Question: Can a dominant species of tree in
Can a dominant species of tree in a forest or coral on a coral reef (see fig. 17.17, p. 386) be an ecosystem engineer? Figure 17.17: 
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Species with low biomass Dominant species are Keystone species are those whose influence but large effects on community structure. on a community is disproportionate to their biomass. ones that have significant influence on community structures by virtue of high biomass. High Keystone species Dominant species (Foundation) Low Low Relative biomass of species High Figure 17.17 What is a keystone species (data from Power et al. 1996)? Total impact of species
> 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?
> The example of El Niño and the Great Salt Lake might lead us to what general conclusion concerning the concepts of top-down and bottom-up control?
> How does the example of El Niño and the Great Salt Lake confound the concepts of top-down and bottom-up control?
> How are the influences of El Niño and La Niña related to the concepts of top-down versus bottom-up control of populations, communities, and ecosystems?
> Why would the soils in tropical rain forests generally be depleted of their nutrients more rapidly compared to the nutrients in temperate forest soils?
> Why do those regions, whether tropical, desert, or temperate, that include high mountains tend to be the most biologically diverse?
> The patterns shown in figure 21.28 support Minnich’s hypothesis that fire protection in southern California would produce a difference in median burn area. However, do these results show conclusively that the differences in burn area in
> Why is there no one factor that seems to explain latitudinal gradients in species diversity?
> The section on avoiding temperature extremes focused mainly on animals. What are some of the ways in which plants avoid temperature extremes? Bring cold and hot environments into your discussion. Some of the natural history included in chapter 2 might be
> How are “landscape engineers” similar to keystone species? How are they different?
> What pattern of colonization by Gigartina in Sousa’s Ulva removal experiment would have been consistent with the facilitation model?
> Suppose Gigartina had colonized the plots where Sousa had removed Ulva and where he had left Ulva in place at the same rates (see fig. 20.21). This result would be consistent with which successional model? Figure 20.21: Rem
> What is the role of disturbance in the Connell and Slatyer succession model (see fig. 20.20)? Figure 20.20: Space available for colonization. Succession begins. Only early successional species can establish. Any species able
> Why might restoration of native plant communities to their original structure be difficult after exotic plants such as Myrica, in Hawaii, have occupied a site for a significant length of time?
> How might nitrogen and phosphorus composition and excretion ratios differ for invertebrate consumers compared to vertebrate consumers?
> The Great Plains of North America once supported bison herds numbering in the tens of millions. How did the near extermination of the bison likely affect nutrient cycling on the Great Plains?
> If plant species richness and functional group composition accounted for one third to two thirds of variation in primary production across study plots, what other f actors likely accounted for the remainder of differences in primary production among plot
> What does the effect of legumes on primary production in the Tilman experiment suggest about other factors limiting production on the experimental plots?
> Can a trait with no heritability, h2= 0, evolve? Explain your answer.
> When we reviewed how some organisms use torpor, hibernation, and estivation to avoid extreme temperatures, we discussed the idea of energy savings. However, organisms do not always behave in a way that saves energy. For instance, when food is abundant hu
> Is the index of resilience used by Valett and his colleagues consistent with the biomass accumulation model of Bormann and Likens?
> How does the combined evidence from studies of the flora of Mediterranean regions (fig. 22.22) and the diversity of trees in temperate forest regions increase confidence that historical differences can outweigh the potential influ
> Why should history have such a strong influence on regional diversity patterns?
> How might taxonomic resolution—that is, how precisely we identify organisms—influence an assessment of community stability?
> What causes community resilience?
> Flood control on streams and rivers has often been cited as a potential threat to populations of aquatic animals and riparian trees that require flooding for reproduction. How might flow regulation also alter stream ecosystem nutrient dynamics?
> What do the results of Likens and Bormann and that of Turner and her colleagues suggest about the role of vegetation in preventing losses of nitrogen in forest ecosystems?
> What major conclusion can we draw from the pioneering experiment by Likens and Bormann?
> Why is it more difficult to obtain evidence for trophic cascades in terrestrial ecosystems such as the Serengeti, compared to the lakes studied by Carpenter and Kitchell?
> Since increased phytoplankton biomass decreases water clarity in lakes, how should increased fishing pressure on the bass population in a lake ecosystem, such as that pictured in figure 18.12, affect lake clarity? Figure 18.12: By reducing plankti
> Butterflies, which are ectothermic and diurnal, are found from the tropical rain forest to the Arctic. They can elevate their body temperatures by basking in sunlight. How would the percentage of time butterflies spend basking versus flying change with l
> In their initial studies, leading to the trophic cascade hypothesis, Stephen Carpenter and his colleagues (1991) found a negative correlation between zooplankton size and phytoplankton primary production. What does this mean (see Investigating the Eviden
> According to the intermediate disturbance hypothesis, could human disturbance sustain higher levels of species diversity than in the absence of human disturbance?
> In many regions, native pollinator insects seem to be declining. Why is this a cause for concern among conservationists and ecologists?
> Bshary studied changes in fish species richness in response to both natural and experimental removals and additions of the cleaner fish Labroides dimidiatus (see fig. 17.18). Why did he not just focus on the response of fish species richness
> If disturbance can foster higher species diversity, why is human disturbance often (though not always) associated with reduced species diversity?
> Could protecting forests that once burned with regular frequency, due to lightning strikes, lead to reduced plant diversity within a mountain forest landscape of 25 km2 (~10 mi2)?
> Why did Brown and colleagues repeat their large granivore experiment (see fig. 13.24)? Figure 13.24: Before removal After removal 30- Dipodomys spp. 25 - • Control plots Removal plots 20 - 15 - Dipodomys numbers were immediat
> Why should there be strong selection on periodical cicadas for highly synchronous emergence?
> What factors make coexistence of predators and prey less likely in a laboratory setting than in nature?
> What does the increase in small granivore populations but lack of response by populations of insectivorous rodents suggest about the nature of competition between rodents in Brown’s Arizona study area (see fig. 13.23)? Fig
> The Applications section reviews how the studies of Bruno Baur and Anette Baur (1993) have documented the local extinction of the land snail Arianta arbustorum. Their research also shows that these extinctions may be due to reduced egg hatching at higher
> What do you think would have happened to the Galium sylvestre on acidic soil if Tansley had continued his experiment for a few more years?
> What are the evolutionary implications of the fact that larger coalitions of male lions consist almost entirely of close relatives (see fig. 8.25)? Figure 8.25: 75 Males in coalitions of two or three are often unrelated,.. 5
> The last major natural reproduction by Rio Grande cottonwoods, which produced the large number of 40- and 50-year-old trees documented by Howe and Knopf (1991), occurred before the last major dam was built on the river. Is there any evidence for reproduc
> Can a healthy population that is not in danger of extinction have an age structure that shows years of reproductive failure?
> Both R0 and r indicate that the mud turtle population in Ellenton Bay is in decline. Is there any way that this population could be maintained for many generations even with such negative indicators?
> Suppose that you are managing a population of an endangered species that has been reduced in numbers throughout its historic range and that your goal is to increase the size of the population. What values of R0 would meet your management goals?
> Of the three populations pictured in figures 10.19, 10.20, and 10.21, which is most likely to have a stable age distribution? Figures 10.19: Figures 10.20: Continue to next pages……. Figures 10.21:
> What evidence does colony structure offer in support of the idea that both leaf-cutter ants and naked mole rats must vigorously defend their colonies from predators and invaders?
> What are two major ecological challenges favoring colony living that are shared by leaf-cutter ants and naked mole rats?
> How would a queen ant, or other eusocial hymenopteran queen, mating with several males affect the relatedness of workers within a colony? If common in social hymenoptera, how would queens mating with several males affect the potential of kin selection to
> Figure 5.8 shows how temperature influences the activity of acetyl cholinesterase in rainbow trout. Assuming that the other enzymes of rainbow trout show similar responses to temperature, how would trout swimming speed change as environmental temperature
> Why did Tilman and Cowan plant several pots of each species in each of their growing conditions?
> Do patterns of feeding by bluegills (see fig. 7.25) include any evidence that these consumers ignore certain potential prey? Figure 7.25: 70 40 The most abundant prey in the environment are approximately I mm long. 20 0- 40-
> According to optimal foraging theory, under what conditions should a predator add a new prey species to its diet?
> Why do the managers of captive breeding and reintroduction programs for endangered species try to maintain high levels of genetic diversity?
> Why might the frequency of torpor and hibernation be more common among animals in tropical dry forest compared to those living in tropical rain forests?
> Why don’t hummingbirds save energy by going into torpor at night even when food supplies are abundant? In other words, what would be a possible disadvantage of routine, nightly torpor?
