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Question: Explain the roles of food and predators

Explain the roles of food and predators in producing cycles of abundance in populations of snowshoe hare. Populations of many of the predators that feed on snowshoe hares also cycle substantially. Explain population cycles among these predator populations.

> Likens and Bormann (1995) found that vegetation substantially influences the rate of nutrient loss from small stream catchments in the northern hardwood forest ecosystem. How do vegetative biomass and rates of primary production in these forests affect t

> Many rivers around the world have been straightened and deepened to improve conditions for navigation. Side effects of these changes include increased average water velocity and decreased movement of water into shallow riverside environments such as eddi

> Melillo, Aber, and Muratore (1982) suggested that soil fertility may influence the rate of decomposition in terrestrial ecosystems. Design an experiment to test this hypothesis. If you test for the effects of soil fertility, how will you control for the

> Review figure 18.2, in which Rosenzweig (1968) plotted the relationship between actual evapotranspiration and net primary production. How do you think that decomposition rates change across the same ecosystems? Using what you learned in chapterÂ&nb

> Parmenter and Lamarra (1991) studied decomposition of fish and waterfowl carrion in a freshwater marsh. During the course of their studies they found that the soft tissues of both fish and waterfowl decomposed faster than the most rapidly decomposing pla

> Of all the naturally occurring elements in the biosphere, why have the cycles of carbon, nitrogen, and phosphorus been so intensively studied by ecologists? (Hint: Think about the kinds of organic molecules of which these elements are constituents. Also

> What is genetic drift? Under what circumstances do you expect genetic drift to occur? Under what circumstances is genetic drift unlikely to be important? Does genetic drift increase or decrease genetic variation in populations?

> In chapter 17, we examined the influences of keystone species on the structure of communities. In chapter 18, we reviewed trophic cascades. Discuss the similarities and differences between these two concepts. Compare the measurements and methods of ecolo

> In chapter 17, we examined the influences of keystone species on the structure of communities. In chapter 18, we reviewed trophic cascades. Discuss the similarities and differences between these two concepts. Compare the measurements and methods of ecolo

> Most of the energy that flows through a forest ecosystem flows through detritus-based food chains, and the detritus consists mainly of dead plant tissues (e.g., leaves and wood). In contrast, most of the energy flowing through a pelagic marine or freshwa

> Suppose you are studying a community of small mammals that live on the boundary between a riverside forest and a semidesert grassland. One of your concerns is to discover the relative contributions of the grassland and the forest to the nutrition of smal

> Compare the pictures of trophic structure that emerged from our discussions of food webs in chapter 17 with those in chapter 18. What are the strengths of each perspective? What are their limitations?

> Shaver and Chapin (1986) pointed out that though the tundra ecosystems they studied consistently increased primary production in response to fertilization, individual species and growth forms showed more variation in response. Some species and growth for

> Field experiments demonstrate that variation in soil fertility influences terrestrial primary production. However, we cannot say that nutrients exert primary control. That role is still attributed to temperature and moisture. Why do ecologists still attr

> Many migratory birds spend approximately half the year in temperate forests during the warm breeding season and the other half of the year in tropical forest. Given the analyses you made in question 2, which forest appears to be more productive from the

> M. Huston (1994b) pointed out that the well-documented pattern of increasing annual primary production from the poles to the equator is strongly influenced by the longer growing season at low latitudes. The following data are from table 14.10 in Huston.

> Population, community, and ecosystem ecologists study structure and process. However, they focus on different natural characteristics. Contrast the important structures and processes in a forest from the perspectives of population, community, and ecosyst

> Review the Hardy-Weinberg equilibrium equation. What parts of the equation represent gene frequencies? What elements represent genotype frequencies and phenotype frequencies? Are genotype and phenotype frequencies always the same? Use a hypothetical popu

> Why do introduced predators possibly threaten the species diversity of a community such as Lake Victoria, while indigenous predators do not? Think in evolutionary timescales as you develop your answer to this question.

> Humans have been living in the tropical rain forests of the New World for at least 11,000 years. During this period, disturbance by humans has been a part of these tropical rain forests. Use the intermediate disturbance hypothesis to explain how recent d

> The dams that have been built on many rivers often stabilize river flow by increasing flows below the dam during droughts and decreasing the amount of flooding during periods of high rainfall. Using the intermediate disturbance hypothesis, predict how st

> All the keystone species work we have discussed in chapter 17 has concerned the influences of animals on the structure of communities. Can other groups of organism’s act as keystones? What about parasites and pathogens?

> Some paleontologists have proposed that overhunting caused the extinction of many large North American mammals at the end of the Pleistocene about 11,000 and 10,000 years ago. The hunters implicated by paleontologists were a newly arrived predatory speci

> Using Tscharntke’s food web (1992) shown in figure 17.5, predict which species would be most affected if you excluded the bird at the top of the web, Parus caeruleus. What species would be affected less? Assume that P. caeru

> When Power (1990) excluded predaceous fish from her river sites, the density of herbivorous insect larvae (chironomids) decreased. Use the food web described by Power to explain this response.

> Explain how the experiments of Lubchenco (1978) showed that feeding preferences, population density, and competitive relations among food species all potentially contribute to the influences of “keystone” consumers on the structure of communities. What r

> What is a keystone species? Paine (1966, 1969) experimented with two sea stars that act as keystone species in their intertidal communities along the west coast of North America and in New Zealand. Describe how the intertidal communities in these two are

> Winemiller (1990) deleted “weak” trophic links from one set of food webs that he described for fish communities in Venezuela (see fig. 17.3). What was his criterion for designating weak interactions? Earlie

> What is the Hardy-Weinberg principle? What is Hardy- Weinberg equilibrium? What conditions are required for Hardy-Weinberg equilibrium?

> According to the intermediate disturbance hypothesis, both low and high levels of disturbance can reduce species diversity. Explain possible mechanisms producing this relationship. Include trade-offs between competitive and dispersal abilities in your di

> Communities in different areas may be organized in different ways. For instance, C. Ralph (1985) found that in Patagonia in Argentina, as foliage height diversity increases, bird species diversity decreases. This result is exactly the opposite of the pat

> Compare the “trophic” niches of warblers and diatoms as described by MacArthur (1958) and Tilman (1977). Why is it important that the ecologist be familiar with the niches of study organisms before exploring relationships between environmental complexity

> What are species richness and species evenness? How does each of these components of species diversity contribute to the value of the Shannon-Wiener diversity index (H ')? How do species evenness and richness influence the form of rank-abundance curves?

> Suppose you are a biologist working for an international conservation organization concerned with studying and conserving biological diversity. On one of your assignments you are sent out to explore the local biotas of several regions. As part of your su

> How does feeding by urchins, which prey on young corals, improve establishment by young corals? Use a diagram outlining interactions among urchins, corals, and algae to help in the development of your explanation.

> What is the difference between a community and a population? What are some distinguishing properties of communities? What is a guild? Give examples. What is a plant life-form? Give examples.

> Outline how the honeyguide-human mutualism could have evolved from an earlier mutualism between honeyguides and honey badgers. In many parts of Africa today, people have begun to abandon traditional honey gathering in favor of keeping domestic bees and h

> We included spatial refuges, predator satiation, and size in our discussions of the role played by refuges in the persistence of exploited species. How could time act as a refuge? Explain how natural selection could lead to the evolution of temporal “ref

> Outline the benefits and costs identified by Keeler’s (1981, 1985) cost-benefit model for facultative ant-plant mutualism. From what perspective does Keeler’s model view this mutualism? From the perspective of plant or ant? What would be some of the cost

> How did the studies of Douglas and Brunner complement the earlier studies of Clausen, Keck, and Hiesey?

> How are coral-centered mutualisms similar to plant-centered mutualisms? How are they different? The exchanges between mutualistic partners in both systems revolve around energy, nutrients, and protection. Is this an accident of the cases discussed or are

> Inouye and Taylor’s study (1979) of the relationship between ants and the aspen sunflower, Helianthella quinquenervis, provides a reasonable representative of temperate ant-plant protection mutualisms. Compare this mutualism with that of the tropical mut

> Janzen (1985) encouraged ecologists to take a more experimental approach to the study of mutualistic relationships. Outline the details of Janzen’s own experiments on the mutualistic relationship between swollen thorn acacias and ants.

> Explain how mycorrhizal fungi may have evolved from ancestors that were originally parasites of plant roots. Do any of Johnson’s results (1993) indicate that present-day mycorrhizal fungi may act as parasites? Be specific.

> Outline the experiments of Johnson (1993), which she designed to test the possibility that artificial fertilizers may select for less mutualistic mycorrhizal fungi. What evidence does Johnson present in support of her hypothesis?

> What contributions do mycorrhizal fungi make to their plant partners? What do plants contribute in return for the services of mycorrhizal fungi? How did Hardie (1985) demonstrate that mycorrhizae improve the water balance of red clover? How do mycorrhiza

> List and briefly describe mutualistic relationships that seem to contribute to the ecological integrity of the biosphere.

> One of the conclusions that seems justified in light of several decades of studies of interspecific competition is that competition is a common and strong force operating in nature, but not always and not everywhere. List the environmental circumstance

> What contributions have laboratory and mathematical models made to our understanding of predator-prey population cycles? What are the shortcomings of these modeling approaches? What are their advantages?

> Review the distribution of water among the major reservoirs of the hydrologic cycle. What are the major sources of freshwater? Explain why according to some projections availability of freshwater may limit human populations and activity.

> Researchers have suggested that predators could actually increase the population density of a prey species heavily infected by a pathogenic parasite (Hudson, Dobson, and Newborn 1992). Explain how predation could lead to population increases in the prey

> Early work on exploitation focused a great deal of attention on predator-prey relations. However, parasites and pathogens represent a substantial part of the discussions in chapter 14. Is this representation by parasites and pathogens just the result of

> In chapter 14 we have seen how a herbivorous stream insect controls the density of its food organisms, how a herbivorous moth larva and pathogenic microbes combine to control an introduced cactus population, and how decimation of a red fox population led

> Predation by one flour beetle species on another can be used as a potent means of interference competition. However, the predatory strategy seems to fail consistently in the presence of the protozoan parasite Adelina tribolii. Explain how the predatory s

> How are manipulation of host behavior by spiny-headed worms and manipulation of plant growth by the rust Puccinia monoica the same? How are they different? The details of these parasitic interactions are very different in many ways from the predatory beh

> Predation is one of the processes by which one organism exploits another. Others are herbivory, parasitism, and disease. What distinguishes each of these processes, including predation, from the others? We can justify discussing these varied processes un

> Discuss how mathematical theory, laboratory models, and field experiments have contributed to our understanding of the ecology of competition. List the advantages and disadvantages of each approach.

> In his experiments on competition between T. confusum and T. castaneum, Park (1954) found that one species usually excluded the other species but that the outcome depended upon physical conditions. In which circumstances did T. confusum have the competit

> How was the amount of food that Gause (1934) provided in his experiment on competition among paramecia related to carrying capacity? In Gause’s experiments on competition, P. aurelia excluded P. caudatum faster when he provided half the amount of food th

> Darwin (1842) was the first to propose that fringing reefs, barrier reefs, and atolls are different stages in a developmental sequence that begins with a fringing reef and ends with an atoll. Outline how this process might work. How would you test your i

> What evidence is there that variation in atmospheric CO 2 concentration is linked to variation in global temperatures? In recent years, the governments of most countries of the world have been working hard to develop international agreements to regulate

> Ecologists are now challenged to study global ecology. The apparent role played by humans in changing the global environment makes it imperative that we understand the workings of the earth as a global system. However, this study requires approaches that

> A grocery clerk helps a customer with purchases to her car, and the clerk says No problem or Not a problem when thanked. What’s the problem with these expressions? What could be said instead? Why do you think some people are now adopting these expression

> In their e-mails, writers sometimes use abbreviations such as FYI (“for your information”) and ASAP (“as soon as possible”). Others sometimes use LOL (“laughing out loud”), 4 u (“for you”), and gr8 (“great”). What’s the difference between these abbreviat

> Is it necessary to follow a writing process when preparing a short message? A long message? Why or why not?

> What might be some advantages and disadvantages to being let go remotely, if any? Why might it be a good idea to rein in one’s frustration and anger?

> Consider times when you have been aware that others were using the indirect strategy in writing or speaking to you. How did you react?

> Should organizations fear websites where consumers post negative messages about products and services? What actions can companies take in response to this potential threat?

> Robert Bies, professor of management at Georgetown University, believes that an important ethical guideline in dealing with bad news is never to shock the recipient: “Bad news should never come as a surprise. Failure to warn senior leadership of impendin

> Why might it be shortsighted to bluntly refuse lending money or issue credit cards to people without a credit history—such as young students—or to consumers with less-than-stellar credit?

> Some marketers employ machines to inflate the number of likes and fans online. So-called bot networks (botnets) operate large numbers of fake accounts on Facebook, Instagram, and Twitter. A rental agency based in Washington, D.C., went from two fans to

> Traditional mainstream media act as so-called gatekeepers that vet the news and decide what kind of content gets published. However, social media networks have changed the game. Now anyone with an Internet connection can publish anything, even fake news,

> Are common abbreviations such as lol and imho and all-lowercase writing acceptable in texting or instant messaging for business?

> On Martin Luther King Jr. Day, four Oklahoma State University students tweeted a group selfie; two of the students were wearing blackface, causing outrage on campus. In another incident, several students were expelled from a Texas university for posting

> The eminent sociologist Zygmunt Bauman had this to say about social media: “Most people use social media not to unite, not to open their horizons wider, but on the contrary, to cut themselves a comfort zone where the only sounds they hear are the echoes

> The use of digital communication has overtaken face-to-face and voice-to-voice communication in the workplace. How has this shift changed the fundamental process of communication?

> Career expert Andrea Kay stresses that knowing oneself and showing empathy are important components of the soft skills that make people employable: “Many, many jobs are lost and careers derailed because of the way people act with each other, respond to s

> Describe the advantages of face-to-face communication as opposed to interactions facilitated by technology such as telephones, e-mail, instant messaging, texting, the Web, social networking sites, and so on. When is face-to-face communication more effect

> Think of typical workplace situations and how you might communicate in each. When would you seek an in-person conversation, pick up the phone, call a virtual meeting, or send an e-mail, IM, or text?

> Employers try to screen for and encourage soft skills such as excellent communication, promptness, a positive attitude, good teamwork skills, and civility. On this difficult mission, they try novel approaches. A recruiter would intentionally drop a piece

> It is quite natural to favor one’s own country over a foreign one. To what extent can ethnocentrism be considered a normal reaction, and when could it become destructive and unproductive? Provide examples to support your answer.

> Imagine that businesspeople from a high-context culture (e.g., Japan or China) meet their counterparts from a low-context culture (the United States) for the first time to negotiate and sign a manufacturing contract. What could go wrong? How about confli

> What arguments could you give for or against the idea that body language is a science with principles that can be interpreted accurately by specialists?

> Why do executives and managers spend more time listening than do workers?

> What could be the career fallout for someone who is unwilling or unable to train to become a better communicator? Can workers today be successful if their writing is and remains poor?

> Los Angeles–based clothing company Barabas used the name and likeness of brutal Mexican drug kingpin Joaquin “El Chapo” Guzmán on its website, flanked by photos of attractive male models wearing the same distinctive cotton shirts of the Fantasy and Crazy

> Is information obtained on the Web as reliable as information obtained from journals, newspapers, and magazines?

> How are direct-mail and e-mail sales messages similar, and how are they different?

> What are some of the underlying motivations that prompt individuals to agree to requests that do not directly benefit themselves or their organizations?

> The word persuasion turns some people off. What negative connotations can it have?

> Many consumers rely on product reviews posted online, presumably by ordinary citizens describing their authentic experiences. Unfortunately, though, Amazon and Yelp, the most prominent of the many Internet review sites, have been called out for fake and

> General Motors CEO Mary Barra inherited a mess when she ascended to the top post in her beleaguered company. Several GM car models had exhibited problems with their ignition switches, which turned off engines at highway speeds, causing 124 deaths and 275

> How can you prevent multimedia presentation software from stealing your thunder?

> Why do many communication consultants encourage businesspeople to move beyond bullet points? What do they recommend instead and why?

> Communication expert Dianna Booher claims that enthusiasm is infectious and “boredom is contagious.” What does this mean for you as a presenter? How can you avoid being a boring speaker?

> Why should even practice speakers plan their presentations when addressing a business audience instead of just “winging it”?

> Conciseness is valued in business. However, can messages be too short?

> How can report writers decide what type of graphic to use in a report?

> Because business writing should have high “skim value,” why not write everything in bulleted lists?

> It’s easy to use clichés because they just roll off the tongue. What’s wrong with tried-and-true expressions such as it is what it is and at the end of the day?


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