floras on three continents in their study?
> The body temperature of the seashore isopod Ligia oceanica is 30 8 C under stones, where the relative humidity is 100%, but 26 8 C on the surface, where it is exposed to full sun and the relative humidity is 70%. Edney (1953) proposed that the isopods in
> What changes in sea surface temperatures and atmospheric pressures over the Pacific Ocean accompany El Niño? What physical changes accompany La Niña? How do El Niño and La Niña affect precipitation in North America, South America, and Australia?
> African annual killifish live in temporary pools, where their populations survive the dry season as eggs that lie dormant in the mud, developing and hatching only when the pools fill each wet season. In contrast, the guppy, a common aquarium fish, lives
> Why do many populations of exotic species, such as zebra mussels in the Great Lakes (see fig. 3.41b) or Eurasian collared doves in Europe, often grow at exponential rates for some time following their introductions into a new environment? Figure 3.41b:
> What was the major assumption underlying Bennett’s (1983) use of pollen deposited in lake sediments to estimate the postglacial population size of Scots pine?
> What do female guppies potentially gain by mating with colorful males?
> Ecologists who have used clear plastic sheets coated with adhesive to trap the adults of aquatic insects flying over rivers have found that the side of the sheets facing downstream generally traps more of the flying adults than the upstream-facing side.
> Why might a species, such as the Eurasian collared dove, be less threatened by rapid climate change than hemlock or maple trees?
> How might biological and physical aspects of the environment interact to influence a species’ geographic distribution?
> How may a species respond to climate change?
> In Endler’s field experiment (see fig. 8.6), why did male colorfulness increase in the absence of effective predators and not just remain unchanged? Figure 8.6: Experimental design Two hundred guppies transferred from high predati
> Why did John Endler take great care to put the same colors of gravel in the same proportions into all of his greenhouse ponds (see fig. 8.5)? Figure 8.5: Experimental conditions No predation Guppies only High predation Low predation Rivulus Pike ci
> In most of the examples discussed in chapter 5, we saw a close match between the characteristics of organisms and their environment. However, natural selection does not always produce an optimal, or even a good, fit of organisms to their environments. To
> Why does the ongoing increase in atmospheric CO 2 (see chapter 23, fig. 23.21) not give guaranteed advantage to C 3 plants over C 4 plants? Figure 23.21: 350 Atmospheric CO, began to increase exponentially in the middle 1800s. 300 250 • Mauna Loa O
> How are C 4 and CAM photosynthesis similar? How are they different?
> What environmental conditions favor plants with C 3 photosynthesis? Why?
> Why are water potentials in nature generally negative?
> Which has a higher free energy content, pure water or seawater?
> Why are the two curves shown in figure 6.2 so similar? Figure 6.2: Water vapor in air can be measured either as grams of vapor per cubic meter of air... ...or by the pressure exerted by the water vapor in air. 40 30 20 10 10
> Contrast the microclimates of the aboveground parts of desert plants to that of their roots.
> Why is evaporative cooling by various animal species so effective?
> What advantages might the warm microenvironments of Dryas flowers offer to the insects attracted to them?
> What is a fundamental evolutionary implication of the large amounts of genetic variation commonly documented in natural populations?
> Some plants and grasshoppers in hot environments have reflective body surfaces, which make their radiative heat gain, H r, less than it would be otherwise. If you were to design a tiger beetle that could best cope with thermal conditions on black beaches
> What would you expect to see in figure 4.4 if alpine, mid-elevation, and lowland populations of P. glandulosa were not different genetically?
> Can we be confident that differences in growth within P. glandulosa clones grown at different elevations were not the result of genetic differences? Why?
