Ecology The Economy of Nature Ninth Edition Test Bank

Ecology The Economy of Nature Ninth Edition Test Bank

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Chapter 1 Multiple Choice 1. Which ecological level would be of most interest to an ecologist studying adaptations? a. ecosystem b. population c. individual d. community ANSWER: c 2. Which of the following is NOT a property used in the study of populations? a. density b. change in size c. composition d. interactions with other populations ANSWER: d 3. Which level of ecological hierarchy includes the movement of water and air? a. community b. population c. ecosystem d. biosphere ANSWER: d 4. A group of organisms that interbreeds in nature and produces fertile offspring is called a a. population. b. species. c. community. d. prokaryote.

ANSWER: b 5. The boundaries of communities are a. difficult for species to cross. b. flexible. c. clear and distinct. d. never overlapping.

ANSWER: b 6. Which is the correct hierarchy of ecological systems, from smallest to largest? a. ecosystem, biosphere, community, population, individual b. individual, community, population, ecosystem, biosphere c. individual, population, ecosystem, biosphere, community Copyright Macmillan Learning. Powered by Cognero.

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Chapter 1 d. individual, population, community, ecosystem, biosphere ANSWER: d 7. Which of the following systems is composed of assemblages of organisms together with their physical and chemical environments? a. organism b. population c. community d. ecosystem ANSWER: d 8. An ecologist who studies populations would most likely be interested in a. adaptations that help individual organisms live in their environment. b. births and deaths of individuals belonging to a particular species in a particular place. c. the number and relative abundance of species living in a particular place. d. physical and chemical transformations of energy and materials in the soil, atmosphere, and water.

ANSWER: b 9. The first law of thermodynamics states that a. life requires energy to be continually added to Earth. b. matter cannot be created or destroyed. c. when energy changes form, some energy is lost. d. energy cannot be created or destroyed, but only change form.

ANSWER: d 10. In a dynamic steady state a. there are no inputs or outputs to the system. b. the second law of thermodynamics does not apply. c. there is no net change in the system. d. the system will continue to grow.

ANSWER: c 11. In evolution by natural selection, which of the following is true? a. All individuals within a population are identical. b. Some individuals have a higher fitness because of their traits. c. Offspring inherit every trait from both parents. d. The fitness of an individual refers to the strength of the individual.

ANSWER: b 12. How can species interactions increase the rate at which species evolve? a. Interactions reduce the effects of natural selection.

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Chapter 1 b. Interactions increase the fitness of all individuals. c. Interactions make certain traits more useful. d. Interactions reduce the genetic variety in individuals.

ANSWER: c 13. A phenotype is a. the traits an individual can pass on to its offspring. b. the expression of an individual’s traits. c. the genes an individual possesses. d. a trait caused by interaction with another species.

ANSWER: b 14. To maintain a dynamic steady state in a community, which two factors must balance? a. new species arrivals and current species extinctions b. immigration and emigration c. births and deaths d. food consumed and energy expended ANSWER: a 15. At what ecological level does evolution occur? a. individual b. population c. ecosystem d. community ANSWER: b 16. Which feature is found in eukaryotic organisms but not in prokaryotic organisms? a. inability to photosynthesize. b. DNA. c. mitochondria. d. single-cell structure.

ANSWER: c 17. Blue-green algae are a. protists. b. bacteria. c. plants. d. fungi.

ANSWER: b 18. Organisms that use photosynthesis or chemosynthesis are Copyright Macmillan Learning. Powered by Cognero.

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Chapter 1 a. autotrophs. b. consumers. c. heterotrophs. d. herbivores.

ANSWER: a 19. Which interaction is characterized by negative effects on the fitness of both species involved? a. predation b. herbivory c. commensalism d. competition ANSWER: d 20. A mixotroph is an organism that a. consumes dead organic matter. b. can be both a parasite and a predator. c. survives only because of a symbiotic relationship. d. can use multiple methods to obtain energy.

ANSWER: d 21. The range of biotic and abiotic conditions a species can tolerate is its a. community. b. habitat. c. niche. d. ecosystem role.

ANSWER: c 22. Which group of organisms function as decomposers? a. plants. b. animals. c. fungi. d. protists.

ANSWER: c 23. Which consumes dead organic matter? a. detritivore b. herbivore c. parasite d. predator ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 1 24. An organism that uses chemosynthesis to form organic compounds is classified as ? a. a consumer b. a mixotroph c. a producer d. a parasitoid ANSWER: c 25. What pair of species would you expect to exhibit commensalism? a. owls and oak trees b. osprey and herons c. coyotes and foxes d. algae and kelp ANSWER: a 26. There are many examples in nature of cooperation among organisms, such as the bacteria that inhabit the root nodules of leguminous plants. Partnerships between organisms that live in close association are called a. networks. b. communities. c. symbioses. d. ecosystems.

ANSWER: c 27. Which type of interaction between species results in positive outcomes for both species? a. Commensalism b. Mutualism c. Herbivory d. Heterotrophism ANSWER: b 28. What method is used to increase experimental reliability? a. replication b. proximate hypotheses c. natural experiment d. mathematical models ANSWER: a 29. An experimental control is a(n) a. experiment performed on randomly selected samples. b. manipulation without the factor of interest. c. manipulation using natural conditions. d. sample size that is large enough to accurately reflect the variance.

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Chapter 1 ANSWER: b 30. Which is the best action if an experiment does not support a hypothesis? a. Create a mathematical model. b. Revise the hypothesis. c. Test the hypothesis again. d. Publish your results.

ANSWER: b 31. Ecologists using global carbon-balance models were overestimating the rate of increase of atmospheric carbon dioxide. This discovery led these ecologists to a. discard their models. b. switch to modeling other phenomena. c. conclude that increase in atmospheric carbon dioxide is not a serious environmental problem. d. search for evidence of other carbon dioxide sinks in the global cycle of carbon.

ANSWER: d 32. Most scientific investigations begin with a set of facts about nature. These facts are obtained by a. observation and description. b. development of mathematical models. c. development of hypotheses. d. experimental testing of hypotheses.

ANSWER: a 33. The formulation of hypotheses is a critical step in the scientific process. In the simplest terms, what is a hypothesis? a. an explanation b. an experiment c. an observation d. a proven fact ANSWER: a 34. Because it is difficult to experiment on large ecological systems, researchers often replicate the essential features of a system in smaller, simplified laboratory or field settings known as a. microcosms. b. approximate systems. c. natural treatments. d. experimental units.

ANSWER: a 35. If you wanted to understand the impact of an introduced species on existing species in an area, what ecological level should you examine?

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Chapter 1 a. population b. individual c. community d. biosphere ANSWER: c 36. What is the mean of these data: 22, 19, 34, 24, 27, 20? a. 24 b. 144 c. 23 d. 26.5 ANSWER: a 37. If the number of fruits on 10 strawberry plants is sampled and E[] is found to be 6 and E[2] is 38, what is the sample variance? a. 32 b. 2 c. 2.2 d. 35.5 ANSWER: c 38. Which would be the most informative about the reliability of data gathered in an experiment? a. low mean b. high mean c. low variance d. high variance ANSWER: c 39. Fishermen living along the North Pacific Rim felt threatened by increased populations of sea otters because sea otters consume commercially valuable abalone, sea urchins, and spiny lobster. What beneficial aspect of sea otter ecology did these fishermen ignore? a. Sea otters are consumed by killer whales, which would otherwise eat commercially valuable fish. b. Sea otters catch and eat trash fish, allowing stocks of commercially valuable fish to increase. c. Sea otters catch and eat sea urchins, thereby protecting kelps, which in turn shelter populations of larval fish. d. Sea otters have been used in medical research to develop vaccines that protect domestic cats from a variety of diseases.

ANSWER: c 40. To better understand what happens in an aquatic system (freshwater lake) when exposed to acid deposition (acid rain), an ecologist would likely look at the lake from the a. species level.

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Chapter 1 b. community level. c. population level d. ecosystem level.

ANSWER: d 41. An ecologist who studies the meadow vole (Microtus pennsylvanicus) in both Michigan and New York State would be looking necessarily at individuals of the same a. community. b. population. c. ecosystem. d. species.

ANSWER: d 42. An organism that does not itself consume its prey but rather its offspring does is termed a a. parasite. b. parasitoid. c. detritivore. d. decomposer.

ANSWER: b 43. Natural selection tends to result in individuals of a species that a. produce the most offspring. b. are the largest in size. c. are the fastest. d. are the strongest.

ANSWER: a 44. A moose, a monarch butterfly, and a wolf are all examples of a. autotrophs. b. producers. c. heterotrophs. d. detritivores.

ANSWER: c 45. All things being equal, one would expect to find _______ species diversity in a stream with a uniform substrate (i.e., bottom bedrock) as compared to a stream with a heterogeneous substrate (i.e., bottom composed of sand, pebbles, stones, cobble, boulders). a. less b. more c. the same d. There is no way to determine.

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Chapter 1 ANSWER: a 46. The relationship between a burdock plant and a fox is a. competition. b. herbivory. c. predation. d. parasitism. e. commensalism.

ANSWER: e Essay 47. Explain how studying a community can provide insight into population changes.

ANSWER: Many species’ interactions play a part in birth and death rates of populations, such as any species that relies on another for food. Understanding these relationships is often essential to understand why a population is growing or shrinking.

48. Explain how the definition of species has become more complicated. Give an example.

ANSWER: While species were originally defined as organisms that could interbreed and produce fertile offspring, exceptions continue to be found. For example, prokaryotic organisms can transfer DNA to each other in horizontal gene transfer. This makes it hard to have a clear difference between species, since they can easily share DNA but are varied enough that they cannot be considered one species.

49. How might one hierarchical level that is not in steady state affect the hierarchical level above it?

ANSWER: If the individual level is not maintained in steady state, this might mean that the organism would not find enough food to meet its energy requirements, reducing its fitness. If continued across multiple individuals, the birth rate might decrease and the death rate increase, leading to the potential for the population to go out of equilibrium as well.

50. Many warm-blooded organisms must maintain a constant temperature that is commonly warmer than their surroundings. What is the cost associated with maintaining the dynamic steady state, and how is this cost met?

ANSWER: To maintain a system in disequilibrium with its environment requires expenditure of energy. A warm-blooded animal in cold surroundings must acquire food (with its associated energy costs in locating and acquiring food) and use the metabolic energy released from that food to maintain its temperature higher than that of its surroundings.

51. How might the use of pesticides to control insects that feed on wheat affect how the insects evolve?

ANSWER: If some insects survive the initial application, they may be resistant to the chemical as a result of their genetic makeup. The surviving insects could pass on that trait to the next generation. Over time, the insect species may evolve to be resistant to the pesticide.

52. The law of conservation of matter states that matter cannot be destroyed. Why, then, are we concerned about the depletion of resources?

ANSWER: Although matter cannot be destroyed, it can be transformed into forms that are not useful or that are difficult to use.

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Chapter 1 53. Why are two species unable to share exactly the same niche?

ANSWER: If two species have the identical niche, they will be competing for the same resources in the same place during the same time. While both species might survive for a brief period, eventually the better competitor will outcompete the other species, leading to the elimination of the lesser competitor from the community.

54. Plants and animals exchange energy and materials with their physical environments. These exchanges occur across surfaces. In animals, surfaces tend to be internal, while in plants, surfaces tend to be external. Discuss the principal reason for this important difference.

ANSWER: Animals obtain energy from foods they consume. This absorption is best accomplished internally, where foods can be subjected to conditions that release molecules to be taken up across large areas of absorptive structures. Most plants obtain energy from sunlight. They must expose relatively large external absorptive surfaces (typically leaves) to sunlight to obtain this energy, which makes internal absorption impractical.

55. Why are protists suited for symbiotic relationships with other species?

ANSWER: The small size of most protists makes it easy for them to live inside other larger species. In symbiotic relationships the diverse nature of protists has led to specialized adaptations that can be very useful to other organisms. An example of this is the protists that live in the gut of termites and break down cellulose. In exchange, the host organism provides a relatively stable environment for the protists, reducing the energy required to survive.

56. Explain the potential difficulties of using a natural experiment to test a hypothesis.

ANSWER: Since a natural experiment relies on existing conditions, it can be difficult to find enough suitable sites to gather sufficient data. The inherent variation in natural systems makes it difficult to isolate the desired variable in the less controlled environment.

57. A scientist hypothesizes that the larvae of a particular species of swallowtail butterfly uses olfaction (the sense of smell) to locate their preferred host plants in the carrot family. To test the hypothesis, the scientist uses extracts from various plants—including some from the carrot family—to moisten small pieces of paper arranged randomly under a wire screen. Swallowtail larvae are released on the wire screen but cannot come into direct physical contact with the pieces of paper. What is the advantage of this experiment compared to simply presenting the larvae with a choice among various plants?

ANSWER: The scientist wants to vary the volatile chemicals presented to the larvae without giving the larvae other cues to the identity of the plants from which these chemicals are extracted. Since all of the pieces of paper look alike, the scientist can eliminate the possibility that the larvae use visual cues to recognize the pieces of paper moistened with extracts from plants in the carrot family. Separating the larvae from the pieces of paper ensures that the larvae cannot use their sense of taste.

58. Scientists ask questions about how the natural world works. These can usually be classified as how questions or why questions. A scientist observes that an owl species can fly silently. Give an example of a how and a why question that the scientist might study and what the differences would be.

ANSWER: One possible question is how the owls can fly so quietly, which would mean studying the structure of the wings and feathers and how they differ from those of other birds. Another question would be why it is advantageous for the owls to fly silently; for example, what prey this allows the owl to Copyright Macmillan Learning. Powered by Cognero.

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Chapter 1 catch that it might not be able to catch otherwise.

59. Explain why a species with a very limited niche is particularly susceptible to human influences.

ANSWER: With a narrow niche a species has small range of conditions in which it can survive and reproduce.

As humans continue to alter and destroy habitat and change ecosystems, smaller niches may be eliminated entirely, causing the species to go extinct.

60. Explain the role of ecology in efforts to reduce the damage humans do to the environment.

ANSWER: Our ability to manage human impact on global systems depends on understanding the structure and function of ecosystems.

61. Describe one specific successful solution to an environmental problem caused by human activity.

ANSWER: There are multiple possible answers for this. For example, one might discuss efforts made to save endangered species from extinction, like captive breeding and reintroduction.

62. Explain why the sample variance is larger than the variance of the mean, especially for small samples.

ANSWER: The sample variance is larger than the variance of the mean because the smaller the sample, the less reliable the results. Thus, for a small sample, the sample variance multiplier of is larger than for large samples.

63. Use the example of the California sea otter to explain why ecologists must study multiple hierarchical levels to understand most environmental problems.

ANSWER: One part of the sea otter story that illustrates this is the population loss due to killer whales. The food preferences of the whales had to be understood (on the individual level), but so did the community and ecosystem interactions between lower seal and sea lion populations due to low fish populations, which drove killer whales to find new food sources.

64. Explain why two competitive species would have greater similarity in their respective niche than two species in which one is a predator and the other the prey (of that predator).

ANSWER: Two competitive species would not only be found in the same habitat and likely feeding at the same time, but would also be feeding at the same trophic level and likely on the same species.

65. The interactions known as herbivory and predation are considered to both result in a +/- outcome between the two species involved in each of the interactions (one species benefits; the other species is harmed). How are these two interactions different?

ANSWER: Predation tends to be lethal to the species negatively impacted, while in herbivory the interaction is not lethal to the species negatively impacted.

66. Explain, in terms of fitness and natural selection, why a species should have adapted to avoid competition.

ANSWER: Competition has a negative impact on both species’ fitness. Energy is spent competing for resources that might have been allocated for reproduction (improving one’s fitness by producing more offspring) if adapted (behaviorally or morphologically) to avoid competition.

67. Explain the difference between organisms identified as decomposers and those identified as detritivores.

ANSWER: Decomposers are typically fungi and bacteria and function by breaking down biological material into elements and compounds that can be reused in the system. Detritivores tend to be invertebrates Copyright Macmillan Learning. Powered by Cognero.

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Chapter 1 that feed off of dead organic material as their food source, breaking the material down into smaller parts that facilitate the action of decomposers by increasing the surface area for bacteria and fungi to act.

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Chapter 2 Multiple Choice 1. The greenhouse effect occurs because of the absorption and re-emission of _______ radiation by the atmosphere. a. visible light b. infrared c. ultraviolet d. shortwave ANSWER: b 2. How much did the average temperature of Earth change between 1880 and 2016? a. 4°C b. 2°C c. 1°C d. –2°C e. no significant change ANSWER: c 3. Which of the following is NOT a greenhouse gas? a. methane b. ozone c. carbon monoxide d. nitrous oxide e. chlorofluorocarbons ANSWER: c 4. Which of the following human activities is NOT a significant source of greenhouse gases in the atmosphere? a. generating electricity b. using landfills c. using refrigerants d. agriculture e. hunting ANSWER: e 5. Excluding water vapor, greenhouse gases make up _____ percent of the atmosphere. a. 7 b. 3 c. 1.5 d. less than 1 ANSWER: d Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 6. How much solar radiation is reflected by Earth's atmosphere and surface? a. 24 percent b. 33 percent c. 45 percent d. 60 percent ANSWER: b 7. The energy of incident solar radiation reaching the surface of Earth declines toward the poles from its maximum in equatorial regions. Which of these is NOT a reason for this? a. The tilt of Earth increases the reflection of solar radiation. b. A given amount of solar radiation is spread over a larger area at higher latitudes. c. Solar radiation travels a longer path through Earth's atmosphere at higher latitudes. d. The rays of the Sun strike Earth at right angles over the equator as compared to oblique angles at the poles.

ANSWER: a 8. Which of the following has the highest albedo? a. grass b. snow c. water d. rainforest e. pavement ANSWER: b 9. Where is the solar equator? a. at the Tropic of Cancer b. between the equator and 23.5° N, depending on the season c. between 23.5° S and 23.5° N of the equator, depending on the season d. along the equator e. between the equator and the Tropic of Capricorn ANSWER: c 10. During summer equinox in the Northern Hemisphere, the Sun shines most directly a. at the Tropic of Capricorn. b. at the Tropic of Cancer. c. north of the solar equator. d. at the equator.

ANSWER: b 11. Why do the tropics receive more precipitation than areas at higher latitudes? a. There is more water in tropical latitudes.

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Chapter 2 b. Water cycles more rapidly through the tropical atmosphere. c. More precipitation falls as snow at higher latitudes. d. The tropics are windier.

ANSWER: b 12. The maximum amount of water vapor air can hold is called the a. saturation point. b. latent heat capacity. c. dew point. d. absolute humidity. e. condensate retention.

ANSWER: a 13. The intertropical convergence zone is a. the dry region at the edge of the Hadley cells. b. at the solar equator. c. the area between polar and Hadley cells. d. the cause of westerlies.

ANSWER: b 14. The Coriolis effect causes what in surface winds? a. wind deflection to the east near the equator b. wind deflection to the right in the Northern Hemisphere c. wind deflection to the west in the Southern Hemisphere d. polar wind deflection to the left ANSWER: b 15. In the area between convection cells the prevailing wind direction is primarily a. north to south. b. east to west. c. west to east. d. nonexistent.

ANSWER: c 16. What kind of oceanic circulation would you predict for the western coasts of continents? a. cold currents moving poleward from the equator b. warm currents moving poleward from the equator c. cold currents moving from the poles toward the equator d. warm currents moving from the poles toward the equator ANSWER: c Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 17. Which of the following phenomena triggers an El Niño–Southern Oscillation event? a. development of an unusually cold high-pressure air mass in the Antarctic region b. increased freshwater added to the surface currents, resulting in low salinity c. reversal of high- and low-pressure areas in the equatorial central Pacific Ocean d. cold water upwelling in the eastern Indian Ocean ANSWER: c 18. Upwelling causes a. increased surface water temperature. b. nutrient-rich zones. c. low productivity in the deep ocean. d. increased evaporation and precipitation.

ANSWER: b 19. Gyres in the Southern Hemisphere rotate _____ and in the Northern Hemisphere rotate _______. a. clockwise; counterclockwise b. clockwise; clockwise c. counterclockwise; clockwise d. counterclockwise; counterclockwise ANSWER: c 20. Which of the following does NOT drive ocean currents? a. the Coriolis effect b. topography of the ocean basins c. temperature differences d. continental water sources e. differences in salinity ANSWER: d 21. Thermohaline circulation is driven by a. upwelling along the coast. b. high precipitation from the intertropical convergence zone. c. sinking polar water with high salinity. d. increased temperatures at the solar equator.

ANSWER: c 22. Which of the following is an effect of an El Niño–Southern Oscillation? a. increased precipitation and productivity in Australia and Africa b. disruption of fisheries off the coast of California c. increased upwelling along the western coast of South America d. drought in the southern United States and Mexico Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 ANSWER: b 23. Water near the equator is at a higher elevation than water near the midlatitudes because of a. gravity. b. salinity. c. temperature. d. precipitation.

ANSWER: c 24. Compared to coastal regions, the interior of a continent usually has _____ precipitation and ______ variation in climate. a. less; less b. more; more c. less; more d. more; less ANSWER: c 25. Rain shadows occur a. on the downwind side of mountains. b. in areas without significant convection currents. c. along coasts with cold air. d. between deserts and coastal areas.

ANSWER: a 26. What is the cause of the higher climatic variability in the Northern Hemisphere? a. Significant mountain ranges interrupt convection currents. b. More human activities affect the climate. c. Water surface area is less. d. More oceanic currents carry cold water from the poles.

ANSWER: c 27. Which of the following changes will increase climate warming? a. melting of glaciers and ice caps b. increased intensity of storms and hurricanes c. changes in oceanic circulation d. increased precipitation ANSWER: a 28. Why is it difficult to predict how climate will change as a response to global warming? a. The future levels of greenhouse gases are difficult to predict. b. It is difficult to predict how human technology might change the climate.

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Chapter 2 c. The global climate is complex. d. Variability resulting from the Sun's effects is unknown.

ANSWER: c 29. A regression equation for algae biomass (micrograms per liter) depending on the amount of phosphorus (micrograms per liter) is determined to be y = 1.5x – 2. What is the biomass if there is 14 μg/L of phosphorus? a. 18 μg/L b. 19 μg/L c. 23 μg/L d. 11 μg/L ANSWER: b 30. A statistical tool used to help one see how one variable changes in response to another variable is called___________ analysis. a. mean b. regression c. standard deviation d. median ANSWER: b 31. The greenhouse effect is so named because a. Earth's oceans act as a greenhouse for phytoplankton. b. Earth's landmasses provide the substrate for all terrestrial producers. c. Earth's atmosphere acts like the glass of a greenhouse. d. Earth's land mass is a heat sink much like a greenhouse.

ANSWER: c 32. Some have proposed that humans might, individually, attempt to combat climate change by replacing their roof shingles with light or white-colored shingles rather than dark or black-colored shingles when replacing the roof of their homes. The notion behind this idea is a. decreasing the albedo of Earth's surface. b. increasing the albedo of Earth's surface. c. decreasing the reflectivity of Earth's surface. d. increasing the absorption of Earth's surface.

ANSWER: b 33. At what time of year does the Northern Hemisphere receive the most direct sunlight? a. December solstice b. June solstice c. September equinox d. March equinox Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 ANSWER: b 34. As the temperature of the air increases, what happens to the saturation point of water vapor in the air? a. The saturation point increases. b. The saturation point decreases. c. The saturation point remains the same. d. The saturation point increases then decreases.

ANSWER: a 35. Dry climates may be the result of a. Hadley cell circulation and the rain shadow effect. b. the Coriolis effect and the rain shadow effect. c. Hadley cell circulation and the Coriolis effect. d. thermohaline circulation and the rain shadow effect.

ANSWER: a 36. The plant hardiness map developed by the U.S. Department of Agriculture shows that the ordering of the zones of plant hardiness is generally related to a. annual rainfall. b. time of first frost. c. longitude. d. latitude.

ANSWER: d 37. Which of the following pairs is an example of convergent evolution? a. dogs and cats b. wolves and deer c. birds and bats d. giraffes and trees ANSWER: c 38. Biomes are geographic regions a. with the same key species. b. with species that have not evolved convergently. c. with the same range of temperatures. d. whose plant communities have similar adaptations.

ANSWER: d 39. Which of the following species does NOT easily fit with the expectations of biome classification? a. organ pipe cactus b. eucalyptus trees Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 c. feral dogs d. cattails ANSWER: b 40. On a climate diagram the growing season of a biome occurs when the a. temperature line is above the precipitation line. b. precipitation line is above the temperature line. c. temperature is above 0°C. d. temperature is above 5°C ANSWER: c 41. Which of the following does NOT have an influence on plant communities in biomes? a. topography b. soils c. herbivory d. fire e. genetic makeup ANSWER: e 42. How much additional precipitation is required to meet water needs for every 10°C increase in temperature? a. 2 cm b. 5 cm c. 6 cm d. 10 cm e. 20 cm ANSWER: a 43. Which of the following is used to distinguish aquatic biomes?

I. salinity II. depth III. flow a. I and II b. I and III c. II and III d. I, II, and III ANSWER: d 44. Why is the biome concept difficult to apply to aquatic systems? a. Temperature is similar over the majority of aquatic biomes, unlike terrestrial systems. b. Aquatic communities vary little from place to place because of the ability of fish to travel between oceans.

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Chapter 2 c. Nutrients from terrestrial biomes limit most aquatic systems, so terrestrial systems must be considered when determining the aquatic biomes. d. Producers in many aquatic systems are algae, which have little characteristic large-scale structure.

ANSWER: d 45. At what average temperatures do we see the greatest variation in precipitation among biomes? a. warm temperatures (approximately 20°C to 30°C) b. moderate temperatures (approximately 5°C to 20°C) c. cold temperatures (approximately –5°C to 5°C) d. very cold temperatures (less than –5°C) ANSWER: a 46. Where could you NOT find an example of a temperate seasonal forest biome? a. United States and southeastern Canada b. Europe c. South America d. eastern Asia ANSWER: c 47. Warmer and drier parts of the temperate seasonal forest biome are dominated by a. rain forests. b. deciduous forests. c. needle-leaved forests. d. grasslands. e. woodlands.

ANSWER: c 48. Which biome occurs at the highest elevation? a. boreal forest b. temperate rainforest c. woodland/shrubland d. tundra ANSWER: d 49. Which biome is home to the coast redwood (Sequoia sempervirens)? a. temperate seasonal forest b. temperate rainforest c. boreal forest d. tropical rainforest e. tropical seasonal forest ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 50. Which biome has the highest biodiversity? a. temperate rainforest b. temperate seasonal forest c. tropical rainforest d. tropical seasonal forest ANSWER: c 51. Overgrazing has caused significant changes in vegetation in a. boreal forest. b. temperate grasslands. c. tropical seasonal forest/savannah. d. woodlands/shrublands.

ANSWER: b 52. Which biome has distinct wet and dry seasons? a. tropical seasonal forest/savannah b. boreal forest c. temperate grasslands d. tropical rainforest e. tundra ANSWER: a 53. Which of the following helps to prevent tree growth in tallgrass prairies? a. low precipitation b. high temperatures c. frequent fires d. human land use e. acidic soils ANSWER: c 54. Which of the following is another name for boreal forest? a. matorral b. pampas c. steppes d. taiga ANSWER: d 55. In which biome is plant growth primarily constrained by precipitation in the summer? a. boreal forest b. temperate seasonal forest Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 c. temperate grassland d. tundra ANSWER: c 56. Which biome has soil that degrades quickly once cut for logging purposes and/or converted to agricultural use? a. temperate seasonal forest b. tropical rainforest c. tropical seasonal forest/savannah d. woodland/shrubland ANSWER: b 57. Succulent plants are a defining feature of a a. temperate seasonal forest. b. temperate rainforest. c. subtropical desert. d. woodland/shrubland.

ANSWER: c 58. Savannah gradually changes to tropical seasonal forest as a. temperature increases. b. temperature decreases. c. precipitation increases. d. precipitation decreases.

ANSWER: c 59. Which combination of factors causes the fastest nutrient cycling in a biome? a. high precipitation and high temperatures b. high precipitation and low temperatures c. low precipitation and high temperatures d. low precipitation and low temperatures ANSWER: a 60. Which is a characteristic agricultural use of the woodland/shrubland biome? a. grapes b. wheat c. cattle d. coffee ANSWER: a 61. Although precipitation is fairly low in boreal forests, soils are often saturated because of Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 a. groundwater recharge. b. frequent flooding. c. prevalence of succulent plants. d. reduced evaporation rates.

ANSWER: d 62. Which of the following global factors accounts for the difference between temperate seasonal forests and temperate rainforests? a. decreased precipitation in the seasonal forests due to the edge of Hadley cells b. increased temperatures in the rainforest due to ocean currents c. decreased precipitation in the seasonal forests due to rain shadows d. increased temperatures in the rainforest due to lower latitudes ANSWER: b 63. The ocean zone with the highest productivity is the a. neritic zone. b. photic zone. c. aphotic zone. d. benthic zone.

ANSWER: a 64. Which of the following is NOT an effect of dams on streams and rivers? a. increased water temperature upstream of the dam b. increased sediment settling c. increased levels of dissolved oxygen downstream of the dam d. habitat fragmentation ANSWER: c 65. The open ocean is most similar to a. subtropical desert. b. temperate seasonal forest. c. tropical rainforest. d. woodland/scrubland.

ANSWER: a 66. A symbiotic relationship with algae is central to a. mangrove swamps. b. intertidal zones. c. coral reefs. d. ponds and lakes.

ANSWER: c Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 67. As a river flows downstream, it generally a. moves faster. b. has more nutrients. c. is more shaded. d. narrows.

ANSWER: b 68. An important characteristic of freshwater wetlands is a. basic soils. b. anoxic soil conditions. c. sections of open water. d. acidic water.

ANSWER: b 69. Coral reefs are most similar to a. subtropical deserts. b. woodlands/shrublands. c. temperate seasonal forests. d. tropical rainforests.

ANSWER: d 70. An important characteristic of streams is a. high allochthonous inputs. b. high autochthonous inputs. c. lack of interaction with the riparian zone. d. many photosynthetic organisms.

ANSWER: a 71. Which is the surface water of thermally stratified lake? a. the epilimnion b. the hypolimnion c. the littoral zone d. the thermocline ANSWER: a 72. The aphotic zone is a feature in a. coral reefs. b. freshwater wetlands. c. mangrove swamps. d. open ocean.

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Chapter 2 e. intertidal zones.

ANSWER: d 73. Lakes are generally divided into zones, each of which has unique physical and biological attributes. In which zone would you expect to find rooted vegetation? a. littoral b. limnetic c. pelagic d. benthic e. neritic ANSWER: a 74. Which is a unique characteristic of estuaries? a. the prevalence of aquatic woody vegetation b. the seasonal overturn of water stratification c. the mixing of fresh and salt water d. the large variety of benthic organisms ANSWER: c 75. Why is water at the bottom of a temperate lake likely to be close to 4°C year-round? a. Cooling water below 4°C requires enormous amounts of energy. b. Soil temperatures are close to 4°C for most of the year in temperate regions. c. Air temperatures in the temperate zone rarely fall below 4°C. d. Water is densest at 4°C. ANSWER: d 76. During which seasons does overturn occur in a lake? a. winter and spring b. winter and summer c. fall and spring d. fall and summer e. winter and fall ANSWER: c 77. In which aquatic environment are organisms most likely to produce bioluminescence? a. aphotic zones b. coral colonies c. intertidal zones d. mangrove swamps ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 78. What important role do mangrove swamps play in maintaining their environment? a. They transfer sediment from terrestrial to aquatic biomes. b. They filter water, which refreshes groundwater reservoirs. c. They prevent coastal erosion. d. They increase the sedimentation of coral reefs.

ANSWER: c 79. Which of the following is NOT a barrier to shifting biomes? a. mountains b. rivers c. large highways d. oceans ANSWER: b 80. In which lake zone would photosynthesis not occur? a. profundal zones b. littoral colonies c. pelagic zones d. limnetic swamps ANSWER: a 81. The shortest growing season is found in which biome? a. taiga b. tundra c. boreal forest d. temperate rainforest ANSWER: b 82. Manure from a farming operation that enters into a stream would be considered? a. allochthonous b. autochthonous c. both allochthonous and autochthonous d. neither allochthonous nor autochthonous as the input is not natural ANSWER: a 83. What are the epilimnion and hypolimnion labels used to identify layers of a lake based on? a. proximity to the shore b. presence of rooted vegetation c. temperature differences d. amount of light penetration ANSWER: c Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 84. A major driver of the spring and fall turnover in lakes is what? a. the formation of ice b. the receding/melting of ice c. the water dropping to 4°C d. the wind ANSWER: d 85. Which areas have the fewest number of biomes present? a. North America and South America b. Africa and Australia c. Africa and South America d. Australia and Asia ANSWER: b Essay 86. The surface temperature of Mars averages approximately –55°C, with carbon dioxide trapped in ice and permafrost. How could humans begin to make the atmosphere more conducive to life?

ANSWER: Adding artificial greenhouse gas molecules with high absorption potential, such as chlorofluorocarbons, to the atmosphere of Mars would begin to heat the atmosphere via the greenhouse effect. As the atmosphere heated, the carbon dioxide would be released and continue the process without further inputs.

87. Urban heat islands are warmer than surrounding areas. How might albedo contribute to urban heat islands?

ANSWER: The albedo of pavement and most roofs is much lower than the albedo of natural surfaces. This lower albedo reduces the reflection of solar radiation and increases the reradiation of infrared, which heats the local air.

88. Explain how an increased angle of Earth's tilt would affect the variation in the heating of Earth.

ANSWER: An increased angle would cause the solar equator to move farther north and south throughout the year. This would make summers warmer and winters colder, since the direct sunlight would be more focused on the hemisphere that is in summer.

89. Imagine Earth as a cylinder with a pole at each end. How would the distribution of heat from the Sun change?

ANSWER: If Earth were cylindrical, there would be no change in atmospheric thickness or the angle at which the Sun hit the surface except for the flat ends, which would receive almost no sunlight and therefore be coldest. The only variable along the sides would be differences in albedo. There would be no significant variation in temperature with latitude.

90. Explain how the Coriolis effect would change if Earth were egg-shaped, with a narrower equatorial region.

ANSWER: A narrower equatorial region would result in a less significant difference in rotation speed between the equator and poles. This would decrease the Coriolis effect, resulting in the prevailing winds Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 going more north-south and less east-west.

91. Additional water vapor in the atmosphere has both positive and negative feedback. Why is this?

ANSWER: Because water vapor is a greenhouse gas, it traps additional heat, which increases the temperature and allows more water vapor to be held in the atmosphere. However, additional water vapor can also increase cloud cover, which reflects more sunlight, decreasing the temperature and thus reducing the amount of water vapor in the atmosphere.

92. Explain how a decrease in atmospheric temperature can cause rain.

ANSWER: Since the capacity of air to hold water depends on temperature, as temperature decreases, the saturation point decreases. Water in the atmosphere that exceeds the new saturation point will fall as precipitation.

93. One potential effect of climate change is that it could disrupt thermohaline circulation. What might cause this disruption?

ANSWER: Thermohaline circulation is driven by the sinking of cold, high-salinity water near the poles. If the polar temperature continues to warm, there will be less ice formation, which concentrates the salt in polar waters. Increased melting of existing ice will also decrease the salinity of polar water. This decreased salinity would make the water less dense and thus slow its effect on the current.

94. Explain how the effects of El Niño–Southern Oscillation illustrate the importance of air and water currents in the global distribution of heat.

ANSWER: El Niño–Southern Oscillation is driven by the change in prevailing wind direction over the Pacific, a regional event. However, this change has global effects, including increased precipitation in North America, drought in Africa, and dry conditions in both South America and Australasia. Only Europe would not be subject to significant effects.

95. Zoologists from Peru and Chile have been examining climate records from the coastal deserts of their countries. These deserts are the driest on Earth, yet they lie within the southward reach of the intertropical convergence during the Southern Hemisphere summer. Explain this curious phenomenon.

ANSWER: Two factors contribute to extreme dryness along the Pacific coasts of Peru and Chile. Both lie in the rain shadow of the Andes. Running northward along the shore is the cold Peru Current of the eastern Pacific Ocean. Moist air masses moving eastward from the Pacific will lose much of their moisture as they are cooled by passage over the cold waters of the Peru Current. These coastal deserts are thus effectively blocked from receiving any precipitation either from the east or the west.

96. Explain why dry climates are commonly found around 30° S and 30° N latitudes.

ANSWER: This is where the cool, dry air from Hadley cells sinks to Earth's surface. Since the air has already lost most of its water vapor while rising, very little precipitation falls in these areas. Rain shadows also contribute to dryness in some areas.

97. Explain why western Europe is much warmer than the same latitudes in eastern Europe.

ANSWER: Western Europe has generally warmer temperatures because the ocean moderates the temperature along the coasts. The warm current along the western coast of Europe magnifies this coastal warming effect, making the Atlantic coast warmer than the areas around the Black Sea and Caspian Sea. Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 98. Describe the path that incoming solar radiation takes and how it is transformed in the greenhouse effect.

ANSWER: Solar radiation (made up of visible light and ultraviolet (UV) light reaches Earth. Approximately one-third of incoming solar radiation is reflected back into space by clouds, the atmosphere, and Earth's surface. Clouds and Earth's surface absorb the remaining incident solar radiation. The absorbed solar radiation is transformed into infrared radiation (IR). The IR is then reradiated back out from Earth's surface. Some of the reradiated IR passes out into space, but much of the reradiated IR is absorbed by greenhouse gases (both natural and anthropogenic) in the atmosphere and returns to Earth.

99. Few biomes have cold temperature combined with high precipitation. Why is this?

ANSWER: The combination of cold temperature and high precipitation is globally rare because in cold biomes little energy is available to evaporate moisture from Earth’s surface, which is a necessary precursor to precipitation. Cold air also has little capacity to hold moisture and thus yields relatively little precipitation.

100. Why are animals NOT used as the distinguishing features for biomes?

ANSWER: Animals are generally less variable in their forms than plants as climate changes. This is partially due to the inability of plants to move; they must adapt to the stresses of each environment. Animals are mobile and can seek shelter or specific microclimates in ways that plants cannot, which means that they often live in multiple biomes.

101. In climate diagrams the location of the temperature and precipitation lines are used to determine which of the two limits plant growth in the biome. Explain why higher temperatures also require increased precipitation.

ANSWER: As the temperature increases, plants transpire more, thus increasing their water use.

102. Biomes occupying the extremes of the precipitation spectrum (very moist or very dry) burn infrequently, while biomes with moderate precipitation and seasonal drought burn readily and regularly. Explain this phenomenon.

ANSWER: Fire is uncommon in very moist forests because fuels are rarely dry enough to sustain fire. Because of their low productivity, dry biomes like deserts rarely accumulate sufficient fuel to burn.

Seasonally dry but still productive grasslands and shrublands have both abundant fuels and the appropriate conditions for fire.

103. Compare and contrast arctic and alpine tundra.

ANSWER: Arctic and alpine tundra are superficially similar in their vegetation and even species composition: They are characterized by low-growing plants adapted to harsh conditions, including extreme winter weather. However, alpine tundra is characterized by warmer and longer growing seasons, less severe winters, greater productivity, better-drained soils, and higher species diversity.

104. Explain how the riparian zone might affect an adjacent terrestrial biome.

ANSWER: The flooding in a riparian zone will bring additional water to an adjacent terrestrial biome, much like increased precipitation. The most noticeable changes will occur in desert biomes. This is what causes a significant increase in vegetation along rivers like the Nile, where the floodplains are much more fertile than the surrounding subtropical desert.

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Chapter 2 105. Explain why the communities in intertidal zones must be adapted to survive a wide range of conditions.

ANSWER: Organisms living in intertidal zones must be able to survive in both high tide and low tide conditions. High tide brings water and lower temperatures, while low tide conditions can be dry and hot because of sun exposure. There can also be variations in salinity as well as harsh conditions from waves.

106. Biological activity is severely limited in a thermally stratified temperate lake in midsummer. Explain this phenomenon with reference to both surface and deeper waters.

ANSWER: Thermal stratification prevents water from circulating between the surface and the depths. Without this circulation, biological processes stagnate. Surface waters are enriched with oxygen and are illuminated by the Sun, but nutrient depletion severely limits the productivity of plants and the activities of animals that ultimately depend on plants for their food. In contrast, the nutrient-rich deeper waters lack sunlight and are oxygen-depleted, which limits biological activity. When the lake turns over in the fall, oxygen levels increase in deeper waters and the surface waters become more nutrient-rich, which stimulates biological activity throughout the lake.

107. Explain the similarities and differences among bogs, marshes, and swamps.

ANSWER: All three are types of freshwater wetlands with plants that have adapted to soil saturated with water.

Bogs are characterized by acidic water and are prevalent in the high latitudes of the Northern Hemisphere. Swamps contain emergent trees, while marshes have primarily nonwoody vegetation such as cattails.

108. How might global climate change affect current agricultural regions?

ANSWER: One negative effect could be the increase in transition from grassland and savannah biomes to desert biomes as temperatures get too high to support more water-dependent plants.

109. Describe some of the similarities and differences between tropical rainforests and tropical seasonal forests.

ANSWER: Tropical rainforests are found within 20° N and 20° S of the equator. Tropical rainforests are always warm and receive at least 2,000 mm of precipitation throughout the year with rarely fewer than 100 mm in any given month. Tropical season forests are generally found beyond 10° N and 10° S of the equator. Tropical seasonal forests are warm but have a definite wet and dry season during the course of the year.

110. In general terms what is the difference between a stream and a river?

ANSWER: Streams are narrow channels of fast-flowing fresh water. Rivers are wide channels of slow-flowing fresh water. Streams typically join with other streams to become larger channels that are then large enough to be considered a river.

111. Explain the differences between autochthonous and allochthonous inputs in a stream or river.

ANSWER: Autochthonous inputs are organic matter produced from within the stream or river ecosystem by producers (algae and plants). Allochthonous inputs are organic matter that enters the stream or river from outside of the stream/river ecosystem (examples: leaves and other plant parts that fall into a stream/river). Organic matter in streams tends to be more allochthonous, and organic matter in rivers tends to be more autochthonous.

112. Why might Earth's temperature continue to increase for a time even if all emission of greenhouse gases Copyright Macmillan Learning. Powered by Cognero.

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Chapter 2 ceased?

ANSWER: Because of the long lifetime of many greenhouse gases, even if emissions ceased, the gases already emitted will remain in the atmosphere for many years. Since it takes time for Earth to heat, the temperature will continue to rise until it stabilizes at the temperature dictated by the current levels of greenhouse gases.

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Chapter 3 Multiple Choice 1. Adding dissolved compounds such as salt to water _____ the boiling point and _____ the freezing point. a. increases; increases b. increases; decreases c. decrease; increases d. decreases; decreases ANSWER: b 2. The high specific heat of water a. means large amounts of heat are needed to change the temperature of water. b. requires significant heat energy to make the transition from solid to liquid. c. requires significant heat energy to make the transition from liquid to gas. d. makes it difficult to increase the temperature of liquid water above 100°C. ANSWER: a 3. Which is NOT an adaptation that exploits the density of water? a. a gas-filled swim bladder b. droplets of oil on algae c. long, filamentous appendages d. high percentages of fat ANSWER: c 4. The low density of ice a. makes it ineffective at insulating water from the cold. b. allows aquatic plants to survive the winter. c. is due to the high viscosity of water. d. prevents it from moving in water.

ANSWER: b 5. Water’s polar nature a. explains its high density. b. makes it a good solvent. c. causes it to freeze at 0°C. d. limits the amount of dissolved nutrients it can hold.

ANSWER: b 6. At what temperature does water reach its maximum density? a. 32°C b. 0°C c. 4°C Copyright Macmillan Learning. Powered by Cognero.

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Chapter 3 d. –12°C e. 100°C ANSWER: c 7. The limit to the amount of minerals water can hold is called a. the dissolution point. b. the solvent point. c. the deposition point d. the saturation point.

ANSWER: d 8. Which is the most basic? a. human blood b. acid rain c. carbonated beverages d. pure water ANSWER: a 9. Which causes acid rain? a. CO2 b. SO2 c. HCO3 d. NaOH ANSWER: b 10. Aquatic organisms have developed streamlined shapes to adapt to the a. density of water. b. viscosity of water. c. polar nature of water. d. basic nature of water.

ANSWER: b 11. Which part of an organism is less dense than water? a. bone b. protein c. muscle d. fat ANSWER: d 12. A liquid with low pH would have a. high OH– concentration.

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Chapter 3 b. low NO2 concentration. c. low CaCO3 concentration. d. high H+ concentration.

ANSWER: d 13. Which of the nutrients listed below is NOT required by all organisms? a. nitrogen b. phosphorus c. potassium d. sulfur e. silicon ANSWER: e 14. Limestone deposits are due to a. the low pH of ocean water. b. the solubility of calcium carbonate. c. the polar nature of water. d. acid deposition.

ANSWER: b 15. Solutes a. are membranes through which nutrients pass into cells. b. reduce the acidity of water. c. are particles that can pass through cell membranes. d. are substances dissolved in water.

ANSWER: d 16. A freshwater fish with a high concentration of dissolved nutrients will a. have high osmotic pressure. b. have low osmotic pressure. c. be hyposmotic. d. actively secrete solutes.

ANSWER: a 17. Hyperosmotic conditions a. cause low osmotic pressure. b. occur in freshwater organisms. c. cause active secretion in gills. d. occur in arid landlocked lakes.

ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 3 18. Why is it important for organisms to osmoregulate? a. Organisms cannot survive in hyposmotic conditions. b. Active transport requires large amounts of energy. c. An imbalance in solutes disrupts cell functions. d. High osmotic pressure can burst cell walls.

ANSWER: c 19. The use of salt on roads in winter has led to a. increased precipitation of salts in nearby ponds b. decreased survival of freshwater organisms in nearby ponds. c. hyperosmotic conditions. d. increased acid deposition.

ANSWER: b 20. Mangroves grow on salt-laden coastal mudflats that are inundated daily by high tides. Which of the following is NOT used by the plant to address the problem of water acquisition and elimination of excess salts? a. growing only when salt content of the coastal mudflats are at the season lowest levels b. maintaining high concentrations of organic solutes in their roots c. excluding salts from their roots by active transport d. actively excreting salt from glands on the surfaces of their leaves ANSWER: a 21. Ammonia is a by-product of a. digesting proteins. b. absorbing excess salts. c. excreting urea. d. active uptake in gills.

ANSWER: a 22. Which of the following is NOT a part of carbon equilibrium in water? a. bicarbonate b. ammonia c. hydrogen ions d. carbonic acid ANSWER: b 23. Why are both carbon dioxide and oxygen limited in aquatic environments? a. They are not very soluble in water. b. They change to different chemical forms in water. c. They cannot diffuse across cell membranes. d. They are rare in the atmosphere and therefore limited in water.

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Chapter 3 ANSWER: a 24. How does the concentration of bicarbonate in water compare to the concentration of carbon dioxide in the air? a. one-tenth b. about the same c. twice as much d. about 30 times more e. over 100 times more ANSWER: e 25. How does water in a bog differ from water in other locations? a. More bicarbonate and more carbon dioxide are available. b. More bicarbonate and less carbon dioxide are available. c. Less bicarbonate and more carbon dioxide are available. d. Less bicarbonate and less carbon dioxide are available.

ANSWER: c 26. Which does NOT limit the ability of aquatic plants to photosynthesize? a. slow diffusion of carbon dioxide in water b. boundary layers c. the size of bicarbonate molecules d. high levels of carbonic acid ANSWER: d 27. The dissolved oxygen levels in water did NOT require adaptation for a. whales. b. sharks. c. squid. d. zooplankton.

ANSWER: a 28. Which is used to increase oxygen extraction? a. hydrogen ions b. boundary layers c. countercurrent circulation d. concurrent circulation ANSWER: c 29. Anaerobic conditions a. decrease photosynthesis.

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Chapter 3 b. are due to increased pH. c. decrease the diffusion of oxygen. d. are more common in deep water than in the shallows.

ANSWER: d 30. Which is a byproduct of anaerobic respiration? a. CO2 b. H2CO3 c. H2S d. HCl ANSWER: c 31. Which is NOT an adaptation to low-oxygen aquatic environments? a. increased hemoglobin b. breathing air c. increased metabolic activity d. symbiotic relationship with algae ANSWER: c 32. In which location would you expect to find the highest levels of dissolved oxygen? a. deep ocean water b. a freshwater bog c. a landlocked lake d. a fast, shallow river ANSWER: d 33. What enables thermophilic bacteria to withstand very high temperatures? a. high glycerol concentrations that protect cell membranes b. low concentrations of isozymes that change form at high temperatures c. cell materials that reduce heat transfer d. high proportions of particular amino acids that form strong bonds ANSWER: d 34. The rate of biological processes increases two to four times for each _____ increase in temperature a. 12°C b. 10°C c. 8°C d. 5°C ANSWER: b 35. What prevents ice formation in blood and tissues of marine animals?

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Chapter 3 a. an increased concentration of glycerol b. an increased concentration of oxygen c. a decreased concentration of salt d. a decreased concentration of trimethylamine oxide ANSWER: a 36. Suppose organisms in a lake are limited by oxygen. How might the lake’s ability to support organisms change if the temperature increased by 10°C, assuming that all the organisms were still within their thermal optima? a. It could support about twice as many organisms. b. It could support about half as many organisms. c. It could support about the same number of organisms. d. More information is required to determine whether it would change.

ANSWER: b 37. Glycoproteins coat ice crystals that begin to form in blood and prevent freezing in a process called a. antifreeze accumulation. b. supercooling. c. isozymal coating. d. osmoregulation.

ANSWER: b 38. What percentage of a normal distribution is within one standard deviation of the mean? a. 34% b. 50% c. 68% d. 76% e. 95% ANSWER: c 39. Nine ponds are sampled, and the mean salt concentration is 121 ppm, with a sample variance of 25 ppm.

What is the standard deviation of the sample? a. 0.6 b. 2.2 c. 3 d. 5 e. 11 ANSWER: d 40. Samples of ocean water are taken from 25 locations, and the mean salt concentration is 36 ppt, with a sample variance of 1 ppt. What is the standard error of the sample?

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Chapter 3 a. 0.2 b. 0.5 c. 1 d. 1.2 e. 5 ANSWER: a 41. The primary cause of coral bleaching is a. decreased water temperature. b. increased water temperature. c. decreased salt concentrations. d. increased water pH. e. decreased water pH. ANSWER: b 42. Coral bleaching a. occurs when coral exoskeletons begin to break down. b. is due to a lack of dissolved nutrients from the surrounding water. c. is a temporary process that is usually reversed within days. d. occurs when algae are expelled from coral.

ANSWER: d 43. The thermal optimum for an organism results from a. the environment in which the organism is found. b. the genetic makeup of the organism. c. the niche of the organism. d. the thermal properties of water.

ANSWER: b 44. Organisms that can withstand high environmental temperatures without having their proteins denatured are termed a. endothermic. b. exothermic. c. thermophilic. d. homeothermic.

ANSWER: c 45. Fish obtain oxygen from the water through their gills using a. countercurrent circulation. b. concurrent circulation.

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Chapter 3 c. unidirectional circulation. d. recurrent circulation.

ANSWER: a 46. Spotted salamanders lay eggs in gelatinous masses on twigs partially submerged in small ponds or vernal pools. Associated with the eggs, scientists have found a species of alga living in a mutualistic relationship with the developing eggs. What benefit does the salamander receive from this relationship? a. The salamander eggs are better camouflaged. b. The salamander embryos receive an increased oxygen supply. c. The salamander embryos receive an increased carbon dioxide supply. d. The salamander embryos receive an increased nitrogen supply.

ANSWER: b 47. The region of unstirred air or water surrounding the leaf surfaces of a terrestrial or aquatic plant is called the a. photosynthetic active region. b. diffusion layer. c. boundary layer. d. transpiration zone.

ANSWER: c 48. A smallmouth bass swimming in colder water of a springtime lake would likely expend _________ energy than when swimming in warmer water of the same lake during the summer (all things being equal). a. less b. more c. the same d. There is no way to determine.

ANSWER: b 49. The intricately designed shells of the algae known as diatoms are made up of which minor nutrient? a. magnesium b. calcium c. iron d. silica ANSWER: d Objective Short Answer 50. Why is it surprising that some organisms are able to live at temperatures above 75°C? ANSWER: Essay Copyright Macmillan Learning. Powered by Cognero.

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Chapter 3 51. You are studying a small stream and find that its pH is 4.5. What does this tell you about the stream, and what might be the cause?

ANSWER: Stream is highly acidic, and likely to have reduced diversity of plants and animals. Natural cause could be proximity to bog environments where pH can be very low. Other factors are input from human activities (power generation, industry, mining).

52. What is unusual about the physical properties of water?

ANSWER: Found in all three states of matter (solid, liquid, gas) under conditions commonly found on earth.

Other important features include (1) polarity (making water a good solvent), (2)lower density as a solid (allowing ice to float and organisms to survive under ice),(3) cohesion-surface tension (allowing water molecules to adhere to one another), (4) high specific heat (provides for thermal stability of environments/organisms.

53. Why is liquid water important for the formation of life on Earth?

ANSWER: The liquid state of water allows it to act as a solvent for many nutrients, making them accessible to early life forms. The heat capacity of water also moderates the temperature of bodies of water and Earth itself.

54. How does a low pH harm aquatic environments?

ANSWER: At high levels hydrogen ions can interfere with enzymes and dissolve heavy metals, many of which are toxic.

55. How does the permeable nature of cells affect evolution in aquatic animals?

ANSWER: Because their cells are permeable, aquatic animals must adapt ways to regulate the transfer of nutrients and water between their cells and their environment. Marine and freshwater organisms have evolved differently because of the opposite conditions in the two environments: Marine organisms must adapt to high salt concentrations, and freshwater organisms must adapt to low salt concentrations.

56. Why do sharks retain urea rather than excrete it? How does this influence their fitness?

ANSWER: Because the urea acts as a solute in their blood, it reduces the osmotic pressure produced by hyperosmotic conditions in the ocean. Their fitness is improved because they require less osmoregulatory energy to survive and therefore need less food to remain healthy.

57. Explain why freshwater fish do not need to drink water.

ANSWER: Since freshwater fish are hyperosmotic in relation to their environment, their cells tend to absorb water from their environment. This means they must work to eliminate excess water and do not need to drink any additional water.

58. Explain why there are relatively few plant species in mangrove forests.

ANSWER: Mangrove forests have both low levels of oxygen and high salinity. Survival in these conditions requires additional energy and specific adaptations. Relatively few plants have evolved to withstand both low levels of oxygen and high salinity.

59. What are some ways to prevent an aquarium from becoming anoxic?

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Chapter 3 ANSWER: One possibility is adding aquatic plants that produce oxygen. Another option is to increase the surface area of water that is exposed to the air (with stirring, for example), since that will increase the rate of diffusion.

60. What concept does the graph illustrate? Explain why it is important.

ANSWER: The graph illustrates the Q10 ratio of physiological processes. This is a measure of how organisms increase their metabolism at higher temperatures and as a result develop faster, up to the point when high temperatures begin to have negative effects.

61. What unique low-temperature challenge are marine organisms likely to encounter?

ANSWER: Because of its high salt content, seawater freezes at –1.9°C. The tissue and blood of most vertebrates contain roughly half as much salt as sea water, meaning they can freeze while the water around them is still liquid.

62. Explain why thermal pollution is relatively rare in oceans.

ANSWER: While local temperatures can be increased by human activities, the large size of the oceans means that any change will have much less impact, since currents and diffusion will reduce the change in temperature unless the effect is global, like the increase in temperature from climate change.

63. Explain how osmotic regulation might make marine organisms better at surviving low temperatures than freshwater organisms.

ANSWER: Because of the higher solute concentration in oceans, marine organisms such as sharks have adapted to higher solute concentrations in their tissues to reduce the energy required for osmotic regulation.

An increase in salt or similar solutes will reduce the freezing point of the organism, potentially allowing it to survive temperatures that could freeze a freshwater organism.

64. What do a large standard deviation and small standard error tell you about the data from several samples?

ANSWER: A large standard deviation means that the data are spread out around the mean, while a small standard error indicates that the calculated mean is close to the actual mean.

65. Explain how increased atmospheric carbon dioxide can affect the ability of coral to build their exoskeletons.

ANSWER: The increased carbon dioxide in the atmosphere increases the diffusion of carbon dioxide into the water, which becomes carbonic acid. This carbonic acid dissociates and recombines with existing carbonate to form bicarbonate, reducing the available carbonate used by coral as calcium carbonate.

66. Explain how acid precipitation indirectly impacts trees.

ANSWER: Acid precipitation causes leaching of soil nutrients, thus making these nutrients unavailable for use by trees.

67. You are studying a river estuary system. Explain why a prolonged summer drought in the river’s watershed might have a potential impact on species living in the estuary.

ANSWER: More salt water would advance up the river from the ocean.

68. Explain from a physiological perspective why it would be advantageous for a temperate freshwater fish species to produce different forms of the same enzyme (isozymes).

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Chapter 3 ANSWER: During the course of the year, temperate freshwater fish are exposed to varying water temperatures (winter to summer). Enzymes mediate physiological reactions in the cells of the fish. Enzymes operate most efficiently with specificity to temperature, and thus the chemical reactions within the cells of fish require multiple forms of an enzyme that function at the varying environmental temperature ranges to which the fish would be exposed.

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Chapter 4 Multiple Choice 1. The field capacity of the soil is the a. number of plants it can support. b. amount of water held against gravity. c. amount of nutrients the soil can hold. d. nutrients accessible to plants.

ANSWER: b 2. Which is NOT a nutrient that plants obtain from the soil? a. carbon b. nitrogen c. calcium d. phosphorus ANSWER: a 3. What soil would you expect to have the highest field capacity? a. loam b. silty clay c. silt d. sandy loam e. silt loam ANSWER: b 4. The potential energy generated by the attractive forces between water molecules and soil particles is a. osmotic potential. b. water potential. c. soil potential. d. matric potential.

ANSWER: d 5. Root cell adaptation to prevent the cell solutes from equilibrating with the water in the soil includes I. semipermeable membranes that prevent the transfer of large molecules.

II. cell membranes that can prevent the transfer of water out of the cell.

III. cell membranes that can actively transport ions across the gradient. a. I and II only b. I and III only c. II and III only d. III only e. I, II, and III ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 4 6. In which soil would the percentage of water be the highest at the wilting point? a. silty clay b. sandy clay loam c. loam d. sandy loam ANSWER: a 7. Salinization a. can be caused by repeated irrigation. b. is a process resulting in sandy soil. c. increases the water potential. d. leaches away the nutrients in soil.

ANSWER: a 8. Which soil has the largest particles? a. clay b. sand c. loam d. silt ANSWER: b 9. The attraction between water molecules causes a. root pressure. b. xylem. c. tension. d. cohesion.

ANSWER: d 10. One factor that drives the movement of water from roots to leaves is a. gravity. b. tension. c. concentration differentials. d. osmotic potential.

ANSWER: b 11. Transpiration is the a. movement of water from the soil to a plant’s roots. b. absorption of carbon dioxide. c. evaporation of water from a leaf. d. loss of energy due to respiration.

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Chapter 4 ANSWER: c 12. A plant with a high number of stomata a. has a high root pressure. b. is resistant to salinization. c. has a low rate of photosynthesis. d. has a high rate of transpiration. e. can survive high water potential conditions.

ANSWER: d 13. Which is NOT an adaptation by camels to low water availability? a. the ability to store excess water b. high surface-area-to-volume ratio c. increased tolerance for high body temperature d. increased cooling of the blood for the brain ANSWER: b 14. Photosynthesis primarily allows plants to produce a. glucose. b. oxygen. c. nitrogen. d. carbon dioxide.

ANSWER: a 15. Carbon-3 photosynthesis a. is the most common form of photosynthesis. b. uses malic acid during the Calvin cycle. c. does not require RuBisCO. d. is common in succulent plants.

ANSWER: a 16. Which photosynthesis method is best suited to warm, dry environments?

I. C3 fixation II. C4 fixation III. CAM (crassulacean acid metabolism) a. I only b. I and II only c. II only d. II and III only e. III only ANSWER: d Copyright Macmillan Learning. Powered by Cognero.

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Chapter 4 17. The first compound formed after light is absorbed by a plant is a. RuBisCO. b. ATP. c. Glucose. d. PEP. ANSWER: b 18. The development of small leaves with many veins is primarily for a. reduced evaporation. b. increased water absorption. c. increased heat dissipation. d. embolism prevention.

ANSWER: d 19. Which compound is NOT used to store energy in photosynthesis? a. ATP b. NADPH c. PEP d. OAA ANSWER: c 20. A unique feature of CAM photosynthesis (crassulacean acid metabolism) is a. the use of oxaloacetic acid. b. a daily cycle of photosynthesis. c. increased photosynthesis at high temperatures. d. the ability to use both phosphoenolpyruvic acid and RuBisCO. ANSWER: b 21. The Calvin cycle in CAM photosynthesis occurs in a. xylem cells. b. mesophyll cells. c. bundle sheath cells. d. lower epidermis cells.

ANSWER: b 22. An organism’s ability to maintain constant internal conditions in the face of a varying external environment is called a. thermoregulation. b. metabolism. c. active regulation.

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Chapter 4 d. homeostasis. e. negative feedback.

ANSWER: d 23. Which organ is responsible for removing salts from mammals? a. liver b. kidney c. lower intestine d. thyroid ANSWER: b 24. What adaptation has occurred in species with limited access to fresh water? a. modified tear glands b. increased skin surface area c. enlarged liver d. small loop of Henle ANSWER: a 25. What is the primary cause of increased nitrogen in animals? a. absorption by the blood during respiration b. high concentrations in water sources c. inability to metabolize nitrogen gas d. the consumption of proteins ANSWER: d 26. Which is NOT used by animals to remove excess nitrogen? a. urea b. ammonia c. uric acid d. nitrite ANSWER: d 27. Which heat transfer method occurs with contact? a. convection b. evaporation c. radiation d. conduction ANSWER: d 28. The amount of heat due to radiation increases with the ______ power of absolute temperature. a. first Copyright Macmillan Learning. Powered by Cognero.

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Chapter 4 b. second c. third d. fourth e. fifth ANSWER: d 29. Wind causes heat transfer by a. convection. b. evaporation. c. radiation. d. conduction.

ANSWER: a 30. Which heat transfer method in organisms causes only cooling? a. convection b. evaporation c. radiation d. conduction ANSWER: b 31. What characteristic of an organism would increase the energy required to maintain its temperature? a. high thermal inertia b. low surface area c. a large temperature difference d. a thick boundary layer ANSWER: c 32. An organism that does not maintain a constant body temperature is a(n) a. ectotherm. b. endotherm. c. homeotherm. d. poikilotherm.

ANSWER: d 33. Which of the following is an endotherm? a. an ant b. a whale c. a tree d. a snake ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 4 34. Which is an adaptation to manage cold in extremities? a. blood shunting b. concurrent circulation c. lack of precapillary sphincters d. increased insulation ANSWER: a 35. Which method of heat transfer is used to assist in population estimates? a. conduction b. convection c. evaporation d. radiation ANSWER: d 36. The primary source of heat on Earth is a. evaporation. b. convection. c. radiation. d. conduction.

ANSWER: c 37. Which of the following is a categorical variable? a. color b. pressure c. light d. energy ANSWER: a 38. A nominal variable is also known as a. dependent. b. independent. c. categorical. d. continuous.

ANSWER: c 39. Which if the following does NOT enhance cotton growing in Texas? a. C4 pathway photosynthesis b. an earlier planting date c. the use of cytokinin d. RuBisCO variations Copyright Macmillan Learning. Powered by Cognero.

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Chapter 4 ANSWER: a 40. An animal curling up into a ball on a cold winter night is attempting to a. increase radiative heat gain. b. increase convective heat gain. c. decrease evaporative cooling. d. decrease conductive heat loss.

ANSWER: d 41. All things being equal, which organism would potentially lose body heat at a greater rate? a. moose b. elephant c. fox d. mouse ANSWER: d 42. Which is NOT an adaptation that plants may have to deal with hot, dry conditions? a. waxy cuticles on the leaf surface b. individual leaves with large surface area c. fine hairs on the surface of the leaf d. no leaves on the plant ANSWER: b 43. Which is NOT a true statement? a. All ectotherms are poikilotherms. b. Ectotherms tend to have lower metabolic rates than endotherms. c. Ectotherms are able to alter their body temperature. d. Ectotherms have body temperatures that are determined largely by their external environment.

ANSWER: a 44. Some species of birds have specific adaptations of their circulatory system to decrease heat loss to the environment. Those adaptations include which of the following? a. increased red blood cell count b. an enlarged spleen c. countercurrent blood circulation d. hemoglobin with a higher affinity for oxygen ANSWER: c 45. To maintain homeostasis in terms of body heat, an organism would need to potentially balance all of the following except a. increased conductive heat loss.

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Chapter 4 b. increased convective heat loss. c. increased radiative heat gain. d. increased evaporative heat gain.

ANSWER: d 46. Which is NOT a characteristic of the plant known as skunk cabbage? a. It is an ectotherm. b. It flowers late in the fall when temperatures drop below freezing. c. It generates metabolic heat by burning glucose in its mitochondria. d. At times it acts like an endotherm.

ANSWER: b 47. The parent material of a soil is the a. organic matter from the vegetation on top of the soil. b. area from which the soil has been transported. c. bedrock underneath the soil. d. type of erosion that contributed to soil formation.

ANSWER: c 48. Which is the correct order of the soil horizons, starting at the surface? a. A, B, C, E, O, R b. R, A, E, B, C, O c. O, E, C, B, A, R d. O, A, E, B, C, R ANSWER: d 49. Which of the following is the most likely reason a soil would not have an O horizon? a. The area has heavy precipitation. b. The soil is in a desert. c. The soil is in a forest. d. The soil is in an area that receives a lot of weathering.

ANSWER: b 50. In areas with significant leaching, which soil horizon would be largest? a. A b. B c. E d. O e. R ANSWER: c Copyright Macmillan Learning. Powered by Cognero.

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Chapter 4 51. Which of the following ions is NOT an important nutrient for plants? a. K+ b. Ca2+ c. Na+ d. H+ e. Mg2+ ANSWER: d 52. Which soil characteristics are the most desirable for agriculture? a. high cation exchange capacity and a large E horizon b. low cation exchange capacity and a large E horizon c. high cation exchange capacity and a small E horizon d. average cation exchange capacity and a small E horizon ANSWER: c 53. Cation exchange capacity depends on the a. amount of clay. b. number of positive ions. c. type of bedrock. d. percentage of hydrogen ions.

ANSWER: a Essay 54. Explain why loam is good for agriculture.

ANSWER: Loam contains a mix of sand, silt, and clay, which is important for water retention. If there is too much sand, the soil will be unable to retain much water, even with fairly regular precipitation.

Although clay soils retain a lot of water, clay particles can hold water molecules so tightly that it can be difficult for plants to extract the water from the soil.

55. How can soil type affect salinization?

ANSWER: Salinization is caused by repeated low amounts of irrigation. Having a soil with higher clay percentage that retains more water will reduce the number of times a field has to be irrigated and thus reduce the chance of salts remaining near the top of the soil. Soil with a higher sand content will retain less water and will have to be watered more often, thus increasing the risk of salinization.

56. Why are stomata necessary? What benefit do they provide, and how?

ANSWER: Stomata allow plants to control the rate of transpiration in their leaves. Stomata are able to open and close, which allows plants to adjust to dry conditions and increase photosynthesis in wet conditions.

57. Explain how the C4 pathway reduces reliance on water.

ANSWER: The enzyme PEP can bind carbon dioxide at lower concentrations than RuBisCO used in C3 photosynthesis. This means that the stomata of C4 plants can remain closed for longer periods, Copyright Macmillan Learning. Powered by Cognero.

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Chapter 4 which reduces water loss.

58. Explain why the C4 pathway accounts for a high proportion of photosynthesis worldwide and why this is unexpected.

ANSWER: The process of photosynthesis that C4 plants follow is less efficient than C3 in nonarid climates, and this makes C4 plants less able to compete. While relatively few species use the C4 pathway, the species that do use the C4 pathway—corn, for example—are important agricultural crops for humans. Agricultural use has increased the prevalence of C4 plants far more than we would have expected given the inefficiency of the C4 process.

59. Explain the similarities and differences between the C4 pathway and CAM pathway for photosynthesis.

ANSWER: Both methods reduce the water loss of the plants, making them resistant to arid conditions. This is done by storing carbon dioxide converted into malic acid; however, the CAM pathway conducts photosynthesis during the day with carbon dioxide stored from the night, while C4 simply reduces the time that stomata are open to collect carbon dioxide during the day.

60. In which soil types would a CAM pathway plant have an advantage over a C3 pathway plant? Explain why.

ANSWER: A CAM pathway plant would have an advantage in soils with high sand and low clay content. This is because they lose much less water during photosynthesis and thus would be better suited to the lower-moisture conditions in sandy soils.

61. Why does limited water increase an organism’s effort to maintain homeostasis?

ANSWER: Water is important for maintaining homeostasis because of the role it plays in dissolving salts and nitrogen in organisms. When plenty of water is available, homeostasis can be maintained without significant effort simply by using water to dilute excess salts. When water is limited, energy must be spent to eliminate salts without losing too much water.

62. Explain negative feedback with an example.

ANSWER: Negative feedback is a mechanism by which a system returns to the original or desired state. For example, as an organism begins to cool, its body may begin shivering to produce additional heat.

63. Explain why uric acid is more costly to excrete than urea.

ANSWER: The energy cost of compounds is sometimes measured by the number of organic carbon atoms used to produce the energy required for excretion. For uric acid, this is 1.25 atoms of carbon per atom of nitrogen versus 0.5 atoms of carbon per atom of nitrogen for urea.

64. How does size affect heat exchange in animals?

ANSWER: Because a large animal will have a lower surface-area-to-volume ratio than a small animal, it will undergo less convection and conduction. This makes it easier to maintain a constant temperature.

While low convection and conduction are useful in cold weather, they can cause overheating in very hot weather.

65. How does fur affect heat transfer?

ANSWER: Fur acts as an insulator that reduces conduction by adding thickness between the animal’s organs and the environment. It also reduces the heat transfer due to convection by trapping air, which Copyright Macmillan Learning. Powered by Cognero.

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Chapter 4 makes a more effective boundary layer.

66. How are independent variables used in scientific experiments? What is an example of an independent variable and a related experiment?

ANSWER: Independent variables are believed to cause a change in other variables. In an experiment the independent variable is the factor that would be changed across different samples to see how it affected the other variables. For example, an independent variable could be soil composition in an experiment on soil water retention.

67. Explain the benefits and costs of increased transpiration in cotton.

ANSWER: Increased transpiration increases evaporation, which cools the cotton and increases the effectiveness of the RuBisCO in photosynthesis. The increased transpiration and evaporation mean that more water is needed, and thus there is an increased chance of salinization due to irrigation.

68. Explain how water moves up in a plant from the roots to the leaves against the pull of gravity.

ANSWER: Water molecules are held together by hydrogen bonds (cohesion). The column of water from root to leaf is continuous. As a result of transpiration at the leaf, water is drawn up through the xylem, overcoming the pull of gravity.

69. Describe the adaptations that a desert animal may possess to survive in such a dry environment.

ANSWER: Desert animals may have behavioral adaptations that include being active and feeding at night and staying in burrows during the heat of the day. Physiological adaptations may include efficient kidneys that allow for greater water reabsorption and less water loss (elongated loops of Henle).

70. If you were designing a pair of chest waders for people fly fishing in cold mountain streams, what would be an aspect of your design to decrease convective heat loss?

ANSWER: The waders would be made with highly insulative material to decrease the loss of body heat to the cold flowing water.

71. Explain why tropical soils often have low fertility.

ANSWER: Tropical soils undergo more weathering, which breaks down clay particles. This causes them to have a low cation exchange capacity. In addition, the high levels of precipitation leach the nutrients from the top of the soil, and because of the high weathering, the bedrock is much deeper than in other soils, so those nutrients are harder to reach.

72. How might the plowing of soil for agriculture change the soil's fertility?

ANSWER: Since plowing is a physical disruption of the soil, it can have an effect similar to that of physical weathering. Over time plowing will break down clay and organic matter in the soil, which reduces the ability of the soil to retain water and lowers the cation exchange capacity, resulting in reduced fertility.

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Chapter 5 Multiple Choice 1. Which of the following is an example of weather? a. The average annual rainfall in a North American desert is 33 cm per year. b. The average summer temperature at a specific location has increased from 30°C in the 1950s to 32°C in the 1990s. c. A single location received 10 cm of snow on January 1, 2011, but no snow on January 2, 2011. d. The composition of the soil differs between the coastal beaches and the eastern forests of North America.

ANSWER: c 2. Which type of variation refers to the typical atmospheric conditions that occur throughout the year and are measured over multiple years? a. weather b. climate c. phenotype d. spatial variation ANSWER: b 3. Long-duration environmental events usually take place over _____ spatial scale(s). a. a small b. an intermediate c. a large d. both large and small ANSWER: c 4. The average annual rainfall measured in a desert over 10 years is which type of variation? a. weather b. climate c. spatial d. phenotypic ANSWER: b 5. Consider an area in which plants change from one group of species to another group of species over a distance of 20 cm. How might this scale of variation affect two herbivores—aphids (very small insects) and moose (large mammals)? a. Aphids would be more strongly affected by this gradient. b. Moose would be more strongly affected by this gradient. c. Neither would be affected by this gradient. d. They would be equally affected by this gradient.

ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 5 6. Phenotypic plasticity a. refers to an environment that varies. b. occurs when a single phenotype has different fitness in different environments. c. is a type of environmental cue. d. is the ability of a single genotype to produce multiple phenotypes.

ANSWER: d 7. When a given phenotype has higher fitness in one environment and different phenotypes have higher fitness in other environments, this is considered to be a. phenotypic plasticity. b. an environmental cue. c. a phenotypic trade-off. d. acclimation.

ANSWER: c 8. This figure shows the tail shape developed by three tadpole genotypes (M, N, and O) when raised in an environment with predators and an environment without predators. In the presence of predators, tadpoles with large tails have high fitness and tadpoles with small tails have low fitness. When predators are not present, tadpoles with large tails have low fitness and tadpoles with small tails have high fitness.

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Chapter 5

Which genotype(s) exhibit(s) phenotypic plasticity in response to predators? a. M only b. N only c. O only d. both M and N e. both N and O ANSWER: c 9. This figure shows the tail shape developed by three tadpole genotypes (M, N, and O) when raised in an environment with predators and an environment without predators. In the presence of predators, tadpoles with large tails have high fitness and tadpoles with small tails have low fitness. When predators are not present, tadpoles with large tails have low fitness and tadpoles with small tails have high fitness.

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Chapter 5

Which genotype(s) would have the highest average fitness across both environments? a. M only b. N only c. O only d. both M and N e. both N and O ANSWER: c 10. This figure shows the tail shape developed by three tadpole genotypes (M, N, and O) when raised in an environment with predators and an environment without predators. In the presence of predators, tadpoles with large tails have high fitness and tadpoles with small tails have low fitness. When predators are not present, tadpoles with large tails have low fitness and tadpoles with small tails have high fitness.

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Chapter 5

Under which of the following situations would the plastic genotype be favored over other genotypes?

I. if all environments have predators II. if no environments have predators III. if environments with predators are as common as environments without predators a. situation I b. situation II c. situation III d. situations I and II e. situations I and III ANSWER: c 11. Which of the following statements about environmental cues is/are TRUE? I. Environmental cues are necessary for an organism to evolve adaptive phenotypic plasticity.

II. Environmental cues can include smell, sight, and sound.

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Chapter 5 III. Environmental cues are used by animals but not by plants. a. I only b. II only c. III only d. I and II e. I, II, and III ANSWER: d 12. Which shows the order of phenotypically plastic traits from those that typically respond most rapidly to those that typically respond least rapidly? a. behavior, morphology, physiology b. physiology, morphology, behavior c. behavior, physiology, morphology d. morphology, behavior, physiology e. morphology, physiology, behavior ANSWER: c 13. Environmentally induced changes in an individual’s physiology are called a. acclimation. b. environmental cues. c. phenotypic trade-offs. d. nonplastic genotypes.

ANSWER: a 14. When the protist Euplotes detects predators, it grows “wings” and other projections to discourage predators.

However, developing the projections and wings slows down growth. This is an example of I. phenotypic trade-offs.

II. phenotypic plasticity.

III. inbreeding depression. a. I only b. II only c. III only d. I and II only e. I, II, and III ANSWER: d 15. Which statement about predator and prey phenotypic plasticity is accurate?

I. Prey can change morphology to avoid predators.

II. Predators can change morphology to capture prey.

III. Both predators and prey exhibit phenotypic trade-offs. a. I only Copyright Macmillan Learning. Powered by Cognero.

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Chapter 5 b. II only c. III only d. I and II only e. I, II, and III ANSWER: e 16. Plants develop trichomes and produce glucosinolates as adaptive phenotypic plasticity to a. reduce competition for resources. b. attract pollinators for reproduction. c. protect against herbivores. d. survive harsh drought conditions.

ANSWER: c 17. What is an example of how jewelweed plants exhibit adaptive phenotypic plasticity in response to competition from other plants? a. develop trichomes and glucosinolates b. grow shorter stems c. grow longer stems d. close stomata in leaves ANSWER: c 18. In response to a specific type of environmental variation, the Burmese python can drastically increase the size of its heart and length of its intestines in fewer than 2 days. What environmental variation causes this drastic change? a. variation in predators b. variation in availability of food c. variation in availability of mates d. variation in temperature ANSWER: b 19. What types of plants and animals are able to reproduce even if they cannot find a mate? a. predators b. competitors c. hermaphrodites d. inbred organisms ANSWER: c 20. One cost of self-fertilization in the absence of mates is a. inbreeding depression. b. physiological acclimation. c. migration.

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Chapter 5 d. handling time.

ANSWER: a 21. Consider the figure, which shows how Virginia pepperweed responds to herbivores. Which of the following conclusions can we make solely using the data shown?

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Chapter 5

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Chapter 5 22. If a goldfish is acclimated at 25°C, at which temperature would we expect the fish to swim fastest? a. 5°C b. 25°C c. 40°C d. equally fast at all temperatures ANSWER: b 23. A specific location within the area where an animal lives and that typically contains more favorable abiotic conditions than other locations in the area is a(n) a. microhabitat. b. torpor. c. acclimation. d. climate.

ANSWER: a 24. Which of the following are phenotypically plastic responses of plants to reduced water availability?

I. develop trichomes and produce more glucosinolate II. close stomata in leaves III. increase the root/shoot ratio a. I only b. II only c. III only d. I and II only e. II and III only ANSWER: e 25. The phenotypic plasticity that allows a copepod to survive being moved from salt water to fresh water is similar to the phenotypic plasticity of a human moved from low elevation to high elevation because both are a. examples of behavioral phenotypic plasticity. b. examples of morphological phenotypic plasticity. c. examples of physiological phenotypic plasticity. d. changes that cannot be reversed.

ANSWER: c 26. Over the course of a day, a snake will move from place to place to reach its preferred body temperature.

This is an example of a. microhabitat use. b. acclimation. c. aestivation. d. migration.

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Chapter 5 ANSWER: a 27. When humans move from low elevations to high elevations, it typically takes one or more weeks for their bodies to improve their ability to carry oxygen. This is an example of a. microhabitat use. b. acclimation. c. aestivation. d. migration.

ANSWER: b 28. The figure shows plant growth responses to variation in availability of water. If this is an example of adaptive phenotypic plasticity, how would we expect the root-to-shoot ratio to be related to fitness?

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Chapter 5

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a. When water is scarce, plants with high root-to-shoot ratios have higher fitness. b. When water is scarce, plants with low root-to-shoot ratios have higher fitness.

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Chapter 5 29. Tigriopus copepods living in ocean tide pools are subject to frequent changes in salt concentrations. In response to these drastic changes in salinity, Tigriopus copepods change the amount of amino acids in their bodies, which allows the osmotic potential of their body fluids to match that of the tide pool. This is an example of a. microhabitat use. b. acclimation. c. aestivation. d. torpor.

ANSWER: b 30. During the course of two generations, monarch butterflies move from southern Canada to Mexico, spend the winter in Mexico, and then return to southern Canada. This is an example of a. climate. b. migration. c. storage. d. foraging.

ANSWER: b 31. Many Arctic animals accumulate fat as an energy reserve that allows them to survive winter when food is difficult to obtain. This strategy is an example of a. migration. b. storage. c. dormancy. d. diapause.

ANSWER: b 32. Torpor is beneficial to animals because it a. allows them to move away from dangerous conditions. b. allows them to acquire additional food. c. allows them to conserve energy. d. prevents them from freezing.

ANSWER: c 33. What form of dormancy do mammals use to conserve energy and survive seasons during which they are unable to obtain food? a. diapause b. hibernation c. torpor d. aestivation ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 5 34. Why is it beneficial for birds and mammals with high surface-area-to-volume ratios to reduce their body temperature for short periods? a. Reducing body temperature makes them less vulnerable to predators. b. Reducing body temperature saves energy that would be consumed producing body heat. c. Reducing body temperature allows them to gather more food. d. Reducing body temperature prevents water loss.

ANSWER: b 35. Desert tortoises shut down metabolic processes for long periods during very hot and dry summer conditions.

What form of dormancy is this? a. diapause b. hibernation c. torpor d. aestivation ANSWER: d 36. An ecologist is studying the relationship between a beetle species and a flower species. She examines six plants and counts the number of beetles and the number of flowers on each plant.

Number of flowers Number of beetles 1 1 2 4 3 9 4 16 5 25 6 36 Which of the following terms best describes the data? a. positive linear correlation b. negative linear correlation c. positive curvilinear correlation d. negative curvilinear correlation ANSWER: c 37. An ecologist is studying the relationship between a beetle species and a flower species. She examines six plants and counts the number of beetles and the number of flowers on each plant.

Number of flowers Number of beetles Number of flowers Number of beetles 1 1 2 4 3 9 4 16 5 25 6 36 Copyright Macmillan Learning. Powered by Cognero.

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Chapter 5 What can we conclude from the data? a. Flowers cause beetles to be more abundant. b. Beetles cause plants to grow more flowers. c. A third unmeasured variable causes both beetles and flowers to increase. d. There is no way to determine causation in the relationship between flowers and beetles based solely on this data set.

ANSWER: d 38. A fox that catches prey in several fields but brings the prey back to a single den to feed its young is an example of a. optimal diet composition. b. diet mixing. c. risk-sensitive foraging. d. central-place foraging.

ANSWER: d 39. Consider a mouse that can forage in one of two fields. The south field has three times more seeds than the north field. However, an owl (a predator that eats mice) lives at the south field. The mouse forages in the north field despite the fact that it contains less food. This is an example of a. optimal diet composition. b. diet mixing. c. risk-sensitive foraging. d. central-place foraging.

ANSWER: c 40. Based on the central-place foraging theory and the figure, identify the optimal number of prey for a forager to catch. In the figure the straight orange line indicates the optimal rate of prey capture.

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Chapter 5

a. 5 prey b. 8 prey c. 10 prey d. 5, 8, and 10 prey are equally optimal ANSWER: b 41. An animal that consumes a varied diet because a single food does not contain all necessary nutrients is an example of a. optimal diet composition. b. diet mixing. c. risk-sensitive foraging. d. central-place foraging.

ANSWER: b 42. A forager that selects food type based on a balance of the energy provided, handling time, and abundance displays a. optimal diet composition. b. diet mixing. c. risk-sensitive foraging. d. central-place foraging.

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Chapter 5 ANSWER: a 43. A heron, a large wading bird, is hunting in a pond that contains three types of prey: fish, frogs, and snakes.

All three types of prey are abundant and provide the same amount of energy to the heron. The heron has the highest handling time capturing fish, an intermediate handling time capturing snakes, and the lowest handling time capturing frogs. What prey item would foraging theory predict that the heron should catch most frequently? a. fish b. snakes c. frogs d. fish and frogs equally frequently ANSWER: c 44. A scientist is studying a bird that forages for worms and takes them back to its nest. If the relation between search time and the number of prey caught remains constant but the scientist moves the food closer, what change in the bird’s behavior would central place foraging predict? a. More worms would be brought back per trip. b. The number of worms brought back would not change. c. Fewer worms would be brought back per trip. d. The bird would enter torpor.

ANSWER: c 45. Experimental studies found that increased CO2 caused some types of plants to increase their overall growth rates. What aspect of phenotypic plasticity contributed to the increase in growth rate? a. increased production of trichomes b. increased production of glucosinolate c. decreased time that stomata are open d. decrease in the size of the roots ANSWER: c 46. Red-backed salamanders (Plethodon cinereus) occur simultaneously in several different color morphs in nature. Individuals may be red backed (having a red stripe down the back), lead backed (a blackish stripe) and erocrystic (a yellow stripe). If these color morphs conferred differing fitness levels in differing environments, this would be considered an example of a. phenotypic plasticity. b. phenotypic trade-off. c. spatial variation. d. temporal variation.

ANSWER: b 47. In gray treefrogs (Hyla versicolor) phenotypic plasticity is found in all of the following areas except Copyright Macmillan Learning. Powered by Cognero.

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Chapter 5 a. physiology. b. behavior. c. sex ratios. d. growth.

ANSWER: c 48. What is the risk to a species of inbreeding depression? a. seed production at a seasonally inappropriate time b. decreased seed production c. an increased likelihood of deleterious genes being inherited from both egg and sperm d. increased offspring production unable to be maintained by the environmental resources available ANSWER: c 49. Different species of birds found feeding in different parts of the same forest canopy at the same time may be an example of a. microhabitat differences. b. climate-induced variation. c. environmental cue response. d. temporal variability.

ANSWER: a 50. A risk to a migratory species like the monarch butterfly may include all of the following except a. increased predation at their overwintering sites. b. lack of suitable refueling (feeding) habitat along the migration route. c. loss of overwintering sites due to habitat fragmentation. d. increased probability for inbreeding depression as the monarch population overwinters in the same small area in Mexico.

ANSWER: d 51. A type of dormancy found in insects in response to unfavorable environmental conditions is called a. diapause. b. hibernation. c. torpor. d. aestivation.

ANSWER: a 52. The time required to subdue and consume a prey item is called a. traveling time. b. searching time. c. handling time. d. foraging time.

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Chapter 5 ANSWER: c Essay 53. Some individuals exhibit adaptive phenotypic plasticity in response to competition from members of their own species. Why would food availability probably be a more reliable cue than the number of conspecifics about the amount of competition for food?

ANSWER: Because a high-quality environment will have much more food than a low-quality environment, the number of individuals in the environment may not be directly related to how much an individual must compete for food. However, food availability is a direct measure of competition. Low food availability can signal high competition whether that competition comes from 2 individuals competing for 2 pieces of food or from 100 individuals competing for 100 pieces of food.

54. Why are phenotypic trade-offs necessary for adaptive phenotypic plasticity to evolve?

ANSWER: Phenotypic trade-offs occur when one phenotype confers the highest fitness in some environments but other phenotypes confer the highest fitness in other environments. If there were no phenotypic trade-offs, a single phenotype would have the highest fitness in all environments, and natural selection would eventually cause only genotypes producing the single phenotype with the highest fitness to remain in the population.

55. Refer to the figure to answer this question.

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Chapter 5

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Chapter 5 56. Explain why many prey species reduce activity when they detect predators but have high activity when they do not detect predators.

ANSWER: Reduced activity is advantageous when predators are present because less active prey are less likely to be observed and captured by predators. Thus, when predators are present, less active prey have higher fitness than more active prey. However, a cost of reducing activity is that the prey spend less time feeding and may grow more slowly and reproduce less. Thus, when no predators are present, prey that are less active have lower fitness than prey that are more active.

57. Based on the figure, describe the phenotypic trade-offs of a fish being acclimated to 25°C compared to a fish acclimated to 5°C.

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Chapter 5

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Chapter 5 58. Describe how a desert iguana can survive high summer temperatures.

ANSWER: A desert iguana may use behavioral plasticity to move among microhabitats that have a suitable temperature at different times of the day.

59. Explain the differences and similarities between storage and dormancy as adaptive strategies, and provide an example.

ANSWER: : In storage, an organism collects a resource when it is abundant and maintains a reserve of that resource when it is scarce. Storage does not require a change in an organism’s physiology, and it can be done without immediately consuming the resource, such as rodents caching seeds underground.

Dormancy is a change in an organism’s physiology that allows it to drastically reduce its metabolic rate to survive periods with very limited availability of resources. Organisms can combine storage and dormancy; for example, bears develop a layer of fat (storage) that allows them to survive while dormant.

60. An active hummingbird maintains its resting body temperature at approximately 40°C, while a torpid hummingbird maintains its resting body temperature at approximately 20°C. Explain how torpor allows hummingbirds to survive cold periods with little available food.

ANSWER: When the air temperature is below the hummingbird’s resting body temperature, the hummingbird must consume energy to maintain the resting body temperature. The greater the difference between the hummingbird’s body temperature and the air temperature, the more energy is needed to maintain the resting body temperature. This energy is derived from food, and if the hummingbird is unable to obtain food before its energy resources are consumed, it may die. Reducing its resting body temperature lowers the difference between the bird’s resting body temperature and the external temperature. This reduction allows the hummingbird to consume less of its energy resources and makes it less likely to deplete all of its energy before food is available again.

61. Use the concept of phenotypic trade-offs to explain how foraging behavior is a type of adaptive phenotypic plasticity.

ANSWER: The type and abundance of food vary over space and time. Different foraging behaviors reflect different behavioral phenotypes. One foraging behavior may be most effective in a certain environment, but in a different environment other foraging behaviors may be more effective. By using different foraging behaviors in different environments, an organism is maximizing its feeding ability and thus its fitness.

62. Consider a species of squirrel that eats acorns and maple seeds. Define the diet-mixing hypothesis and describe an experiment that would test whether squirrels eat both acorns and seeds because of the diet-mixing hypothesis. As part of your answer, describe the experimental treatments, the response variable that would be measured, and results that would both support and reject the diet-mixing hypothesis.

ANSWER: According to the diet-mixing hypothesis, foragers consume a varied diet because one type of food does not provide all necessary nutrients. A biologist could raise young squirrels in three treatments: (1) acorns only, (2) maple seeds only, and (3) both acorns and maple seeds. At the end of the experiment, the growth rate of the squirrels would be measured. The diet-mixing hypothesis would predict that the squirrels have the greatest growth rate if they eat acorns and maple seeds. The dietmixing hypothesis would be rejected if squirrels in the combined acorn and maple seed cohort had Copyright Macmillan Learning. Powered by Cognero.

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Chapter 5 growth equal to or lower than that of squirrels in the treatments with only acorns or only maple seeds.

63. What would the characteristics of an optimal foraging species be?

ANSWER: An optimal foraging species would likely select the prey based on several factors, including: which prey have the highest energy, the availability of the varying prey types (and their energy content), and the handling time (and the energy associated with subduing and consuming the prey). An optimal foraging species should maximize energy content of the prey based on availability while minimizing prey handling time.

64. Explain a difference between hibernation and aestivation.

ANSWER: Hibernation is a type of dormancy that tends to occur with mammals during periods of cold temperatures (winter) when food acquisition is not possible. Aestivation is a type of dormancy that tends to occur with reptiles during periods of hot/dry conditions (summer).

65. Describe the difference between a plastic and nonplastic genotype.

ANSWER: A genotype that is considered plastic is one that results in more than one phenotype, and the phenotypes may change as environmental conditions change. A nonplastic genotype is one that results in a single phenotype and is likely not to change as rapidly or at all.

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Chapter 6 Multiple Choice 1. Different forms of a particular gene are known as a. chromosomes. b. alleles. c. polygenic. d. pleiotropic.

ANSWER: b 2. A trait that is determined by multiple genes is referred to as a. polygenic. b. pleiotropic. c. homozygous. d. heterozygous.

ANSWER: a 3. Which of the following types of allele would we expect to have the lowest frequency in a population? a. beneficial recessive allele b. beneficial dominant allele c. harmful recessive allele d. harmful dominant allele ANSWER: d 4. Consider a gene that affects fur color in mice. This gene has two alleles, A and a. If AA mice have white fur, Aa mice have gray fur, and aa mice have black fur, how would we describe the effect of these alleles? a. A is dominant and a is recessive. b. A is recessive and a is dominant. c. A and a are codominant. d. A and a are epistatic.

ANSWER: c 5. Consider a gene that affects number of seeds in a plant. This gene has two alleles, G and g. If GG plants produce 50 seeds, Gg plants produce 50 seeds, and gg plants produce 25 seeds, how would we describe the effect of these alleles? a. G is dominant and g is recessive. b. G is recessive and g is dominant. c. G and g are codominant. d. G and g are polygenic.

ANSWER: a 6. What term refers to the alleles of all the genes of every individual in a population? a. polygenic Copyright Macmillan Learning. Powered by Cognero.

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Chapter 6 b. heterozygous c. gene pool d. random assortment ANSWER: c 7. What process creates new alleles in a population? a. random assortment b. mutation c. recombination d. epistasis ANSWER: b 8. For mutations that enter a population of a diploid organism, which type of mutation is most likely to be affected by natural selection when it first appears? a. synonymous mutation b. nonsynonymous recessive mutation c. nonsynonymous dominant mutation d. All are equally likely to be affected by natural selection.

ANSWER: c 9. The shuffling of genes that occurs when DNA is copied during meiosis is known as a. recombination. b. mutation. c. random assortment. d. epistasis.

ANSWER: a 10. What term describes making new combinations of alleles using existing genetic variation when gametes are formed? a. pleiotropy b. epistasis c. random assortment d. mutation ANSWER: c 11. A process that occurs when genetic variation is lost because of random variation in mating, mortality, fecundity, and inheritance is known as a. mutation. b. genetic drift. c. stabilizing selection. d. disruptive selection.

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Chapter 6 ANSWER: b 12. The rate at which allele frequencies change because of genetic drift is a. highest in large populations. b. the same regardless of population size. c. highest in intermediate-sized populations. d. highest in small populations.

ANSWER: d 13. Consider three populations of a plant species, each isolated from other populations of the same species.

Population X has contained approximately 100 individuals in each generation for the past 200 generations.

Population Y has contained approximately 10,000 individuals in each generation for the past 200 generations.

Population Z has contained approximately 1 million individuals in each generation for the past 200 generations.

If genetic drift is the only evolutionary process acting on these populations, how can we expect the amount of genetic variation to differ among these populations? a. X will have the highest variation, Y will have intermediate variation, and Z will have the lowest variation. b. X will have the lowest variation, Y will have intermediate variation, and Z will have the highest variation. c. X and Z will have high variation, while Z will have low variation. d. All three populations will have the same amount of genetic variation.

ANSWER: b 14. Which is/are correct about founder effect?

I. Founder effect occurs when individuals are transplanted to a new location.

II. Founder effect produces new alleles.

III. Founder effect may see further reduction in genetic variation. a. I only b. II only c. III only d. I and II e. I and III ANSWER: e 15. Consider a situation in which overharvesting causes the number of fish in a population to become drastically smaller, which causes genetic variation in that fish to decrease over a few generations. This is an example of a. bottleneck effect. b. founder effect. c. directional selection. d. recombination.

ANSWER: a 16. Stickleback fish exhibit variation in a morphological trait known as gill rakers. Fish with long gill rakers are Copyright Macmillan Learning. Powered by Cognero.

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Chapter 6 very good at eating plankton, and fish with short gill rakers are good at eating deep-water invertebrates.

However, fish with intermediate-length gill rakers are poor at eating either type of food. Fish that are better at consuming food have higher survival and reproduction rates than poorer consumers. Based on this information, what type of selection is likely acting on stickleback gill raker length? a. no natural selection b. stabilizing selection c. disruptive selection d. directional selection ANSWER: c 17. When a parental generation undergoes stabilizing selection, how will the distribution of phenotypes in the population change between the parental generation and their progeny? a. Mean phenotype increases, but variability decreases. b. Mean phenotype stays the same, but variability decreases. c. Mean phenotype stays the same, but variability increases. d. Mean phenotype and variability both increase.

ANSWER: b 18. When an extreme phenotype has higher fitness than an average phenotype in a population, it is an example of a. stabilizing selection. b. directional selection. c. disruptive selection. d. genetic drift.

ANSWER: b 19. If a population of butterflies is under strong natural selection favoring large wings but there is no genetic variation for wing size, what do we expect to occur in the next generation? a. Wings will evolve to be smaller. b. There will be no evolutionary change in wing size. c. Wings will evolve to be larger. d. Wings will evolve to be more variable.

ANSWER: b 20. When a phenotype is under disruptive selection, which parts of the phenotypic distribution are expected to have the highest fitness? a. individuals with the extreme largest values of the phenotype b. individuals with the extreme smallest values of the phenotype c. individuals with both extreme large and extreme small values of the phenotype d. individuals with the intermediate phenotype ANSWER: c Copyright Macmillan Learning. Powered by Cognero.

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Chapter 6 21. Consider three populations of a plant species, each of which is isolated from other populations of the same species. Population X has had approximately 100 individuals in each generation for the past 200 generations.

Population Y has had approximately 10,000 individuals in each generation for the past 200 generations.

Population Z has had approximately 1 million individuals in each generation for the past 200 generations. If the environment changed and a new environmental condition exerted the exact same strength of directional selection on all three populations, which population would we expect to evolve most rapidly? a. Population X b. Population Y c. Population Z d. All three populations would evolve at the same rate.

ANSWER: c 22. What is the term for evolution acting at the level of populations? a. microevolution b. macroevolution c. speciation d. key innovations ANSWER: a 23. The human activity of controlling the survival and reproduction of organisms to produce offspring with specific sets of traits is known as a. artificial selection. b. natural selection. c. industrial melanism. d. speciation.

ANSWER: a 24. The drastic phenotypic differences between large dogs, such as bloodhounds, and small dogs, such as Chihuahuas, are a result of a. genetic drift. b. founder effect. c. artificial selection. d. natural selection.

ANSWER: c 25. Evolution by artificial selection is similar to evolution by natural selection because I. both require traits to be heritable.

II. both incorporate founder effects.

III. both favor certain traits over others. a. I only b. II only c. III only Copyright Macmillan Learning. Powered by Cognero.

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Chapter 6 d. I and III only e. I, II, and III ANSWER: d 26. Which is a prediction of the hypothesis that predation caused industrial melanism? a. Dark moths seek out dark trees to rest on. b. Birds more frequently capture dark moths on dark trees than those on light trees. c. Birds more frequently capture dark moths on light trees than those on dark trees. d. Industrial pollution led to higher mortality of light moths.

ANSWER: c 27. The phenomenon by which moths in England evolved from light-colored forms to dark-colored forms over several decades is known as a. speciation. b. epistasis. c. genetic drift. d. industrial melanism.

ANSWER: d 28. Which of the following insights about microevolution is demonstrated by industrial melanism? a. Artificial selection cannot be reversed. b. Microevolution is primarily caused by genetic drift. c. Humans affect the evolution only of domestic animals. d. Microevolution can occur in a very short time.

ANSWER: d 29. Body size is a heritable trait in the amphipod, an aquatic crustacean. Fish preferentially consume large amphipods, leaving primarily small amphipods to breed. Based on these observations, how would we expect evolution to affect ponds with and without fish? a. Ponds with fish should have larger amphipods. b. Ponds with fish should have smaller amphipods. c. Amphipod body size should not differ between ponds with and without fish. d. Ponds with fish should have amphipods that are either very large or very small.

ANSWER: b 30. Which of the following statements about evolution by artificial selection is correct? a. It occurs very slowly. b. It was discovered only in the 1900s. c. It may have negative effects for humans. d. It does not require genetic variation.

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Chapter 6 31. The evolution of pesticide resistance in insects is an example of a. microevolution. b. industrial melanism. c. selective predation. d. macroevolution.

ANSWER: a 32. Microevolution includes a. speciation. b. diversification c. genetic drift. d. polyploidy.

ANSWER: c 33. Artificial selection can cause evolutionary change when there is a. genetic variation in traits with accompanying differences in reproduction. b. geographic separation. c. a founder effect. d. genetic drift ANSWER: a 34. Darwin supported his argument for evolution by natural selection with the observation that artificial selection caused large changes in a short period because a. natural selection had millions of years to operate. b. genetic drift could not cause the same rate of change. c. natural selection had to have occurred in only a few generations. d. allopatric speciation requires geographic barriers.

ANSWER: a 35. Based on the phylogeny in the figure, which traits are shared by bony fishes and amphibians?

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Chapter 6

a. jaws and lungs b. bony skeleton and lungs c. jaws and bony skeleton d. legs and lungs ANSWER: c 36. Based on the phylogeny in the figure, which group is most closely related to the reptiles?

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Chapter 6

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a. lampreys

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Chapter 6 37. What is the term for evolution that acts at the level of species, genera, and higher levels of organization? a. microevolution b. macroevolution c. genetic drift d. epistasis ANSWER: b 38. Which of the following is a component of macroevolution? a. artificial selection b. epistasis c. founder effect d. sympatric speciation ANSWER: d 39. Which of the following three statements is/are correct?

I. Speciation through polyploidy can occur through hybridization.

II. Speciation through polyploidy never occurs in vertebrates; it occurs only in plants.

III. Speciation through polyploidy generates phenotypic differences among the resulting species. a. I only b. II only c. III only d. I and II e. I and III ANSWER: e 40. Which of the following is a necessary component of allopatric speciation? a. hybridization b. polyploidy c. a geographic barrier d. migration ANSWER: c 41. When an error in meiosis causes sexually reproducing species to generate zygotes with three or more sets of chromosomes, this is known as a. pleiotropy. b. epistasis. c. polyploidy. d. genetic drift.

ANSWER: c 42. Which of the following is/are correct?

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Chapter 6 I. Allopatric speciation can occur without geographic barriers.

II. Allopatric speciation is the most common form of speciation.

III. Allopatric speciation can be facilitated through genetic drift. a. I only b. II only c. III only d. I and III e. II and III ANSWER: e 43. Which of the following is/are correct?

I. Sympatric speciation occurs without geographic barriers.

II. Sympatric speciation can occur through polyploidy.

III. Sympatric speciation is less common than allopatric speciation. a. I only b. II only c. III only d. I and III e. I, II, and III ANSWER: e 44. Based on the phylogeny of the Galápagos finches, which statement is correct?

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Chapter 6

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Chapter 6 45. At the Seneca Army Depot in upstate New York, a mutant variety (white coat color) of white-tailed deer composes a much higher percentage of the population than one might consider normal for such a mutation.

What is the reason for this? a. The mutant phenotype produces more offspring than the nonmutant. b. The mutant phenotype is better adapted at avoiding predators in the winter. c. Predator pressures were manipulated by humans at the Depot. d. Genetic drift led to greater numbers of the mutant phenotype.

ANSWER: c 46. Recombination and polyploidy both occur during the process known as a. disruptive selection. b. meiosis. c. directional selection. d. genetic drift.

ANSWER: b 47. Tremblay’s salamander, the result of a diploid egg from a blue-spotted salamander being fertilized by a haploid sperm of a Jefferson’s salamander, would be considered a. haploid. b. diploid. c. triploid. d. tetraploid.

ANSWER: c 48. Natural selection will select for individuals that carry what genotype? a. homozygous dominant b. heterozygous dominant c. homozygous recessives d. There is no way to determine without additional information.

ANSWER: d 49. The example of the peppered moth in nineteenth-century England showed a. changes in the gene pool. b. changes in speciation rate. c. changes in the rate of polyploidy. d. results due to genetic drift.

ANSWER: a 50. An example of the bottleneck effect having a detrimental impact on a species and its inability to evolve against new pathogen strains has been documented in the a. cheetah.

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Chapter 6 b. white-tailed deer. c. Mexican cavefish. d. greater prairie chicken.

ANSWER: a 51. Scientists working with phylogenetic trees assume that species that are more closely related are those species that have a. the larger gene pools. b. the greatest number of traits in common. c. the oldest known fossils. d. the most similar habitat and niche.

ANSWER: b Essay 52. Clonal animals do not reshuffle their genes through genetic recombination, whereas sexually reproducing animals do. Explain how this difference could affect how pathogens interact with clonal animals and how they interact with sexually reproducing animals.

ANSWER: Since recombination creates new genotypes every generation, pathogens cannot become fully adapted to the genotypes of sexually reproducing animals. Because recombination does not occur in clonal animals, they gain new genetic variation only through mutation, which is a very rare process.

Thus, pathogens can more easily adapt to the genetic variation in clonal animals.

53. Describe the difference between synonymous and nonsynonymous mutation. Which type is more likely to be affected by natural selection, and why?

ANSWER: A synonymous mutation does not affect an organism’s phenotype, whereas a nonsynonymous mutation does affect phenotype. Natural selection acts on variation among phenotypes, and so natural selection will act only on nonsynonymous mutations, because they are the only mutations that affect an organism’s phenotype.

54. Many genetic diseases have severe or lethal effects in the homozygous form, yet alleles for these diseases are not entirely removed by natural selection. Explain how dominance relationships among alleles allow deleterious mutations to remain in a population.

ANSWER: When genetic diseases are caused by recessive alleles, they do harm to the carrier only in the homozygous form. The heterozygotes do not express the deleterious phenotype, and thus heterozygotes do not have reduced fitness. Deleterious genetic diseases thus can remain in the population because they are not selected against in the heterozygous form.

A synonymous mutation does not affect an organism’s phenotype, whereas a nonsynonymous mutation does affect phenotype. Natural selection acts on variation among phenotypes, and so natural selection will act only on nonsynonymous mutations, because they are the only mutations that affect an organism’s phenotype.

55. You conduct an experiment in which you raise six replicated lines of fruit flies for eight generations. You keep population size constant at 20 adults per generation. You are interested in a gene, bw, that affects eye color. This gene has two alleles, bw-1 and bw-2. You start each replicated line with the frequency of the bw-1 Copyright Macmillan Learning. Powered by Cognero.

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Chapter 6 allele at 50 percent. Do the data in the graph better match the prediction for the bw alleles evolving by genetic drift or by directional selection? Be sure to define directional selection and genetic drift and describe the prediction of both hypotheses.

ANSWER: These data better match the bw alleles evolving by genetic drift. Genetic drift is random changes in allele frequencies, while evolution by directional selection would consistently favor one allele over another. With genetic drift, we would predict some lines to show an increase in bw-1 allele frequency, some lines to decrease, and some to stay roughly the same. However, under directional selection, we would expect all six lines to consistently change in the same direction. For example, if bw-1 were favored by directional selection, we would expect bw-1 to increase in frequency in all six lines each generation.

56. A small species of fly lays its eggs in plant stems. The developing fly larvae cause a gall, or large round structure, to form in the stem. Genetic differences among flies cause variation in the size of the galls they produce. Both birds and wasps feed on the larvae in the galls. The proportions of small, medium, and large galls able to survive attacks by either birds or wasps are shown in the table. If a population of flies lives in a field with equal abundance of birds and wasps, will gall size evolve by directional, stabilizing, or disruptive selection? Explain your answer.

Gall size (mm) Gall survival with birds Gall survival with wasps (%) (%) 15 100 25 20 100 100 25 25 100 ANSWER: The galls would be under stabilizing selection because neither predator would attack the intermediate-sized galls, but predators attack both large (25 mm) and small (15 mm) galls. This meets the definition of stabilizing selection: that intermediate phenotypes have highest fitness, while the two extreme phenotypes have low fitness.

57. A group of island birds have beaks that are on average 20 mm long with a standard deviation of 1 mm. Beak length is a genetically based trait with a heritability of 0.5. Only small seeds are available for these birds to consume, and some of the large-beaked birds are unable to reproduce. The group of birds that successfully Copyright Macmillan Learning. Powered by Cognero.

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Chapter 6 reproduces has an average beak size of 16 mm. Based on this information, predict how much the beak size is expected to change in the next generation.

ANSWER: Use the equation R = h2S. h2 is the heritability 0.5. (Note that we do not square the heritability.)

S is the selection differential, (16 – 20) ÷ 1. We divide by 1 for the standard deviation.

R = 0.5 × –4 = –2.

We thus predict the bird beak size will decrease by two standard deviations in the next generation.

58. If climate change were to cause a tree with very dark bark to become common in England, what would we expect to happen to the color patterns of the peppered moth, and why would we expect it to happen?

ANSWER: Color pattern is genetically controlled in the peppered moth, and it also affects the survival of moths. Dark-colored moths resting on dark trees are less likely to be eaten by birds than dark moths on light trees. The opposite pattern is true for light-colored moths. Thus, if dark trees became common, the light moths would be more likely to be killed than the dark moths. In each generation the selective consumption of light moths would lead to an increase in the proportion of dark-colored genotypes in the moth population. Eventually the light-colored moths would be rare or absent.

59. How might understanding microevolution have a direct benefit to humans in the fight against diseases?

ANSWER: A major danger to humans is the evolution of drug-resistant pathogens such as drug-resistant tuberculosis. One reason drug-resistant pathogens evolve is widespread use of antibiotics and other drugs. Understanding the evolutionary processes that increase the rate of the evolution of drug resistance can help us develop strategies to limit or prevent it.

60. The drug chloroquine has been widely used to treat the human parasite malaria. Mutations in the malaria gene pfcrt confer resistance to chloroquine. In some countries, more than 90 percent of malaria parasites had the pfcrt resistance alleles. When these countries stopped using chloroquine, the frequency of the pfcrt resistance alleles rapidly declined. Provide an evolutionary explanation for the decline in pfcrt resistance alleles after chloroquine was discontinued.

ANSWER: Although the pfcrt resistance alleles had the highest fitness when chloroquine was used, it is likely that the pfcrt resistance alleles had lower fitness than other alleles in the absence of chloroquine.

Thus, in the absence of chloroquine, natural selection removed the pfcrt resistance alleles from the population.

61. Describe how genetic drift and natural selection can play a role in allopatric speciation.

ANSWER: After an original population has been split into two populations by a geographic barrier, genetic drift and natural selection can change the allele frequencies and the resulting phenotypes such that the two populations are no longer capable of breeding with one another. This can occur through genetic drift if the populations are small enough to allow large changes in allele frequencies in each population. It can occur through natural selection if different alleles are favored by different environments on either side of the geographic barrier.

62. Explain how a diversity of habitats combined with natural selection can lead to sympatric speciation.

Provide an example.

ANSWER: When a single location, such as an island or a lake, contains multiple habitats, each of these habitats may contain environmental conditions that exert selection for different phenotypes. Over time, adaptation to specific habitats in that location can lead to phenotypic differences large enough that Copyright Macmillan Learning. Powered by Cognero.

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Chapter 6 new species are formed. An example of this is the diverse group of cichlid fish species living in Lake Tanganyika in Africa.

63. Why is polyploid speciation useful to humans?

ANSWER: Polyploid species are typically larger than diploid species and consequently can produce greater yields of crops. People use naturally occurring polyploid species as crops and have also developed methods to artificially generate new polyploid species. The new polyploid species that contain desirable traits can then be further bred and farmed.

64. What is the difference between speciation referred to as allopatric in origin and speciation referred to as sympatric in origin?

ANSWER: Allopatric speciation results from a geographic barrier separating a once-contiguous population into two separate populations. Since the barrier prevents breeding between the two new isolated populations, over time, they may evolve independently from one another, thus leading to two species. Sympatric speciation does not involve a geographic barrier. Instead, sympatric speciation may occur in a single area with a diversity of distinct habitat types. In addition, sympatric speciation may occur as a result of polyploidy.

65. Assuming the starting point is the same phenotypic distribution, describe the outcome, in terms of phenotype, of stabilizing, directional, and disruptive selection.

ANSWER: Stabilizing selection sees the narrowing of distribution of phenotypes while maintaining the still dominant (in terms of frequency) phenotype. Directional selection sees the resulting phenotype displaced from the average phenotype toward a more extreme phenotype. Disruptive selection sees the resulting phenotype being displaced from the average in two directions toward both extremes, resulting in two dominant phenotypes.

66. How is the process known as genetic drift different from the process known as the bottleneck effect?

ANSWER: The bottleneck effect is a reduction in genetic variation as a result of severe reduction in population size. Genetic drift is a reduction in genetic diversity as a result of random variation in mating, mortality, fecundity, or inheritance. The bottleneck effect requires a small population. Genetic drift is more likely in a small population, but it may occur in larger populations as well.

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Chapter 7 Multiple Choice 1. Fecundity is the a. number of reproductive episodes of an organism. b. amount of overall energy expended to reproduction over the life of an organism. c. number of offspring produced by an organism per reproductive episode. d. period in the life of an organism when it can produce offspring.

ANSWER: c 2. Which life history type do large mammals exhibit? a. slow b. delayed c. fast d. accelerated ANSWER: a 3. Which does NOT have slow life history attributes? a. oak tree b. herbaceous weeds c. elephant d. giant tortoise e. bald eagle ANSWER: b 4. Which does NOT have fast life history attributes? a. rabbit b. fruit fly c. grasses d. albatross e. shrimp ANSWER: d 5. Grime proposed that combinations of life history traits in plants are mainly determined by three factors.

Which is NOT one of these factors? a. disturbance b. herbivory c. competition d. stress ANSWER: b 6. Consider a species with a fast potential growth rate, reproduction at a relatively early age, allocation of a small proportion of net production to seeds, and reliance on vegetative spread. According to Grime’s Copyright Macmillan Learning. Powered by Cognero.

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Chapter 7 classification of life history traits, this species fits the profile of a a. stress-tolerant species. b. facilitator. c. ruderal. d. competitor. e. fixed-trait strategist.

ANSWER: d 7. Consider a species with a slow potential growth rate, reproduction at a relatively late age, allocation of a small proportion of net production to seeds, and reliance on vegetative spread. According to Grime’s classification of life history traits, this species fits the profile of a a. stress tolerator. b. facilitator. c. ruderal. d. competitor. e. fixed-trait strategist.

ANSWER: a 8. The principle of allocation states that life history traits are adapted to maximize a. fitness. b. frequency of reproduction. c. number of offspring in the population. d. ability of offspring to start populations in new habitats. e. fecundity.

ANSWER: a 9. Which life history trait is most likely to be fixed for a species? a. timing of reproduction in the life span b. number of offspring c. survival rate of offspring d. total energy given to reproduction e. growth rate of offspring ANSWER: a 10. Having a large number of offspring potentially affects a parent’s fitness for subsequent breeding seasons.

Which of the following outcomes is the LEAST likely? a. It could limit the number of offspring the adult produces in its life. b. The increased energy needed to feed many offspring may lower adult survival in the following breeding season. c. The energy required to feed many offspring could trigger smaller broods in the future. d. Competition with offspring for food could reduce energy for future reproduction.

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Chapter 7 ANSWER: d 11. Which of the following does NOT apply to determinate growth? a. growth in body size throughout life b. cessation of growth upon maturation (adulthood) c. a fixed age of maturation d. characteristic of bird and mammals e. iteroparity ANSWER: a 12. Which of the following does NOT apply to indeterminate growth? a. growth in body size throughout life b. cessation of growth upon maturation (adulthood) c. flexible age of maturation d. characteristic of plants and insects e. semelparity ANSWER: b 13. When adults have a high probability of survival from one year to the next and offspring survival is relatively poor, the best strategy for an adult to maximize fitness is to a. increase fecundity at the expense of survival. b. delay reproduction for the next cycle. c. increase survival at the expense of fecundity. d. invest all excess energy in offspring. e. maintain a balance of fecundity and survival.

ANSWER: c 14. Some marine snails (species L) produce large numbers of small eggs that are shed into the sea, hatch at an early stage of development, and feed on microscopic plants. Other marine snails (species S) produce few eggs that are retained for a long time within the body of the mother snail in a brood pouch, hatch at an advanced stage of development, and immediately begin to feed on the surfaces of large plants like the adults. If a biologist discovers approximately equal numbers of adults of species L and S in the same area over many generations, which of the following is most likely? a. Young that parents care for until they reach a more advanced stage (species have a greater chance of survival. b. Approximately the same percentage of young produced by each species survive to maturity. c. Organisms that produce a greater number of offspring will likely replace organisms with fewer offspring. d. The young of species L grow more rapidly than the young of species S. ANSWER: a 15. Some marine snails (species L) produce large numbers of small eggs that are shed into the sea, hatch at an Copyright Macmillan Learning. Powered by Cognero.

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Chapter 7 early stage of development, and feed on microscopic plants. Other marine snails (species S) produce few eggs that are retained for a long time within the body of the mother snail in a brood pouch, hatch at an advanced stage of development, and immediately begin to feed on the surfaces of large plants like the adults. A biologist discovers approximately equal numbers of adults of species L and S in the same area over many generations.

While studying the two species of snails, the biologist hypothesizes that the two species expend approximately the same amount of energy producing young. What assumption is the biologist making? a. Species S snails could produce as many eggs as species L snails under certain conditions. b. An egg of species S contains more energy than an egg of species L. c. Since species L snails produce more eggs, these eggs probably contain more energy. d. Species S snails provide some energy to the young when they are in the brood pouch.

ANSWER: b 16. For birds, age at maturity a. varies directly with annual survival rates of adults. b. varies inversely with annual survival rates of adults. c. varies with the productivity of the environment. d. is not related to annual survival rates of adults.

ANSWER: a 17. Which panel best illustrates the most direct effect of predation?

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Chapter 7

a. a b. b c. c d. d ANSWER: a 18. Which variable best summarizes the response to increased predation mortality for adults and suggests that putting more energy into reproduction provides an improved fitness benefit?

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a. mature male guppy size b. offspring volume (percent of adult mass) c. number of offspring d. embryo weight ANSWER: b 19. What is the reproduction pattern of most insects? a. semelparity b. iteroparity c. annual d. perennial ANSWER: a 20. Red foxes mature after their first year of life and may live for 5 to 10 years. Foxes often reproduce many times over their life. The term to describe this aspect of their life history is Copyright Macmillan Learning. Powered by Cognero.

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Chapter 7 a. opportunistic. b. precocious. c. iteroparous. d. semelparous.

ANSWER: c 21. What type of reproduction will be favored if adult plant survival is low because of a disturbance such as fire? a. semelparity b. iteroparity c. annual d. perennial ANSWER: a 22. A mature female sockeye salmon swims up to 5,000 km from her Pacific Ocean feeding ground to the mouth of a coastal river in British Columbia and then another 1,000 km upstream to her spawning ground. Once there, she lays thousands of eggs in her single reproductive event and promptly dies. The salmon’s reproductive life history is a. semelparous. b. iteroparous. c. annual. d. perennial.

ANSWER: a 23. Which feature found in semelparous organisms such as Coho salmon and Agave is typical of “Fast life histories”? a. short life span b. fewer offspring c. greater number of offspring d. greater parental investment e. smaller parental investment ANSWER: c 24. Bet hedging (spreading reproduction over both good and bad years) has been proposed as an advantage to a. iteroparity. b. semelparity. c. both iteroparity and semelparity. d. neither iteroparity nor semelparity.

ANSWER: a 25. A gradual decrease in fecundity and increase in the probability of mortality is known as a. logistic growth.

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Chapter 7 b. acclimation. c. senescence. d. semelparity.

ANSWER: c 26. In human females the increased prevalence of birth defects in offspring and of infertility after 30 years of age is one indication of a. iteroparity. b. semelparity. c. senescence. d. middle age. e. reproductive failure.

ANSWER: c 27. If maintaining high survival and reproduction would increase an individual’s fitness at any age, what is the most likely reason these traits decline with age in humans? a. fewer reproductive opportunities b. increased risk of death from childbirth c. DNA damaged over time d. increased exposure to toxins e. less efficient metabolism ANSWER: c 28. Which characteristic of frogs that lay their eggs on land where they develop directly into froglets is typical of organisms at the slow end of the life history continuum? a. fewer offspring b. shorter life span c. faster growth d. earlier sexual maturation ANSWER: a 29. What environmental factor would likely lead to later maturation with an iteroparous reproductive strategy? a. fewer interspecific competitors b. higher rainfall over several years c. a lower severity and frequency of disturbance d. global warming ANSWER: c 30. Which of the following is NOT a potential benefit of increased resource availability? a. fast growth b. early development Copyright Macmillan Learning. Powered by Cognero.

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Chapter 7 c. large size at maturation d. reduced predation risk ANSWER: d 31. For some organisms, warmer spring temperatures have led to a. larger adult size. b. larger offspring at birth. c. later offspring production. d. earlier offspring production. e. delayed maturation ANSWER: d 32. Many animals undergo a dramatic metamorphosis from larval to adult form. Poorly nourished animals cannot grow as fast as well-nourished animals and therefore do not reach a given mass as quickly as their wellnourished counterparts. If metamorphosis occurs when a specific minimum body mass is reached, which of the following costs is most likely incurred by a poorly nourished animal? a. longer period of risk of predation prior to reproduction b. reduced lifetime reproductive output c. deformed offspring d. offspring with poor competitive ability e. reduced parental care ANSWER: a 33. Research on frogs has shown that compared to well-nourished counterparts, poorly nourished frogs mature at a. the same size but at a much later age. b. the same age but at a much smaller size. c. a somewhat later age and at a somewhat smaller size. d. a somewhat earlier age and at a somewhat smaller size.

ANSWER: c 34. The equation Y = mx + b is for a a. parabola. b. hypotenuse. c. straight line. d. intercept.

ANSWER: c 35. The error sum of squares in a regression is based on a. the difference between the observed and expected values of yi. b. the degree of change in y per unit x.

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Chapter 7 c. on how close the y-intercept is relative to 0. d. how much the best-fit line deviates from linearity.

ANSWER: a 36. which statement about the coefficient of determination is INCORRECT? a. it ranges from a value of 0 to 1.0 b. low values indicate that most data points fall close to the calculated regression line c. high values indicate that variations in one trait are closely associated with variations in a second trait d. the error sum of squares needs to be calculated for a data set needs to be calculated prior to calculating the coefficient of determination ANSWER: b 37. The number of reproductive episodes that an organism experiences is called a. fecundity. b. parity. c. longevity. d. life history.

ANSWER: b 38. Reproductive trade-offs that an organism might face include all of the following except a. the number of offspring produced versus the size and development of the offspring. b. the number of offspring versus the level of parental care provided the offspring. c. the energy expended by the parent in caring for the offspring versus energy available for the growth and survival of the parent. d. the costs of hibernation during the nonbreeding season versus the costs of migration.

ANSWER: d 39. Birds and mammals tend to have shorter times to sexual maturity as compared to reptiles and fish. Why? a. Endotherms grow more rapidly than ectotherms. b. Birds and mammals have smaller surface-area-to-volume ratios than reptiles and fish. c. Birds and mammals are internal fertilizers. d. Birds and mammals live in more stable environments than reptiles and fish.

ANSWER: a 40. Which of the following statements regarding semelparous and iteroparous organisms is true? a. An organism that has an annual life history must be semelparous. b. An organism that has a perennial life history must be iteroparous. c. An organism that has an annual life history must be semelparous. d. There is no general statement that can be made regarding an organism’s life history and the organism’s frequency of breeding.

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Chapter 7 41. Migratory birds are likely responding to what environmental cue to initiate the behavior leading to migration from the northern breeding grounds to their more southern overwintering areas? a. changes in temperature as seasons change b. changes in food supply as seasons change c. changes in predator activity as seasons change d. changes in day length as seasons change ANSWER: d 42. The amount of light that occurs each day and changes as the seasons progress is termed a. photosynthetic potential. b. photosynthetic active period. c. photoperiod. d. seasonal photosynthetic level.

ANSWER: c 43. Research on the 17-year periodical cicada emergence pattern has shown that this semelparous organism appears to be sensitive to a. changing soil temperature. b. changing soil pH. c. the reproductive cycles of the host plant it will grow on. d. the age of the host plant that it will grow on.

ANSWER: c Essay 44. Explain why life history variables, such as number of offspring, size of offspring, and degree of parental care, are often correlated.

ANSWER: Species cannot maximize all of these traits. For example, if many offspring are produced, they will probably be smaller than if few are produced. Parental care is much more effective with few offspring.

45. Explain the main life history trait that differentiates ruderals and stress-tolerators.

ANSWER: The main difference is the proportion of energy devoted to reproduction. Stress-tolerant plants live in growth-limiting environments, so they increase their fitness by reducing the amount of energy used for seed production; seeds are energetically costly and are likely to have low survival in a stressful habitat. Instead they rely on vegetative propagation. Ruderals are adapted to disturbance, meaning that mature plants cannot depend on long-term survival. Because their fitness is maximized by ensuring future generations, they allocate a high proportion of energy to reproduction and produce high quantities of seeds that can persist in the environment until favorable conditions occur.

46. Which plant life history type, fast or slow, would best describe a weed species that is a good invader of new habitats?

ANSWER: The fast life history would foster the development and spread of an opportunistic weed species that can rapidly populate a new or disturbed habitat.

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Chapter 7 47. Which life history type, fast or slow, is more likely to describe an endangered animal species?

ANSWER: Most endangered species probably have a slow life history type. While parental care provides high juvenile survivorship, the few offspring produced result in low recovery from population declines.

48. Frogs exhibit a wide range of life history strategies, ranging from metamorphosis of tadpoles into juvenile frogs to direct development, where the tadpole stage is largely eliminated. Explain how this diversity illustrates the different types of fitness trade-offs seen in life-history strategies.

ANSWER: Frogs with the ancestral, metamorphic life history frequently lay numerous small eggs that hatch relatively quickly so that the larvae can begin feeding and growth. Other species have developed mechanisms to protect eggs from predation such as constructing foam nests, or laying eggs in branches above water. These strategies permit tadpoles to begin development before being exposed to aquatic predators, but result in higher energy costs that may reduce parental fecundity. Strategies that eliminate the feeding tadpole stage require larger eggs that have enough energy to support development into a froglet. One consequence of larger eggs size is that many fewer eggs can be produced, a trade-off between number and size.

49. For seed-producing trees, what conditions might favor production of few relatively large seeds? What conditions might favor production of many relatively small seeds?

ANSWER: Trees of closed forests with little opportunity to disperse seeds into new habitats might be expected to produce relatively few large seeds. Each seed could be supplied with substantial reserves of food and nutrients, giving the developing seedling an opportunity to compete successfully for limited resources. Trees of open forests with opportunities to disperse seeds into new habitats might be expected to produce larger numbers of lighter seeds. Such seeds might be more readily dispersed by wind, water, or small animals into open habitats. The larger numbers of seeds would also increase the chances that some seeds will land in favorable sites, and opportunities for rapid population expansion could be readily exploited.

50. Tropical songbirds tend to lay fewer eggs in each clutch than birds nesting at higher latitudes. David Lack of Oxford University first placed this observation in a life history context. To what relation did Lack attribute this pattern?

ANSWER: Lack recognized that life history traits vary in predictable ways with environmental factors and constraints. He hypothesized that clutch size was commensurate with availability of resources (food, in this case), which tend to decrease with latitude.

51. We might expect natural selection to favor organisms that produce more offspring. Why is this not the case for species with a high degree of parental care?

ANSWER: When parental care requirements are high, parents are not able to provide adequate care for larger broods, and survival rates will be lower than if they had fewer offspring.

52. Use the information in the figure to explain whether the fitness of the parent increases with more eggs produced and why.

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ANSWER: The ratio of chicks fledged per number of eggs is relatively constant (approximately 0.5) up to seven eggs, but fewer chicks are fledged with an eighth egg.

53. According to the figure, what are the implications of producing five versus eight eggs? Which option should be favored by natural selection?

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ANSWER: The number of chicks fledged is the same whether five or eight eggs are produced. Since it takes more parental energy to produce eight eggs and care for eight chicks, the survival rate per egg is lower with eight eggs. Therefore, natural selection should favor the production of five rather than eight eggs.

54. The number of chicks fledged in a brood may not be independent of the number of eggs produced. How might researchers test these variables independently to determine whether there is a relationship between them?

ANSWER: Researchers can add or subtract the number of eggs in a nest to see whether this influences the number of chicks fledged.

55. Explain two significant ways in which environmental productivity and stability can influence the number of offspring produced and their probability of survival.

ANSWER: A productive and stable environment will allow females to dedicate a relatively high level of energy to reproduction, which means more offspring for most species. In addition, such an environment will allow for a larger food supply for both the female and offspring.

56. Compare the relative influence of determinate and indeterminate growth patterns on natural selection for adult female size.

ANSWER: An indeterminate growth pattern is more likely to influence adult size, especially that of females, than determinate growth patterns. Since females with determinate growth stop growing at maturation, the fitness of offspring should be due to other factors than size of the female. Females with indeterminate growth will vary greatly in size and thus fecundity.

57. How would fecundity and age at maturity be influenced by adult and juvenile survival rates?

ANSWER: If the ratio of adult to juvenile survival is high, then either adults should not put much energy into reproduction or maturation should be delayed or both. In the opposite situation, the ratio of adult to juvenile survival is low. This would encourage semelparity, in which the adult puts as much energy as possible into one mortality-causing reproductive event.

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Chapter 7 58. Is senescence inevitable? Please explain your answer, accounting for the great variation in patterns of aging among different species.

ANSWER: Yes, it appears that all mechanisms, biological and otherwise, inevitably wear out. However, organisms differ greatly in their longevity, and some apparently invest more resources in processes that prevent or repair damage. The degree to which resources are allocated to such processes appears to be related to the hazards of life. Species for which external factors (accidents, predation, bad weather) greatly reduce the likelihood of adult survival receive little fitness benefit from investment in processes that prevent or repair damage. Among these species, resources devoted to maintenance and repair would detract from early fecundity. Species with greater likelihood of adult survival are more likely to reap the reproductive benefits of an extended life span, and the cost of somewhat reduced early fecundity is likely to be more than offset by the advantages conferred by multiple reproductive events.

59. Many life history events are matched to seasonal changes in environmental conditions, such as the onset of winter. Explain why photoperiod is a more reliable seasonal indicator for plants than air temperature.

ANSWER: Although air temperature changes are seasonally predictable, actual temperatures on a given date vary unpredictably from year to year. However, solar angles and the time of sunrise and sunset do not change from year to year and are therefore much more reliable seasonal cues than air temperatures.

60. One might suppose that an earlier, longer summer would be beneficial for most species, because it offers a longer growing season for offspring. How might earlier offspring births in a predator species be detrimental to it?

ANSWER: If the prey species of the predators are not similarly affected, offspring may not have an available food source.

61. Size limits for fish catches typically refer to the minimum size of individuals that can be harvested and retained. How might size limits affect the spawning strategy of a fish population compared to no size limits, assuming the fish captured are representative of the size distribution of the population?

ANSWER: A size limit to catches would disproportionally increase mortality on larger and older fish. A very high fishing mortality of older and larger fish would tend to select for earlier reproduction at a smaller size, or a semelparous strategy, especially if the fish were harvested shortly after they became mature.

62. How might population density affect life history?

ANSWER: A high population density can imply severe competition for resources. Competition for resources could increase the mortality rate of offspring and limit the number of offspring a female can produce.

63. The data in the figure show a relationship between the mean flowering date for many plant species around Concord, New Hampshire, and the mean spring temperature over a time span exceeding 150 years. However, there is a lot of scatter around the best-fit line in panel b. What information in the chapter might suggest the source of this scatter, and what does it imply about the plant species’ cues for flowering?

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ANSWER: The scatter in the data could be due to the fact that some of the plants did not change their flowering date over time despite an increase in spring temperatures. This suggests that these plants probably use a cue such as photoperiod rather than temperature to determine flowering date.

64. Would human removal of large fish from a population influence both the age of maturation in the population and the proportion of energy dedicated to reproduction? Explain your answer.

ANSWER: If the mortality rate of large fish is high, then the juvenile survival rate will either remain unchanged or—if there is less competition for a shared food resource—increase. This difference in mortality rates would suggest that fish entering maturation should put more energy into reproduction than a population not exposed to size-selective fishing.

65. What is meant by the principle of allocation and how is this concept related to fitness?

ANSWER: According to the principle of allocation, an organism has limited available resources. When these limited available resources are devoted to a particular body structure, physiological function, or behavior, then the resource is not available to another structure, function, or behavior. Natural selection will select those individuals that allocate the limited resources available in a way that maximizes individual fitness.

66. Using Grime’s categories, describe the general environment in which one is likely to find competitors, stress Copyright Macmillan Learning. Powered by Cognero.

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Chapter 7 tolerators, and ruderals.

ANSWER: Stress tolerators are often found in environments with extreme conditions (low water availability, extreme temperatures, and/or high salt content); examples include the tundra and deserts.

Competitors are often found in a variety of environments that have low stress levels and low levels of disturbance; examples include many mature forest environments. Ruderals are often found in environments that have low stress and high levels of disturbance; examples include areas of disturbance whether caused by natural causes or humans.

67. Describe the difference between an organism that displays determinate growth and an organism that displays indeterminate growth. Provide examples of organisms that display each growth type.

ANSWER: Organisms that show determinate growth stop growing when they reach sexual maturity. Organisms that show indeterminate growth continue growing even after reaching sexual maturity. Birds and mammals tend to show determinate growth, while fish, reptiles, amphibians, invertebrates, and plants tend to show indeterminate growth.

68. Explain how human fishing for larger individuals from a population of fish can reduce the average maturation time in the population.

ANSWER: If individuals delay maturation to achieve large size and increase fecundity, they risk increased mortality due to fishing. Therefore, natural selection should favor individuals that mature prior to reaching a large size.

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Chapter 8 Multiple Choice 1. In honeybees, drones arise from _____ eggs, and workers arise from _____ eggs. a. diploid; fertilized haploid b. unfertilized haploid; diploid c. unfertilized haploid; fertilized diploid d. fertilized haploid; unfertilized haploid ANSWER: c 2. Reproduction in which offspring receive genetic material from two parents is called a. asexual reproduction. b. parthenogenesis. c. vegetative reproduction. d. sexual reproduction. e. binary fission.

ANSWER: d 3. In sexual reproduction, meiosis produces _____ cells from one parent that join with _____ cells from the other parent to form a _____ zygote. a. haploid; diploid; diploid b. haploid; haploid; diploid c. diploid; diploid; haploid d. haploid; diploid; haploid e. diploid; diploid; diploid ANSWER: b 4. What process produces gametes for sexual reproduction? a. mitosis b. binary fission c. clonal duplication d. meiosis e. parthenogenesis ANSWER: d 5. Production of offspring from the nonsexual tissues of a parent is called a. mitosis. b. binary fission. c. clonal duplication. d. vegetative reproduction. e. parthenogenesis.

ANSWER: d Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 6. Clones are offspring produced _____ and have the same _____ as the parent. a. sexually; phenotype b. sexually; genotype c. asexually; phenotype d. asexually; genotype ANSWER: d 7. Asexual reproduction a. occurs when offspring are produced by two parents without copulation. b. occurs when offspring are produced by and receive genetic material from only one parent. c. occurs when offspring are produced by and receive genetic material from both parents. d. is accomplished only via parthenogenesis. e. is accomplished only via vegetative reproduction.

ANSWER: b 8. Parthenogenesis occurs when offspring are produced a. from a parent’s gonad tissue. b. by a cell dividing into two identical cells. c. from an unfertilized diploid gamete embryo. d. from a parent’s nonsexual tissue. e. clonally.

ANSWER: c 9. Scientists have confirmed a rare case of a virgin female hammerhead shark (Sphyrna tiburo) giving birth to offspring that were genetically identical to the mother. What process accounts for this phenomenon: a. binary fission b. hermaphroditism clonal reproduction c. vegetative reproduction d. parthenogenesis ANSWER: d 10. Which statement best describes the cost of meiosis? a. Production of haploid gametes for sexual reproduction has a higher energy cost than direct production of diploid offspring. b. Males pass on only 75 percent of their genetic material through sexual reproduction rather than 100 percent through asexual reproduction. c. Sexual reproduction puts individuals at greater risk for predation. d. Females pass on only 50 percent of their DNA through sexual reproduction rather than 100 percent through asexual reproduction.

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Chapter 8 e. Sexual reproduction results in fewer offspring than asexual reproduction.

ANSWER: d 11. All of the following are benefits of sexual reproduction EXCEPT that a. deleterious mutations are more likely to be purged. b. offspring are more likely to possess traits to help cope with future environmental challenges. c. offspring are likely to have greater resources for reproduction than asexually produced offspring. d. offspring are able to evolve to overcome the ever-evolving pathogens and parasites (i.e., fight the evolutionary arms race).

ANSWER: c 12. Which of the following is NOT a mechanism by which organisms can purge deleterious mutations? a. random assortment in meiosis b. production of homozygous recessive nonviable offspring c. random assortment in mitosis d. production of offspring without the mutation ANSWER: c 13. Which statement best describes the Red Queen hypothesis? a. Asexual reproduction allows organisms to increase survival by keeping up with the evolution of parasites. b. Sexual reproduction allows organisms to increase survival by keeping up with the evolution of parasites. c. Parasites evolve at such a rapid a rate that organisms cannot evolve countermeasures. d. Organisms are able to survive parasites because they evolve at a more rapid rate than parasites.

ANSWER: b 14. Which describes a plant species with perfect flowers? a. Individuals of a plant have flowers that contain either female structures or male structures but not both, yet both types of flowers can be found on the same individual. b. Some individual plants have flowers that contain only female structures, and other separate individuals have flowers that contain only male structures. c. Individual plants have flowers that contain neither female nor male structures. d. Individual plants have flowers that contain both female and male structures.

ANSWER: d 15. Plant species with separate male and female flowers on the same individual are called _____, and plant species with only male or only female flowers on an individual are called _____. a. dioecious; monoecious b. monoecious; dioecious c. hermaphrodites; perfect Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 d. simultaneous hermaphrodites; sequential hermaphrodites ANSWER: b 16. An organism starts out its life as female but later changes into a male. This is an example of a. sequential hermaphroditism. b. simultaneous hermaphroditism. c. monoecism. d. dioecism.

ANSWER: a 17. Evolution favors hermaphroditism when fitness of the hermaphrodite is _____ the fitness of the _____. a. less than; male b. less than; female c. less than; male or female d. greater than; male or female e. equal to; male or female ANSWER: d 18. Hermaphroditism is a. rare in species that engage in brood care. b. common in mobile aquatic animals. c. common in species that actively seek mates. d. rare in flowering plants.

ANSWER: a 19. An individual that uses its male gametes to fertilize its female gametes is reproducing through a. outcrossing. b. self-fertilization. c. cloning. d. parthenogenesis.

ANSWER: b 20. Organisms can avoid self-fertilization by a. sequential hermaphroditism. b. simultaneous hermaphroditism. c. cloning. d. binary fission.

ANSWER: a 21. In some perfect flowers, the receptiveness of the stigma is delayed until after its anthers have released pollen. This delay prevents Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 a. outcrossing. b. self-incompatibility. c. parthenogenesis. d. self-fertilization.

ANSWER: d 22. Which type of mating strategy is most likely to result in self-fertilization? a. sequential hermaphrodite b. simultaneous hermaphrodite c. dioecious plant d. binary fission ANSWER: b 23. Why might an organism self-fertilize rather than outcross? a. Self-fertilization reduces inbreeding depression. b. Self-fertilization produces more viable offspring than outcrossing. c. Attracting mates is expensive. d. Self-fertilization produces more offspring than outcrossing.

ANSWER: c 24. Scientists have demonstrated that as herbivory on orange jewelweed (Impatiens capensis) flowers increases, the proportion of selfing to outcrossing flowers increases. This occurs because a. herbivores prefer the nectar of outcrossing flowers because of their increased sugar content. b. the plant requires increased genetic variation to compensate for biomass loss due to herbivory. c. selfing flowers contain more phenolics and tannins that herbivores avoid. d. the loss of resources due to herbivory causes plants to make less expensive selfing flowers.

ANSWER: d 25. In genetic sex determination, if a genotype of XX is female and XY is male, what will be the natural percentage of female offspring? a. 25 b. 75 c. 50 d. 80 ANSWER: c 26. Which of the following is NOT a genetic mechanism for sex determination? a. There are two sex chromosomes, W and Z, and ZZ results in a male and ZW results in a female. b. Fertilized eggs develop into females, and unfertilized eggs develop into males. c. Eggs incubated at higher temperatures develop into females, and eggs incubated at lower temperatures develop into males.

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Chapter 8 d. Individuals with two sex chromosomes are female, and individuals with one sex chromosome are male.

ANSWER: c 27. In vertebrates, what is the most common factor in environmental sex determination? a. pH b. ambient light level c. humidity d. temperature ANSWER: d 28. An animal begins its life as a female. Later the dominant male dies and the female changes sex to become male. This is an example of a. environmental sex determination. b. frequency-dependent selection. c. genetic sex determination. d. frequency-independent selection.

ANSWER: a 29. Natural selection favoring the rarer sex in a population leads to evolution of sex ratios. This process is the result of a. environmental sex determination. b. frequency-dependent selection. c. genetic sex determination. d. frequency-independent selection.

ANSWER: b 30. In most species, what process is responsible for sex ratios of approximately one to one? a. genetic sex determination b. frequency-dependent selection c. environmental sex determination d. selective abortion ANSWER: b 31. Female red deer (Cervus elaphus) of different ages were found to give birth to fawns of differing sex ratios by means of a. temperature-dependent sex determination. b. frequency-dependent selection. c. local mate competition. d. selective abortion.

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Chapter 8 32. When researchers studied sex ratios in red deer (Cervus elaphus), they found that yearling females selectively aborted male offspring because males a. were more expensive to raise. b. were less reproductively valuable. c. required longer gestation periods. d. required longer periods of parental care.

ANSWER: a 33. Fig wasp populations contain a high proportion of females to males because of local mate competition. This occurs because a. most of the females do not mate, so fewer males are required. b. a large number of females can mate with a single male. c. females reproduce asexually, which does not require males. d. higher temperatures inside figs result in mostly female offspring.

ANSWER: b 34. Which of these terms describes a general mating system in which individuals mate with multiple partners without a lasting social bond? a. polyandry b. promiscuity c. polygamy d. polygyny e. monogamy ANSWER: b 35. Salmon reproduce when many males and females release large quantities of their gametes into a stream.

This process, spawning, is a type of a. monogamy. b. polyandry. c. promiscuity. d. polygyny.

ANSWER: c 36. Some species of anglerfish have a unique mating strategy. Males are significantly smaller than females, and early in development they permanently attach to females. A female usually has multiple males attached, and when the female is ready to reproduce, one of the attached males provides sperm for fertilization. This mating strategy is an example of a. polyandry. b. promiscuity. c. polygyny.

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Chapter 8 d. monogamy.

ANSWER: a 37. What is the main difference between promiscuity and polygamy? a. Polygamy entails the establishment of a long-term social bond, whereas promiscuity does not. b. Promiscuity entails the establishment of a long-term social bond, whereas polygamy does not. c. Polygamy always involves one male with multiple females, whereas promiscuity can involve one female with multiple males. d. Promiscuity and polygamy are the same mating system.

ANSWER: a 38. What is the main difference between polygyny and polyandry? a. Both are forms of polygamy; polygyny occurs when one male mates with multiple females, and polyandry occurs when one female mates with multiple males. b. Polyandry involves the establishment of a long-term social bond, whereas polygamy does not. c. Polygamy always involves one male with multiple females, whereas polyandry can involve one female with either a single male or multiple males. d. Polyandry and polygamy are the same mating system.

ANSWER: a 39. Multiple spermatophores are involved in a. promiscuity. b. polygyny. c. polyandry. d. monogamy.

ANSWER: c 40. Which mating system do honeybees employ? a. monogamy b. polygyny c. promiscuity d. polyandry ANSWER: d 41. Which is TRUE about monogamy? a. Insects often form monogamous relationships because males provide significant parental care to offspring. b. Monogamous relationships are favored when males provide significant parental care to offspring. c. Animals in monogamous relationships do not mate outside of the relationship. d. Birds rarely form monogamous relationships because offspring require less parental care.

ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 42. Which organisms are most likely to form monogamous relationships? a. mammals b. birds c. insects d. reptiles ANSWER: b 43. Which is NOT a benefit of extra-pair copulation? a. increased fitness of offspring due to better genotype b. increased fitness of extra male due to increased numbers of offspring c. increased fitness of monogamous female due to greater fitness of offspring d. increased fitness of monogamous male due to less energy expended on reproduction ANSWER: d 44. Which partner in a monogamous relationship might participate in extra-pair copulation? a. paired females b. paired males c. paired males and paired females d. unpaired males and females ANSWER: c 45. Mate guarding is selected for as a result of extra-pair copulation in a. polygyny. b. polyandry. c. polygamy. d. monogamy.

ANSWER: d 46. The male golden orb-weaving spider (Nephila clavipes) dies while still joined with the female following copulation. This is an example of a. extra-pair copulation. b. mate guarding. c. monogamy. d. the handicap principle.

ANSWER: b 47. The evolution of physical traits of males to attract females or to compete with other males to mate with females is known as a. sexual dimorphism. b. sexual selection. c. sexual polymorphism.

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Chapter 8 d. mate guarding.

ANSWER: b 48. Traits such as the large, colorful tail feathers of male peacocks are known as _____ because they are related to _____. a. primary sexual characteristics; fertilization b. primary sexual characteristics; courtship c. secondary sexual characteristics; fertilization d. secondary sexual characteristics; courtship ANSWER: d 49. Which of the following is a primary sexual characteristic? a. testicles of males b. manes of male lions c. antlers in male elk d. male birds having more colorful feathers than females ANSWER: a 50. Which of the following is a secondary sexual characteristic? a. testicles of males b. mammary tissues of females c. fallopian tubes of females d. tusks of male elephants ANSWER: d 51. Which of the following traits would NOT be considered a material benefit? a. quality nesting site b. high-quality territory c. long tail feathers d. abundant food ANSWER: c 52. Which of the following is NOT a reason that the infection rate of sweet potato whiteflies (Bemisia tabaci)

by Rickettsia bacteria increased dramatically? a. Bacteria increased female whitefly reproductive rates b. Bacteria altered whitefly sex ratios and increase the percentage of female offspring c. Bacteria increased survival of offspring d. Bacteria altered the sperm of male whiteflies to prevent them from fertilizing the eggs of noninfected females ANSWER: d Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 53. Scientists have found that offspring of male tree frogs with long calls spend more time feeding and grow faster than offspring of male tree frogs with short calls. This supports the a. good health hypothesis. b. good genes hypothesis. c. concept of runaway sexual selection. d. handicap principle.

ANSWER: b 54. A peacock is significantly more colorful than a peahen and has a much larger tail. These traits allow the peacock to attract a mate but also make the peacock more visible to predators. This is an example of a. runaway sexual selection. b. sexual conflict. c. the good health hypothesis. d. the good genes hypothesis.

ANSWER: a 55. Sexual traits that are disadvantageous to male survival may be attractive to a female because they suggest the male possesses a superior genotype to counteract the disadvantageous trait. This is known as a. runaway sexual selection. b. the handicap principle. c. the good genes hypothesis. d. the good health hypothesis.

ANSWER: b 56. According to the handicap principle, if a signal is honest, the perceived advantage linked to the disadvantageous trait is a. directly beneficial to the female. b. genetically linked to the sexual trait. c. inherited by offspring. d. not inherited by offspring.

ANSWER: c 57. In ring-necked pheasants (Phasianus colchicus), long spurs on the lower legs of males are genetically linked to a gene that influences the bird’s susceptibility to disease (birds with longer spurs have histocompatibility complex genes that are linked to longer life spans). This is called a. an honest signal. b. a true signal. c. the handicap principle. d. the good health hypothesis.

ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 58. Infanticide by a new dominant male lion confers which primary benefit to the dominant male? a. Resources are not spent on cubs not related to the dominant male. b. The dominant male does not have to care for unrelated cubs. c. The aggressiveness of the act establishes the male’s dominance in the pack. d. Female lions are ready to breed again sooner when they are not caring for cubs.

ANSWER: d 59. Why has the microbe Wolbachia evolved mechanisms to alter the sex ratio of fruit flies and mosquitos? a. Wolbachia are passed only through infected eggs. b. Wolbachia reproduce only in males. c. Females are more susceptible to Wolbachia than males. d. Males are more susceptible to Wolbachia than females.

ANSWER: a 60. When compared to asexual reproduction, costs of sexual reproduction potentially include all of the following EXCEPT a. increased numbers of genes passed on to one’s offspring. b. increased predator exposure risks. c. increased energy costs involved in reproductive organs. d. increased energy costs involved with mating behaviors.

ANSWER: a 61. What is the idea that a female selects the mate with a superior genotype called? a. the handicapped principle b. the good genes hypothesis c. the good health hypothesis d. the runaway sexual selection concept ANSWER: b 62. What is the idea that a female selects the healthiest mate called? a. the handicapped principle b. the good genes hypothesis c. the good health hypothesis d. the runaway sexual selection concept ANSWER: c 63. The idea that when selection for female preference of a sexual trait and selection on males for that trait continue to reinforce each other and lead to extreme male traits is called what? a. the handicapped principle b. the good genes hypothesis c. the good health hypothesis Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 d. the runaway sexual selection concept ANSWER: d 64. In many species females are different from males in appearance. This difference in phenotype between the sexes is called a. sexual selection. b. sexual dimorphism. c. sexual diversity. d. sexual richness.

ANSWER: b 65. Research using DNA analysis has shown that, with most bird species, the eggs within a nest being incubated at the same time may be the product of a single female and more than one male. This is finding is evidence of a. polygyny. b. polyandry. c. extra-pair copulation. d. promiscuity.

ANSWER: c 66. An organism at times mates by outcrossing and other times mates by self-fertilization. What is the least likely environmental variable the organism is responding to? a. changes in daily temperature profile b. changes in mate availability c. changes in age of the organism d. seasonal changes ANSWER: a Essay 67. Lions have been hunting gazelles in the savannahs of Africa for hundreds of thousands of years. Over time both gazelles and lions have incrementally increased their speed. What might be occurring? What hypothesis could explain this phenomenon?

ANSWER: As lions and gazelles have evolved together, gazelles have become faster to outrun the lions, and the lions have become faster to catch the gazelles. This is an example of the Red Queen hypothesis, according to which each species evolves to overtake the other.

68. One of the disadvantages of selfing in hermaphrodites is inbreeding depression. How does inbreeding depression impair fitness?

ANSWER: Inbreeding depression occurs when offspring inherit deleterious alleles from both the sperm and the egg. If an individual carries a deleterious allele, the chances of receiving two copies is, obviously, greater when selfing as opposed to outcrossing.

69. Over many decades, how might the presence of pathogens influence the proportion of individuals in a plant Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 population that reproduce by self-fertilization versus the proportion that reproduce by outcrossing? Why would pathogens cause this outcome?

ANSWER: In the presence of pathogens, plants that breed via outcrossing would have a higher relative abundance than self-fertilizers over time. Because the self-fertilizers produce offspring with the same genes as the parent, pathogens eventually adapt to overcome the defenses of the self-fertilizers.

In contrast, each new generation of outcrossing plants would have a novel combination of genes, and as a result the pathogen would have a more difficult time overcoming the defenses of these individuals.

70. Females of American crocodiles (Crocodylus acutus) produce on average 50 eggs. Consider one population composed of 13 females and 7 males and another population composed of 9 females and 11 males. Use the number of gene copies for females and males to determine the female and male fitness of each population.

Predict what will happen over time to the sex ratio of each population.

ANSWER: Scenario 1—13 females and 7 males Total number of eggs per female: 50 Average female fitness: 50 female gene copies ÷ 13 females = 3.85 gene copies per female Average male fitness: 50 male gene copies ÷ 7 males = 7.14 gene copies per male Over time the number of males will increase because of their greater fitness, which will tend to equalize the sex ratio.

Scenario 2—9 females and 11 males Total number of eggs per female: 50 Average female fitness: 50 female gene copies ÷ 9 females = 5.56 gene copies per female Average male fitness: 50 male gene copies ÷ 11 males = 4.55 gene copies per male Over time the number of females will increase because of their greater fitness, which will tend to equalize the sex ratio.

71. Why is monogamy more frequently seen in birds than mammals?

ANSWER: While males can be involved in rearing of young in both mammals and birds, male birds can offer the same care as females, including incubating eggs, defending the nest, and procuring food. In mammals, males cannot provide the same care as females because they do not lactate.

72. When researchers experimentally altered tail lengths of male long-tailed widowbirds (Euplectes progne), they found that females chose males with longer tails even when tail length did not correlate with any tangible benefit to a male’s ability to defend territory. What are two possible reasons that females prefer longer tails?

ANSWER: According to the good genes hypothesis, females prefer males that can produce long tails because the tails indicate the male has superior genes. Alternatively, according to the good health hypothesis, females prefer males that can produce long tails because the tail indicates that the male is very healthy. These hypotheses are not mutually exclusive, and both processes could be occurring.

73. You discover a new species of wasp with females that lay their eggs inside tree branches. While the tree material is not a good source of nutrients, the offspring are well protected and are seldom consumed by predators. After the eggs hatch, only the females possess the mouthparts needed to chew through the wood and escape. All of the males die in the nest. However, because the wasps cannot digest and obtain nutrients from the wood, the young females must obtain the strength necessary for eating their way out of the branch by ingesting spermatophores (small packets containing sperm and nutrients) that each male releases in the nest. These Copyright Macmillan Learning. Powered by Cognero.

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Chapter 8 spermatophores also fertilize the females. Once a male releases his spermatophore, he dies. While the spermatophores contain nutrients, the likelihood that a female will escape the nest is highly positively correlated with the number of spermatophores that she ingests.

In this wasp species, would you predict a sex ratio bias? Explain why or why not. Would this mating system be classified as promiscuity, polygyny, polyandry, or monogamy?

ANSWER: A male-biased sex ratio is likely in this wasp species because a mother’s fitness will be highest if she produces a few females and abundant males to ensure that the few females are able to escape the nest. If the sex ratio is even or female-biased, then all males will still die and most or all females will die because they will not consume enough spermatophores to have the strength to escape. This is an example of polyandry, because a single female typically mates with multiple males, while a given male can mate with only a single male.

74. Describe the fundamental differences among the three mating systems, including the number of individuals involved and the presence/absence of social pair bonds.

ANSWER: Promiscuity is a mating system that sees an individual mating with multiple partners, and no longterm social bond is formed between individuals. Polygamy is a mating system that sees an individual of one sex mating with multiple individuals of the other sex. Two forms of polygamy exist: polygyny, which is one male with multiple females, and polyandry, which is one female with multiple males. In the case of polygamy, long-term social bonds are formed. Monogamy is a mating system between a single male and a single female with long-term social bonds formed.

75. The sex of an offspring may be determined in two different ways: genetically or environmentally. What is the difference between the two mechanisms?

ANSWER: Genetic sex determination is the process by which, depending on the species, what gametes the embryo receives determine the sex of the individual. In birds the male produces sperm that only carry the Z chromosome, while the female produces eggs that either carry the Z chromosome or the W chromosome. If the Z-carrying sperm fertilizes an egg carrying the Z chromosome, the offspring is male. If the Z-carrying sperm fertilizes an egg carrying the W chromosome, the offspring is female. Environmental sex determination involves some environmental factor that determines the sex of the offspring. In reptiles, the temperature in which the embryo develops determines the sex of the offspring. In turtles, for instance, embryos incubated in lower temperatures become males and embryos incubated in higher temperatures become females.

76. Describe the costs of sexual reproduction in terms of energy, risk, and genetics.

ANSWER: An organism that reproduces sexually must expend energy to create the necessary structures and/or organs to carry out sexual reproduction. These structures may be gonads, flowers, or secondary sex characteristics, among others. Additional organisms that reproduce sexually may employ mating behaviors/rituals that are energy expensive as well as potentially exposing the individuals conducting such behavior to increased risk of predation and parasitism, among others. More fundamentally, when compared to asexually producing organisms, sexually reproducing organisms see a 50 percent reduction in genes passed to the next generation as a result of the meiotic process of making eggs or sperm.

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Chapter 9 Multiple Choice 1. When leaf-cutter ants age and become less efficient at their tasks, they a. are killed. b. change tasks. c. are evicted from the colony. d. are eaten by other colony members.

ANSWER: b 2. Which of the following is NOT a strategy that leaf-cutter ants use to avoid parasitoid flies specialized to hunt large ants? a. Small ants forage during the day, when the flies are active. b. Large ants forage at night, when the flies are inactive. c. Small ants guard larger ants during the day, when the flies are active. d. Small ants perform all foraging tasks for the ant colony.

ANSWER: d 3. In animals, which of the following is NOT considered social behavior? a. interactions between mates b. interactions between parents and offspring. c. interactions between individuals of the same species. d. interactions between different species ANSWER: d 4. Which is the most important factor in determining territory quality? a. size of territory b. season of the year c. territory resources d. closeness to other territories ANSWER: c 5. Animals that live in groups have a reduced individual probability of predation. This is known as a. the dilution effect. b. a lek. c. altruism. d. cooperation.

ANSWER: a 6. Which of the following is NOT a tactic that animals living in groups use to reduce the overall probability of predation? a. group defense used to protect from predators Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 b. many individuals looking out for predators at any given time c. sheer numbers of individuals in the group d. avoidance of predation by scattering ANSWER: d 7. A lek is the location of an aggregation of animals a. to reduce the rate of predation. b. for hunting. c. for feeding. d. for mating displays.

ANSWER: d 8. Researchers have found that on coral reefs where fishing occurs, the fish have fewer parasites than fish on coral reefs where fishing is excluded. What explains this observation? a. Fishing eliminated fish with inferior genetics, which were more susceptible to parasites. b. On coral reefs that excluded fishing, larger populations of fish made them subject to more transmission of parasites. c. The sites where fishing was excluded had more parasites than the sites with fishing. d. Fishing removed the largest fish and the largest fish had the most parasites.

ANSWER: b 9. In the example of the ruff (Philomachus pugnax), researchers found that males in leks had more success in a. attracting females. b. copulating with females. c. attracting females and copulating with females. d. none of the above ANSWER: c 10. Which of the following is NOT a cost of living in groups? a. decreased likelihood of mating b. increased transmission of pathogens c. increased individual risk of predation d. increased competition ANSWER: a 11. Increased competition for food among individuals living in groups may lead to increases in all of the following except a. movement between habitats in search of food. b. time dedicated to locating food by individuals. c. aggression between group members. d. time spent in parental care of offspring Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 ANSWER: d 12. Large groups are particularly vulnerable to parasites and pathogens because they a. have low numbers of resistant individuals. b. can cause pathogens to mutate and become more dangerous. c. can rapidly become infected by a single individual. d. decrease the likelihood of immunity developing.

ANSWER: c 13. Group living _____ the individual’s risk of predation and _____ the likelihood the group will be detected by a predator. a. increases; increases b. increases; decreases c. decreases; increases d. decreases; decreases ANSWER: c 14. Researchers found that as the flock size of European goldfinch (Carduelis carduelis) increased, the time needed to find new food patches also increased because large populations a. have high per capita food consumption. b. are forced to live in lower-quality habitat. c. have more aggressive individuals. d. depleted the food source in the original patch more quickly.

ANSWER: d 15. An area that one or more individuals defend against intrusion by others is a a. dominance hierarchy. b. lek. c. home range. d. territory.

ANSWER: d 16. Which is NOT true about territoriality? Territoriality develops a. when a resource can be defended. b. when the benefits of defending a resource outweigh the costs. c. when fitness is increased by having the territory. d. during the nonbreeding season only.

ANSWER: d 17. Animals living in packs, such as wolves, establish an order that dictates social behavior. This is an example of Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 a. territoriality. b. spitefulness. c. a dominance hierarchy. d. a lek.

ANSWER: c 18. Which of the following is NOT a benefit of a dominance hierarchy? a. organization of conspecifics to reduce intraspecific competition b. quick resolution of conflicts c. group defense of ephemeral resources d. aggregation of individuals to increase probability of mating ANSWER: d 19. Which statement about social interactions is TRUE? a. The recipient is the individual who directs behavior toward another individual, the donor. b. Donors and recipients direct behaviors toward one another. c. The donor is the individual who directs behavior toward another donor. d. The donor is the individual who directs behavior toward another individual, the recipient.

ANSWER: d 20. A social interaction in which both the donor’s fitness and the recipient’s fitness are increased is called a. cooperation. b. altruism. c. spitefulness. d. selfishness.

ANSWER: a 21. A hummingbird guarding a hummingbird feeder is an example of a. dominance hierarchy. b. altruism. c. territoriality. d. selfishness.

ANSWER: c 22. Based on fitness effects on donors and recipients, which type of social interaction is expected to occur LEAST often or not at all? a. altruism b. cooperation c. selfishness d. spitefulness Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 ANSWER: d 23. In the social interaction of altruism, the donor receives a(n) _____ in fitness and the recipient receives a(n) _____ in fitness. a. decrease; increase b. decrease; decrease c. increase; increase d. increase; decrease ANSWER: a 24. Which social interaction is best described as the opposite of altruism in terms of its effect on donor and recipient fitness? a. cooperation b. selfishness c. spitefulness d. dominance ANSWER: b 25. In the wattled jacana (Jacana jacana), a species of tropical wading bird, males perform all brood care.

Females protect nests and defend territory. Females sometimes attack and kill chicks cared for by a male. The male then fertilizes the female attacker and cares for the resulting young. This type of social interaction that sees one female killing the young produced by another female so as to be fertilized by the male caring for the original brood is an example of a. cooperation. b. selfishness. c. spitefulness. d. altruism.

ANSWER: b 26. Why is altruistic behavior an evolutionary problem? a. It does not lead to an increase in direct fitness. b. It does not lead to an increase in indirect fitness. c. It does not lead to an increase in fitness. d. It decreases fitness.

ANSWER: a 27. What is another term for kin selection? a. indirect selection b. direct selection c. natural selection d. sexual selection Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 ANSWER: a 28. Fitness that an individual gains by passing on copies of its genes to its offspring is favored by _____ selection. a. indirect b. direct c. natural d. sexual ANSWER: b 29. Indirect fitness is favored by _____ selection. a. natural b. sexual c. kin d. direct ANSWER: c 30. The coefficient of relatedness measures a. the probability of an individual and its relatives carrying copies of the same genes from a recent common ancestor. b. the number of generations separating individuals in a population. c. indirect fitness as the benefit given to a recipient relative by the donor individual. d. the direct fitness cost of altruistic behavior to a recipient by the donor.

ANSWER: a 31. The evolution of altruistic behavior is most likely to be between a. parent and offspring. b. identical twins. c. cousins. d. half siblings.

ANSWER: b 32. Based on the coefficient of relatedness, to which of the following relatives would a donor be most likely to provide altruism? a. grandparent b. cousin c. half sibling d. full sibling ANSWER: d 33. For calculations of the indirect fitness benefit of altruistic behavior and kin selection, r is the Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 a. coefficient of relatedness between the donor and recipient. b. benefit given to a recipient relative. c. direct fitness cost to the donor. d. indirect fitness cost to the donor.

ANSWER: a 34. Which equation calculates the indirect fitness benefit of altruistic behavior and kin selection? a. C × r b. B × r c. B ÷ r d. B + r ANSWER: b 35. The equation C < B × r describes conditions under which a(n) _____ behavior will ______in the population. a. altruistic; increase b. altruistic; decrease c. selfish; increase d. selfish; decrease ANSWER: a 36. C/B describes the ratio of a. donor benefits to recipient costs. b. donor costs to recipient benefits. c. indirect fitness costs to direct fitness benefits. d. direct fitness costs to indirect fitness benefits.

ANSWER: b 37. Altruism is likely to evolve when a. B/C > r. b. C/B > r. c. C/B < r. d. C/B = r.

ANSWER: c 38. Wild turkeys (Meleagris gallopavo) perform mating displays at leks alone or in coalitions of related males.

In the coalitions, only dominant males copulate with females. Why do nondominant males join coalitions? a. A nondominant male obtains greater inclusive fitness by helping a brother mate than by mating on his own. b. A nondominant male obtains greater direct fitness by helping his brother mate than by mating on his own. c. A nondominant male obtains less indirect fitness by helping his brother mate than by mating on his Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 own. d. A nondominant male may eventually become the dominant male in a coalition.

ANSWER: a 39. Which of the following is a characteristic of eusocial species, but is NOT found in species that exhibit cooperative breeding? a. adults living together in a group b. overlapping generations of parents and offspring c. cooperation in nest building or brood care d. presence of sterile individuals or castes ANSWER: d 40. Which is NOT a characteristic of a eusocial species? a. reproductive dominance by many individuals b. cooperation in nest building and brood care c. several adults living together in a group d. sterile individuals ANSWER: a 41. Which group does NOT contain a eusocial species? a. corals b. termites c. ants d. mammals ANSWER: a 42. Which of the following is NOT an ecosystem process associated with eusocial insects? a. pollination b. consuming detritus c. herbivory d. decomposition ANSWER: d 43. Which does NOT have a haplodiploid mating system? a. ants b. bees c. termites d. wasps ANSWER: c 44. How many castes do bees have?

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Chapter 9 a. four b. three c. two d. five ANSWER: b 45. In haplodiploid mating systems, males are a. haploid and fertile. b. haploid and infertile. c. diploid and fertile. d. diploid and infertile.

ANSWER: a 46. In haplodiploid mating systems, nonqueen females are a. haploid and fertile. b. haploid and infertile. c. diploid and fertile. d. diploid and infertile.

ANSWER: d 47. The worker caste in bees consists entirely of a. reproductive females in an arrested stage of development. b. reproductive females. c. reproductive males in an arrested stage of development. d. reproductive males.

ANSWER: a 48. In eusocial hymenoptera, there is a strong asymmetry in the genetic relatedness of siblings. What is the coefficient of relatedness between female workers? a. 1.0 b. 0.5 c. 0.75 d. 0.25 ANSWER: c 49. The sex determination system in hymenopterans such as ants, bees, and wasps is a. triplodiploid. b. haplodiploid. c. diplohaploid. d. haplotriploid.

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Chapter 9 ANSWER: b 50. In haplodiploid societies, a _____ produces male gametes by _____. a. diploid female; mitosis b. haploid female; meiosis c. haploid male; mitosis d. haploid female; mitosis ANSWER: c 51. In haplodiploid societies, which would be expected to show most cooperation? a. all-male group b. all-female group c. mixed male and female group d. All of these groups would show equal cooperation.

ANSWER: b 52. What prevents nondominant mole rats from reproducing? a. Nondominant mole rats are born sterile. b. Haplodiploid sex determination means that sibling mole rats are more related to each other than to their parents. c. Harassment by the dominant members prevents nondominant mole rats from breeding. d. Once nondominant mole rats reach sexual maturity, they leave to form new colonies.

ANSWER: c 53. In termite colonies, which of the following does NOT reproduce? a. drone b. soldier c. king d. queen ANSWER: b 54. Which type of plant is most likely to exhibit altruistic social behaviors? a. species that rely on animals for dispersal b. clonal species that reproduce through vegetative growth c. clonal species that rely on wind pollination d. species that rely on wind pollination not animal pollination ANSWER: b 55. Which of the following most likely influences whether neighboring plants alter their growth patterns altruistically? a. growth rate Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 b. seasonal changes in sunlight c. ability to recognize related individuals d. growing season length ANSWER: c 56. You are studying flocks of European starlings (Sturnus vulgaris). You notice that flock size varies quite a bit from just a few individuals to hundreds within the same flock. What might you expect when observing starling feeding behavior in open fields and lawns between individuals in the small flocks and those in the large flocks? a. Individuals in the small flocks have more offspring. b. Individuals in the large flocks have more offspring. c. Individuals in small flocks spend more time looking for predators. d. Individuals in large flocks spend more time looking for predators.

ANSWER: c 57. As a result of group living, an individual living in a group might a. be less likely to be exposed to disease. b. be less likely to migrate. c. be larger in size. d. have a higher rate of consumption.

ANSWER: d 58. One of the benefits of group living is increased vigilance. Vigilance in this sense refers to a. identifying food sources. b. identifying possible mates. c. identifying predator locations. d. identifying potential competitors.

ANSWER: c 59. Chronic wasting disease (a disease of white-tailed deer) is of particular concern on deer farms where it can spread much faster than among wild deer. Why might that be the case? a. Deer on deer farms do not have the same robust immune system as deer in the wild. b. Deer on deer farms are fed processed deer food as opposed to natural browse. c. Deer on farms are in large numbers and in close proximity and thus disease can spread more rapidly. d. The sex ratios of deer on deer farms are skewed compared to in the wild.

ANSWER: c 60. If individuals in groups must compete with other group members for food, why would an individual be found in a group? a. The food items/unit of area of habitat is greater. b. The food items/unit of area of habitat is less.

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Chapter 9 c. The costs of competition are greater than the benefits of group living. d. The costs of competition are less than the benefits of group living.

ANSWER: d 61. In most caribou (Rangifer tarandus), both males and females have antlers. What might you hypothesize about antlers in caribou? a. There is no metabolic cost to caribou to grow antlers. b. Antlers play no role in caribou since they are found in both sexes. c. Both males and females may be involved in dominance hierarchies. d. Caribou retain their antlers throughout their life span.

ANSWER: c 62. Which is NOT true about the social interaction termed cooperation? a. It is more common than spitefulness in wild animal populations. b. It is less common than spitefulness in wild animal populations. c. Donor and recipients do not necessarily receive the same level of benefit. d. It may occur between unrelated individuals of the same species.

ANSWER: b Essay 63. You discover a small reef fish species in the Great Barrier Reef off the Australian coast. You study its ecology and discover that many midsized and large predatory fish consume the new species. Further, you find that this species consumes the same prey as many other species of similar-sized fish. However, many of those other small species tend to live in large schools, whereas individuals of this newly discovered species live alone.

Propose a general evolutionary hypothesis to explain what ecological conditions could cause a small species to live alone rather in a large school.

ANSWER: Individuals of the newly discovered species do not live in schools because they achieve higher fitness by living alone. Ecological conditions that could cause this behavior include individuals having more success in mating or competition for food when they live alone than when they live in schools. In addition, if predators are so abundant that because of a dilution effect individuals who live in schools are more likely to be eaten than those that live alone, natural selection could favor solitary living over schooling.

64. What is a lek? How is it beneficial?

ANSWER: A lek is the place where an aggregation of animals put on displays to attract mates. Leks are beneficial because they increase the likelihood of males and females finding a mate.

65. Why would evolution favor a social structure that relies on dominance hierarchies rather than individual territories?

ANSWER: Dominance hierarchies form when there are too many conspecifics to defend a territory from, when resources are available for only short periods, or when benefits of living in groups outweigh the benefits of defending territories.

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Chapter 9 66. Why would an individual in a social group of a diploid species help to rear the young of its siblings rather than reproducing itself? Describe the expected relative importance of direct and indirect fitness benefits and explain your answer.

ANSWER: An individual is more likely to help rear the young of its siblings than to reproduce itself if the indirect fitness benefits of helping pass more of the individual’s genes to the next generation outweigh the direct fitness benefits of having its own offspring. This situation could arise if the individual were inferior in quality to the sibling and likely to have fewer reproductive opportunities.

Even though the offspring of the fitter sibling would on average carry only 25 percent of the individual’s genes (as opposed to the 50 percent of its genes that its own offspring would carry), if the sibling produces far more offspring than the individual could, the individual would receive a greater fitness benefit by helping its sibling to rear as many young as possible.

67. If the direct fitness cost to a donor is 6 and the indirect fitness benefit to the recipient is 30, is altruistic behavior likely to evolve between cousins? Is the altruistic behavior likely to evolve between full siblings?

ANSWER: C/B = 6/30 = 0.2 Since the cost-benefit ratio is greater than the coefficient of relatedness for cousins (0.125), the altruistic behavior is unlikely to evolve between cousins. The cost-benefit ratio is less than the coefficient of relatedness for full siblings (0.5), and altruistic behavior is likely to evolve between full siblings.

68. What evidence do we have that eusociality appeared to evolve independently, many times?

ANSWER: Because eusociality appears in hymenopterans, termites, and mole rats, it seems unlikely that one evolutionary event can explain all eusociality. Also insects and mammals are phylogenetically distant lineages.

69. The term henpecked in chickens refers to chickens pecking at injured spots on other chickens, exacerbating the original injury. How did researchers overcome the problem of henpecked chickens?

ANSWER: Researchers started grouping chickens by the best performing (in terms of egg production) groups rather than the best individual performers. Eventually, hen mortality declined because the hens fought less, and egg production increased dramatically.

70. In general terms, what type of habitat would one likely see territoriality and in what type of habitat would one not expect to see territoriality?

ANSWER: One would expect to see territoriality when resources within the area in question (to be defended) are in ample supply and the need for resources by the individual is present. Should resources be present in an “unlimited” amount that exceeds the needs of the individual such that defending the resource is not necessary, then one would not expect to see territoriality. Likewise, if the area in question is without resources, then territoriality should not be observed.

71. The two social interactions called altruism and selfishness both have one individual in the interaction obtaining a positive fitness effect and one individual in the interaction obtaining a negative fitness effect.

However, these two interactions are not the same. How are these two interactions different?

ANSWER: Altruism sees the donor of the behavior being negatively affected while the recipient of the behavior is positively affected. Selfishness sees the donor of the behavior being positively affected while the Copyright Macmillan Learning. Powered by Cognero.

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Chapter 9 recipient of the behavior is negatively affected. Evolution of selfish behavior can be explained through direct fitness, while evolution of altruism relies on increases in indirect fitness 72. In some eusocial, haplodiploid species, the coefficient of relatedness is said to display strong asymmetries.

What does this mean?

ANSWER: Because of the haplodiploid sex determination system, the relatedness coefficients are different. The queen has the same relatedness to her sons as to her daughters (r=0.5). However, the coefficient of relatedness (r) is different when one considers siblings: between any female and her sister r=0.75, between brothers r=0.5, and the coefficient of relatedness between any female and her brother is yet again different, r=0.25. These relatedness coefficients are unlike those found in a diploid system.

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Chapter 10 Multiple Choice 1. What was the main factor that led to declines in collared lizard (Crotaphytus collaris) populations in the Ozark Mountains of Missouri? a. Increased forest fires killed collared lizards and their preferred insect prey species. b. Suppression of forest fires decreased the open habitat that collared lizards require. c. Increased forest fires removed the cool, closed-canopy habitat that collared lizards require. d. Suppression of forest fires led to an increase in the populations of collared lizard predators.

ANSWER: b 2. The pattern of density and spacing of individuals in a population is called the a. niche. b. ecological envelope. c. spatial structure. d. geographic range.

ANSWER: c 3. The range of abiotic conditions under which a species can persist is called its a. fundamental niche. b. geographic niche. c. realized niche. d. geographic range.

ANSWER: a 4. A species of tree is found from the Canadian border down to the southeast United States. This is called the species’ a. fundamental niche. b. realized niche. c. geographic niche. d. geographic range.

ANSWER: d 5. An endangered frog species lives in only a few forest patches found throughout the Pacific Northwest of the United States. The Pacific Northwest is its _____, and the forest patches are its _____. a. realized niche; geographic range b. fundamental niche; realized niche c. geographic range; realized niche d. geographic range; fundamental niche ANSWER: c 6. Determining the suitable habitat conditions for a species is called _____ modeling. a. fundamental niche Copyright Macmillan Learning. Powered by Cognero.

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Chapter 10 b. ecological niche c. geographic niche d. spatial structure ANSWER: b 7. When a species is in danger of becoming extinct, scientists use ecological niche modeling to assess where the species might have the highest probability of successful reintroductions. What does ecological niche modeling determine? a. geographic range b. fundamental niche c. realized niche d. ecological envelope ANSWER: d 8. What is the difference between a species’ realized niche and its ecological envelope? a. The ecological envelope is the range of conditions under which a species lives, whereas the realized niche is a prediction of the range of conditions under which a species can live. b. The realized niche is the range of conditions under which a species lives, whereas the ecological envelope predicts the range of conditions under which a species can live. c. The realized niche is the range of conditions under which a species lives, whereas the ecological envelope is a measure of the total area in which a population lives. d. The realized niche and the ecological envelope are essentially the same.

ANSWER: b 9. Species with very large geographic ranges that can span several continents are called a. abundant. b. endemic. c. cosmopolitan. d. dispersed.

ANSWER: c 10. The orange-breasted sunbird (Anthobaphes violacea) lives only in the fynbos region in the Western Cape of South Africa. This is an example of a(n) a. extinct species. b. endemic species. c. cosmopolitan species. d. localized species.

ANSWER: b 11. The number of individuals _____ best defines abundance. a. per unit area or volume b. in a defined area Copyright Macmillan Learning. Powered by Cognero.

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Chapter 10 c. in a geographic range d. in a species ANSWER: b 12. Which of these measurements is NOT an example of density? a. 26.8 rabbits per hectare b. 17 birds per square mile c. 13 colonies per square meter d. 1021 bacteria per cubic centimeter ANSWER: c 13. When there are direct competitive interactions among individuals in a population, _____ dispersion is favored. a. random b. clustered c. clumped d. evenly spaced ANSWER: d 14. What type of dispersion do many agricultural crops exhibit? a. random b. clustered c. even d. clumped ANSWER: c 15. Which dispersion should be favored among plants that compete intraspecifically by casting shade? a. clumped b. evenly spaced c. random d. clustered ANSWER: b 16. Populations whose individuals _____ favor clustered dispersion. a. live in social groups b. directly compete with each other c. aggressively defend resources d. do not interact with each other ANSWER: a 17. How do dispersal and migration differ?

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Chapter 10 a. Dispersal is seasonal, and migration is usually permanent. b. Dispersal is usually permanent, and migration is seasonal. c. Dispersal is back-and forth-movement between two areas, and migration is unidirectional. d. Migration is movement to colonize a new habitat, and dispersal is seasonal movement.

ANSWER: b 18. A researcher who wants to know how many tree seedlings are in a 1-hectare site counts the number of seedlings within five 2-square-meter subplots and then calculates the average. This method of determining the number of individuals in an area is known as a a. census. b. survey. c. tally. d. count.

ANSWER: b 19. A researcher who counts the number of individuals of a tree species between two fixed points is making a(n) _____ survey. a. area-based b. volume-based c. line-transect d. mark-recapture ANSWER: c 20. During the annual Christmas bird count conducted by the Audubon Society, volunteers count the number of individuals of every bird species they can see or hear along a predetermined path within a 24-kilometer circle.

This is an example of a(n) _____ survey. a. volume-based b. area-based c. mark-recapture d. line-transect ANSWER: d 21. The best way to quantify organisms that are well camouflaged is a(n) _____ survey. a. line-transect b. mark-recapture c. volume-based d. area-based ANSWER: b 22. Which of the following populations would be best estimated by an area-based survey? a. flowers in a field b. rodents in a grassland Copyright Macmillan Learning. Powered by Cognero.

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Chapter 10 c. fish on a coral reef d. migratory birds on a pond ANSWER: a 23. For a mark-recapture survey, the ratio of the number of marked individuals to the total population is equal to the ratio of the a. number of marked individuals recaptured to the total number of individuals in the second capture. b. total number of individuals in the second capture to the number of marked individuals recaptured. c. total number of individuals in the first capture to the number of marked individuals recaptured. d. number of individuals in the second capture to the number of individuals marked in the first capture.

ANSWER: a 24. Methods such as area-based, volume-based, and line-transect surveys would be best for estimations of _____ populations. a. clustered b. random c. evenly spaced d. mobile ANSWER: c 25. Scientists commonly use _____ dispersal distance to quantify an organism’s dispersal. a. average b. maximum c. lifetime d. median ANSWER: c 26. Measuring the lifetime dispersal distance of a species helps scientists to estimate how rapidly a growing population can increase its a. geographic range. b. fundamental range. c. realized niche. d. fundamental niche.

ANSWER: a 27. Populations with high abundance tend to have a _____ range. a. small geographic b. small fundamental c. large geographic d. large fundamental ANSWER: c Copyright Macmillan Learning. Powered by Cognero.

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Chapter 10 28. If the geographic range of a population is decreased, it is generally considered that the a. size of the population will decrease. b. size of the population will increase. c. population will go extinct. d. size of the population will stay the same.

ANSWER: a 29. Why does reduction of a population lead to decreased geographic range? a. Fewer individuals need fewer resources. b. Populations will clump tightly when populations reduce. c. Smaller populations use fewer resources per capita. d. Marginal habitats will receive fewer dispersing individuals.

ANSWER: d 30. What is the relationship between population density and adult body size? a. Population density is positively correlated to adult body size. b. Population density is negatively correlated to adult body size. c. Populations with high density generally have large-bodied species. d. Populations with low density generally have small-bodied species.

ANSWER: b 31. Ants should live in _____ populations, and rhinoceroses should live in _____ populations. a. high-density; high-density b. low-density; low-density c. high-density; low-density d. low-density; high-density ANSWER: c 32. What factors drive the relationship between population density and adult body size? a. resources and predation b. space and predation c. availability of mates and predation d. space and resources ANSWER: d 33. Dispersal limitation occurs when a. there has not been sufficient time for a species to disperse into suitable habitat. b. there is a barrier to dispersal into suitable habitat. c. the new habitat is unsuitable for the species. d. the new habitat is already occupied by a competing species.

ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 10 34. Which of the following is an example of dispersal limitation? a. A species of bird is not aware of the habitat. b. The preferred prey of a species of lizard is absent. c. All mice that try to cross the highway to reach the new habitat are killed. d. The soil moisture in the habitat is too low for a species of tree.

ANSWER: c 35. Although there is suitable habitat for sugar maple (Acer saccharum) in Europe and Asia, it is limited to North America because of lack of a. habitat corridors to Europe and Asia. b. dispersal mechanisms. c. pollinators in Europe and Asia. d. sufficient soil nutrients in Europe and Asia.

ANSWER: b 36. In some parts of the United States, pathways for wildlife are built over or under highways to allow animals to cross safely. This is an example of a(n) a. dispersal limitation. b. habitat corridor. c. ecological envelope. d. ecological passage.

ANSWER: b 37. When individuals have perfect knowledge of habitat variation and distribute themselves in a way that allows all of them to have the same per capita benefit, they display a(n) _____ free distribution. a. optimum b. ideal c. perfect d. best ANSWER: b 38. Per capita benefit is the amount of resources a. per individual. b. for the total population. c. per group of individuals. d. per species.

ANSWER: a 39. Which of the following does NOT explain why an ideal free distribution might not be achieved in nature? a. Individuals may not be aware that other habitats exist. b. An individual’s fitness is not solely determined by maximizing its resources.

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Chapter 10 c. Presence of predators or territoriality may preclude free movement between habitats. d. Individuals may not be able to differentiate between high- and low-quality habitat.

ANSWER: d 40. According to an ideal free distribution, individual organisms would be expected to move into low-quality habitat when a. the quality of the low-quality habitat increases to equal the high-quality habitat. b. the per capita benefit of the low-quality habitat equals the per capita benefit of the high-quality habitat. c. habitat corridors open up between the two habitats. d. the per capita benefit of the high-quality habitat is greater than the per capita benefit of the lowquality habitat.

ANSWER: b 41. In the experiment in which stickleback fish (Gasterosteus aculeatus) were presented with high- and lowquality habitats, why would fish disperse from the high-food side of the aquarium to the low-food side? a. The low-food side increased in quality. b. The high-food side decreased in quality. c. The low-food side per capita benefit equaled that of the high-food side. d. The low-food side per capita benefit was less than the high-food side.

ANSWER: c 42. In the example of the Ozark Mountain collard lizard, what would the glades be considered? a. high-quality patches b. low-quality patches c. high-quality intervening habitat d. low-quality intervening habitat ANSWER: a 43. What is not true about a species’ geographic range? a. The geographic area is always contiguous. b. The geographic range may span more than a single biome. c. Individuals may be absent from some regions of a species’ geographic range. d. The geographic range may have variable vegetation types, soil types, and topography within its border.

ANSWER: a 44. Individuals of a species will disperse themselves among different quality habitats such that they all have the same per capita benefit. What is that model called? a. geographic range model b. ideal free distribution model c. realized niche model Copyright Macmillan Learning. Powered by Cognero.

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Chapter 10 d. source-sink metapopulation model ANSWER: b 45. What is true about habitat corridors? a. They always connect two low-quality habitat patches. b. They always connect two high-quality habitat patches. c. They are a natural feature of the landscape. d. They are the same habitat type as the patches connected.

ANSWER: d 46. Plants that grow by vegetative reproduction likely will have what type of dispersion pattern? a. random b. clustered c. evenly spaced d. ideal free ANSWER: b 47. Which of the following is NOT a reason we might see differences in density of a species within its geographic range? a. seasonal migration patterns b. habitat quality differences c. Patches and intervening habitats are of the same type and quality. d. Populations are larger in the center versus the edge of the geographic range.

ANSWER: c 48. If one were looking at the characteristic related to how an individual in a population interacts others of its species in a given area, one would likely be looking at what? a. abundance b. density c. geographic range d. dispersion ANSWER: d Essay 49. Sugar maple (Acer saccharum) is a tree species that is found throughout the northeastern United States in higher-elevation sites without sandy soils. What can you conclude about the distribution of sugar maples in terms of their geographic range and realized niche?

ANSWER: The northeastern United States is their geographic range. Within this range they are restricted to narrower habitats defined by the abiotic conditions under which they can persist (high elevation, non-sandy soils).

50. Researchers examined data collected between 1985 and 2006 on diversity of fish in the North Sea, average Copyright Macmillan Learning. Powered by Cognero.

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Chapter 10 bottom temperatures, and how species diversity was affected by temperature. According to the figure, what did they find? What did they conclude about the cause of the change in fish diversity?

ANSWER: Over this period of increasing bottom-water temperatures, the diversity of fish increased. This is likely because species from more southern waters moved into the North Sea, where they could survive newly warmed bottom-water temperatures.

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Chapter 10 51. Why are endemic species more at risk for becoming rare or endangered than cosmopolitan species?

ANSWER: Endemic species live in a single, often isolated location. If habitat is lost through natural or anthropogenic disturbance, there may be no other habitat available to these species. Cosmopolitan species have very large geographic ranges that can span several continents, so they can tolerate a much greater habitat loss or other disturbance.

52. Compare and contrast the terms dispersion and dispersal.

ANSWER: Both terms are related to spatial patterns of organisms. Dispersion refers to the spatial patterning of individuals of a particular species, and it can be described as clustered, evenly spaced, or random.

Dispersal refers to movements of individuals within a population. The dispersal of individuals can affect their dispersion. For example, if individuals remain close to the place where they were born, a clumped dispersion may result. More active dispersal away from the natal site may result in evenly spaced or random dispersion patterns.

53. You conduct a mark-recapture survey of eastern fence lizards (Sceloporus undulatus) in a 2-hectare plot in eastern Arizona. You mark 250 lizards and are able to recapture 75, of which 24 are marked. What is the estimated size of the population of fence lizards in this plot? Calculate the estimated population size for the plot and the estimated lizard density per hectare and per square meter. Use the following formula: where M is the number of initially marked individuals, N is the population size, R is the number of recaptured marked individuals, and C is the total number of individuals recaptured.

ANSWER:

54. Imagine that you are conducting a mark-recapture survey of common pill bugs (Armadillidium vulgare), a terrestrial isopod, in a field. Unbeknownst to you, the majority of the pill bugs molt between marking and recapturing. How does this affect your estimate of the population size? How could you have foreseen this? How could you prevent this in the future?

ANSWER: Based on the equation for estimating population size using mark-recapture surveys, if the number of recaptured and marked (R) individuals was very small compared to the original number, the population estimate would be much higher than the actual population size. To avoid this problem, you could do a side experiment in which pill bugs captured at the same time as the original capture were placed in a contained terrarium to see what happened to marked pill bugs over the course of the study. You could also research the interval between molting and try to time the survey between molts.

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Chapter 10 55. Based on the relationship between geographic range and population, what would you expect to happen if a large portion of a species’ habitat is converted to agriculture?

ANSWER: Habitat converted to agriculture would probably not be suitable for the species, and total geographic range for this species would decline. The decline in geographic range would most likely cause the population of the species to decline.

56. The relationship between population density and adult body size is demonstrated in many organisms. Would you expect this relationship to hold true for body size averaged across all developmental stages (juveniles to adults)? Why or why not?

ANSWER: For some species, such as mice, the difference between sizes of adults and juveniles is not great, and the relationship would hold true. In other organisms the size difference can be immense. For example, adult giant sequoia trees are much larger than seedlings. Many seedlings of giant sequoia may die over time, until a small number reach adulthood. In the case of giant sequoias, the relationship would not hold true.

57. Researchers used an experimental design in which they cleared large patches of pine forest in five areas.

The central cleared area served as the source of dispersers. The four remaining cleared patches were (1) a rectangular unconnected patch, (2) a rectangular patch connected to the central patch by a cleared path that served as a corridor, and (3) two rectangular patches with wings (patches with corridors that did not connect to other patches). The researchers were interested in the importance of habitat corridors to the movement of seeds, pollen, and butterflies between central and peripheral habitat patches. What was the purpose of the unconnected winged patches?

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Chapter 10

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Chapter 10 58. Researchers used an experimental design in which they cleared large patches of pine forest from five areas.

The central cleared area served as the source of dispersers. The four remaining cleared patches were (1) a rectangular unconnected patch, (2) a rectangular patch connected to the central patch with a cleared path that served as a corridor, and (3) two rectangular patches with wings (patches with corridors that did not connect to other patches). The researchers were interested in the importance of habitat corridors to the movement of seeds, pollen, and butterflies between central and peripheral habitat patches. What was the purpose of planting male winterberry plants in central patches and female winterberry plants in peripheral patches? Based on the results, what would you conclude about the importance of habitat corridors?

ANSWER: The purpose of planting male winterberry plants in central patches and female winterberry plants in peripheral patches was to track the movement of plant pollen by seeing if the female winterberry became fertilized. Based on the results of this experiment, the presence of connected habitat corridors increased the movement of butterflies, seeds, and pollen between patches.

59. The emerald ash borer (Agrilus planipennis) is an insect from eastern Asia that has invaded North America.

The larvae of the emerald ash borer consume the cambium and phloem under the bark of American ash trees and eventually kill the trees. How can biologists predict the spread of this invasive pest? What might explain why the emerald ash borer is more of a problem in North America than in its native range?

ANSWER: Biologists could use ecological niche modeling to predict the spread of the emerald ash borer. By mapping known locations of the emerald ash borer and the habitat conditions, scientists can predict the ecological envelope of this species. The Red Queen hypothesis likely explains why the emerald ash borer is more of a pest in North America than in Asia. Unlike Asian ash trees, American ash trees have not evolved with the emerald ash borer and therefore have not evolved effective defenses against the pest.

60. As part of a scientific study, you are quantifying the reproductive success of individuals in a wildflower population in an isolated area. The total geographical range of this wildflower is only a few square kilometers, and you know from a previous ecological modeling study that this population occupies its entire ecological envelope. On average, an individual member of this species disperses its seeds an intermediate distance (about 100 meters) in a random direction via wind. You quantify reproductive success as the proportion of seeds released by a parent plant that successfully germinate. Considering only the abiotic environment, in which parts of the wildflower’s geographic range would you predict average individual reproductive success to be the highest and the lowest? Explain why.

ANSWER: Average reproductive success should be highest for individuals living in the center of the population’s geographic range because no matter which direction the seed travels, it is likely to land within the ecological envelope of the population, meaning that the abiotic environment should be amenable to germination of the seeds. In contrast, average reproductive success should be lowest at the fringes (edges) of a population’s geographic range because the abiotic environment will not be conducive for seed germination if the seed is randomly dispersed away from the edge of the geographic range.

61. Explain how the quality of the habitat between suitable habitat patches can limit the ability of a species to exhibit an ideal free distribution among suitable habitat patches.

ANSWER: Factors that limit the ability of a species to disperse to and from suitable habitat patches could prevent the species from exhibiting an ideal free distribution. Even if a suitable patch is high in quality, we may observe fewer individuals there than we would expect based on an ideal free distribution because the habitat surrounding the highly suitable habitat could be poor. Similarly, the Copyright Macmillan Learning. Powered by Cognero.

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Chapter 10 habitat around a suitable habitat of poor quality may be highly conducive to dispersal, which would cause an unexpectedly high number of individuals to move there.

62. Explain the difference between a species’ fundamental and realized niche. What might cause a species to have a smaller (in terms of area) realized niche?

ANSWER: The fundamental niche of a species is the range of abiotic conditions under which the species can exist. The realized niche of a species is the range of abiotic and biotic conditions under which a species does exist. A species may have a smaller realized niche compared to its fundamental niche because of competitors, predators, and/or pathogens that may preclude a species from regions of its fundamental niche.

63. Explain how a conservation biologist/ecologist might employ ecological niche modeling when considering the probability of an invasive species spreading into a new habitat in the future.

ANSWER: Ecological niche modeling allows the ecologist to look at the characteristics of various non-invaded habitats as well as the habitat requirements of the particular species (in this case an invasive species) and then model how successful the invasive species would be in the new, non-invaded habitat based in large part on the documented history of previous invasions into other habitat types.

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Chapter 11 Multiple Choice 1. In what way is the geometric growth model different from the exponential growth model? a. The geometric growth model uses continuous time. b. The geometric growth model uses regular time intervals. c. The geometric growth model includes carrying capacity (K). d. The exponential growth model includes carrying capacity (K).

ANSWER: b

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Chapter 11

2.

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Chapter 11

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Chapter 11 4. Which is likely to follow an exponential increase in population size?

I. a population of mice that has consumed most of the food in its habitat II. a small population of rats recently introduced to an island with many resources III. bacteria recently placed on a new petri dish with suitable growth medium a. I only b. II only c. III only d. I and II only e. II and III only ANSWER: e 5. In a population growing according to the exponential growth model, population size is a. limited by density-dependent factors. b. limited by density-independent factors. c. limited by both density-dependent and density-independent factors. d. not limited.

ANSWER: d 6. In the exponential growth model, which term indicates the intrinsic rate of increase? a. N0 b. e c. r d. t ANSWER: c 7. Consider a biologist studying a population of deer. At the beginning of the year, there are 100 adult deer in the population. Over the course of the year, 15 adult deer die, and an additional 25 deer are born. What can we conclude about  for this year? a.  < 0 b. = 0 c.  > 0 d.  = 1 e.  > 1 ANSWER: e 8. The intrinsic growth rate, r, is the a. number of new individuals produced minus the number that die. b. highest possible per capita increase in population size under ideal conditions. c. time it takes for a population to double in size. d. maximum population size that can be supported by the environment.

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Chapter 11 ANSWER: b 9. According to the exponential growth model, which would reduce a population's doubling time? a. an increase in the initial population size b. a decrease in the initial population size c. an increase in the intrinsic growth rate d. a decrease in the intrinsic growth rate ANSWER: c 10. According to an exponential growth population model, when the number of births is less than the number of deaths, a. r < 0. b. r = 0. c. 0 r 1. d. r > 1.

ANSWER: a 11. Negative density dependence occurs when the a. per capita population growth rate increases as population becomes larger. b. per capita population growth rate remains constant as population becomes larger. c. per capita population growth rate decreases as population becomes larger. d. population increases without limit. e. population decreases until it becomes extinct.

ANSWER: c 12. Under positive density dependence, population growth rate a. increases as populations become larger. b. remains the same as populations become larger. c. decreases as populations become larger. d. is highest at intermediate population size and lowest when population is large or small.

ANSWER: a 13. Which reflects density-independent population regulation?

I. a winter storm that kills birds with equal probability regardless of bird abundance II. a drought that kills a higher proportion of plants when there are many plants and a smaller proportion when there are fewer plants III. a lethal disease that is more easily transmitted when animals are found in high abundance than in low abundance a. I only b. II only c. III only Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 d. I and III e. II and III ANSWER: a 14. Which reflects positive density-dependent population regulation?

I. Small populations of flowers produce fewer seeds per individual than large populations of flowers.

II. Large groups of birds are better able to detect and avoid predators than small groups of birds.

III. The probability that a forest predator will kill a squirrel does not depend on the size of the squirrel population. a. I only b. II only c. III only d. I and II e. I and III ANSWER: d 15. Which reflects negative density dependence?

I. A fungus infects and kills plants at a higher rate when they are abundant than when they are rare.

II. A group of birds has a higher per capita survival rate when it is large than when it is small.

III. A large population of deer exhausts local food supplies and has a high risk of death; a small population has plentiful food and low risk of death. a. I only b. II only c. III only d. I and II e. I and III ANSWER: d 16. A species of louse (an external parasite) infests salmon. Researchers have found that the lice have difficulty finding a mate when there are only a few lice on an individual fish. The lice find mates more easily and produce more offspring when there are many lice on an individual fish. This is an example of a. the geometric growth model. b. positive density-dependent population regulation. c. negative density-dependent population regulation. d. density-independent population regulation.

ANSWER: b 17. The Allee effect describes a. density-independent population regulation. b. negative density-dependent population regulation. c. positive density-dependent population regulation.

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Chapter 11 d. logistic population growth.

ANSWER: c 18. Which illustrates a negative relationship between population density and the average size of individuals over time? a. an exponential growth curve b. a J-shaped curve c. a survivorship curve d. a self-thinning curve ANSWER: d 19. The larvae of a carnivorous species of salamander inhabit ponds. When the pond contains few larvae, they mostly eat small invertebrates and have a high survival rate. When there are many salamander larvae in a pond, the larvae will also cannibalize each other and have a low survival rate. This is an example of a. geometric growth. b. positive density-dependent population regulation. c. negative density-dependent population regulation. d. density-independent population regulation.

ANSWER: c 20. Alpine ibex are a type of wild goat that lives high in the mountains. During winters with heavy snow, Alpine ibex have high mortality rates regardless of the population size. This is an example of a. geometric growth. b. positive density-dependent population regulation. c. negative density-dependent population regulation. d. density-independent population regulation.

ANSWER: d 21. The logistic growth model describes a maximum population size that is a. limited by density-dependent factors. b. limited by density-independent factors. c. limited by both density-dependent and density-independent factors. d. not limited by any factors.

ANSWER: a 22. A biologist grew 10 groups of flowers in 1-square-meter plots of soil. In five plots, the biologist planted 20 flowers, and in the other five plots, the biologist planted 100 flowers. At the end of the summer, the biologist counted the seeds that each flower produced and found 100 seeds per plant in the plot with 20 plants and 500 seeds per plant in the plot with 100 plants. This is an example of a. density-independent population regulation. b. positive density-dependent population regulation.

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Chapter 11 c. negative density-dependent population regulation. d. a self-thinning curve.

ANSWER: b 23. Which describes the figure of logistic population growth shown in the graph?

a. r > 0; K > 300 b. r < 0; K > 300 c. r > 0; K < 300 d. r < 0; K < 300 ANSWER: c 24. In the logistic growth model, under which condition is the per capita rate of increase the highest? a. N = K b. N = c. N = Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 d. N = K + r ANSWER: c 25. Which is the most accurate statement about the conservation biology of species with positive densitydependent population regulation? a. If the population is small, it may not be able to increase. b. The population will quickly exhaust all resources. c. Species with positive density dependence are not at risk for extinction. d. Population growth rate is highest when N > K. ANSWER: a 26. Which accurately describes the inflection point in the logistic growth model?

I. Population growth slows after the inflection point.

II. The inflection point is equal to the carrying capacity.

III. The highest growth rate occurs at the inflection point. a. I only b. II only c. III only d. I and II e. I and III ANSWER: e 27. Which form of population growth results in an S-shaped curve? a. exponential growth b. geometric growth c. logistic growth d. density-independent growth ANSWER: c 28. Which factors could limit a species' carrying capacity?

I. the amount of food available II. the number of eggs a female can produce III. the number of nesting sites present a. I only b. II only c. III only d. I and II e. I and III ANSWER: e 29. In the logistic growth model, which term determines the maximum number of individuals a population can Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 sustain? a. r b. N c. K d. dN/dt ANSWER: c 30. In the logistic growth model, which term determines how quickly a population will initially grow from low density? a. r b. N c. K d. dN/dt ANSWER: a 31. Which of the following statements about the logistic growth model is accurate?

I. The per capita rate of population increase declines as population size increases.

II. The overall rate of population increase is highest at K/2.

III. The overall rate of population growth is negative when N is greater than K/2. a. I only b. II only c. III only d. I and II only e. I and III only ANSWER: d 32. The figure shows the change in population size of Paramecium from Gause's experiment, raised in either high-food or low-food conditions. Based on this figure, how was the logistic growth model for Paramecium changed by adding food?

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Chapter 11

a. High food increased r. b. High food decreased r. c. High food increased K. d. High food decreased K. ANSWER: c 33. The age structure of a population is often represented by a pyramid. What does an age structure pyramid with a broad base and a narrow top indicate about a population? a. The population is declining. b. The population is growing. c. The population is stable. d. The shape of the pyramid does not provide information on population growth.

ANSWER: b 34. If a population has relatively few individuals in the young classes but many in the medium-aged and old classes, what can we conclude about population growth? a. The population is declining. b. The population is growing.

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Chapter 11 c. The population is stable. d. The population is below carrying capacity.

ANSWER: a 35. What type of survivorship curve describes a species that has a high rate of juvenile mortality but low adult mortality? a. type I curve b. type II curve c. type III curve d. type I and type III curve ANSWER: c 36. The following table shows the survival and fecundity of a flowering plant.

Age in Survival Rate Survivorship Fecundity Years (x) (sx) (lx) (bx) 1 0.1 1.0000 2 0.8 0.1000 3 0.8 0.0800 4 0.8 0.0640 10 5 0.0512 20 What is the R0 for this species? a. 30 b. 24 c. 1.664 d. 0.1152 ANSWER: c 37. The following table shows the survival and fecundity of a flowering plant.

Age in Survival Rate Survivorship Fecundity (bx) Years (x) (sx) (lx) 1 0.1 1.0000 2 0.8 0.1000 3 0.8 0.0800 4 0.8 0.0640 10 5 0.0512 20 What is the generation time (T) of this species? a. 4 years b. 4.6 years c. 5 years d. 7.7 years ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 38. The following table shows the survival and fecundity of a flowering plant.

Age in Survival Rate Survivorship Fecundity (bx) Years (x) (sx) (lx) 1 0.1 1.0000 2 0.8 0.1000 3 0.8 0.0800 4 0.8 0.0640 10 5 0.0512 20 This plant species has a(n) a. type I survivorship curve b. type II survivorship curve c. type III survivorship curve d. S-shaped survivorship curve ANSWER: c 39. A biologist is studying a population of raccoons that live in a park. The population contains 50 males and 50 females. The biologist determines that R0 = 2. How many female raccoons are expected to be in the park next year? a. 25 b. 48 c. 50 d. 52 e. 100 ANSWER: e 40. For 5 years, a biologist studied a population of mice living in a field. The mice have three age classes: 1 year old, 2 years old, and 3 years old. The number of individuals in each age class over the course of the study is shown in the table.

Age Class 1 year old 2 year old 3 year old

Year 1 12 8 4

Year 2 36 24 12

Year 3 108 72 36

Year 4 324 216 108

Year 5 972 648 324

The geometric mean growth rate (λ) from year 1 to year 2 is a. 0.33. b. 3. c. 24. d. 81.

ANSWER: b 41. For 5 years, a biologist studied a population of mice living in a field. The mice have three age classes: 1 year old, 2 years old, and 3 years old. The number of individuals in each age class over the course of the study Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 is shown in the table.

Age Class Year 1 Year 2 Year 3 Year 4 Year 5 1 year old 12 36 108 324 972 2 year old 8 24 72 216 648 3 year old 4 12 36 108 324 Which describes this population?

I. The population has a stable age distribution.

II. The population's growth is consistent with a geometric model.

III. The population's growth is consistent with a logistic model in which K = 1,900. a. I only b. II only c. III only d. I and II only e. I and III only ANSWER: d 42. When a population has a stable age distribution, a. the total number of individuals stays constant over time. b. the proportion of individuals in each age class remains constant. c. the net reproductive rate is less than one. d. it is at its carrying capacity.

ANSWER: b 43. All cohort life tables a. follow individuals born at the same time from birth to death. b. quantify the survival and fecundity of all individuals at a single time interval. c. have a stable age distribution. d. describe a population at its carrying capacity.

ANSWER: a 44. A disadvantage of static life tables is that a. they require following individuals for their entire life span. b. environmental conditions in any given year may confound survival data for a specific age group. c. environmental conditions at the time of data collection may confound survival data across all age classes. d. they cannot be used for long-lived organisms.

ANSWER: c 45. Applying life tables to sea turtle conservation demonstrated that the most effective way to increase sea turtle populations is to a. raise large numbers of hatchlings and release them into the ocean.

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Chapter 11 b. protect nests from human poaching and other predators. c. protect adults from being captured in fishing nets. d. harvest small numbers of adults for human consumption each year.

ANSWER: c 46. Plants are more likely to show which type of survivorship curve? a. type I b. type II c. type III d. All three survivorship curves are found equally among plant species.

ANSWER: c 47. An age structure graph that appears rectangular in overall shape would likely see what in the future? a. an increase in population size b. a decrease in population size c. an increase, followed by a decrease in population size d. no change in population size ANSWER: d 48. The net reproductive rate refers to a. the total number of offspring that a population produces per year (or breeding cycle). b. the total number of female offspring a population produces per year (or breeding cycle). c. the largest number of offspring a female can produce under ideal conditions. d. the total number of female offspring an average female can produce over its lifetime.

ANSWER: d 49. When looking at plants, what would be considered a plant's generation time? a. Plants do not have generation times; only animals have generation times. b. the time it takes for a seed to grow into a mature plant and produce seeds of its own c. the time it takes for a seed to germinate d. the time it takes for a seed to flower ANSWER: b 50. What is true about the life table data and resulting survivorship curve for Dall sheep as published by O. Murie in 1944? a. The survivorship curve showed a definitive type II curve. b. Age class 0–1 had higher survivorship then any of the next three ages classes. c. When the population size for a particular age class was small, survivorship rates were unreliable. d. The real-world survivorship curve based on the collection of 608 Dall sheep skeletons did not differ from the expected, generalized curve for similar species.

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Chapter 11 51. When working with life tables, we work with many variables and make many calculations. One such variable of importance is bx or fecundity. An important calculation we make as we determine the net reproductive rate is lxbx. This calculation is often referred to as “realized fecundity.” Why might that be the case? a. because we are looking at fecundity rate for females as well as considering how many females survive (survivorship rate) to each reproductive age class b. because we are looking at both male and female survivorship at each age class c. because we are looking at survivorship only at prereproductive age classes d. because we are looking at survivorship only at postreproductive age classes ANSWER: a 52. That individuals are more likely to find mates and reproduce when populations are larger as compared to when populations are smaller might be termed a. the Allee effect. b. negative density dependence. c. a density-independent variable. d. self-thinning ANSWER: a Essay 53. Describe how the geometric growth model is different from the exponential growth model.

For each growth model, give an example of an organism that fits the growth pattern it describes. Explain why the organism fits the model.

ANSWER: The exponential growth model is based on organisms that continuously reproduce, while the geometric growth model is based on organisms that reproduce at regular intervals. Bacteria fit the exponential growth model because they can continuously reproduce. Migratory birds fit the geometric growth model because they breed during a specific season each year and then wait until the next season to breed again.

54. Define population doubling time. Starting with the model for exponential population growth, explain how to derive the formula for population doubling time.

ANSWER: Population doubling time is the time required for the number of individuals in a population to double—for example, the amount of time it takes a population to go from 10 individuals to 20 individuals.

To derive the doubling time, start with the exponential growth model, then divide both sides by N0.

Then replace Nt/N0 with 2 to represent that the population has doubled between time t and time 0.

Next, take the natural log of both sides of the equation. At this point, you have rt = loge(2). Divide both sides by r, and you now have the equation for population doubling time, t = loge(2)/r.

55. Using the logistic growth model, draw a line that shows the relationship between per capita growth rate (y axis) and population size (x axis) for a hypothetical population with a carrying capacity of 500 individuals.

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Chapter 11 Explain how the slope relates to changes in population size over time and give an example of an environmental factor that could cause a population to follow a logistic model of population growth.

ANSWER: The students should plot a line with a negative slope that intersects the x axis at 500 individuals.

The negative slope indicates that as the population becomes larger, the population grows more slowly. However, since population growth is positive until there are 500 individuals in the population, the population continues to grow. Population growth becomes zero at 500 individuals.

The carrying capacity could be the number of nest sites available for breeding; once 500 individuals have nests, there are no additional nests for other individuals to use.

56. A park biologist is planting saplings (young trees) in an old field that has recently been turned into a park.

Draw a hypothetical self-thinning curve for these trees over 5 years. Be sure to label the axes. Describe a practical use of this curve.

ANSWER: Plant biologists may use self-thinning curves to determine how many seeds should be planted in an area to obtain the optimal yield for a crop.

The graph shows one possible answer. The figure should show log-transformed mass on the y axis and log-transformed survival on the x axis. The points they plot should form a negative slope.

57. A biologist studies a population of birds for 25 years. Each year the biologist records the amount of rainfall and the density of birds (number of birds per 100 square meters). In addition, the biologist determines the survival rate for eggs laid that year. The biologist then plots egg survival rate against both rainfall (graph a) and density (graph b). In each plot the individual points represent the data for one year of the study. Based on these data, does this population of birds appear to be subject to positive density-dependent population regulation, negative density-dependent population regulation, or density-independent population regulation? As part of Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 your answer, list the prediction for each type of population regulation and explain whether the data meet that prediction.

(a)

(b)

ANSWER: These data indicate that the birds are regulated by negative density dependence but not positive density-dependent or density-independent factors. Under negative density dependence, we would expect to see egg survival decline as the number of birds per 100 square meters increases, as illustrated in figure b. Under density-independent population regulation, we predict that changes in population growth rate will be due to some environmental factor not related to density. Here, we see that egg survival, a component of population growth rate, is not related to variation in rainfall.

Under positive density dependence, we would expect egg survival to increase as the number of birds per 100 square meters increases; the data do not meet that prediction.

58. Consider a biologist who is studying a fish populations. The biologist conducts an experiment with four treatments in artificial ponds of the same size. In the first treatment he adds 10 fish to each pond. In the second treatment he adds 100 fish to each pond. In the third treatment he adds 10 fish and additional food. In the fourth treatment he adds 100 fish and additional food. At the end of the experiment he finds that female fish in ponds with only 10 fish produce many more eggs than female fish in ponds with 100 fish. However, adding food did not alter the number of eggs each female fish produced. Explain what this experiment tells us about how these fish are affected by density-independent, positive density-dependent, or negative density-dependent factors.

ANSWER: This experiment indicates that these fish are affected by negative density-dependent factors because female fecundity declined as the number of individuals in the population increased. Female fecundity directly contributes to population growth by adding more individuals to the next generation, and so populations with higher fecundity will have a higher population growth rate. So Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 when the initial number of individuals increased, the per capita population growth rate declined through a reduction in female fecundity. However, the number of fish in the population do not appear to be limited by the amount of available food because adding food did not improve population growth.

Positive density-dependent factors did not affect these fish because there was no increase in growth rate as more fish were added to the pond.

No information was provided on whether other environmental conditions affected fish in a densityindependent manner, so we have no evidence for density-independent factors controlling fish population size.

59. Describe the similarities and differences between a cohort life table and a static life table. Give an actual example of each.

ANSWER: Both types of life table describe age-specific survival and fecundity and can be used to estimate the direction and magnitude of changes in population size. Cohort life tables are determined by following individuals from birth to death and estimating the survival and fecundity at each life stage.

An example of cohort life tables comes from Grant and Grant's work marking and following finches in the Galápagos Islands to determine survival and fecundity. Static life tables are estimated by gathering data on age-specific survival and fecundity at a single point in time. An example is Murie's work on sheep, in which sheep skulls were aged according to horn characteristics, allowing Murie to evaluate survival at multiple age classes.

60. You are a biologist studying deer populations in four parks: Chagrin, Bedford, Bradley, and Brookside.

These four parks are all the same size, and they have similar weather. You estimate deer population size in October 2011, before winter comes. Then you estimate the size of the herd the next year, in October 2012. The data are listed in the table: Park October 2011 Population October 2012 Population Chagrin 125 90 Bedford 50 77 Bradley 150 68 Brookside 75 96 Explain whether each of the following statements is supported by the data and why or why not.

I. These populations have exponential growth.

II. The changes in population size are density dependent.

III. All of these populations are below their carrying capacity.

ANSWER: I is not supported by the data because some populations are declining.

II is supported by the data. The two herds with the largest populations in October have smaller populations in May, while the two herds with the smallest populations in October have larger populations in May. III is not supported by the data. Two populations increase, which is consistent with their being below their carrying capacity. But two populations decrease, which is consistent with their being above their carrying capacity.

61. Consider a perennial plant with four life stages: seed, seedling, small adult, and large adult. Seeds survive to seedlings with a probability of 50 percent; seedlings survive to be small adults with a probability of 20 percent; small adults survive to be large adults with a probability of 20 percent. Both small adults and large adults Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 produce an average of 10 seeds. Use this information to fill in the life table that follows; then calculate the R0 and explain whether the population is increasing, stable, or decreasing.

Age Class (x) Seed Seedling Small adult Large adult

Survival Rate (sx) Survivorship (lx)

Fecundity (bx)

R0: _____________________ ANSWER: Age Class (x) Survival Rate (sx) Survivorship (lx) Fecundity (bx) Seed 0.50 1.00 0 Seedling 0.20 0.50 0 Small adult 0.20 0.10 10 Large adult 0.00 0.02 10 R0: 1.2 Because R0 is greater than 1, we can conclude the population is increasing.

62. The following table for a species of plant that has four life stages was constructed from research done in the 1960s.

Age Class (x) Survival Rate (sx) Survivorship (lx) Fecundity (bx) Seed 0.3 1.000 Seedling 0.2 0.300 Small adult 0.1 0.060 20 Large adult 0.006 50 Forty years later, biologists went back to the same site and determined the life table for the population, shown in the following table. On account of changing climatic conditions, seed survival decreased from 30 percent to 10 percent. However, these changing climactic conditions also cause large adults to produce four times as many seeds, so that they now produce 200 seeds. All other variables stay the same.

Age Class (x) Seed Seedling Small adult Large adult

Survival Rate (sx) 0.1 0.2 0.1

Survivorship (lx) 1.000 0.100 0.020 0.002

Fecundity (bx)

20 200

Explain whether the change in climate is beneficial or harmful to this plant population based on these tables. Be sure to reference any relevant calculations you should make and explain the relative importance of the decreased seed survival and increased seed production.

ANSWER: This change in climate is harmful to the population. Prior to the change in climate, the population had an R0 of 1.5, indicating that these plants were increasing in abundance. After the change in climate, the population had an R0 of 0.8, indicating that these plants were decreasing in abundance.

A population with an R0 of 0.8 every generation will eventually go extinct. Although the change in climate did increase the number of seeds, the reduction in seed survival reduced the total number of Copyright Macmillan Learning. Powered by Cognero.

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Chapter 11 seeds surviving to each of the subsequent age classes.

63. Explain the difference between positive density dependence and negative density dependence.

ANSWER: Positive density dependence describes a population that sees its rate of growth increase as the population density increases. Negative density dependence describes a population that sees its rate of growth decrease as the population density increases.

64. The exponential growth model and the logistic growth model both initially look the same. Explain the difference between the two models. What causes the logistic model to change trajectory?

ANSWER: Both models grow rapidly when population numbers are low. Once the logistic model reaches the inflection point, the logistic model sees slowing population growth rates eventually reaching a population size that shows no growth, known as the carrying capacity (the maximum population size that the environment can support). The population at carrying capacity grows no further due to limits of the environment: food, predation pressure, disease, and so forth. The exponential growth model is not constrained by the carrying capacity; rather, species growing exponentially have unlimited resources and thus population size continues to increase.

65. Describe the difference in appearance of the type I and type III survivorship curves. What do the shapes of the curves tell us about the species that have these curves? In addition, how do these curves instruct us as to the comparative reproductive strategies of type I versus type III species?

ANSWER: The type I survivorship curve starts out with high survivorship early on within the life span of the species in question. Type I species see dramatic increases in mortality (low survivorship) late in life.

The type III survivorship curve is the opposite of the type I curve. Type III species see high mortality (low survivorship) very early on within the life span of the species in question. Type III species then see higher survivorship until very late in the life span of the species. Regarding reproductive strategies: Type I species might be expected to produce fewer offspring and be able to provide greater levels of parental care for those fewer offspring (since survivorship is high at very young ages). Type III species might be expected to produce larger number of offspring with less parental care for those offspring (since survivorship is so low at very young ages).

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Chapter 12 Multiple Choice 1. Which trait(s) is/are likely to cause less-stable populations to fluctuate more dramatically over time?

I. short generation time II. small body size III. high sensitivity to environmental conditions a. I only b. II only c. III only d. I and II only e. I, II, and III ANSWER: e 2. Based on the figure, which year produced an unusually high number of offspring?

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Chapter 12

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Chapter 12 3. Which conclusion does the figure support?

a. Recruitment of all species has been constant. b. Oak may have had increased recruitment since 1650. c. White pine may have had decreased recruitment since the late 1700s. d. Eastern hemlock has had decreased recruitment since 1650.

ANSWER: c 4. In population dynamics following the logistic model, an overshoot occurs when a. N = . b. N = . c. N > K. d. N > r.

ANSWER: c 5. What eventually occurs when the number of individuals in a population exceeds the population's carrying capacity? a. The number of individuals continues to increase but at a faster rate. b. The number of individuals continues to increase but at a slower rate. c. The number of individuals reaches equilibrium and becomes constant. d. The number of individuals declines.

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Chapter 12 ANSWER: d

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Chapter 12

6.

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Chapter 12 A herd of 25 reindeer was introduced to St. Paul Island in 1911. The line shows the number of reindeer on the island. Which describe(s) the entire figure correctly?

I. The pattern fits the exponential model of population growth.

II. The population experienced an overshoot.

III. The population experienced a die-off. a. I only b. II only c. III only d. II and III only e. I, II, and III ANSWER: d 7. A population die-off occurs when I. a species' resources are depleted.

II. an overshoot occurs.

III. carrying capacity is exceeded. a. I only b. II only c. III only d. II and III only e. I, II, and III ANSWER: e 8. Population cycles I. are increases and decreases of population size occurring at regular time intervals.

II. can be caused by overshooting carrying capacity and subsequent die-offs.

III. indicate that a species is about to become extinct. a. I only b. II only c. III only d. I and II only e. II, and III only ANSWER: d 9. Consider moose that breed in the fall and give birth in the spring. During breeding, the moose population is below carrying capacity, but once the young moose are born, the moose population far exceeds carrying capacity. This is an example of a. delayed density dependence. b. demographic stochasticity. c. dampened oscillations. d. rescue effect.

ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 10. Delayed density dependence a. occurs when a population is larger than the carrying capacity. b. occurs when density dependence is based on population density in the past. c. is the observation that populations increase and decrease over time. d. is a form of environmental stochasticity.

ANSWER: b 11. Which of the following is an example of delayed density dependence?

I. The per capita growth rate of a coyote population decreases as the number of coyotes increases.

II. The fecundity of two-year-old frogs is based on their density as tadpoles.

III. The number of seeds produced by flowers in the fall depends on the amount of rainfall the previous spring. a. I only b. II only c. III only d. I and II only e. II and III only ANSWER: b 12. In the logistic growth model that includes delayed density dependence, the term τ indicates the a. strength of density dependence. b. previous carrying capacity. c. length of the time delay. d. current population size.

ANSWER: c 13. In the logistic growth model with time delays, the product of rτ indicates the a. carrying capacity of a population. b. extent of oscillations in population size. c. amount of demographic stochasticity. d. amount of environmental stochasticity.

ANSWER: b 14. Which is TRUE about damped oscillations?

I. They are a pattern of population growth in which a population continues to exhibit large oscillations over time.

II. They are a form of demographic stochasticity.

III. They are expected to occur when rτ= 1. a. I only b. II only c. III only d. I and II only Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 e. II and III only ANSWER: c

15.

Which panel illustrates a stable limit cycle? a. a b. b c. c d. d ANSWER: c

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Chapter 12

16.

Which panel is most likely to indicate a population with a constant environment and no time delays in density dependence? a. a b. b c. c d. d ANSWER: a 17. In the logistic model with delayed density dependence, an increase in the length of the time delay will affect population dynamics by a. making it more likely that the population approaches K without oscillations. b. making it more likely that the population will oscillate. c. decreasing the mean population size. d. increasing the mean population size.

ANSWER: b 18. Consider a logistic model that includes a time delay in density dependence and exhibits damped oscillations.

If the intrinsic rate of increase is reduced but all other parameters remain the same, which of the following Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 outcomes is most likely? a. The overall population will decrease. b. The overall population will increase. c. The population will approach carrying capacity without any oscillations. d. The population will oscillate as a stable limit cycle.

ANSWER: c 19. Consider a logistic model that includes a time delay in density dependence and exhibits damped oscillations.

If the carrying capacity is increased but all other parameters remain the same, which of the following outcomes is most likely? a. The population will approach carrying capacity without any oscillations. b. The population will continue to exhibit damped oscillations. c. The population will oscillate as a stable limit cycle. d. The population will go extinct.

ANSWER: b 20. For populations growing under the logistic growth model with delayed density dependence, which of the following combinations of parameter values is most likely to lead to damped oscillations? a. r = 0.1; K = 200; = 2 b. r = 0.1; K = 20; = 2 c. r = 0.5; K = 200;  = 3 d. r = 1; K =20;  = 3 ANSWER: c 21. Consider a population with the following numbers of individuals over time. year 1: 100 year 2: 150 year 3: 200 year 4: 250 If the population size in year 5 is determined by a logistic model with delayed density dependence, r = 1.1, and K = 200 individuals, what value of  would cause the population to decrease from year 4 to year 5? a.  = 0 b. = 1 c.  = 2 d.  = 3 ANSWER: a 22. Consider a population with the following numbers of individuals over time. year 1: 10 year 2: 25 year 3: 30 If the population size in year 4 is determined by a logistic model with delayed density dependence from a 1-year Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 time lag (i.e., τ = 1) and K = 50 individuals, what value of r would lead the population size to exceed carrying capacity in year 4? a. r = 0.2 b. r = 0.5 c. r = 1.0 d. r = 2.0 ANSWER: d 23. Consider the time series of population sizes in years 1 and 2 for populations a, b, c, and d. If the population size in year 3 is determined by a logistic model with delayed density dependence from a 1-year time lag (i.e.,  = 1), r = 1, and K = 10 individuals, which of the following time series of population sizes would lead to an overshoot of the carrying capacity in year 3? a. year 1, 5 individuals; year 2, 10 individuals b. year 1, 10 individuals; year 2, 5 individuals c. year 1, 5 individuals; year 2, 5 individuals d. year 1, 10 individuals; year 2, 10 individuals ANSWER: a 24. Of the following species, which is most likely to exhibit a stable limit cycle or dampened oscillations? a. a species with limited energy reserves such that resource availability in previous years does not affect its current ability to survive or produce offspring b. a species whose fecundity in the present year is highly dependent on the amount of rainfall 2 years previous c. a species whose only food resources for juveniles are limited and juvenile food availability affects adult fecundity and survival d. a species whose population growth is following the exponential model ANSWER: c 25.

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Chapter 12

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Chapter 12 26. Which statement correctly identifies the relationship between population size and extinction risk? a. Small populations are most likely to go extinct. b. Intermediate-sized populations are most likely to go extinct. c. Large populations are most likely to go extinct. d. Population size does not correlate with extinction risk.

ANSWER: a 27. Which type of model always includes random variation? a. stochastic b. deterministic c. logistic d. exponential ANSWER: a 28. Which is an example of demographic stochasticity?

I. increased moose mortality when the population exceeds carrying capacity II. variation in death rate of mice due to chance differences between individuals III. increases and decreases in seed production due to changes in rainfall a. I only b. II only c. III only d. I and II only e. II and III only ANSWER: b 29. Which is an example of environmental stochasticity?

I. changes in the weather that increase or decrease survival by a small amount II. variation in individual health that affects likelihood of death III. forest fires that kill large numbers of individuals every 10 to 50 years a. I only b. II only c. III only d. I and III only e. I, II and III ANSWER: d 30. Consider four populations of island birds. Each island has a different carrying capacity, and the birds are subject to environmental and demographic stochasticity. Which population is LEAST likely to go extinct? a. island 1, K = 100 b. island 2, K = 300 c. island 3, K = 900 Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 d. island 4, K = 1,200 ANSWER: d 31. A biologist is developing models to describe the population dynamics of a species. Four models are listed.

Each model is based on the logistic model, with r equal to 1 and K equal to 100. The initial population size is given by N0. In which of the models of population growth would the population be most likely to go extinct? a. deterministic model, N0 = 5 b. stochastic model, N0 = 10 c. deterministic model, N0 = 100 d. stochastic model, N0 = 150 ANSWER: b 32. Which population model incorporates random variation in population growth? a. deterministic b. stochastic c. stable limit d. metapopulation ANSWER: b 33. Variation in birth and death rates due to random differences among individuals is a. overshooting the carrying capacity. b. demographic stochasticity. c. environmental stochasticity. d. habitat fragmentation.

ANSWER: b 34. Variations in birth and death rates due to random changes in environmental conditions are a. damped oscillations. b. delayed density dependence. c. environmental stochasticity. d. stable limit cycles.

ANSWER: c 35. The females of a certain species of fish produce on average 1,000 eggs each year. By chance some females produce a few more eggs than average, and others produce slightly fewer eggs than average. This is an example of a. demographic stochasticity. b. environmental stochasticity. c. damped oscillations. d. population cycles.

ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 36. A species of grass is affected by the amount of rainfall in the spring. In years of high rain, the grass survives better than in years of low rain. This is an example of a. demographic stochasticity. b. environmental stochasticity. c. damped oscillations. d. population cycles.

ANSWER: b 37. Grasslands used to be spread across large portions of North America. However, human land use has separated formerly large, continuous grassland into many smaller isolated patches. This is an example of a. habitat fragmentation. b. rescue effect. c. extinction. d. dampened oscillations.

ANSWER: a 38. Which correctly describes metapopulations?

I. They can arise from habitat fragmentation.

II. The frequency of occupied habitats is due to the balance of extinction and colonization.

III. The basic metapopulation model assumes that all patches are equal in quality. a. I only b. II only c. III only d. II and III only e. I, II, and III ANSWER: e 39. Metapopulations a. occur when suitable habitat for a species is separated by unsuitable habitat. b. are populations whose intrinsic rate of increase (r) is greater than 1. c. are composed of subpopulations that do not go extinct. d. are small populations likely to go extinct as a result of demographic stochasticity.

ANSWER: a 40. A group of subpopulations that has independent population dynamics over space is an example of a. habitat fragmentation. b. a metapopulation. c. the rescue effect. d. environmental stochasticity.

ANSWER: b 41. When immigrants supplement a declining subpopulation, they prevent the subpopulation from going extinct.

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Chapter 12 This phenomenon is known as a. a metapopulation. b. the rescue effect. c. demographic stochasticity. d. habitat fragmentation.

ANSWER: b 42. Under the basic model of metapopulation dynamics, when the extinction rate is equal to the colonization rate, we predict that the proportion of patches occupied will equal a. 0. b. 0.25. c. 0.50. d. 0.75. e. 1.

ANSWER: a 43. Under the basic model of metapopulation dynamics, which of the following conditions is necessary to prevent the species from going extinct? a. colonization rate greater than zero b. colonization rate equal to extinction rate c. colonization rate less than extinction rate d. colonization rate greater than extinction rate e. extinction rate less than 1 ANSWER: d 44. Which is an example of the rescue effect?

I. A small population of birds maintains a stable population size near carrying capacity.

II. A population of mice in a low-quality habitat persists because of immigration from high-quality habitats.

III. Habitat destruction reduces the quality of an environment and causes a population of lizards to decline every year until they go extinct. a. I only b. II only c. III only d. I and II e. II and III ANSWER: b 45. Which is an example of a metapopulation?

I. Insects live in isolated patches of forest surrounded by agriculture. Sometimes the population in a patch goes extinct, but eventually the insects recolonize that patch.

II. A species of bird is found in Canada during the summer. In the fall, the species migrates to the Caribbean and spends the winter there. In the spring it returns to Canada.

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Chapter 12 III. A species of fish lives in a fast-flowing cold river. A dam is constructed on the river, causing the fish to go extinct because of warmer water. a. I only b. II only c. III only d. I and II e. II and III ANSWER: a 46. Human activity can affect metapopulations. Under the basic model of metapopulation dynamics, when humans make it easier for individuals to travel between patches, the probability of _____ and the proportion of occupied patches _____. a. extinction increases; decreases b. extinction increases; increases c. colonization increases; increases d. colonization decreases; decreases ANSWER: c 47. Human activity can affect metapopulations. In the basic model of metapopulation dynamics, if humans improve habitat quality (and thus carrying capacity) of subpopulations, the probability of _____ and the proportion of occupied patches _____. a. extinction increases; decreases b. extinction decreases; increases c. colonization increases; increases d. colonization decreases; decreases ANSWER: b 48. Based on the predictions of metapopulation biology, which scenario can be expected to exhibit the largest fraction of occupied habitat patches? a. small patches isolated from one another b. large patches isolated from one another c. large patches close to one another d. small patches close to one another ANSWER: c 49. A species of frog is found separated into many subpopulations living in ponds that are surrounded by agricultural fields. Sometimes one frog subpopulation goes extinct because of disease or environmental stochasticity. Frogs from other subpopulations will occasionally move across fields to recolonize ponds where subpopulations have gone extinct. This is an example of a. a metapopulation. b. the rescue effect. c. a sink population.

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Chapter 12 d. damped oscillations.

ANSWER: a 50. Which of the following contributed to the success of conservation programs that reintroduced ferrets to the wild? a. Ferrets were introduced into multiple subpopulations. b. Diseases that kill ferrets were eliminated. c. Habitat destruction was prevented. d. Stochastic causes of extinction were removed.

ANSWER: a 51. Which contributed to the decline and extinction of black-footed ferrets?

I. Habitat destruction reduced carrying capacity of ferrets.

II. Lethal diseases like canine distemper killed many ferrets.

III. Poisoning of prairie dogs. a. I only b. II only c. III only d. I and II only e. I, II, and III ANSWER: e 52. When comparing larger animals to smaller animals we tend to see more stable population sizes in larger animals. What might be a reason this is the case? a. Larger animals can better respond to (are less impacted by) environmental stochasticity. b. Smaller animals can better respond to (are less impacted by) environmental stochasticity. c. Larger animals reproduce more rapidly. d. Smaller animals reproduce more slowly.

ANSWER: a 53. A population that exceeds its carrying capacity will a. immediately die off, reducing its population. b. level off at its inflection point and then remain at that population level indefinitely. c. continue to grow until density-dependent diseases increase to such an extent that growth ceases. d. likely continue to increase for a time but then die back to below the carrying capacity.

ANSWER: d 54. Which of the following is NOT true about the 1911 St. Paul Island, Alaska, reindeer introduction? a. The reindeer numbers crashed because they relied on the same food item throughout the entire year. b. Natural predators did not play a role in controlling reindeer numbers. c. Habitat fragmentation was not an issue on the island in regard to reindeer numbers. d. Environmental stochasticity played a role in the decrease in reindeer numbers.

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Chapter 12 ANSWER: a 55. The observation that three species of grouse in Finland all experience natural population cycles every 6–7 years in synchrony is evidence that a. the species are more closely related than originally thought. b. the species arose from convergent evolution. c. the drivers of population cycles can happen over a large area. d. climate change impacts all species equally.

ANSWER: c 56. The observation that a predator in an environment with increased prey does not immediately convert the prey consumed in such a resource-rich environment into offspring is the foundation for the idea of a. overshoot and die-off. b. delayed density dependence. c. extinction modeling. d. metapopulation dynamics.

ANSWER: b 57. When a population is small there is an abundance of resources for all individuals, so the per capita resource availability is high, thus leading to more rapid growth rates (as compared to larger populations). Why then are small populations more likely to go extinct compared to large populations? a. Large populations are more impacted by stochastic events. b. Small populations are more impacted by stochastic events. c. Small populations are impacted by demographic stochasticity and not environmental stochasticity. d. Small populations are impacted by environmental stochasticity and not demographic stochasticity.

ANSWER: b 58. Which of the following is NOT a factor that determines whether a patch is likely to be occupied by a species? a. size of the patch b. proximity to other occupied patches c. resource availability in the patch d. history of extinction in the patch ANSWER: d 59. When a larger population is broken up into smaller groups that live in isolated patches, the smaller groups are called a. subpopulations. b. copopulations. c. side populations. d. sink populations.

ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 60. Which population model applies to the situation in which habitat patches of equal quality are embedded within a matrix of unsuitable habitat? a. the basic metapopulation model b. the basic subpopulation model c. the source-sink metapopulation model d. the landscape metapopulation model ANSWER: a 61. Which model specifically addresses the situation in which subpopulations in poor-quality habitats are maintained by immigration of individuals from other subpopulations that produce surplus individuals? a. the basic metapopulation model b. the source-sink metapopulation model c. the landscape metapopulation model d. the habitat metapopulation model ANSWER: b 62. Which population model specifically addresses the situation where the patches differ in quality and regions of the surrounding matrix also differ in quality (leading to differences in dispersal potential)? a. the landscape metapopulation model b. the basic subpopulation model c. the basic metapopulation model d. the source-sink metapopulation model ANSWER: a 63. Which of the following is NOT a characteristic of a source subpopulation? a. high-quality habitat b. high emigration rate c. high level of resources d. high immigration rate ANSWER: d 64. In populations that fit a source-sink metapopulation model, organisms in _____ subpopulations disperse into _____ subpopulations. a. higher-quality sink; lower-quality source b. lower-quality sink; higher-quality source subpopulations c. lower-quality source; higher-quality sink subpopulations d. higher-quality source; lower-quality sink subpopulations ANSWER: d Essay Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 65. Many species exhibit population cycles with peaks at regular intervals, such as peaks in population size that occur every 6 years. Explain why is it not likely that environmental variation is the underlying cause of these regular cycles. As part of your explanation, include a description of expected differences between changes in population size due to environmental variation and changes in population size due to density-dependent population regulation.

ANSWER: Most types of environmental variation that might cause population cycles do not happen at regular intervals. Environmental variation often is irregular; for example, an area might have 3 years of abundant rainfall, followed by a year of drought, followed by 5 years of abundant rainfall. Changes in population size due to environmental variation are likely to occur at irregular intervals, coinciding with the patterns of environmental variation. In contrast, population cycles caused by densitydependent population regulation often occur in regular intervals.

66.

Consider these two populations, which exhibit variation in population size over time. In which population is the fluctuation most likely due to environmental variation, and in which population is fluctuation most likely due to density dependence? Explain your answer.

ANSWER: The fluctuations in population 2 are most likely due to environmental variation, while the fluctuations in population 1 are most likely due to density dependence. Most environmental variation occurs irregularly over time, and thus if environmental variation is driving population dynamics, then population fluctuations are likely to be irregular, as displayed by population 2. In Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 contrast, delayed density dependence often leads to cyclic variation in population size due to overshoots of carrying capacity and recovery. Population 1 displays such a regular cyclic pattern.

67. Two species of mice are similar in many characteristics. However, species A has large fat reserves that increase survival over periods when environmental resources are depleted, while species B has no fat reserves.

Which species is more likely to exhibit oscillating population dynamics? Explain your answer.

ANSWER: Species A is more likely to exhibit oscillating population dynamics because the large fat reserves act to incorporate a time delay into density dependence. The time delay prevents the population from declining immediately when it exceeds the carrying capacity. After the increase over carrying capacity, there is a die-off until the population is below carrying capacity; this pattern repeats, leading to oscillations. In contrast, species B, without substantial fat reserves, will begin to decline with little or no time delay when the population size exceeds the carrying capacity.

68. Riverview has 200 individuals, Oak Park has 600 individuals, and Mountainside has 50 individuals. Rank the populations in order from the most likely to go extinct to the least likely. Explain your reasoning.

ANSWER: The population most likely to go extinct is Mountainside. The population with an intermediate probability of going extinct is Riverview. And the population least likely to go extinct is Oak Park.

This order is based on the observation that smaller populations are more likely to go extinct as a result of demographic and environmental stochasticity than larger populations.

69.

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Chapter 12

This figure shows a metapopulation for the California spotted owl. Describe two ways in which this real metapopulation differs from the assumptions of the basic model of metapopulation dynamics, = (1 – e/c).

ANSWER: The basic model of metapopulation dynamics assumes that all patches have equal probabilities of extinction and colonization. However, the California spotted owl metapopulation contains patches that vary in size and distance from one another. Smaller patches are more likely to go extinct, Copyright Macmillan Learning. Powered by Cognero.

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Chapter 12 violating the assumption of equal extinction probability. More-isolated patches are less likely to be colonized, violating the assumption of equal colonization probability.

70. Define the three components of the basic model of metapopulation dynamics, = (1 – e/c). Explain one way in which conservation biologists can affect each of the variables e and c to protect a species.

ANSWER: In this model, is the equilibrium fraction of patches occupied by a species, e is the extinction probability, and c is the colonization probability. Conservation biologists could improve habitat quality to reduce extinction probability of each patch (e) and thus increase the fraction of occupied patches. They could also make habitat corridors between patches to allow species to move between patches, increasing the colonization probability (c) and increasing the fraction of occupied patches.

71.

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Chapter 12

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Chapter 12 72. Describe how the moose population has been "controlled" on Isle Royale since the early 1900s.

ANSWER: Initially when the moose reached the island, the moose found an environment free of predators with abundant resources (given the size of the initial moose population). At this time the moose numbers grew and were limited only by the island's carrying capacity for moose. The moose population repeatedly grew, overshot the carrying capacity, and experienced a subsequent die-off. This pattern continued until the late 1940s when wolves (predators) reached the island. Now the moose population was controlled by not only available resources but also predator numbers. As the data shows, when wolf numbers were higher, moose numbers dropped and when wolf numbers were lower, moose numbers increased—in somewhat of an oscillating fashion. In the early 1980s a new variable was introduced when the lethal canine parvovirus reached the island. This virus has had a devastating impact on wolf numbers and may lead to the extinction of wolves on the island and a return to moose being controlled by vegetation as opposed to predation.

73. Describe what is meant by delayed density dependence.

ANSWER: Density dependence refers to the concept of a population's growth rate either increasing as population density increases (positive density dependence) or decreasing as population density increases (negative density dependence). When density dependence occurs based on a past population density (not the current density), we refer to this as delayed density dependence.

74. Vernal pools are ephemeral bodies of water that form in small depressions within the forested landscape during early spring in the northeastern United States (as well as elsewhere). The water in the vernal pools has its origin with winter snowmelt and spring rains. These vernal pools are important breeding grounds for some amphibian species. Describe how environmental stochasticity might influence amphibian populations at vernal pools.

ANSWER: Since the pools are formed from snowmelt and spring rains, the amount of snow that fell the preceding winter may determine the depth of the pools. Likewise the amount of spring precipitation (rain) may influence pool depth. Even with adequate snowmelt and early rain, if a dry stretch (warm temperatures and little rain) follows for an extended period of time, the pool may dry up before successful amphibian reproduction may be completed.

75. A southern European songbird, the blue tit (Parus caeruleus), breeds in two habitats that differ greatly in quality: downy oak forest and holm oak forest. In downy oak habitats, there are six times as many breeding pairs of blue tits and they produce 60 percent more total offspring per year than the holm oak blue tit populations. The downy oak blue tit populations have the potential to grow at the rate of 9 percent annually. In holm oak habitats, blue tits perform poorly and populations have the potential to decline 13 percent annually.

Given the differences in the two habitats, why do blue tits persist in both? Be sure to include a discussion of the relevant metapopulation model in your answer.

ANSWER: This is an example of a source-sink metapopulation model. Excess individuals (typically young birds) move out of overcrowded high-quality downy oak habitats (the sources), replenishing populations in the poor-quality hold oak habitats (the sinks).

76. Describe the difference between the source-sink metapopulation model and the landscape metapopulation model.

ANSWER: The source sink metapopulation model recognizes that suitable habitat patches are not equal in quality. Some are high-quality patches and are sources of dispersers (called source subpopulations).

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Chapter 12 Other patches are of inferior quality and are maintained only by outside dispersers (called sink subpopulations). The landscape metapopulation model builds on the source-sink model by incorporating differences in the surrounding matrix (around the patches) such that some matrix is high-quality habitat and facilitates dispersal while other surrounding matrix is inferior-quality habitat discouraging dispersal.

77. Explain the biological reason that higher intrinsic growth rates and longer delays lead to greater oscillations in population size.

ANSWER: Longer delays lead to greater oscillations in population size because they increase the amount of time that a population will either increase above the carrying capacity or decline below the carrying capacity. For example, with a delay of only a year, a population will only have a year to grow above carrying capacity before it declines. In contrast, with a delay of 2 years, the population will grow for 2 years above carrying capacity before it starts to decline. Similarly, higher intrinsic growth rates allow a species to increase by a larger amount over the carrying capacity or decline a larger amount below the carrying capacity before the population begins to return to carrying capacity.

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Chapter 13 Multiple Choice 1. What is the driving force in the 10-year cycle of lynx and hare abundance? a. competition b. low resources c. climate change d. predation ANSWER: d 2. In the study of brown anole lizards (Anolis sagrei) and orb-weaving spiders (Metepeira datona) on islands in the Bahamas, researchers concluded that a. spiders reduced lizard populations. b. lizards reduced spider populations. c. reintroduction of spiders caused increases in their population. d. lizards did not affect spider populations.

ANSWER: b 3. The introduction of the brown tree snake (Boiga irregularis) to Guam decimated the native fauna because a. the brown tree snake was a superior predator. b. animals on Guam had no defenses against snakes. c. the brown tree snake carried a virulent pathogen. d. animals on Guam were very susceptible to a parasite carried by the brown tree snake.

ANSWER: b 4. A species has been transplanted to a region of the world where historically it did not exist. It spreads rapidly and harms native species. This is known as a(n) a. introduced species. b. exotic species. c. invasive species. d. non-native species.

ANSWER: c 5. Which would be considered a mesopredator? a. wolves b. mountain lions c. coyotes d. bears ANSWER: c 6. Top predators are predators that eat a. plants and herbivores. b. herbivores and top predators.

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Chapter 13 c. mesopredators and plants. d. herbivores and mesopredators.

ANSWER: d 7. How does the removal of top predators affect mesopredator populations? a. The mesopredator population declines because there is no control on population size. b. The geographic range and abundance of mesopredators decline. c. Mesopredator populations remain unchanged. d. The geographic range and abundance of mesopredators increase.

ANSWER: d 8. Australian authorities removed dingoes and feral dogs because they killed sheep. As a result a. sheep populations increased. b. populations of the mesopredator, the red fox, decreased. c. populations of the mesopredator, the red fox, increased. d. rabbit populations increased dramatically.

ANSWER: c 9. Reductions in bay scallops in the Atlantic Ocean were caused by a(n) a. increase in the top predator shark population. b. increase in the mesopredator cownose ray population. c. decrease in the mesopredator cownose ray population. d. decrease in the food supply of bay scallops.

ANSWER: b 10. The biocontrol species cactus moth (Cactoblastis cactorum) has not been able to eradicate the invasive prickly pear cactus from Australia because a. cactus moths prefer to consume other cactus species rather than prickly pear. b. prickly pear cactus is able to disperse to moth-free areas. c. cactus moth populations are declining because of parasitic infection. d. prickly pear cactus has evolved defenses against the cactus moth.

ANSWER: b 11. How was the invasive plant the Klamath weed (Hypericum perforatum) controlled in California? a. A leaf-feeding beetle was introduced to control the weed. b. The weed was killed off with herbicide. c. The weed was killed off by a plant pathogen. d. More cows were released to eat the weed.

ANSWER: a 12. Experiments with fences that exclude deer and other plant herbivores from grazing showed greater plant Copyright Macmillan Learning. Powered by Cognero.

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Chapter 13 biomass in fenced areas than in unfenced control areas. The few plant species that remain in unfenced areas are those that a. are tolerant to herbivory. b. herbivores prefer not to eat. c. herbivores cannot locate. d. have high growth rates to compensate for herbivory.

ANSWER: b 13. Predators that live in the Canadian tundra and feed on larger herbivores tend to have _____ population cycles, and predators that feed on smaller herbivores tend to have _____ population cycles. a. short; long b. long; short c. short; short d. long; long ANSWER: b 14. Huffaker's laboratory experiment of predator and prey species of mites demonstrated that predator and prey cycles a. stabilize with increased food sources. b. stabilize when males are added. c. stabilize when prey have refuges. d. are always unstable.

ANSWER: c 15. In Lotka–Volterra models of predator–prey interactions, c represents the a. probability of an encounter leading to prey's capture. b. efficiency of converting consumed prey into predator offspring. c. per capita mortality rate of predators. d. intrinsic growth rate.

ANSWER: a 16. In Lotka–Volterra models of predator–prey interactions, the growth rate of the prey population is represented by a. cNP – rN. b. r – cP. c. crN – NP. d. rN – cNP. ANSWER: d 17. In Lotka–Volterra models of predator–prey interactions, the growth rate of the predator population is represented by a. NP – acmP. Copyright Macmillan Learning. Powered by Cognero.

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Chapter 13 b. acN – m. c. acNP – mP. d. cNP – amP. ANSWER: c 18. Lotka–Volterra models of predator–prey interactions show that a. predator populations lag behind prey populations. b. prey populations lag behind predatory populations. c. predator and prey populations cycle together. d. predator–prey cycles are inherently unstable.

ANSWER: a 19. In Lotka–Volterra models, a population is stable when its rate of change is a. greater than zero. b. less than zero. c. equal to zero. d. None of the above ANSWER: c 20. In Lotka–Volterra predator–prey models, prey populations decrease when a. P < r ÷ c. b. P > r ÷ c. c. P ÷ c > r. d. P ÷ c < r.

ANSWER: b 21. In Lotka–Volterra predator–prey models, predator populations decrease when a. N ÷ ac < m. b. N ÷ ac > m. c. N < m ÷ ac. d. N > m ÷ ac.

ANSWER: c 22. In Lotka–Volterra predator–prey models, the equilibrium isocline for prey is represented as a. P = c ÷ r. b. P ÷ r = c. c. P ÷ c = r. d. P = r ÷ c.

ANSWER: d 23. At the equilibrium isocline for prey, the population of predators Copyright Macmillan Learning. Powered by Cognero.

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Chapter 13 a. causes the prey population to be stable. b. causes the prey population to increase. c. causes the prey population to decrease. d. and prey both stabilize.

ANSWER: a 24. Simultaneous examination of predator and prey population trends is called a a. dual population trajectory. b. joint population trajectory. c. dual population isocline. d. joint population isocline.

ANSWER: b 25. At the joint equilibrium point, a. both predator and prey populations are increasing. b. both predator and prey populations are decreasing. c. both predator and prey populations have zero growth. d. one population is increasing and the other population is decreasing.

ANSWER: c 26. A functional response in predatory–prey cycles is the relation between the density of a. predators and an individual prey's rate of food consumption. b. prey and an individual predator's rate of food consumption. c. predators and an individual prey's rate of growth. d. prey and an individual predator's rate of growth.

ANSWER: b 27. In a functional response, the a. prey can regulate the fitness of the predator population. b. predator can regulate the fitness of the prey population. c. prey can regulate the growth of the predator population. d. predator can regulate the growth of the prey population.

ANSWER: d 28. For some predators, as prey density increases, the rate of consumption slows and eventually levels off with satiation. This is a type _____ functional response. a. I b. II c. III d. IV ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 13 29. A type _____ functional response occurs when a predator's rate of prey consumption increases linearly with increasing prey and then satiates. a. I b. II c. III d. IV ANSWER: a 30. A numerical response is a change in the number of predators due to all of the following EXCEPT a. changes in prey abundances. b. population growth. c. immigration. d. emigration.

ANSWER: a 31. Wolves hunt in packs that chase down their prey. This is an example of a. sit-and-wait hunting. b. ambush hunting. c. active hunting. d. trap hunting.

ANSWER: c 32. Which of the following is NOT a behavioral defense against predation? a. alarm calling b. spatial avoidance c. camouflage d. reduced activity ANSWER: c 33. The color pattern and texture of the body of a horned lizard (Phrynosoma platyrhinos) allows it to blend into the ground of the desert in which it lives. This is an example of a. a structural defense. b. a behavioral defense. c. spatial avoidance. d. crypsis.

ANSWER: d 34. The crucian carp (Carassius carassius) develops a muscular hump on its back that increases its acceleration in response to predators. This is an example of a. a chemical defense. b. crypsis.

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Chapter 13 c. a structural defense. d. a behavioral defense.

ANSWER: c 35. Many organisms that employ chemical defenses also display a. crypsis. b. aposematism. c. camouflage. d. Batesian coloration.

ANSWER: b 36. Alarm signals in primates are an example of a. a chemical defense. b. a structural defense. c. a behavioral defense. d. aposematism.

ANSWER: c 37. Chameleon color patterns are an example of a. structural defenses. b. aposematism. c. behavioral defenses. d. crypsis.

ANSWER: d 38. The bombardier beetle (Stenaptinus insignis) deters predators by releasing boiling hot fluid from its abdomen. This is an example of a. crypsis. b. structural defense. c. chemical defense. d. behavioral defense.

ANSWER: c 39. Which is a warning coloration? a. Batesian coloration b. Müllerian coloration c. crypsis d. aposematism ANSWER: d 40. The resemblance of poison dart frog species of the genus Ranitomeya to one another in Peru is an example Copyright Macmillan Learning. Powered by Cognero.

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Chapter 13 of a. Batesian mimicry. b. Müllerian mimicry. c. crypsis. d. a chemical defense.

ANSWER: b 41. The viceroy (Limenitis archippus) is an unpalatable North American butterfly that has coloration similar to that of another species of unpalatable butterfly, the monarch (Danaus plexippus). This is an example of a. crypsis. b. Müllerian mimicry. c. Batesian mimicry. d. camouflage.

ANSWER: b 42. The nonpoisonous scarlet king snake (Lampropeltis elapsoides) found in the eastern United States has similar coloration to that of the poisonous eastern coral snake (Micrurus fulvius). This is an example of a. aposematism. b. crypsis. c. Müllerian mimicry. d. Batesian mimicry.

ANSWER: d 43. Reduced growth and development due to reduced feeding and foraging activity is a cost of a. chemical defenses. b. structural defenses. c. behavioral defenses. d. crypsis.

ANSWER: c 44. The Indian gray mongoose (Herpestes edwardsii) is a small mammal that is known for its ability to kill venomous king cobras (Ophiophagus hannah). Mongooses have evolved acetylcholine receptors that make them resistant or immune to the cobra's venom. What is likely responsible for this? a. coevolution b. phenotypic plasticity c. structural defenses d. chemical defenses ANSWER: a 45. Plant alkaloids act as chemical defense against herbivory because they a. are toxic to herbivores. b. are difficult for herbivores to digest.

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Chapter 13 c. make the plant unpalatable. d. are difficult to consume.

ANSWER: a 46. Which of the following is an example of a plant alkaloid? a. tannin b. lignin c. caffeine d. latex ANSWER: c 47. Which of the following chemical defenses makes plants difficult for herbivores to digest? a. alkaloids b. latex c. resins d. tannins ANSWER: d 48. Researchers studying production of nicotine in tobacco plants (Nicotiana sylvestris) treated some of the plants with a hormone that prevents the chemical defenses from responding to herbivory. What did they find to be the cost of nicotine production? a. reduced growth rate b. increased herbivory c. plant death d. reduced seed production ANSWER: d 49. Milkweeds use _____ as a chemical defense against herbivory. a. alkaloids b. tannins c. glycosides d. resin ANSWER: c 50. On Macquarie Island invasive rabbits were causing declines in palatable vegetation, and feral cats were preying on native birds. What was the primary result when a flea carrying a virus that killed the rabbits decreased rabbits' numbers on the island? a. Feral cats switched from eating rabbits to eating native birds. b. Feral cats also died off because of the loss of the rabbit prey. c. Native bird populations on the island increased. d. Native plant populations on the island declined.

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Chapter 13 ANSWER: a 51. Which term best describes the brown tree snake based on its impact on the island of Guam? a. invasive species b. introduced species c. non-native species d. exotic species ANSWER: a 52. Humans have had the largest impact on natural systems as a result of a. eliminating mesopredators. b. introducing mesopredators. c. eliminating top predators. d. introducing top predators.

ANSWER: c 53. According to Lotka and Volterra, what information was required to calculate the change in population size of the prey over time (dN/dt)? a. the intrinsic rate of growth of the predator b. the population size of the prey's closest competitor c. the number of parasite species impacting the prey d. how efficient the predator was in capturing the prey ANSWER: d 54. According to Lotka and Voltera what information was required to calculate the change in population size of the predator over time (dP/dt)? a. the efficiency rate of converting prey consumed into predator offspring b. the efficiency rate of converting vegetation consumed by the prey into prey offspring c. the overall death rate of the prey by all causes d. the death rate of prey by all causes other than predation ANSWER: a 55. What is true about the Lotka–Volterra model for predator and prey? a. The model includes recognition of the carrying capacity for prey. b. The model includes recognition of the carrying capacity for predators. c. The model results in oscillating populations of predator and prey with the prey population lagging behind the predator population. d. The model results in oscillating populations of predator and prey with the predator population lagging behind the prey population.

ANSWER: d 56. Which functional response curve shows a slower rate of consumption of prey at low prey density levels due Copyright Macmillan Learning. Powered by Cognero.

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Chapter 13 to the predator learning a search image for the prey? a. type I functional response b. type II functional response c. type III functional response d. type IV functional response ANSWER: c 57. Which functional response curve shows a satiation of the predator at high prey densities? a. type I functional response curve only b. type II functional response curve only c. type III functional response curve only d. type I, II, and III all show satiation ANSWER: d Essay 58. In rocky shore communities in which sea urchins lived among populations of brown algae and other species of algae, sea urchins were experimentally removed. What happened in response to sea urchin removal?

ANSWER: When sea urchins were removed, brown algae populations increased so much that they shaded out other algae species. The removal of the sea urchins affected species composition of the entire community because sea urchins controlled populations of large brown algae through herbivory.

59. The graphs show the result of experiments involving the crop pest the California red scale insect Aonidiella aurantii and the parasitoid wasp Aphytis melinus. What did the results show about the populations of wasps and scale insects on control and outbreak trees? Is the parasitoid wasp a good biocontrol candidate for reducing scale insects?

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Chapter 13

ANSWER: Increases in scale insects led to increases of juvenile and adult parasitoid wasps. As wasps increased in abundance, scale insect populations declined. This research demonstrated that the parasitoid wasp successfully controlled the populations of scale insect.

60. In experiments with the backswimmer (Notonecta glauca), a predatory insect, and two types of prey species, isopods (Asellus aquaticus) and mayflies (Coeon dipterum), predator preference seemed to be affected by the percentage of mayflies. What explains the results presented in the figure? What type of functional response is being demonstrated?

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Chapter 13

ANSWER: The backswimmers consumed fewer mayflies than expected when mayflies were rare and consumed more mayflies than expected when mayflies were common. This may occur because the backswimmers develop a search image for mayflies. This is a type III functional response, since the Copyright Macmillan Learning. Powered by Cognero.

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Chapter 13 predator exhibits low prey consumption under low prey densities, rapid consumption under moderate prey densities, and slowing consumption under high prey densities.

61. The figure shows results of a study in which scientists observed the responses of tadpoles to a caged predator and an empty control cage in tubs of water. The caged predator emitted a chemical that alerted the tadpoles to its presence but was not able to kill tadpoles. Based on the figure, how did tadpoles respond to the experiment, and what type of defense did they exhibit?

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Chapter 13 ANSWER: The tadpoles in the caged predator treatment sensed the presence of the predator and to avoid predation reduced their activity below that of the control subjects. This is an example of a behavioral defense against predation.

62. The common wasp (Vespula vulgaris), the hover fly (Helophilus pendulus), and the hornet clearwing (Sesia apiformis) all exhibit similar color patterns, but only the wasp is harmful. What benefit, if any, do the hornet and fly gain from having coloring similar to that of the wasp?

ANSWER: The hornet and fly are employing Batesian mimicry; they are palatable species that are attempting to avoid predation by displaying warning coloration similar to that of a harmful species, the wasp.

Predators may see this coloration and assume that the fly and hornet are harmful.

63. Ladybugs (Coccinella septempunctata) produce bad-tasting alkaloids as a chemical defense against predators. Researchers wanted to determine the costs of this chemical defense. They fed ladybugs either small or large amounts of food and measured alkaloid production and concentrations of carotenoids in the ladybug bodies. Carotenoids are the chemicals responsible for the red color of the ladybug, which advertises its unpalatability to predators. What do the results of this experiment, shown in the figure, indicate about costs of chemical defenses?

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Chapter 13

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Chapter 13 64. What does it mean when scientists set the alpha at .05 for a statistical test?

ANSWER: An alpha of .05 means that two distributions would be considered statistically significant only if random sampling of the two distributions resulted in overlap less than 5 percent of the time.

65. Describe the difference between Batesian Mimicry and Müllerian Mimicry.

ANSWER: Batesian Mimicry involves an organism that is palatable/edible evolving to resemble a species that is unpalatable/noxious/inedible. In doing so the palatable species would get the advantage that predators that have learned not to attack/attempt to consume the unpalatable species will also not attack/attempt to consume the mimic as they cannot distinguish between the two species based on appearance. Müllerian Mimicry involves two (or more) unpalatable species evolving to resemble each other. Müllerian mimicry provides for quicker learning by the predator (i.e., enhance reinforcement of the unpalatable nature) to avoid both species; thus, the mimics obtain that advantage.

66. Discuss the costs associated with defending against predation.

ANSWER: Prey employ a wide range of defense strategies to avoid being consumed by a predator. These defense strategies are not without costs to the prey. Mechanical defenses are costly from an energetic as well as material perspective. The prey must expend energy and use material that they could have used for other functions; for example, reproduction (think: principle of allocation).

Behavioral defenses may incur costs associated with reduced growth and development as the prey may avoid areas or decrease movement to avoid being detected by predators and in doing so decrease the prey's ability to forage for food. Chemical defenses also incur energetic and material costs similar to mechanical defenses. However, not to employ these defenses may lead to the prey being taken by the predator and thus it loses its ability to reproduce (a reduction in fitness).

67. The two basic hunting strategies [active hunting vs. ambush (sit-and-wait hunting)] are both successful strategies under differing conditions. What characteristics of the prey might be associated with these two hunting strategies?

ANSWER: An active hunting strategy relies, in part, on a prey that is likely less mobile, whereas an ambush hunting strategy relies, in part, on a prey that is more highly mobile.

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Chapter 14 Multiple Choice 1. Why does the parasitic flatworm (Leucochloridium paradoxum) of the amber snail (Succinea putris) alter the behavior of the snail so that it moves to the top of a plant stem? a. The flatworm needs the snail to move off the ground to avoid predation. b. The flatworm needs the snail to be eaten by a bird to complete its life cycle. c. The conditions at the top of plant stems are better for flatworms. d. There is more food for the snail at the top of plant stems than on the ground.

ANSWER: b 2. The ability of a host to prevent infection by parasites is called a. tolerance. b. avoidance. c. resistance. d. reluctance.

ANSWER: c 3. Infection tolerance is the ability of a host to a. minimize harm that an infection can cause. b. prevent infection by parasites. c. prevent a parasite from reproducing. d. recover from an existing infection.

ANSWER: a 4. The number of parasites of a given species that an individual host can harbor is its a. infection rate. b. infection load. c. parasite rate. d. parasite load.

ANSWER: d 5. The World Health Organization estimates that more than _____ of all human deaths are caused by infectious diseases. a. 30 percent b. 45 percent c. 25 percent d. 15 percent ANSWER: c 6. Which of the following in NOT an example of an ectoparasite? a. a tick b. a tapeworm Copyright Macmillan Learning. Powered by Cognero.

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Chapter 14 c. a flea d. a mite ANSWER: b 7. Because of its relationship with its host, the ectoparasite has a. low exposure to the host's immune system. b. low exposure to its natural enemies. c. low exposure to the external environment. d. difficulty moving between hosts.

ANSWER: a 8. Which of the following statements is NOT true about the endoparasite life cycle? a. It has low exposure to its natural enemies. b. It has low exposure to the host's immune system. c. It finds it easy to feed on the host. d. It has low exposure to the external environment.

ANSWER: b 9. What types of endoparasites replicate by altering their host's proteins and do not contain any nucleic acids? a. viruses b. hemiparasites c. helminths d. prions ANSWER: d 10. Malaria in humans and animals is caused by a a. prion. b. protozoan. c. fungus. d. virus.

ANSWER: b 11. Dutch elm disease is caused by a a. fungus. b. virus. c. prion. d. protozoan.

ANSWER: a 12. Crop rust is a _____ disease. a. protozoan Copyright Macmillan Learning. Powered by Cognero.

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Chapter 14 b. prion c. viral d. fungal ANSWER: d 13. Endoparasitic roundworms and flatworms that live in the tissues of plants and animals are called a. protozoans. b. prions. c. helminths. d. hemiparasites.

ANSWER: c 14. Which of the following is NOT a characteristic of an emerging infectious disease? a. high fatality rate b. recent discovery c. increased occurrence d. recent jump to a new host ANSWER: a 15. When a new disease is discovered, it is called an _____ disease. a. emerging invasive b. increasing infectious c. emerging infectious d. increasing virulent ANSWER: c 16. Parasites generally have _____ reproductive rates than their hosts and often _____ them. a. lower; do not kill b. higher; do not kill c. higher; kill d. lower; kill ANSWER: b 17. A parasite moving between individuals other than parents and their offspring uses _____ transmission. a. horizontal b. vertical c. diagonal d. vector ANSWER: a 18. Vertical transmission of parasites is Copyright Macmillan Learning. Powered by Cognero.

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Chapter 14 a. intraspecific transmission through a vector. b. interspecific transmission through a vector. c. direct transmission from parent to offspring. d. direct interspecific transmission.

ANSWER: c 19. In the disease malaria, the Anopheles mosquito is the a. vector. b. reservoir species. c. host. d. parasite.

ANSWER: a 20. The bacterium that causes chlamydia in humans can be transmitted from mother to fetus by _____ transmission or between any two individuals by _____ transmission. a. horizontal; horizontal b. vertical; vertical c. horizontal; vertical d. vertical; horizontal ANSWER: d 21. Which of the following is NOT an example of horizontal transmission? a. transmission of the flu virus between adult humans b. transmission of West Nile virus between bird conspecifics via a mosquito c. transmission of HIV to a human infant from its mother via breast milk d. transmission of liver fluke to a sheep via a helminth ANSWER: c 22. How do reservoir populations allow parasites to persist in nature? a. Reservoir species transmit the parasite more frequently than host species, so the parasite infects a larger number of individuals. b. Reservoir species are necessary for reproduction of the parasite. c. Reservoir species do not die of the parasite and can be a continuous source of the parasite. d. Without the reservoir species, the parasite could not disperse from one host to another.

ANSWER: c 23. Diseases such as HIV and African sleeping sickness can avoid the host's immune system by a. having little negative effect on the host. b. making themselves undetectable. c. living in a reservoir species. d. resembling red blood cells.

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Chapter 14 ANSWER: b 24. Which of the following strategies do schistosomes use to circumvent the host's immune system? a. They produce chemical factors that suppress their host's immune system. b. They produce surface proteins that mimic the host's own proteins. c. They continually produce novel surface proteins to confuse their host's immune system. d. They produce a protective outer layer around their bodies that prevents them from being detected by the host’s immune system.

ANSWER: d 25. The prion that causes bovine spongiform encephalopathy is _____ transmitted _____. a. horizontally; via a mosquito vector b. vertically; from parent to offspring c. horizontally; via a helminth d. horizontally; directly via ingestion of infected cow tissue ANSWER: d 26. What does the S-I-R model characterize for infectious diseases? a. immunity rates b. treatments c. fatality rates d. transmission ANSWER: d 27. In S-I-R models of infectious disease transmission, I represents _____ individuals. a. immune b. immigrated c. infected d. infectious ANSWER: c 28. In S-I-R models of infectious disease transmission, R represents _____ individuals. a. resistant b. recovered c. relocated d. resilient ANSWER: a 29. In S-I-R models, which of the following does NOT determine the proportion of S, I, and R individuals in a population? a. recovery of infected individuals Copyright Macmillan Learning. Powered by Cognero.

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Chapter 14 b. rates of transmission of the disease c. acquisition of immunity d. birth of new susceptible individuals ANSWER: a 30. In S-I-R models, which of the following represents the probability of contact between susceptible and infected individuals? a. S × I b. S ÷ I c. I ÷ S d. S + I ANSWER: a 31. In S-I-R models, if R0 > 1, the a. infection fails to take hold in the host population. b. population becomes resistant to the infection. c. infection becomes an epidemic. d. population is immune to the infection.

ANSWER: c 32. In S-I-R models, if the ratio of new infections to recoveries is less than 1, a. the infection becomes an epidemic. b. all individuals in the population become resistant to the infection. c. the infection fails to take hold in the host population. d. all infected individuals in the population recover.

ANSWER: c 33. In S-I-R models, the variable g represents the a. rate of recovery. b. rate of infection. c. proportion of infected individuals. d. rate of transmission.

ANSWER: a 34. Which characterizes the rate of infection between susceptible and infected individuals in an S-I-R model? a. b × I × S b. g ÷ (I × S) c. I + (S ÷ g) d. S + (I × g) ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 14 35. Which of the following characterizes the rate of recovery of infected individuals in an S-I-R model? a. I ÷ g b. I × g c. I + g d. I – g ANSWER: b 36. In S-I-R models, which of the following models the ratio of new infections to recoveries? a. S × (b ÷ g) b. g × (S ÷ b) c. S × (g ÷ b) d. S ÷ (g × b) ANSWER: a 37. Which of the following diseases has the highest R0 value? a. HIV b. malaria c. measles d. chicken pox ANSWER: b 38. Which of the following is NOT an assumption of the S-I-R model? a. There are no births of new susceptible individuals. b. Individuals retain any resistance they develop. c. The epidemic continues until all individuals are resistant or there are too few susceptible individuals to sustain the spread of the disease. d. All infected individuals die.

ANSWER: d 39. Vaccinations slow or stop the spread of diseases by a. reducing the virulence of the disease. b. increasing the rate of recovery. c. reducing the size of the susceptible population. d. increasing the number of reservoirs.

ANSWER: c 40. According to an S-I-R model, if a pathogen can kill its host, the a. pathogen should decrease in abundance until hosts begin to die. b. pathogen should increase in abundance until the hosts begin to die. c. disease will not become an epidemic. d. individuals in the population will either die or become resistant.

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Chapter 14 ANSWER: b 41. The amphibian pathogen the chytrid fungus does not fit the S-I-R model because the a. host does not recover from the fungal infection. b. host has no resistance to the fungus. c. fungus kills the host. d. fungus infects many species of amphibians.

ANSWER: d 42. When parasites require a series of hosts to complete their life cycle, they often evolve adaptations that a. help them reproduce more quickly. b. help them get transmitted from one host to the next. c. protect them from multiple hosts' immune systems. d. allow them to reproduce in any of their hosts.

ANSWER: b 43. Mice infected with Toxoplasma gondii are often attracted to bobcat urine. This is an example of a. a host adaptation. b. coevolution. c. a parasite adaptation. d. a reservoir species adaptation.

ANSWER: c 44. The parasitic worm Acanthocephalus dirus has evolved an adaptation that causes its isopod host, Caecidotea intermedius, to a. spend more time out in the open. b. be attracted to larger fish. c. spend more time in refuges. d. be scared of larger fish.

ANSWER: a 45. Chimpanzees infected with intestinal worms sometimes eat Aspilia leaves. This is an example of a. coevolution. b. a reservoir species adaptation. c. a parasite adaptation. d. a host adaptation.

ANSWER: d 46. Organisms that produce antibacterial or antifungal chemicals have developed this ability as the result of a. coevolution. b. a parasite adaptation.

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Chapter 14 c. a host adaptation. d. a prey adaptation.

ANSWER: c 47. Reduction in virulence of myxomatosis in rabbits in Australia in the second outbreak was a result of a. a parasite adaptation. b. coevolution. c. horizontal transmission. d. a host adaptation.

ANSWER: b 48. Two populations with sample sizes of 25 and 27 are compared with a t-test. What is the value for the degrees of freedom? a. 52 b. 54 c. 50 d. 26 ANSWER: c 49. Which species is a reservoir for Borrelia burgdorferi, the bacterium that causes Lyme disease? a. deer b. mouse c. dog d. human ANSWER: b 50. What is the difference between an intercellular endoparasite and an intracellular endoparasite? a. Intercellular endoparasites attach to the organelles of the cell. b. Intercellular endoparasites are only found in the nucleus of cells where the genetic material (DNA & RNA) is found. c. Intracellular endoparasites are never organisms. d. Intercellular endoparasites tend to be larger in size.

ANSWER: d 51. The black-legged tick (or deer tick) associated with Lyme disease is a. an intracellular endoparasite. b. an intracellular ectoparasite. c. a vector. d. intercellular ectoparasite.

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Chapter 14 52. Hemiparasites are a. organisms that live part of their lives as hosts and part of their lives as parasites. b. organisms that live part of their lives as endoparasites and part as ectoparasites. c. organisms that live part of their lives as hosts and part as vectors. d. organisms that obtain some materials by parasitic means and some by nonparasitic means (i.e., photosynthesis).

ANSWER: d 53. Chestnut blight that devastated the American Chestnut tree in the eastern United States was caused by a. a bacteria. b. a fungus. c. a purported prion, though research continues. d. a virus.

ANSWER: b 54. Fungal parasites a. affect animals only. b. affect plants only. c. affect both plants and animals. d. affect neither plants nor animals as a parasite.

ANSWER: c 55. White-nose syndrome in North American bats is an example of a parasite that was likely transmitted by a. vertical transmission. b. horizontal transmission. c. both horizontal and vertical transmission. d. neither horizontal nor vertical transmission.

ANSWER: b 56. Which is true about reservoir species? a. Reservoir species are always aquatic. b. Reservoir species transmit the parasite by direct contact with noninfected individuals. c. Reservoir species may be resistant to the parasitic disease. d. Reservoir species are always brightly colored so as to attract vectors for the purpose of transmitting the parasitic disease.

ANSWER: c Essay 57. Endoparasites (such as tapeworms) seem to lead an ideal life in the interior of the host, protected from natural enemies and the external environment while having a continual supply of nutrients. What are challenges that endoparasites face?

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Chapter 14 ANSWER: The main challenges facing endoparasites are attacks by the host's immune system and survival outside the body of the host. In addition, endoparasites have difficulty moving from host to host.

58.

The graph shows survival rates for North American populations of the little brown bat (Myotis lucifugus) after exposure to either a North American or European strain of white-nose fungus (Geomyces destructans). What did researchers conclude about the two strains?

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Chapter 14 ANSWER: Exposure to either strain of white-nose fungus caused high rates of bat death. However, bats did not die as quickly when exposed to the North American strain, which may suggest that bats in North America are evolving some resistance to the North American strain of the fungus.

59. Anthropologists studying a tribe on an island in the South Pacific ask you to help them with an intriguing health problem: The chiefs of the tribe keep dying at a much more rapid rate than other members of the population. You travel to the island to observe the tribe, and you find that each time an animal is killed during a hunt, the body of the animal is shared communally among all of the members of the tribe. However, one part of the animal, its brain, is reserved exclusively for the tribal chief. The chief consumes the brain raw because it is believed that this allows him to assimilate the animal's knowledge of the island. What would you suggest is causing the death of the tribal chiefs, how is it killing them, and what is the mechanism of transmission?

ANSWER: It is likely that a prion in the animal's brain is causing the death of the tribal chiefs. Death occurs because the misfolded prion proteins in the animal's brain are horizontally transmitted to the chief's body when the chief eats the brain, causing the misfolding of proteins in the chief's own brain.

60. Unlike predators, most parasites do not kill their hosts. Why is this beneficial?

ANSWER: Because parasites rely on their hosts for resources, killing the host would require the transmission of the parasite to a new host or result in the death of the parasite. Not killing the host lets the parasite exploit its host indefinitely.

61. Describe two ways a parasite can decrease the likelihood that it will run out of potential hosts.

ANSWER: A parasite can increase the number of potential hosts by evolving the ability to infect other species.

The parasite can also evolve the ability to live within a reservoir species until a host is available.

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Chapter 14

62.

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Chapter 14

63.

In the figure showing dynamics of an infected population over time, what do the blue, purple, and green curves represent?

ANSWER: The blue curve is the percentage of individuals susceptible to the infection. The purple curve is the Copyright Macmillan Learning. Powered by Cognero.

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Chapter 14 percentage of infected individuals. The green curve is the percentage of recovered individuals.

64. While you are conducting a study of the optimal growing conditions for commercially grown sunflowers in Maryland, all of the sunflower plants in the field you are studying die. You discover that an emerging fungal pathogen kills sunflowers by destroying their roots. The fungus uses honeybees, which pollinate your flowers, as a vector to transmit fungal spores among sunflower plants. The next year the farm reseeds, hoping that the fungus has died over the winter. Early in the growing season some plants begin dying again, but then the honeybee population develops colony collapse disorder and all of the honeybees die. To compensate for the loss in pollinators, the farmers introduce large numbers of bumblebees. The number of new sunflower plants that become infected during the remainder of the growing season drops to near zero. Using the variables in the susceptible-infected-resistant (S-I-R) model equation: R0 = (S × I × g) ÷ (I × b), explain what has happened to alter the disease dynamics in the second year of your study and how this has occurred.

ANSWER: While the number of susceptible sunflowers in the population may not have changed, the collapse of the honeybee vector population dramatically decreased the rate of infection between susceptible and infected individuals (i.e., decreased g). The bumblebees are not a viable vector for the fungal pathogen.

65. Researchers set up an experiment in which they treat plants with a new fertilizer and compare plant height after 2 months to a control (untreated) group of plants. Using the data that follow, perform a t-test (α = 0.05) to determine whether the fertilizer affected plant height in this experiment. Use this formula:

Fertilized Plants Height (cm) 13.1 11.8 10.7 12.3 9.9

Control Plants Height (cm) 6.2 5.9 10.2 9.7 8.3

Degrees of Freedom 5 6 7 8 9 10

Critical t 2.015 1.943 1.895 1.860 1.833 1.812

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Chapter 14 ANSWER:

Since the t-statistic for these data is greater than the critical t of 1.860, the fertilizer caused a significant increase in plant height.

66. Describe the 2-year cycle of Lyme disease, including all hosts and how the parasite is transmitted between hosts.

ANSWER: In year 1, a female tick lays eggs that hatch into larvae. The tick larvae parasitize a rodent that is infected with Borrelia burgdorferi. (Mice are a reservoir species.) The tick larvae become a vector of B. burgdorferi and molt into tick nymphs that overwinter in leaf litter. In year 2, the infected tick nymphs parasitize various animals (e.g., birds and humans). At this stage, humans and other tick hosts can be infected with B. burgdorferi and get Lyme disease. When the tick nymphs fall off and molt into adult ticks, they parasitize deer. While on the deer, adult ticks mate and adult females fall off and lay eggs to start the cycle again.

67. Describe the differences between those organisms classified as endoparasites and those classified as ectoparasites. How does the difference between these two types of parasites provide an understanding of their life history?

ANSWER: Endoparasites are parasites that live inside the body of the host organism, while ectoparasites live on the outside of the body of the host organism. Endoparasites thus are protected to a greater extent from natural enemies and environmental stochasticity as compared to ectoparasites. However, endoparasites are more likely to be exposed to the host’s immune system response as compared to ectoparasites. Thus, endoparasites may employ a variety of strategies (including biochemical) to avoid being impacted by the host immune system. Because endoparasites are found within the host organism, it is much easier for the endoparasite to feed on the host as well as move from the host.

68. Viruses and prions are both intracellular endoparasites. How are they different?

ANSWER: Viruses are endoparasites that contain genetic material (DNA or RNA). Viruses reproduce within the host, making copies of their own viral genetic material by using the host’s infrastructure but the viruses’ genetic code, thus producing more viruses. Unlike viruses, prions do not contain any genetic material (neither RNA nor DNA). Rather, prions are incorrectly folded proteins that when they come in contact with normal proteins can cause the normal proteins to fold incorrectly, leading to parasitic impacts on the host.

69. Parasites can move between hosts either by horizontal or vertical transmission. Why might those parasites Copyright Macmillan Learning. Powered by Cognero.

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Chapter 14 that employ horizontal transmission be more impacted by environmental stochasticity?

ANSWER: Parasites that move by horizontal transmission require a vector (e.g., mosquito) to move from one conspecific to another or from one species to another. The vector (e.g., mosquito) may be more likely influenced by random environmental changes (rainfall, temperature changes, etc.) and thus transmission may be enhanced or diminished. Parasites that move by vertical transmission do not require a vector. Rather, the parasite is passed from parent to offspring. Thus, vertical transmission is less likely to be impacted by varied environmental changes.

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Chapter 15 Multiple Choice 1. Intraspecific competition occurs a. when any two species compete for a limited resource. b. when two species of hummingbird compete for nectar. c. when bald eagles compete for fish out of the same lake. d. only among plant species.

ANSWER: c 2. Interspecific competition occurs a. when two mountain lions compete for deer. b. when any two species compete for a limited resource. c. when bald eagles compete for fish out of the same lake. d. only among animal species.

ANSWER: b 3. Which of the following is NOT an example of a resource? a. temperature b. holes that allow prey to hide from a predator c. soil nitrogen d. nesting sites in a dead tree ANSWER: a 4. Which of the following is a limiting resource for sessile organisms in rocky intertidal habitats? a. food b. space c. dissolved nitrogen d. mates ANSWER: b 5. Which of the following is NOT a renewable resource? a. soil nitrogen b. water c. prey d. space ANSWER: d 6. Which of the following is NOT a renewable resource for a species of predatory bird? a. prey b. water c. oxygen Copyright Macmillan Learning. Powered by Cognero.

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Chapter 15 d. nest sites ANSWER: d 7. Abiotic environmental factors are NOT considered resources for all of these reasons EXCEPT that a. organisms do not compete for them. b. they cannot be consumed. c. they cannot be used up. d. they do not affect growth and reproduction.

ANSWER: d 8. Hemlocks cast much deeper shade than birch trees. The tree that competes more successfully for light is a. hemlock, because it casts deeper shade. b. the tree with the largest canopy. c. the tree that can persist as saplings in deep shade in the forest understory. d. the most abundant species of saplings in the understory.

ANSWER: c 9. In the study of the diatoms Synedra and Asterionella, Synedra was a better competitor than Asterionella because Synedra a. had a higher carrying capacity than Asterionella. b. had a lower carrying capacity than Asterionella. c. reduced the shared limiting resource to the lowest level at its carrying capacity. d. was more tolerant of predators than Asterionella.

ANSWER: c 10. Leibig's law of the minimum a. fails to consider that the interaction of resources can limit growth. b. fails to consider competition for resources. c. assumes that the resource in lowest supply is always the most limiting. d. fails to consider other processes like predation and disease.

ANSWER: a 11. If a plant is primarily limited by nitrogen and secondarily by phosphorus, according to Leibig's law of the minimum, under which circumstances would adding phosphorus increase the plant's growth rate? a. if nitrogen and phosphorus are added together b. if the phosphorus is added to alleviate limitation before the nitrogen is added c. if the nitrogen is added to alleviate limitation before phosphorus is added d. Phosphorus would never increase the growth rate because the primary limitation is nitrogen.

ANSWER: c 12. The competitive exclusion principle states that two organisms cannot coexist indefinitely when they Copyright Macmillan Learning. Powered by Cognero.

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Chapter 15 a. live in the same habitat. b. are similar species. c. are limited by the same resources. d. consume the same prey.

ANSWER: c 13. Darwin argued that closely related species are more likely to compete because they a. almost always live close together. b. are the same size. c. face the same predators. d. have similar traits and consume similar resources.

ANSWER: d 14. Tansley's experiments with bedstraw (Galium) showed that when two closely related species of bedstraw are grown together, a. one is always the superior competitor regardless of habitat. b. bedstraw in its preferred soil type is always the superior competitor. c. bedstraw in its preferred soil type is the better competitor for soil nitrogen. d. one was a better competitor for light and the other for water, depending on soil type.

ANSWER: b 15. Tansley's experiments with bedstraw (Galium) showed that closely related species reduce competition by a. partitioning soil resources. b. growing in distinct patches. c. growing in distinct habitats. d. altering nutrient requirements so that there is no overlap.

ANSWER: c 16. Closely related species a. often share similar niches. b. are unlikely to compete with one another. c. are often distributed among different habitats to minimize competition. d. grow together because they thrive in similar habitats.

ANSWER: c 17. Distantly related species are most likely to compete if they a. consume a common resource. b. live close together. c. live in similar habitat. d. face the same predator species.

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Chapter 15 18. The mathematical models for competition between species are based on the _____ equation. a. energy balance b. exponential population growth c. logistic population growth d. life table ANSWER: c 19. Populations approach a stable equilibrium when a. all resources have been consumed. b. resources are plentiful relative to demand. c. growth rate nears zero. d. the population exceeds carrying capacity.

ANSWER: c 20. In Lotka–Volterra population models, α12 and β21 are referred to as a. isoclines. b. competition coefficients. c. carrying capacities. d. rates of growth.

ANSWER: b 21. In Lotka–Volterra competition models, the variable K represents the a. size of the population. b. intrinsic growth rate. c. carrying capacity. d. time component of the model.

ANSWER: c 22. In the logistic growth equation a. carrying capacity. b. intrinsic growth rate. c. size of the population. d. competition coefficient.

ANSWER: b

, the variable r represents the

23. In Lotka–Volterra competition models, what does the term α1,2 N2 represent? a. instantaneous rate of population increase of species 1 b. carrying capacity of the environment for species 1 c. reduction of species 1's carrying capacity by individuals of species 1 Copyright Macmillan Learning. Powered by Cognero.

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Chapter 15 d. reduction of species 1's carrying capacity by individuals of species 2 ANSWER: d 24. Competition coefficients can be used to a. identify which limiting resource two species compete for. b. determine the time it takes for the competitive exclusion principle to operate. c. determine whether species are likely to coexist. d. convert between the number of individuals of one species and the number of individuals of another species.

ANSWER: d 25. Imagine a population of 600 mice and 350 chipmunks. The chipmunks and mice eat some of the same food, but the food to support 1,000 mice would support only 300 chipmunks. What would α and β be for this population in which mice are species 1 and chipmunks are species 2? a. α = 3.3; β = 0.3 b. α = 0.3; β = 3.3 c. α = 1.7; β = 0.6 d. α = 0.6; β = 1.7 ANSWER: a 26. If an individual of species 2 has a greater effect on species 1 than the reverse, which of the following would be TRUE? a. α = 1; β = 1 b. α < 1; β < 1 c. α > 1; β > 1 d. α < 1; β > 1 e. α > 1; β < 1 ANSWER: d 27. Graphical models of competition tell us that a. closely related species are less likely to compete than distantly related species. b. closely related species are more likely to compete than distantly related species. c. coexistence of two competing species is most likely if intraspecific competition is stronger than interspecific competition. d. coexistence of two competing species is most likely if interspecific competition is stronger than intraspecific competition.

ANSWER: c 28. Which of the following make(s) coexistence of species 1 and 2 more likely? a. higher values of both r1 and r2 b. lower values of both N1 and N2 c. higher values of both K2 and K1 Copyright Macmillan Learning. Powered by Cognero.

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Chapter 15 d. lower values of both 1,2 and 2,1 ANSWER: d 29. A zero-growth isocline is best defined in terms of a. time. b. population. c. carrying capacity. d. growth rate.

ANSWER: b 30. Which of the following equations is a zero-growth isocline? a. N2 = K1 ÷  b. N2 =  ÷ K2 c. N1 =  ÷ K1 d. N2 = K2 ÷  ANSWER: a 31. The resource requirements of two plant species, A and B, have been carefully studied. Researchers have determined the levels of a particular resource that will support equilibrium levels of each species. Species A needs more of this resource to maintain equilibrium than does species B. When these two species are set in competition (under conditions in which this resource is limiting), what is likely to happen to the populations of species A and B? a. Species A will displace species B. b. Species B will displace species A. c. Species A and B will continue to coexist. d. There is not enough information to determine the outcome.

ANSWER: b 32. In David Tilman's experiments with the diatoms Cyclotella and Asterionella, when the diatoms were grown at silicon/phosphorus ratios between 6 and 90, why did the two species coexist? a. Both species were phosphorus limited. b. Both species were silicon limited. c. Neither species was limited by phosphorus or silicon. d. One species was limited by phosphorus, and the other was limited by silicon. e. Tilman continually supplemented the cultures with individuals of the two species.

ANSWER: d 33. In experiments with competitive barnacle species distributed along upper and lower intertidal zones, researchers found a trade-off between ability to _____ and ability to _____. a. compete; colonize b. compete; tolerate desiccation Copyright Macmillan Learning. Powered by Cognero.

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Chapter 15 c. compete; tolerate strong tides d. tolerate harsh dry conditions; colonize deeper water ANSWER: b 34. In Connell's experiment with upper and lower intertidal barnacles, the rock barnacle excluded the Poli's stellate barnacle from deeper water because a. it was the better competitor for a limiting nutrient at that depth. b. intraspecific competition was stronger than interspecific competition. c. it could survive for long periods underwater. d. it grew faster and pushed the stellate barnacle off the rock substrate.

ANSWER: d 35. Connell's research on competition between the rock barnacle and Poli's stellate barnacle in upper and lower intertidal zones is an example of a. a manipulative experiment. b. a long-term observational study. c. how predation determines the superior competitor. d. how colonization determines where species live in an intertidal zone.

ANSWER: a 36. In the example of competition dynamics with longleaf pine (Pinus palustris) and other woody plants, fire suppression a. caused increases in important herbivore predators of longleaf pine. b. allowed the persistence of superior competing species that would otherwise be eliminated by fire. c. allowed increased growth of wiregrass (Aristida beyrichiana). d. decreased germination of longleaf pine, which requires heat from fire.

ANSWER: b 37. In Morin's competition experiment, ponds contained tadpoles of three species and a species of newt. Newts in increasing numbers were added to ponds containing the tadpoles. How did the number of newts affect competition among tadpoles? a. Predation by newts reversed the outcome of competition between the tadpoles. b. Predation by newts extirpated tadpoles in the ponds. c. Predation by newts had no effect on tadpoles in the ponds. d. Predation by newts equalized tadpole survival between the tadpoles.

ANSWER: a 38. When an individual drives down a resource to a point where another individual cannot persist, it is called a. interference competition. b. allelopathy. c. apparent competition. d. exploitative competition.

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Chapter 15 ANSWER: d 39. When two species interact directly to aggressively defend resources, it is called a. allelopathy. b. exploitative competition. c. interference competition. d. apparent competition.

ANSWER: c 40. When two species compete for soil water, it is called a. exploitative competition. b. interference competition. c. apparent competition. d. allelopathy.

ANSWER: a 41. When long-legged ants plug the nest entrances of red harvester ants with which they compete for seeds, it is called a. allelopathy. b. exploitative competition. c. interference competition. d. apparent competition.

ANSWER: c 42. Researchers have determined that common reed damages roots of other species by secreting gallic acid. This is an example of _____ competition. a. passive b. exploitative c. interference d. apparent ANSWER: c 43. When organisms use chemicals to suppress competitors, it is called a. exploitative competition. b. interference competition. c. apparent competition. d. allelopathy.

ANSWER: d 44. Scientists believe that some species of eucalyptus in Australia promote frequent fires by means of flammable oils in their leaf litter. These fires kill completing plants. What type of competition does this example describe?

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Chapter 15 a. exploitative competition b. allelopathy c. scramble competition d. apparent competition ANSWER: b 45. What type of competition is allelopathy? a. exploitative b. interference c. apparent d. scramble ANSWER: b 46. The research on competition between sage and grasses in California demonstrated that the bare zone surrounding purple sage shrubs (Salvia leucophylla) was due to a. foraging by small mammals and not competition. b. apparent competition. c. exploitative competition. d. interference competition.

ANSWER: a 47. When wolves and coyotes compete, reductions in numbers of coyotes are attributed to a virus the wolves carry that is more harmful in coyotes. This is an example of a. apparent competition. b. exploitative competition. c. interference competition. d. allelopathy.

ANSWER: a 48. The result of a chi-square test gives χ2 = 35.95, χ2 critical = 14.98. What is the conclusion of the analysis? a. null hypothesis retained b. alternative hypothesis not supported c. null hypothesis rejected d. There is not enough information to make a determination.

ANSWER: c 49. In a chi-square test what is the null hypothesis? a. There is no difference between expected and observed. b. Observed and expected are different. c. Observed is greater than expected. d. Observed is less than expected.

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Chapter 15 ANSWER: a 50. According to the competitive exclusion principle, two species limited by the same resource will _____. a. see both species coexist at large population sizes b. see one species persist while the other dies out c. see both species die out d. see both species coexist at small-to-moderate population sizes ANSWER: b 51. To use the Lotka–Volterra model for competition, which of the following information is NOT needed? a. the population sizes of both the competitive species involved b. the intrinsic growth rate of both of the competitive species involved c. the carrying capacities of both of the competitive species involved d. the efficiency of conversion of resources (food items) to offspring for both of the competitive species involved ANSWER: d 52. When looking at a competitive interaction between chipmunks and gray squirrels, you determine the competition coefficient for chipmunks is 0.25. How many chipmunks would need to be added to the chipmunk population to have the same effect as adding one gray squirrel to the gray squirrel population (relative to resource use and carrying capacity)? a. 4 b. 40 c. 25 d. 10 ANSWER: a 53. Which is NOT a possible outcome of the Lotka–Volterra competition model between two species labelled x and y? a. Species x will reach its carrying capacity and species y will go extinct. b. Species y will reach its carrying capacity and species x will go extinct. c. Both species x and y will go extinct. d. Both species x and y will persist at population sizes below their respective carrying capacities.

ANSWER: c 54. A gray squirrel consuming acorns in a forest impacting other species' ability to do the same would be an example of what type of competition? a. exploitative b. interference c. apparent d. aggressive ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 15 55. Black walnut trees (Juglans nigra) produce a chemical called juglone in many parts of the tree, including the roots. In producing the chemical, the tree is able to decrease growth of some plants around the tree (from the trunk outward to the drip line/edge of canopy). This would be an example of what type of competition? a. exploitative b. interference c. apparent d. intraspecific ANSWER: b 56. In the pine bush/pine barrens of the northeastern United States, fire suppression has seen native, firedependent pitch pine trees (Pinus rigida) replaced by black locust (Robinia pseudoacacia). This would be an example of the role that a. allelopathy plays in competition. b. disturbance plays in competition. c. predation plays in competition. d. herbivory plays in competition.

ANSWER: b Essay 57. Organisms often have specific environmental requirements. For example, many organisms can live only within a narrow range of temperatures, nutrient levels, pH, humidity, soil moisture, and soil type. They require specific nesting sites, mates, and prey. Which (if any) of these factors are considered resources? What distinguishes resources from the other environmental factors?

ANSWER: Nutrients, soil moisture, nesting sites, mates, and prey are considered resources because they are consumed. The other factors are environmental but are not consumed.

58. Researchers perform an experiment on a long-lived perennial shrub in a semiarid site where the soil is low in nitrogen. They fertilize the plants with nitrogen, but the treated plants do not increase their growth compared to control plants. What is a reasonable hypothesis for this result?

ANSWER: Although the nitrogen is limiting in this site, something else is likely more limiting than nitrogen.

Water may be the most limiting resource because the site is semi-arid.

59.

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Chapter 15

Compare the outcomes of competition between species 1 and 2 in the above graphs.

ANSWER: In Figure 15.8c, the carrying capacities are outside the zero-growth isoclines for each species, so the species with the largest initial population will outcompete the other species. In Figure 15.8d, the carrying capacities are within the zero-growth isoclines for each species, so the species will coexist.

60. In the experiment in which goldenrod fields were either sprayed with insecticide or left as untreated controls, the treated goldenrod increased growth and shaded out all of the other species. The result was near monocultures of goldenrod in the treated fields compared to the control fields, where the density and height of goldenrod was reduced. What did researchers conclude from this result?

ANSWER: Goldenrod was a superior competitor that shaded out the other plant species, and the goldenrodconsuming insect reversed this competitive outcome.

61. Researchers studying sex ratios among field mice expect to find a 50:50 ratio of males to females. Instead they find 1,120 females and 975 males at their site. Use a chi-square analysis to determine whether the field mouse population at their site significantly differs from a 50:50 sex ratio. Assume a critical chi-square value of 3.841 for  = 0.05 and 1 degree of freedom.

ANSWER: The total population of field mice is 2,095 (1,120 + 975). The expected number of females and males would be 1,047.5 (2,095 ÷ 2).

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Chapter 15 62. You are studying the competitive interactions between two desert plant species, the prickly pear cactus and the ocotillo. During your research, you discover that the ocotillo produces a flower that is preferentially consumed by mule deer, a major desert herbivore. When the deer population is large and has consumed most of the available ocotillo flowers, it eats the flowers of the prickly pear cactus, which reduces the prickly pear's fecundity. Further, you know that the ocotillo and prickly pear compete for water, nutrients, and light. You also discover that the prickly pear secretes a chemical into the soil that inhibits the growth and survival of the ocotillo. For each of these examples of competition between the prickly pear cactus and the ocotillo, name and describe what type of competitive interaction is taking place.

ANSWER: The fact that the mule deer consume prickly pear cacti when their populations outgrow the supply of the ocotillo flower is an example of apparent competition because the negative effect of the ocotillo on the prickly pear is mediated through a shared consumer. The competition for water, nutrients, and light are all examples of exploitation competition because when one species uses these resources, it decreases availability for other species. Finally, the ocotillo being unable to grow in the soil taken from under a prickly pear cactus is an example of interference competition because the prickly pear cactus is secreting allelopathic compounds that directly inhibit the growth or survival of the ocotillo.

63. Researchers studying the effects of hay-scented fern on the recruitment of red maple and sugar maple expected to find that the fern employed interference competition on the tree seedlings by casting shade. What did researchers actually discover when they employed fences to exclude rodents?

ANSWER: Researchers found that the hay-scented fern was a refuge for rodents that preyed on seeds and seedlings of some species and was a case of apparent competition. For other species, the fern directly competed for resources.

64. Describe what researchers have discovered about the invasive species garlic mustard that makes the plant such an effective competitor in the forests of the northeast.

ANSWER: Garlic mustard produces a chemical called sinigrin. Garlic mustard releases sinigrin from its roots where this chemical is toxic to soil fungi. Soil fungi are critically important to native plants as they are instrumental in the native species' ability to obtain minerals from the soil. Without these minerals the native plants do not thrive. Interactions involving allelopathy are examples of interference competition.

65. Species that produce chemicals for whatever reason pay a price. Whether the chemical allows them to be less likely to be taken by a predator or a better competitor, the chemical produced by the organism has a cost that must be accounted for and could have been used for other purposes (i.e., reproduction). Discuss the costs associated with garlic mustard's production of the chemical sinigrin. How should the production of the chemical change as the species residency time in a particular forested area increases? Why would this change in production make sense?

ANSWER: Garlic mustard produces sinigrin, a very effective chemical that is toxic to soil fungi. As a result, native plants find it difficult to thrive in forests where garlic mustard has invaded. Garlic mustard's advantage is quite dramatic as entire forest herbaceous layers can be dominated by garlic mustard and little else. However, the cost to garlic mustard of producing the chemical is substantial. It would make sense from a natural selection perspective that as garlic mustard's tenure in an area increases, individual garlic mustard plants that produce less sinigrin should be selected for. The plant has already achieved a dominant position in the herbaceous layer, so the redundancy associated with increased high levels of sinigrin production would not be necessary.

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Chapter 15 66. Describe the concept of Leibig's law of the minimum and how it relates to the reality of species requirements of multiple resources for population growth.

ANSWER: Leibig's law of the minimum recognizes that multiple resources determine the population growth of a species. That said, however, Leibig suggested that the resource in shortest supply (most scarce relative to demand) will be the resource that determines how large the population will grow irrespective of the quantity of other resources. Once the limiting resource is exhausted, then growth in population size will cease.

67. In the study of the gray partridge and ring-necked pheasant in the United Kingdom, researchers found that gray partridges were declining. A parasitic nematode seemed to negatively affect partridges. The pheasants that carried the parasites were not negatively affected. Researchers performed an experiment in which they allowed both species to feed in one of two enclosures: enclosures with parasite eggs scattered on the floor or enclosures without parasite eggs. The results are shown in the figure. What did the researchers conclude? Was competition occurring, and if so what type?

ANSWER: Although it initially appeared that the two bird species were directly competing for a shared resource, the shared parasite was actually causing the decline of the gray partridge. This is an example of apparent competition.

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Chapter 16 Multiple Choice 1. Consider a species of fig tree that is pollinated by a single species of wasp. Without the wasp, the fig tree will not produce seeds. Without the fig tree, the wasp will not produce offspring. The relationship between these species is an example of a. parasitism. b. obligate mutualism. c. facultative mutualism. d. negative interaction.

ANSWER: b 2. A mutualist that interacts with many other species is a a. generalist. b. specialist. c. mutualist. d. parasite.

ANSWER: a 3. A specialist is a mutualist that a. interacts with many other species. b. interacts with one of a few closely related species. c. provides fitness benefits to another species. d. receives fitness benefits from another species.

ANSWER: b 4. Which of the following are specialists that form a mutualism?

I. Honeybees pollinate many species of flower.

II. The crayfish snake eats only crayfish.

III. The yucca plant is pollinated by a single species of moth. a. I only b. II only c. III only d. I and II only e. II and III only ANSWER: c 5. When two species provide fitness benefits to each other but do not require each other to persist, they are a. obligate mutualists. b. facultative mutualists. c. parasites. d. predators and prey.

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Chapter 16 6. Coral and zooxanthellae algae have a mutualism in which coral provide shelter for algae. What do algae provide for coral? a. reduced fitness b. protection from enemies c. water d. nutrients ANSWER: d 7. Which of the following are benefits that many mutualists provide one another?

I. shelter II. protection from predators III. nutrients a. I only b. I and II only c. I and III only d. II and III only e. I, II, and III ANSWER: e 8. Which of the following statements about the hyphae of ectomycorrhizal fungi are correct?

I. They provide plants with minerals and water from the soil.

II. They obtain sugars that plants produce by photosynthesis.

III. They grow between root cells. a. III only b. I and II only c. I and III only d. II and III only e. I, II, and III ANSWER: e 9. What benefit do Rhizobium bacteria provide to plants that plants cannot provide for themselves? a. a place to live b. products of photosynthesis c. conversion of atmospheric nitrogen to a form that plants can use d. protection from herbivorous mammals ANSWER: c 10. Which of the following three interactions are mutualisms?

I: Wasp and butterfly larvae. The wasp lays its eggs inside the body of a butterfly larva. The eggs hatch and the wasp larvae feed on the body of the butterfly larva. By the time the wasp larvae metamorphose from the butterfly larva, the butterfly larva is killed.

II: Fig and fig wasp: The adult wasps crawl into the cluster of fig flowers to lay eggs. By moving around, the Copyright Macmillan Learning. Powered by Cognero.

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Chapter 16 adult wasp pollinates the fig flowers, allowing them to produce fruit and seeds. As the fig fruit develops, it provides shelter for the wasp larvae.

III: Ants and acacias: Acacia plants develop hollow thorns that provide shelter for ant colonies and produce nectaries on their leaves that provide food for ants. The ants defend the acacia plant from herbivores. a. I only b. II only c. III only d. I and II e. II and III ANSWER: e 11. What benefit do Pseudomyrmex ants obtain from their mutualism with acacia trees?

I. shelter in hollow thorns II. food from nectaries III. nitrogen from atmospheric sources a. I only b. II only c. III only d. I and II only e. II and III only ANSWER: d 12. If you removed mutualistic ants from acacia trees, there would be a. fewer herbivorous insects on the acacia. b. more herbivorous insects on the acacia. c. less atmospheric nitrogen available to acacia. d. more atmospheric nitrogen available to acacia.

ANSWER: b

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Two species of ant that live on acacia are Pseudomyrmex ferruginea and P. gracilis. The figure shows how the

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Chapter 16 14. Which of the following benefits do acacia plants obtain from mutualisms with ants?

I. Ants kill herbivorous insects.

II. Ants keep competitive plants from growing nearby.

III. Ants spread antibacterial compounds on the plant. a. I only b. II only c. III only d. I and III only e. I, II, and III ANSWER: e 15. Endophytic fungi a. live within a plant's tissue. b. provide shelter to ants. c. fix atmospheric nitrogen. d. are removed from mammals by oxpecker birds.

ANSWER: a 16. If oxpecker birds went extinct, what would be the most likely consequence? a. Acacia plants would no longer be protected by ants. b. Plants would no longer be able to fix atmospheric nitrogen. c. Large African mammals would have more parasites. d. Large African mammals would have fewer parasites.

ANSWER: c 17. What condition of large mammals do oxpecker birds seek out? a. thin skin b. thick skin c. many parasites d. few parasites ANSWER: c 18.

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A biologist is studying three species of small fish (sp 1, sp 2, and sp 3) that cling to the bodies of bigger fish and consume parasites on the larger fish. She conducts an experiment with three treatments. In each treatment, she removes a different one of the small fish species from a large fish and examines the number offspring produced by the large fish. Which of the following conclusions are supported by the data shown in the figure? a. Species 1 is a mutualist. b. Species 2 is a mutualist. c. Species 3 is a mutualist. d. Species 1 and 2 are mutualists. e. Species 2 and 3 are mutualists.

ANSWER: c 19. You are studying a plant species that has a fungus growing in its roots. You remove the fungus and evaluate what happens to the plant. Which outcome indicates a mutualistic relationship? a. The plant becomes toxic to herbivores. b. There is no change in the toxicity of the plant. c. The plant becomes less toxic to herbivores. d. The plant can acquire atmospheric nitrogen.

ANSWER: c 20. Ants are often observed with aphids, small insects that feed on plants. The ants obtain nutritious nectar from the aphids. A biologist wants to test whether ants and aphids are mutualists. She removes ants from groups of aphids and compares them to controls. Which of the following outcomes is consistent with a mutualistic relationship between ants and aphids? a. Aphids consume more of the plant. b. Plants with aphids produce fewer seeds. c. More aphids are eaten. d. Fewer aphids are eaten.

ANSWER: c 21. The association between bees and flowering plants is a well-known mutualism. What benefit do bees Copyright Macmillan Learning. Powered by Cognero.

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Chapter 16 provide flowering plants? a. Bees spread pollen from one flower to the next. b. Bees lay eggs on the flowers. c. Bees disperse the plant's seeds. d. Bees allow plants to fix nitrogen.

ANSWER: a 22. The association between bees and flowering plants is a well-known mutualism. What benefit do flowers provide bees? a. Parasites are removed during the visits. b. Bees are sheltered from predators in flowers. c. Bees are fertilized by visiting flowers. d. Bees obtain nutrients from the flowers.

ANSWER: d 23. Which of the following statements about the mutualism between the yucca plant and the yucca moth is/are accurate?

I. This is an obligate mutualism.

II. Yucca moth caterpillars eat yucca seeds.

III. Yucca moths pollinate yucca flowers. a. I only b. II only c. III only d. I and III only e. I, II, and III ANSWER: e 24. The yucca moth a. provides shelter to the yucca plant. b. protects the yucca flowers from herbivores. c. improves yucca photosynthesis. d. pollinates yucca flowers.

ANSWER: d 25. Yucca moths typically lay about six eggs in a yucca flower. If a biologist were to experimentally add 12 moth eggs to a yucca flower, what would be the most likely result? a. More seeds would be dispersed by yucca moths. b. The yucca plant would selectively abort that flower. c. The yucca plant would stop fixing nitrogen from the atmosphere. d. The yucca plant would receive more protection from herbivores.

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Chapter 16 27. What benefit do mammals and birds provide to a plant when they eat its fruit? a. They disperse the seeds in the fruit to new areas. b. They allow the seeds to fix atmospheric nitrogen. c. They provide the seeds with defense against herbivores. d. They provide seeds with sugars produced by photosynthesis.

ANSWER: a 28. The seeds of plants are moved to new areas by many animals, including birds, mammals, and insects. What benefit do animals gain from the plant in this mutualism? a. defense against predators b. food c. shelter from the elements d. removal of parasites ANSWER: b 29. Ants have a mutualism with the forest herb trillium. A plant structure known as an elaiosome is part of this mutualism. What does the elaiosome do? a. fixes atmospheric nitrogen b. contains toxins that kill herbivores c. provides proteins and lipids for the ants to eat d. provides shelter for ants to nest in ANSWER: c 30. Whitebark pine seeds are dispersed through a mutualism with Clark's nutcracker birds. If Clark's nutcracker went extinct, what is the most likely immediate outcome for pines? a. increased competition between seedlings and parents b. increased photosynthesis by pines c. reduced pollination of pines d. reduced benefits from mycorrhizal fungi ANSWER: a 31. Imagine that an acacia tree in the ant–plant mutualism is introduced to an island without ants. Over evolutionary time, natural selection from the lack of ants would probably lead to acacia trees that produce a. more nectar. b. less nectar. c. larger seeds. d. smaller seeds.

ANSWER: b 32.

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Chapter 16 33. Which of the following situations is/are likely to cause a mutualistic relationship to change to a parasitic or predatory relationship?

I. A damselfish has no parasites for a cleaner fish to eat.

II. Acacia plants provide nectar to ants living in their thorns.

III. A plant and its mycorrhizal fungi are living in nutrient-rich soil. a. I only b. II only c. III only d. I and II only e. I and III ANSWER: e 34. In the interaction between damselfish and cleaner fish, if a damselfish has few parasites, the cleaner fish will a. add parasites. b. ignore the damselfish. c. feed on parts of the damselfish. d. not change its behavior toward the damselfish.

ANSWER: c 35. If yucca plants did not selectively abort flowers with many yucca moth eggs, over several generations the frequency of moths that lay many eggs will likely a. increase. b. not change. c. decrease. d. fluctuate.

ANSWER: a 36. When two species have evolved a mutualistic relationship, if one species begins to provide less of a benefit, we predict that the other species will a. evolve to provide more of a benefit. b. not change the benefit it provides. c. evolve to provide less of a benefit. d. increase its population size.

ANSWER: c 37. In the mutualism between ants and trillium flowers, if the trillium stopped producing the elaiosome on its seeds, the ants would probably a. discard the seeds near their nest. b. not carry the seeds to their nest. c. protect the seeds from herbivores. d. pollinate the trillium flowers.

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Chapter 16 ANSWER: b 38. Which would be a reason to use a Mann-Whitney rank sum test rather than a t-test to compare two groups? a. You are measuring fish. b. Your data are normally distributed. c. Your data are not normally distributed. d. Your data can be arranged in ranks.

ANSWER: c 39. Garlic mustard is a plant that has been introduced to North America. It produces a chemical that kills mycorrhizal fungi in the forest where it grows. How would killing mycorrhizal fungi affect native trees in the forest? a. Tree seeds will not be dispersed. b. Tree flowers will not be pollinated. c. Trees will be more vulnerable to herbivores. d. Tree growth will be reduced.

ANSWER: d 40. If cleaner fish went extinct, damselfish would a. become more abundant. b. carry more parasites. c. be less susceptible to predators. d. be healthier.

ANSWER: b 41. If Rhizobium bacteria were to go extinct, most plants would a. not be able to obtain atmospheric nitrogen. b. be more damaged by herbivory. c. not be able to obtain energy from photosynthesis. d. not be able to survive drought.

ANSWER: a 42. Of the following types of mutualisms, which would likely have the largest impact on other species if one member of the mutualism went extinct? a. generalist obligate b. generalist facultative c. specialist obligate d. specialist facultative ANSWER: c

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Chapter 16 Researchers manipulated the number of species of mycorrhizal fungi living in the soil and measured the effects on plant biomass and phosphorus uptake. Their results are shown in the figure. Based on their results, the most likely way the extinction of mycorrhizal fungi species would affect the ecosystem is to a. reduce plant growth. b. increase plant growth. c. reduce plant extinction. d. increase plant extinction.

ANSWER: a

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Chapter 16 45.

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Chapter 16 46. Ants are often associated with aphids, small insects that feed on plants. The ants obtain nutritious honeydew from the aphids, and in return the ants protect the aphids from predatory insects. If the mutualism between aphids and ants broke down such that the ants no longer protected the aphids, a. aphids would produce more honeydew. b. aphids would have higher fitness. c. plants would be damaged more by the aphids. d. plants would be damaged less by the aphids.

ANSWER: d 47. Several animal species have gone extinct on the islands of Mauritius. These extinct animals, including the dodo bird and tortoises, once ate the fruit of many plant species. As a result of the extinction of these animals, I. the flowers of the plants can no longer be pollinated.

II. the parental plants are strongly competing with their offspring.

III. many plants are growing together in tight groups instead of being spread over the island. a. I only b. II only c. III only d. I and III only e. II and III only ANSWER: e 48. Biologists have recently introduced wild turkeys and Aldabra tortoises to the islands of Mauritius. How have these introductions affected native plants of Mauritius? a. Plants are now growing more closely together. b. Plants are being damaged by herbivory from turkeys and tortoises. c. The seeds have better rates of germination. d. Plant diseases have become more common.

ANSWER: c 49. Under which circumstance do we tend to NOT see mutualism? a. between animal species only b. between plant species only c. between plants and fungi d. between plants and bacteria ANSWER: b 50. Why is the relationship between termites and the gut protozoans considered mutualism? a. Protozoans fix nitrogen from the atmosphere for the termites to use. b. Termites defecate into holes in wood and the protozoans in the fecal material are provided a safe area to live. c. Protozoans are able to photosynthesize, providing energy to termites.

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Chapter 16 d. Protozoans are able to break down the lignin and cellulose that compose wood.

ANSWER: d 51. Plants like beans, peas, and alfalfa (legumes) form a mutualistic relationship with a. fungi. b. bacteria. c. ants. d. protozoans.

ANSWER: b 52. The difference between ectomycorrhizal fungi and endomycorrhizal fungi has to do with a. whether the fungal hyphae are connected to the plant above ground or below ground. b. whether the fungal hyphae of the fungi penetrate the root cells of the plants involved. c. whether the fungal hyphae provide the plant with minerals or sugars. d. whether the fungal hyphae are specific to a single plant or generalized to many plants.

ANSWER: b 53. A plant may defend itself from herbivores through mutualism with fungi that produce chemicals that can repel insect herbivores. These fungi are called a. endophytic fungi. b. arbuscular mycorrhizal fungi. c. ectomycorrhizal fungi. d. endomycorrhizal fungi.

ANSWER: a 54. Studies have shown that the herbaceous plant garlic mustard can impact forest growth of certain tree species. How does garlic mustard impact tree growth? a. by decreasing water uptake from the soil b. by shading seedlings and saplings in the herbaceous layer c. by preventing seed germination d. by disrupting the colonization of mycorrhizal fungi in the soil ANSWER: d 55. In the classic work of Dan Janzen and acacia trees, Janzen supported his contention that ants were critical to the survival and growth of acacia trees with a variety of data and observations. Which of the following was NOT evidence of Janzen's contention? a. Trees with ants had fewer herbaceous insects as compared to trees without ants. b. Trees with ants tend to be heavier than trees without ants. c. Trees with ants produced more flowers that lasted longer than trees without ants. d. Trees with ants had higher comparative survival rates than trees without ants.

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Chapter 16 Essay 56. A gardener grows pea plants in two pots. One pot has a low amount of ammonia in the soil, while the other pot has normal levels of ammonia. Which group of pea plants would benefit the most from the addition of Rhizobium bacteria to the soil? Explain your answer.

ANSWER: The pea plants in the pot with low levels of ammonia would most benefit from the addition of Rhizobium bacteria. Nitrogen is an important plant nutrient, and plants cannot get it from the atmosphere. Plants obtain nitrogen from ammonia in the soil. Rhizobium can convert atmospheric nitrogen into a form that plants can use, and so adding Rhizobium will most benefit the plant in the pot with limited nitrogen.

57. Cattle egrets are birds that often follow herds of mammals. As the mammals walk through vegetation, insects fly into the air, where the egrets catch them. Is the relationship between cattle egrets and mammals a mutualism? Explain your answer.

ANSWER: This is not a mutualism. In a mutualism, both partners receive fitness benefits. The cattle egrets receive a fitness benefit from mammals by eating the insects the mammals startle. However, based on the description, there is no fitness benefit for the mammals. For this to be a mutualism, the mammals would also have to receive a fitness benefit from the cattle egrets.

58. A group of biologists are studying an interaction between coral and three species of crab (crab 1, crab 2, and crab 3). They discover that all three species of crab benefit from coral by feeding on lipid-rich coral mucus.

They conduct an experiment in which they remove each species of crab from the coral and then measure the extent to which the coral were overgrown by noxious algae. Based on the data in the figure, explain whether or not each of the three crab species is a mutualist with coral.

ANSWER: To be a mutualist, the crab species must confer a fitness benefit to the coral. Crab 1 is not a mutualist, because when crab 1 is removed, the coral becomes less overgrown by the algae. This suggests that crab 1 actually harms the coral. Crab 2 is a mutualist, because when it is removed, the algae overgrow the coral. This result indicates that crab 2 is preventing the algae from growing over the coral. Crab 3 is not a mutualist, because when it is removed, there is no change in the extent to which the algae grow over the coral. This suggests that crab 3 neither harms nor benefits the coral.

59. Oxpeckers are African birds that fly around large mammals and pick at both ticks and wounds on the Copyright Macmillan Learning. Powered by Cognero.

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Chapter 16 animals. Scientists have debated whether oxpeckers are parasites or mutualists with large mammals. Draw bar graphs in the blank figures to show the relationships if oxpeckers are mutualists with large mammals. Plot a should show the abundance of ticks on large mammals in two conditions: if oxpeckers are present and if oxpeckers are absent. Plot b should show the number of offspring produced by oxpeckers if they are nesting near mammals with many ticks or nesting near mammals with few ticks. Explain why your drawings are consistent with mutualism.

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ANSWER: Mutualisms are positive interactions between two species in which each species receives benefits.

The figures show that mammals benefit from oxpeckers by having fewer parasites when oxpeckers are present. Oxpeckers benefit by having more offspring when there are mammals with many ticks present. Thus, the graphs show the two species benefiting from each other's presence. (Graphs should show a qualitative pattern, but do not have to match numbers in the answer.)

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60. In the interaction between yucca plants and yucca moths, yucca moths pollinate flowers and lay eggs in the flowers. If many eggs are laid in a flower, the yucca moth caterpillar will eat all the seeds. Explain why the relationship is considered a mutualism, even though the caterpillars eat the seeds. Be sure to discuss how both the yucca and yucca moth gain fitness benefits from this interaction.

ANSWER: The yucca gain the benefit of having their flowers pollinated, while the moths gain nectar from the flowers and food for their caterpillars. To prevent the costs of caterpillar seed consumption becoming greater than the benefit of pollination, the yucca plant selectively aborts flowers with too many eggs. This exerts natural selection against moths that lay too many eggs on the flowers.

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Chapter 16 61. Many animals disperse seeds away from parent plants. What benefits do animals gain from this mutualism?

Give a specific example.

ANSWER: Animals typically obtain food resources as the benefit for dispersing seeds. An example of this is the elaiosome on trillium seeds. Ants collect trillium seeds to consume the nutrients in the elaiosome and then leave the seeds near their nests.

62. A small forest herb does not normally develop nectaries. However, when herbivorous insects attack it, the herb develops nectaries that attract ants to the plant. Explain why this plant develops nectaries only when attacked by herbivorous insects.

ANSWER: Mutualisms require two species to gain a fitness advantage. To produce nectaries, the plant expends energy that otherwise could be used to make seeds or otherwise improve the plant's fitness. Thus, there is no benefit to producing the nectaries when there are no herbivores. But when the plant is attacked by herbivores, it gains a benefit by attracting ants that will kill or drive off the herbivores.

The ants drive off the herbivores to gain the fitness benefit that comes from nutrients from the plant's nectaries.

63. A shrub species lives in low-nutrient soil that contains mycorrhizal fungi. The plant provides sugars from photosynthesis to the fungi. The fungi provide the plants with nitrogen and phosphorus. If you add enough nitrogen and phosphorus fertilizer to the soil so that the plant can maximize its reproductive success without nutrients from the fungi, would you expect the mutualism to change? Why or why not?

ANSWER: In mutualisms, each partner provides fitness benefits to the other. The addition of the nutrients to the soil changes the situation so that the plant no longer needs the fungus to obtain nutrients. By providing sugars to the fungus, the plant incurs a cost—for example, giving up sugars to the fungus that could be used to grow flowers—while no longer gaining a benefit. For this reason, we would expect the plant to stop providing sugars to the fungi.

64. Consider a simple food web consisting of plants, aphids, ants, and ladybird beetles. Aphids are herbivores that consume the plants, and ladybird beetles are a predator that eats aphids. The ants obtain nutritious honeydew from the aphids, and in return the ants protect the aphids from predatory insects. What is likely to happen to the ladybird beetles, aphids, and plants if the ants go extinct?

ANSWER: Since the ants no longer defend the aphids, the ladybird beetles will consume more aphids, and the ladybird population will increase. Because more aphids are being consumed, the numbers of aphids will decrease. The decrease in the number of aphids will lead to less damage to the plants, and consequently plant fitness will increase.

65. In Palmer's experimental manipulation of large herbivore abundance on acacia trees, he found that exclusion of large herbivores often caused the ant species Crematogaster mimosa to abandon acacia trees and the ant species C. sjostedti to move into acacia trees. What were the effects of the shift from C. mimosa to C. sjostedti on the acacia trees?

ANSWER: The presence of C. sjostedti allows beetles to live on the acacia and bore holes into its trunk. Acacia trees with beetles die more quickly than those without beetles.

66. Some mutualists are said to be generalists, while other mutualists are said to be specialists. Discuss the advantages and disadvantages of being a generalist versus a specialist.

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Chapter 16 with generalizing or specializing. A specialized mutualist can be "guaranteed" a payoff by evolving a specific relationship with another species to the exclusion of all other species (less competition). A generalized mutualist can "hedge one’s bets" should environmental or demographic stochasticity lead to decreases in the population size of a species with which it has a mutualistic relationship.

67. How is facultative mutualism different from the relationship known as commensalism?

ANSWER: Facultative mutualism is the interaction between two species where both species receive a fitness benefit from the interaction. However, facultative mutualism is not a requirement for either of the species involved. In other words, neither species lives depend on the interaction. Commensalism is the interaction between two species where one of the participating species receives a fitness benefit from the interaction, while the other participating species receives neither a benefit nor is harmed by the interaction (the second species is thought to be neutral relative to fitness).

68. Describe why the relationship between the pitcher plant (Nepenthes lowii) on the island of Borneo and the mountain tree shrew is considered to be an example of mutualism.

ANSWER: The pitcher plant provides nectar to the mountain tree shrew. By visiting the pitcher plant the mountain tree shrew benefits by acquiring the energy-rich nectar. In acquiring the nectar from the pitcher plant, the mountain tree shrew must position itself so that its posterior is directly above the pitcher plant's opening. As the mountain tree shrew feeds, it defecates into the opening of the pitcher plant, depositing nitrogen-rich fecal material that the pitcher plant can use since it is growing in an area where insect visitation to pitcher plants is at a minimum. The mountain tree shrew acquires nectar and the pitcher plant acquires nitrogen, a win-win for both species, hence mutualism.

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Chapter 17 Multiple Choice 1. How does an ecologist determine the presence of an ecotone? a. Measure the abundance of plant species over space and abrupt changes in species composition. b. Perform controlled crosses among all plant species within a community to determine the extent to which the species are reproductively isolated. c. Measure microclimate and soil variables for abrupt changes. d. Measure elevation, since many environmental and ecological variables change with elevation.

ANSWER: a 2.

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Chapter 17 6. Based on the data that follow, which of the following statements is FALSE? Seagrass Habitat African Plains Australian Grassland Species N Species N Species N green turtle 3,000 wildebeest 1,000 red kangaroo 1,000 dugong 2,990 zebra 200 wallaby 20 hartebeest 250 walleroo 2 rhino 18 wombat 2 gazelle 2,000 gray kangaroo 6 a. The seagrass habitat has the lowest species richness. b. The African plains and Australian grasslands have identical species richness. c. The rank abundance curves for the African plains and Australian grasslands data would have the same shape. d. The Australian grasslands have lower species evenness than the African plains. e. The seagrass habitat has the highest species evenness.

ANSWER: c 7. Communities with _____ species are _____ stable. a. few; more b. few; consistently c. many; more d. many; consistently ANSWER: c 8. What community measure does Shannon's index quantify? a. the number of species b. relative abundance of species c. species richness d. species diversity ANSWER: d 9.

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The plot shows that most species in this community are a. moderately abundant. b. very rare. c. very abundant. d. about evenly distributed.

ANSWER: a 10.

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What would be the most likely species richness–productivity relationship for a community in which the species were not resource limited? a. U-shaped b. negative c. none d. positive e. hump-shaped ANSWER: b 11.

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What species richness–productivity relationship has the Park Grass Experiment in England demonstrated over the past 150 years? a. U-shaped b. negative c. none d. positive e. hump-shaped ANSWER: b 12. How would adding resources such as fertilizer to an area affect the species in a community? a. It would reduce richness. b. It would increase richness. c. It would increase the abundance of all species. d. It would reduce the abundance of all species.

ANSWER: a 13.

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Chapter 17 According to the experimental results shown in the figure, what factor best explains the reduction in plant species richness with addition of fertilizer? a. inhibition of photosynthesis b. intolerance to fertilizer c. competition for light d. interaction of fertilizer and light ANSWER: c 14.

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Chapter 17 What is a reasonable explanation of the results in the figure? a. The plants are light limited. b. Plants that competed more successfully with additional fertilizer shaded out other plants. c. Plant growth is best supported by addition of fertilizer and light. d. Addition of fertilizer reduces plants' ability to use light efficiently for photosynthesis.

ANSWER: b 15. What is the relation between habitat diversity and species diversity? a. decrease with altitude b. hump shape c. positive d. negative if many invasive species are present ANSWER: c 16. Which is an example of an ecosystem engineer? a. beavers, which build dams on streams b. termites, which build very large hives and eat the wood in buildings c. bees, which pollinate many types of flowers and crops d. zebra mussels, which clog water intake structures ANSWER: a 17. Keystone species a. have the most biomass in a community. b. are usually top predators. c. can affect community structure regardless of population size. d. are invasive predator species that eat native herbivores.

ANSWER: c 18. Keystone species that are predators in a food web can increase species diversity by a. increasing the biomass of primary producers. b. removing competitive dominants. c. creating an intermediate disturbance. d. increasing production efficiency.

ANSWER: b 19. Carbon dioxide with radioactive carbon was bubbled into an illuminated aquarium containing unfiltered pond water. In what order will radioactivity appear in various organisms in the aquarium? a. herbivores, carnivores, producers b. producers, herbivores, carnivores c. producers, carnivores, herbivores d. herbivores, producers, carnivores Copyright Macmillan Learning. Powered by Cognero.

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Chapter 17 e. All organisms will take up radioactive carbon simultaneously.

ANSWER: b 20. A researcher removed predatory starfish from sections of intertidal rock and found that the number of prey species decreased by 50 percent relative to control plots within a short time. This indicates that a. predators compete with prey for space. b. predator species are competing for prey. c. starfish predation increases prey diversity. d. starfish predation reduces prey diversity.

ANSWER: c 21. You have been keeping a list of the bird species that frequent your property. At the end of the year you have tallied eight seedeaters, one nectar sipper, three woodpeckers, six insectivores, two frugivores, four predators, and one carrion feeder. You have organized your tally according to a. habitat. b. community. c. population. d. guild.

ANSWER: d 22. Which is an example of a trait-mediated indirect effect? a. A predator causes a consumer to change its foraging pattern, affecting the amount of food consumed. b. Predators consume most of their main prey, then switch to omnivory. c. Herbivores migrate in and out of communities depending on perceived predation risk. d. Herbivores consume vegetation, which reduces hiding places for predators stalking their prey.

ANSWER: a 23. A trophic cascade is an example of a(n) _____ effect. a. direct b. indirect c. ecotone d. disturbance ANSWER: b 24. When Hairston, Smith, and Slobodkin suggested that Earth is green because carnivores depress the populations of herbivores that would otherwise consume most vegetation, they were focusing on _____ control of community structure. a. top-down b. bottom-up ANSWER: a 25. What is a major distinction between direct and indirect effects in a community?

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Chapter 17 a. Indirect effects always include a resource such as water or light; direct effects do not. b. Direct effects result in competitive exclusion; indirect effects do not. c. Direct effects occur between species in different trophic levels; indirect effects include species from the same trophic level. d. Indirect effects always include more than two species; direct effects do not.

ANSWER: d 26. Which of the following is NOT an example of a trait-mediated indirect effect? a. The presence of raptors causes squirrels to forage at night instead of during the day. b. Greater numbers of aspen trees grow in areas where predation risk from wolves prevents elk from browsing. c. Grasses increase because the presence of spiders has reduced grasshopper foraging. d. Zooplankton abundance in a pond increases because piscivorous largemouth bass cause small fish (zooplanktivores) to take refuge in pond margins away from zooplankton.

ANSWER: a 27.

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Chapter 17 28. What most accurately describes a trophic cascade? a. bottom-up effects b. top-down effects c. found in waterfall habitats d. is based on two trophic levels ANSWER: b 29.

What organisms in the figure appear NOT to be indirectly affected by insecticide? a. zooplankton b. tadpoles c. phytoplankton d. periphyton ANSWER: a 30. Which of the following statements would NOT be true about the species relationship in the figure?

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Chapter 17 31. What is the suggested mechanism by which the presence of insecticide influences phytoplankton abundance?

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Chapter 17 32. In hiking up a mountain you are likely to pass through various community types as you proceed from the low-elevation lands to the summit. This change in community is called a. succession. b. zonation. c. trophic cascade. d. bottom-up control.

ANSWER: b 33. In hiking up a mountain you are likely to pass through various community types as you proceed from the low-elevation lands to the summit. As you proceed from one community type to another, a boundary between community types, created by changing environmental conditions, will be observed. This boundary area of overlap/blending is termed the _____ and has _____ level of biodiversity as compared to each of the two communities on either side of the boundary area. a. ecotone; a lower b. ecotone; a higher c. transition zone; the same d. transition zone; lower ANSWER: b 34. Whitaker's classic study of trees in the Great Smoky Mountains provided evidence of the fact that a. ecotones are only temporary. b. in a community, as environmental conditions change, all tree species respond in the same manner relative to abundance. c. changes in tree species abundance impacts herbivores. d. when environmental changes occur in a community-specific tree species, abundance values change independently of other trees.

ANSWER: d 35. You are sampling a stream with a net, collecting 100 macroinvertebrates. You have been told the stream has high richness but low evenness. Which of the following collections would best represent the stream if what you were told is true (assume the different macroinvertebrate types noted are all the same species e.g., 20 mayflies are all of the same species)? a. 80 caddisflies, 20 mayflies b. 60 caddisflies, 20 mayflies, 10 stoneflies, 5 damselflies, 4 dobsonflies, 1 cranefly c. 60 caddisflies, 8 mayflies, 8 stoneflies, 8 damselflies, 8 dobsonflies, 8 cranefly d. 60 caddisflies, 37 mayflies, 1 damselflies, 1 dobsonflies, 1cranefly ANSWER: b 36. You are sampling a stream with a net, collecting 100 macroinvertebrates. Your collection is as follows (assume the different macroinvertebrate types noted are all the same species e.g., 17 mayflies are all of the same species): 5 caddisflies, 17 mayflies, 48 stoneflies, 6 dragonflies, 10 damselflies, 4 alderflies, 2 dobsonflies, 2 midges, 3 Copyright Macmillan Learning. Powered by Cognero.

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Chapter 17 crayfish, 1 aquatic sowbug, 1 water penny, 1 cranefly If you were to take this data and construct a rank abundance curve, what would it look like? a. a straight line sloped upward b. a straight line sloped downward c. a curve that starts off relatively level on the left side and curving steeply upward on the right d. a curve initially very steeply downward on the left side and leveling off on the right ANSWER: d 37. The variable (pi) used in the Shannon’s Diversity Index (or Shannon-Wiener Index) is a. the number of trophic levels in the food web under study. b. the number of connections between species in the food web under study. c. the relative abundance value for each of the species in the community under study. d. the relative evenness value for each of the species in the community under study.

ANSWER: c 38. Shannon's index and Simpson's index are both measurements of a community's level of diversity. What does it mean when, after calculating these two indices for a given community, the results show the Simpson's index = 1, while the Shannon's index = 0? a. Something is in error with one of the calculations. b. The community’s diversity level is so high that the values are inconsistent. c. The community has no diversity. d. The community is in transition from low to high diversity ANSWER: c Essay 39. What, in addition to tolerance to soil characteristics, might account for the distribution of plant species over different soil types?

ANSWER: The distribution could be due to relative competitive ability in different soil types. Competitive ability could be tested with experiments in which species are grown in the presence and absence of each other across different soil types.

40. Briefly describe an experiment to test whether species are independent or interdependent on each other for existence.

ANSWER: Species removal experiments. If one species does not respond to the removal of another species (e.g., a decline in the community in population size or overall presence), then they are regarded as independent in their local distribution.

41. What particular type of environmental conditions favor independent or interdependent communities?

ANSWER: Communities in harsh environmental conditions appear to support interdependent species distributions/communities.

42. How would sampling the same community with much less effort affect the shape of the plot?

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Chapter 17 ANSWER: Lower sampling effort would remove or reduce the data representing very rare species that would only be likely to be detected with a high degree of sampling effort or time.

43. How can predation increase prey species richness and evenness in a community?

ANSWER: Predators are likely to select the most abundant prey species. Abundant prey are typically competitively dominant. Reducing the abundance of dominant prey species allows more species to establish and existing species to increase in abundance.

44. Using the figure that follows, compare species richness and evenness.

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Chapter 17 45. What population trait allows a species to have high resilience to disturbance?

ANSWER: r-Selected populations would be able to recover quickly from disturbance by using good colonization ability and fast population growth rate.

46. Consider invertebrates such as starfish and mussels on a rocky intertidal habitat where tidal cycles cause the animals to move between exposure and submersion. Are these changing conditions considered a disturbance?

ANSWER: This is not a disturbance, since it is a regular and predictable cycle to which the community members are adapted.

47. Why are keystone species important in food webs?

ANSWER: Their presence or absence can dramatically alter the direct and indirect trophic interactions among species, thus altering the major types of food web connections.

48. Explain what the intermediate disturbance hypothesis predicts for the comparison of species richness in forests where fires have been suppressed versus those with unsuppressed natural fire.

ANSWER: The intermediate disturbance hypothesis predicts that species richness will be higher in forests with fires.

49. Explain whether species would be limited more by resources or interspecific interactions in tropical rainforests (low latitude) or taiga (high latitude).

ANSWER: Tropical rainforests have abundant light, heat, and water compared with taiga biomes. Species richness is much lower at high latitudes, which is thought to be primarily because relatively few species can tolerate cold, dark, and dry conditions. So species richness in high-latitude biomes is likely to be limited by resources, whereas species richness in tropical rainforests is more likely to be limited by factors such as predation and competition.

50. What is the difference between a food chain and food web?

ANSWER: A food chain is a linear pathway of consumers through the trophic levels in a food web, which is a complete representation of all of the feeding relationships in a community.

51. How would a relatively high proportion of omnivore species in a food web affect the connectedness of the food web?

ANSWER: Since omnivores can feed at more than one trophic level, such a food web would have relatively high connectedness (number of trophic connections per number of species).

52. What can we learn about the roles of species in a community from food web structure alone?

ANSWER: A food web would allow for identification of species as producers, primary consumers, and higher trophic levels. It would also indicate the potential for competition between species that consume similar prey species.

53. Hairston, Smith, and Slobodkin suggested that Earth is green because carnivores depress the populations of herbivores that would otherwise consume most vegetation. Is this the only possible explanation for the greenness of Earth?

ANSWER: No, the phenomenon could also be due to chemical and structural defenses of plants against herbivory.

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Chapter 17 54. Explain how the second law of thermodynamics limits the number of trophic levels in a food web.

ANSWER: The second law of thermodynamics includes entropy, which states that with each transformation of matter, less usable energy is available. Therefore, little of the energy originally at the base of food webs as plant material is available by the time that energy is transferred up to fifth or higher trophic levels, for example.

55. Explain the relationships that appear to reduce tadpole abundance when insecticide is present, even though insecticide does not directly affect tadpoles.

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Chapter 17 56. Which relationships in the figure indicate top-down control? Which relationships indicate bottom-up control?

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Chapter 17 57. Explain the difference between a trophic level and a guild with an example to illustrate the difference.

ANSWER: A trophic level is a level within a food web representing species that all obtain their energy from the same generalized source. An example would be the primary consumer trophic level in a forest community. All primary consumers (herbivores) obtain their energy from the same generalized source, that being the producers. A guild is a subset of a trophic level and represents a group of species of the same trophic that obtains their energy (feeds on) from similar sources. Within the forest primary consumer trophic level there are many guilds: nectar feeders, leave feeders, seedeaters, and so forth.

58. Explain the shape of the intermediate disturbance hypothesis (IDH) graph. Why does it have the appearance that it does?

ANSWER: The IDH graph's x axis is a continuum from (on the left) infrequent and/or low-intensity disturbances to (on the right) frequent and/or high-intensity disturbances. The y axis is number of species or species richness. The IDH graph shows low species richness when disturbances are infrequent and/or low intensity as well as when disturbances are frequent and/or high intensity. The IDH graph shows the highest species richness at disturbances that are intermediate (in frequency and/or intensity)—hence the name. The reason for the curve's shape is at infrequent/low-intensity levels, species that dominate will be those that fare well in stable environments (species with lower growth rates—k selected). At frequent/high-intensity levels, species that dominate will be those that can deal with high disturbance levels (higher growth rates – r selected). At the intermediate levels of disturbance, both types of species (both r and k selected species) will be present; thus, species richness will reflect that.

59. Describe the difference between what is referred to as a direct effect and an indirect effect of species in a food web.

ANSWER: A direct effect refers to when two species interact and affect the abundance of each other without involving any additional species in a food web. In theory this might include predator–prey relationships, mutualism, interference, competition, and the like. In reality, however, what is likely to happen is that when two species interact in a food web, and because of the interconnectedness of the web, the interaction may impact other species as well. When two species interact and that interaction involves one or more additional species, this is called an indirect effect.

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Chapter 18 Multiple Choice 1. The receding glacier at Glacier Bay in Alaska has been used to study a. competition. b. predation. c. succession. d. nutrient cycling.

ANSWER: c 2. Succession is change in _____ over time. a. species interactions b. species competition c. species composition d. land use ANSWER: c 3. Each stage of community change during succession is called a _____ stage. a. succession b. seral c. serial d. community ANSWER: b 4. A pioneer species is _____ species to arrive at a site. a. the final b. the penultimate c. the most abundant d. the first ANSWER: d 5. Which of the following is a pioneer species? a. annual plants with small, light seeds b. plants with large, heavy seeds c. animals that stay affixed to a substrate, like sea anemones d. animals that tend to stay very close to where they were born ANSWER: a 6. The last seral stage in the process of succession is called the _____ community. a. apex b. baseline c. climax Copyright Macmillan Learning. Powered by Cognero.

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Chapter 18 d. final ANSWER: c 7. A climax community is generally composed of organisms a. that dominate in a given biome. b. that were present throughout succession. c. from surrounding communities. d. that are common.

ANSWER: a 8. Succession is best studied using a. indirect observations. b. chronosequences. c. pollen. d. direct observations.

ANSWER: d 9. To apply the concept of chronosequence, ecologists assume that a. most terrestrial communities go through the same seral stages. b. the layers in pond sediments are stacked from the youngest at the top to the oldest at the bottom. c. older sites and younger sites have undergone the same disturbances. d. wider tree rings represent periods of rapid population growth.

ANSWER: c 10. Succession studied at Glacier Bay, Alaska, and on the island of Krakatau, Indonesia, has been done using a. direct observations. b. indirect observations. c. chronosequences. d. pollen.

ANSWER: a 11. A sequence of communities that exist over time at a given location is a. a transient climax community. b. never found without soil or organic material. c. a chronosequence. d. an example of secondary succession. e. always showing the same sequence in intertidal areas.

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Chapter 18 b. tree rings c. construction of a pond followed by direct observation. d. observation of a chronosequence near the pond ANSWER: a 13. Indirect observations of succession are often done by using a. chronosequences and seral stages. b. seral stages and climax communities. c. climax communities and pollen. d. chronosequences and pollen.

ANSWER: d 14. Why might direct observation of succession be easier in intertidal communities than in terrestrial communities? a. It is easier to see all of the organisms in an intertidal area. b. Facilitation happens less easily in terrestrial communities, which makes it more difficult to see transitions among seral stages. c. There are many more organisms in a forest than in an intertidal area. d. Organisms in an intertidal area have shorter generation times than organisms in terrestrial communities.

ANSWER: d 15. Why were wind- and sea-dispersed seeds the first to colonize and survive on Krakatau? a. The seeds of these plants were more resistant to dry conditions than those of animal-dispersed plants. b. In the early days of colonization, there were no forests to attract animals that could disperse seeds. c. Plants with wind-dispersed seeds were able to survive the volcanic blast better than animal-dispersed plants d. Animal-dispersed plant seeds are more likely to be digested than wind- and sea-dispersed plants.

ANSWER: b 16. The age of pollen grain is determined using a. carbon dating. b. elemental dating. c. chronosequences. d. seral dating.

ANSWER: a 17. When succession was initially observed on the island of Krakatau, plants with _____ seeds dominated. a. animal-dispersed b. wind-dispersed c. sea-dispersed Copyright Macmillan Learning. Powered by Cognero.

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Chapter 18 d. ballistic-dispersed ANSWER: b 18. Primary succession a. begins with soil containing organic matter. b. lasts much longer than secondary succession. c. has rarely occurred in terrestrial environments. d. usually begins with lichens and mosses.

ANSWER: d 19. Development of communities in habitats that are initially devoid of plants and organic soil is known as _____ succession. a. climax b. initial c. secondary d. primary ANSWER: d 20. Over the course of terrestrial succession, what is the general pattern of species richness? a. a constant increase over time b. an increase followed by an abrupt decline c. no change over time d. an increase that plateaus, followed by a slight decline e. a decline followed by an abrupt increase ANSWER: d 21. Secondary succession takes place in habitats that a. are initially devoid of plants and organic soil. b. have some plants following disturbance. c. have some plants following disturbance but do not have organic soil. d. have been disturbed and contain no plants but still contain organic soil.

ANSWER: d 22. Which of the following is NOT an example of a habitat that could undergo primary succession? a. lava flow b. bare bedrock c. tree-fall gap d. sand dune ANSWER: c 23. In primary succession of sand dunes, the first species to colonize are Copyright Macmillan Learning. Powered by Cognero.

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Chapter 18 a. lichens. b. grasses. c. herbs. d. mosses.

ANSWER: b 24. Which of the following habitats could NOT undergo secondary succession? a. mud slide b. bare rock c. clear-cut forest d. abandoned agricultural fields ANSWER: b 25. Why does secondary succession occur faster than primary succession? a. Direct observation of secondary succession is easier than for primary succession. b. Lichens are better able to colonize soil than bare rock. c. Soil in secondary sites can contain plant seeds and roots. d. Primary succession areas get too much sunlight for succession to happen quickly.

ANSWER: c 26. Can you tell what plant seral state you are in by looking at the bird species in a given area? a. yes, because bird species are usually associated with a particular seral stage b. yes, because each bird species eats only a particular type of plant c. no, because some bird species are associated with a number of plant seral stages d. no, because birds eat a wide variety of insects as well ANSWER: c 27. If you were assigned the task of starting a plant community that could thrive on Mars, where there is no soil on the surface, which might be good to bring for the initial colonization? a. alders b. pines c. lichens d. low-growing bushes e. cacti ANSWER: c 28. You observe three beech–maple forests in Indiana that began as ponds. How might you determine whether they all started succession with the same community composition? a. Carbon date the maple and beech trees to see how long they have been living; older trees would suggest a more diverse starting community. b. Calculate the species diversity of lichens found on the trees.

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Chapter 18 c. Try growing different types of pioneer species at each site. d. Sample the soils at each site for pollen and carbon date them to get an estimate of the species that appeared first at the site.

ANSWER: d 29. What is the clearest way to document succession? a. pollen sediments from a pond b. direct observation c. tree rings d. carbon dating of wood ANSWER: b 30. When succession was studied at the Duke Forest in the Piedmont region of North Carolina, how many years did it take for the forest to revert to deciduous climax forest from agricultural field? a. 300 years b. 200 years c. 50 years d. 25 years ANSWER: b 31. Which is true about terrestrial succession? a. Initial conditions do not affect the trajectory of succession. b. Primary and secondary succession result in different climax communities. c. The sequence of seral stages is variable. d. The sequence of seral stages is linear.

ANSWER: c 32. Succession in aquatic environments a. is often faster than succession in terrestrial environments. b. is often slower than succession in terrestrial environments. c. has more seral stages than succession in terrestrial environments. d. never reaches a climax community.

ANSWER: a 33. Succession in intertidal communities is rapid because a. the climax community has only a small number of species. b. the generation time of the dominant species is shorter. c. species easily disperse into the disturbed habitat. d. algae have a very rapid growth rate.

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Chapter 18 34. Why does stream succession rely less on how fast organisms can move themselves than terrestrial succession? a. Most streams are short. b. Water can carry organisms from less-disturbed to more-disturbed sites. c. Most stream organisms are algae. d. Succession happens very slowly in streams.

ANSWER: b 35. Stream succession is rapid because a. disturbed sites receive constant inputs of nutrients via runoff. b. organisms that live in streams have rapid growth rates. c. organisms can move downstream from less-disturbed sites. d. disturbances that occur in stream communities are often not severe.

ANSWER: c 36. Why does succession in intertidal communities tend to happen faster than succession after a disturbance in terrestrial communities? a. The ocean has a higher concentration of organisms than soil. b. There are many more disturbances in the intertidal zones than in terrestrial areas. c. The generation time of dominant species in the intertidal zone is shorter than that of the dominant species in terrestrial habitats. d. The generation time of dominant species in terrestrial habitats is shorter than that of the dominant species in the intertidal zone.

ANSWER: c 37. In the study of stream succession following a major flood event at Sycamore Creek in Arizona, what was the first organism to recolonize the stream? a. fish b. Cladophora c. cyanobacteria d. diatoms ANSWER: d 38. Researchers have recently proposed a new way lake succession can occur. What is one feature of this new model? a. Lake succession is slow and steady. b. Colonization of plants happens from the lakeshore. c. Colonization of plants occurs on the sediments at the lake bottom. d. The production of a peat layer is not necessary in lake succession.

ANSWER: c 39. What role does disturbance play in the recently discovered mechanism of pond succession that isn’t found in Copyright Macmillan Learning. Powered by Cognero.

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Chapter 18 the classical mechanism of succession? a. Droughts lower water levels so that plants can colonize lake sediments. b. Rushing water scours the bottom of the lakes, allowing diatoms to colonize. c. Glaciers scour the land, leaving depressions that can fill up with melting water. d. Peat fires remove the vegetation, allowing secondary succession to proceed.

ANSWER: a 40. Which type of succession would be expected to be the slowest? a. intertidal b. lake c. mountain stream d. canyon stream ANSWER: b 41. What characteristic shared by diatoms and cyanobacteria might make them good colonizers of nutrient-poor habitats? a. They are both extremely tough to eat. b. They are both unicellular. c. They both photosynthesize light to make carbohydrates. d. They both have adaptations that allow them to survive droughts.

ANSWER: c 42. Why must oxygen concentrations remain at low levels for pond succession to occur? a. High oxygen levels would cause succession to run too quickly, leaving no climax community. b. High oxygen levels increase the chance of drought in areas around the pond. c. Low oxygen levels allow for easier colonization of plants at the pond edge. d. Low oxygen levels decrease decomposition rates, resulting in peat production.

ANSWER: d 43. How do herbivores affect the outcome of succession in intertidal zones? a. They alter the abiotic environment with their waste products. b. They forage on particular types of algae, allowing others to dominate. c. They trample algae, allowing sea anemones to colonize. d. They have little effect on the outcome of succession.

ANSWER: b 44.

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Chapter 18

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Chapter 18 These graphs show that succession is associated with a rapid increase in species richness that slows and levels off over time. How might you explain why a graph showing succession with exhibits an initial increase in species richness followed by a decline in species richness over time? a. a disturbance such as fire b. facilitation c. inhibition d. tolerance ANSWER: c 45. Jaccard’s index quantifies a. similarity between communities. b. differences between communities. c. community diversity. d. community species richness.

ANSWER: a 46. What information about species is needed to calculate Jaccard’s index? a. diversity b. growth rate c. those present d. mortality ANSWER: c 47. Which of the following is TRUE about succession? a. Species richness initially decreases with time in aquatic succession. b. Species richness initially increases with time in terrestrial succession. c. Species richness shows no change with time in aquatic succession. d. Species richness shows no change with time in terrestrial succession.

ANSWER: b 48. Which of the following is NOT a trait of a pioneer species? a. many seeds b. shade tolerant c. small seeds d. fast growing ANSWER: b 49. What are the characteristics of plants found immediately after a drought in a pond? a. They have few large seeds. b. They have low root-to-shoot ratios. c. They are large and have high tolerance to shade.

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Chapter 18 d. They have extremely slow growth rates.

ANSWER: b 50. One of the traits common in late-succession plant species is a. small seed size. b. low root-to-shoot ratio. c. fast growth rate. d. few seeds.

ANSWER: d 51. When seeds of early- and late-succession species were raised under low light conditions similar to those found in the understory of a mature forest, researchers found that species with _____ seeds had _____ seedling survivorship in shade. a. small; high b. large; low c. large; high d. There was no relation between seed size and seedling survivorship.

ANSWER: c 52. Why do plants in early seral stages exhibit high levels of tolerance? a. Early plants cannot inhibit the growth of other plants. b. Early plants must deal with harsh conditions, such as fluctuating temperatures. c. Early plants are poor competitors and thus must tolerate other plants. d. Early plants have small and light seeds that germinate well under shade.

ANSWER: b 53. Early-succession species are likely to have a. wind-dispersed seeds. b. high shade tolerance. c. short seed viability. d. large size at maturity.

ANSWER: a 54. Why are there no spruces in the early seral stages of succession at Glacier Bay? a. Spruce seeds are not likely to disperse to the pioneer and low-shrub stages. b. Spruce seedlings are inhibited by the presence of low shrubs. c. Spruce seedlings are not tolerant to the environmental fluctuations in the pioneer stage. d. There are few alder trees in the early seral stages to facilitate spruce establishment.

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Chapter 18 a. wind-dispersed seeds. b. large seeds. c. many seeds. d. fast growth rate.

ANSWER: b 56. When considering the effect of one species on the probability of a second species becoming established, facilitation is_____, inhibition is _____, and tolerance is _____. a. neutral; positive; negative b. positive; neutral; negative c. positive; negative; neutral d. negative; positive; neutral ANSWER: c 57. A mechanism of succession in which the presence of one species increases the probability that a second species can become established is a. facilitation. b. tolerance. c. inhibition. d. priority effect.

ANSWER: a 58. Legumes contain nitrogen-fixing bacteria in their roots that increase soil nitrogen for use by other species.

This is an example of a. inhibition. b. tolerance. c. suppression. d. facilitation.

ANSWER: d 59. Inhibition is a mechanism of succession in which a. the probability that a species can become established depends on the presence of another species. b. the arrival of one species at a site affects the subsequent colonization of other species. c. one species decreases the probability that a second species will become established. d. one species increases the probability that a second species will become established.

ANSWER: c 60. Which of the following is NOT an example of inhibition? a. A species outcompetes another species. b. A species suppresses other species using allelopathy. c. A species casts deep shade to prevent growth of another species.

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Chapter 18 d. A species acts as a nurse plant and increases water available to other species.

ANSWER: d 61. Electrical companies have discovered that dense shrub thickets, once established, can prevent growth of trees under power lines. Which mechanism of succession are these companies using by planting shrubs under power lines? a. facilitation b. inhibition c. tolerance d. shade tolerance ANSWER: b 62. The priority effect occurs when the a. first species to arrive at a site have a greater probability of becoming established than subsequent species. b. first species to arrive at a site have a lower probability of becoming established than subsequent species. c. arrival of one species at a site affects the subsequent colonization of other species. d. arrival of one species at a site improves conditions so there is an increased probability of subsequent species becoming established.

ANSWER: c 63. Garlic mustard (Alliaria petiolata) is a common invasive species in the eastern United States. One mechanism that allows it to dominate in some areas is the production of chemicals that interfere with the ability of other plants to gain nutrients through mutualistic fungi. This mechanism is an example of a. tolerance. b. inhibition. c. the priority effect. d. facilitation.

ANSWER: b 64. _____ is a mechanism of succession in which the probability that a species can establish itself depends on its dispersal ability and its ability to persist under the physical conditions of the environment. a. Facilitation b. Inhibition c. Tolerance d. Resilience ANSWER: c 65. Some of the first species to colonize an area following disturbance have to persevere under inhospitable conditions such as disturbed soils, low soil moisture, and altered nutrient levels. This is an example of a. the priority effect.

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Chapter 18 b. facilitation. c. inhibition. d. tolerance.

ANSWER: d 66. Which mechanisms of succession depend on one species arriving at a site before another species? a. inhibition and tolerance b. facilitation and inhibition c. tolerance and facilitation d. inhibition, facilitation, and tolerance ANSWER: b 67. Why is tolerance a mechanism that can be found in both early and late seral stages? a. Both early and late seral species need to be tolerant to low levels of moisture. b. Both early and late seral species require high temperatures to germinate. c. Early seral species need tolerance of stressful environments, while late seral species need tolerance of deep shade. d. Early seral species are tolerant to insects and late seral species are tolerant to fire.

ANSWER: c 68. Which mechanism of succession is independent of the presence or absence of other species? a. inhibition b. tolerance c. facilitation d. facilitation and tolerance ANSWER: b 69. If a legume inhibits the growth of other plants around it by using noxious chemicals, a. the plant will eventually kill itself with the chemicals. b. nitrogen will build up in the soil over time. c. no birds will come to the area to help distribute the legume’s seeds. d. the legume’s bacteria will die off, killing the plant.

ANSWER: b 70.

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Chapter 18

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Chapter 18 71. Experimental removal of a single species in succession would a. help determine whether that species facilitated the growth of a later-successional species. b. usually have very little effect on succession. c. happen only in the intertidal zones. d. always increase the energy available for climax species.

ANSWER: a 72. In the Sonoran Desert of Arizona, young saguaro cacti often begin life in the shade of mesquite trees; they usually die if they begin life in out in the open. This is an example of a. tolerance. b. facilitation. c. a disturbance. d. inhibition. e. a gap-maintained climax community.

ANSWER: b 73. Plants _____ should be used for initial seeding of abandoned strip mines. a. with few large seeds b. that are adapted to fire c. with high tolerance to shade d. with long seed viability e. with high root-to-shoot ratios ANSWER: d 74. In the study of Oregon intertidal communities, little brown barnacles (Chthamalus dalii) are first to colonize disturbed areas. Over time, the acorn barnacle (Balanus glandula) dominates the community. Which mechanism of succession explains the relationship between the two species of barnacles? a. tolerance b. facilitation c. inhibition d. None of the above ANSWER: c 75. How are floods that remove organic matter on the surface of rocks similar to gaps observed in forests? a. Both scour the landscape clean. b. Both uncover seeds in the soil. c. Both allow early-succession species to colonize. d. Both happen only in climax seral stages.

ANSWER: c 76.

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Chapter 18

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Chapter 18 77. Changes in North American forest climax communities a. never occur. b. can occur but may happen very slowly. c. don’t occur unless there is a gap in the canopy. d. don’t occur unless there is an environmental gradient.

ANSWER: b 78. Why might a forest contain both climax tree species and a few early-succession species? a. Grazers ate most of the grass species in the area. b. Legumes have not established everywhere in the forest. c. Disturbances have produced gaps of intense sunlight. d. Fire has removed most of the understory species.

ANSWER: c 79. In some areas of the western United States, pines are an important part of the climax community. Fires occur at regular intervals in these areas. How could fire maintain these pine populations? a. Fires allow pioneer species like annual grasses to colonize. b. Fires cause gaps in the canopy that allow early-succession species to thrive. c. Fires kill understory species, allowing pine seedlings to thrive. d. Fires make it easier for legumes to colonize, increasing soil nitrogen.

ANSWER: c 80. During succession, communities a. do not change. b. always have a fixed trajectory to the climax stage. c. are always changing. d. are usually shaped by abiotic factors only.

ANSWER: c 81. What kinds of disturbances might change climax communities on the steep slopes of the Rocky Mountains? a. tornados b. avalanches c. snowstorms d. human hunting of bears ANSWER: b 82. Terrestrial primary succession begins with a. lichens and mosses. b. grasses and herbs. c. lichens and grasses.

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Chapter 18 d. mosses and grasses.

ANSWER: a 83. In deciduous forests of Pennsylvania, the climax community used to be composed of large trees of mostly oak, hickory, and tulip poplar, but over time the composition of the understory changed to sugar maple and beech. What was the cause of this shift? a. The original species were infected by a pathogen. b. Sugar maple and beech were facilitated by the original species. c. Deer browsing caused reductions in species that were not browse tolerant. d. The seedlings of the original species were less shade tolerant.

ANSWER: c 84. What causes variation in climax communities over space? a. variation in predators b. shifting biomes c. environmental gradients d. variation in parasites ANSWER: c 85. A climax community that is not persistent is called a _____ climax community. a. shifting b. transient c. variable d. chaotic ANSWER: b 86. Transient climax communities can occur when a site a. undergoes rapid environmental change. b. is frequently disturbed. c. is attacked by a pathogen. d. is colonized by invasive species.

ANSWER: b 87. Which of the following is an example of a transient climax community? a. vernal pool b. wetland c. bog d. intertidal zone ANSWER: a 88. Canopy gaps change local forest composition primarily by increased Copyright Macmillan Learning. Powered by Cognero.

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Chapter 18 a. nutrient supply. b. coarse woody debris. c. light. d. soil moisture.

ANSWER: c 89. When the path of succession is dependent upon which species arrives first, what is this termed? a. priority effect b. inhibition c. facilitation d. tolerance ANSWER: a 90. It is known that as succession progresses from an early seral stage to a later seral stage, not only do the plants change but so too do the animals. A possible reason for this change in animals present may be a. a release of inhibition by plants in later seral stages. b. increased facilitation in earlier seral stages. c. later seral stages tend to have greater spatial heterogeneity than earlier seral stages. d. animals are more likely to be found in older habitat types.

ANSWER: c 91. Three different wildlife management areas (X, Y, and Z) are surveyed for nesting birds. When compared using the Jaccard index of similarity, the results are as follows: Area X and Y – J = 0.6 Area Y and Z – J = 0.2 Area X and Z – J = 0.8 Which two areas are most similar? a. X and Y b. Y and Z c. X and Z d. There is no way of knowing without further information as to which specific species are present.

ANSWER: c 92. Early seral stages of terrestrial succession are dependent upon rates of a. seed dispersal. b. herbivory. c. parasitic invasion. d. predation, particularly as related to seed predators.

ANSWER: a 93. The mechanism of succession in a forest gap (an opening in the canopy caused by a disturbance, i.e., a microburst) would likely be Copyright Macmillan Learning. Powered by Cognero.

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Chapter 18 a. facilitation. b. tolerance. c. inhibition. d. facilitation and inhibition.

ANSWER: b 94. Succession typically progresses from _____ to _____. a. slow-growing species; fast-growing species b. shade-tolerant species; shade-intolerant species c. species that produce few seeds; species that produce many seeds d. species dispersed by the wind; species dispersed by gravity ANSWER: d 95. Why would seed viability be longer with early-successional species versus late-successional species? a. Early-successional species produce fewer seeds. b. Seeds from early-successional plants may not germinate until conditions change after a disturbance. c. Early-successional species’ seeds often are eaten by animals. d. Early-successional species’ seeds are shade tolerant.

ANSWER: b Essay 96. The assumptions behind the valid use of chronosequences are usually not all met. How, then, do researchers establish the most likely scenario of terrestrial succession in a given area?

ANSWER: Because chronosequences by themselves may not be accurate, researchers also use pollen records and direct, long-term studies of the area to establish what succession looked like.

97. As succession progresses, what is similar and what is different among fields, sand dunes, and wetlands in Indiana near Lake Michigan?

ANSWER: Similar: They all end with the same climax community of beech and maple trees. Different: They begin with different pioneering plant species.

98. Typical colonizers in primary succession are mosses and lichens that inhabit bare rock. What colonizers in primary succession do not inhabit bare rock?

ANSWER: Drought-tolerant grasses can colonize dry sand dunes.

99. Describe the process that forms bogs in lakes.

ANSWER: Plants colonize the lake edge and begin to spread across open water along the edge. Under the layer of vegetation is a layer of partially decomposed vegetation called peat. The vegetation continues to grow over the surface of the lake, and the peat layer thickens. Detritus from the peat layer accumulates on the bottom of the basin. Eventually the vegetation covers the surface of the lake and peat sediments fill in the basin to form a bog.

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Chapter 18 100. Researchers studying succession in three forest sites want to determine how similar the forests are in terms of species composition. Using Jaccard’s index, rate the similarity of the three forests (A, B, C). Show your calculations.

Tree Species Acer saccharum Fagus grandifolia Quercus rubra Quercus alba Acer rubrum Prunus serotina Liriodendron tulipifera Carya ovata

Forest A X X X X X X X

Forest B X X

Forest C X X X

X X X X

ANSWER: Forests A and B

Forests A and C

Forests B and C

The two forests that are most similar are A and C, followed by A and B because they have the highest Jaccard’s index. Forests B and C are least similar because they have the lowest Jaccard’s index.

101. Suppose two species of trees are able to colonize an area disturbed by fire. One species typically grows to 5 meters, while the other species tends to stay under 2 meters in height. The two species have seeds of the same shape that are relatively light. Which one is more likely to colonize the disturbed area and why?

ANSWER: The tall species is more likely to colonize because increased height will likely allow light seeds to disperse farther than seeds from a shorter species.

102. How could a priority effect be important in the mechanism of facilitation?

ANSWER: [Many correct answers, as long as one species facilitates the establishment of another species.] If a plant species arrived in an early stage and made the soil ready for the colonization of the next seral stage, you would have a priority effect through facilitation.

103. Early-succession plant species are often shade intolerant, whereas late-succession plant species are often shade tolerant. Why are differences in shade tolerance important in succession?

ANSWER: Early in succession, there is often little plant biomass. Plants that establish are often doing so in relatively strong light. Later in succession, there are established plants that cast a lot of shade. Plants growing in late-succession stages need to tolerate at least some time in low light.

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Chapter 18 104.

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Chapter 18

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Chapter 18 Researchers in Glacier Bay, Alaska, planted Sitka spruce seeds (Picea sitchensis) in four seral stages recovering from deglaciation: pioneer stage (dominated by lichens, mosses, and herbs), low-shrub stage (dominated by Dryas drummondii), alder stage (dominated by Alnus sinuate shrubs), and spruce stage (dominated by P. sitchensis). The researchers originally hypothesized that each seral state facilitates species in the subsequent stage. Do the data shown in the figure support their hypothesis? If so, explain. If not, what would explain the results? What type of succession is this area undergoing?

ANSWER: The data shown do not support the facilitation hypothesis. Although spruce can germinate and grow in seral stages other than the alder stage, the reason it is not present naturally is that spruce seeds do not disperse into the other locations (tolerance). The alder seral stage seemed to inhibit germination and growth of spruce (likely due to shading by the low shrubs). The type of succession occurring after deglaciation is primary succession.

105. How does detritus—dead organic matter—play a role in terrestrial succession?

ANSWER: In the formation of some plant communities from ponds, detritus in the form of peat forms a substrate where terrestrial plants can survive. In chaparral vegetation, thick layers of detritus can accumulate, eventually making the community susceptible to fires. This can keep the climax community free of plants that are not fire tolerant.

106. Why don’t freezing and drying cycles cause primary succession to happen over and over again in vernal pools?

ANSWER: Although most species are killed with these cycles, some organisms can persist in the soil in resting states, which permits secondary succession to occur repeatedly.

107. Why don’t climax species colonize gaps in the forest?

ANSWER: Most climax species do not have the fast growth rates and sun tolerance that early seral-stage plant species exhibit.

108.

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Chapter 18

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Chapter 18 109. Why don’t gaps in a forest canopy always help early-succession species establish?

ANSWER: If the gap is small enough, neighboring trees can close it quickly. This would cause deep shade that early-succession species could not tolerate.

110. Suppose that seeds from large canopy trees land in an area where facilitators made the soil fertile for their germination. What are two factors that might prevent these trees from growing to maturity?

ANSWER: (possible answers based on abiotic factors): 1. too much sunlight to allow shade-tolerant seedlings to thrive 2. too little moisture to support the growth of mature trees 3. disturbances destroying the trees before they reach maturity 111.

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Chapter 18

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Chapter 18 112. How do gaps affect climax communities? Does gap size matter, and why or why not?

ANSWER: When gaps form in climax communities, the change in conditions allows for species from earlier seral stages to grow under the stronger light. This allows for mature climax forest to have a few early-succession trees. Gap size matters. The surrounding canopy trees can quickly fill in a small gap by growing into the space and filling it. In this case, the gap closes, and change to the climax community is minimal. If the gap is large, canopy trees cannot fill in the gap quickly, and increased light will allow early-succession species to grow and alter the climax 113. Describe the difference in seed strategy between early successional and late successional plants.

ANSWER: Early successional plants would likely produce many small seeds that are easily dispersed by the wind or animals. Likewise, early successional plant seeds would have long viability. In contrast, late successional plants would likely produce far fewer seeds that would be larger in size and likely dispersed by gravity or via animal digestion. Seed viability would be much shorter for late successional plants.

114. Describe the difference in seedling strategy between early successional and late successional plants and explain why such a strategy makes sense.

ANSWER: Because early successional abiotic conditions are characterized by full Sun, early successional seedlings would likely have a low root-to-shoot ratio as the seedling grows quickly to take advantage of the ample sunlight at these early seral stages. Likewise, early successional plant seedlings would be small at maturity (investing in reproduction as opposed to mature biomass) and display low shade tolerance as sunlight is abundant. In contrast, late successional seedlings would likely have a high root-to-shoot ratio as the plant grows much slower and invests energy into substantial root growth. Then, size at maturity is larger and the plant ensures that it has the necessary biomass to compete with the early successional species that they will ultimately replace.

Shade tolerance is high as seedlings grow under the canopy of the early successional species.

115. Discuss how the classic explanation of lake/pond succession differs from the new model proposed in 2012.

ANSWER: The classic explanation of lake/pond succession sees the driver of succession being the lateral expansion of plants from the edge of the lake/pond and the slow, gradual, and steady accumulation of dead plant material over time, leading to a thicker peat layer eventually filling in the basin. The new model views the succession process in lakes/ponds as being one that might be more punctuated by intermittent periods of lengthy droughts that allow plants to colonize newly exposed sediment.

When the drought ends, plants released from the bottom of the lake/pond float on the surface of the body of water. Growth and subsequent death of this floating mat of vegetation lead to deposition of organic matter, leading to thicker peat layers eventually filling in the basin.

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Chapter 19 Multiple Choice 1. Why have non-native earthworms caused a decline in salamander populations in North America? a. Earthworms are predators of newly hatched salamanders. b. Earthworms caused reductions in insects that salamanders eat. c. Earthworms disturb soil, which makes it less hospitable to salamanders. d. Earthworms outcompete salamanders for soil nutrients.

ANSWER: b 2. What is the source of most energy that moves through ecosystems? a. oceans b. soil nutrients c. the Sun d. Earth’s core ANSWER: c 3. The rate at which solar or chemical energy is captured and converted to chemical bonds by photosynthesis or chemosynthesis is called a. secondary productivity. b. net primary productivity. c. gross primary productivity. d. primary productivity ANSWER: d 4. What percentage of solar energy is captured by plants for photosynthesis? a. 50 percent b. 1 percent c. 99 percent d. 25 percent ANSWER: b 5. The biomass of producers in a given area of an ecosystem at a particular moment is called a. net primary production. b. ecosystem mass. c. the standing crop. d. the standing harvest.

ANSWER: c 6. Standing crop is determined by _____ productivity. a. net primary b. gross primary Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 c. net secondary d. gross secondary ANSWER: a 7. Net primary productivity is calculated as a. Gross Primary Productivity (or GPP) ÷ respiration. b. GPP × respiration. c. respiration – GPP. d. GPP – respiration.

ANSWER: d 8. What proportion of solar radiation captured by photosynthesis is used for plant growth and reproduction? a. 60 percent b. 80 percent c. 50 percent d. 40 percent ANSWER: d 9. Which of the following units is commonly used to express GPP? a. kJ/m2/y b. kPa/m2/y c. kg/m2/y d. kmol/m2/y ANSWER: a 10. Which of the following factors is NOT used for quantifying primary productivity over time? a. the change in consumer biomass b. the change in producer biomass c. the movement of carbon dioxide d. the movement of oxygen ANSWER: a 11. Measuring the change in biomass from the beginning to the end of the growing season gives an estimate of a. herbivory. b. standing crop. c. gross primary productivity. d. net primary productivity.

ANSWER: d 12. Terrestrial primary productivity can be quantified by measuring the uptake and release of a. carbon dioxide.

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Chapter 19 b. water vapor. c. nitrate. d. methane.

ANSWER: a 13. Which of the following is NOT used to measure primary production? a. uptake and release of O2 b. net movement of 14C c. release of CO2 d. changes in standing crop ANSWER: c 14. Which technique allows measurement of conditions on Earth from a distant location? a. remote sensing b. remote monitoring c. satellite sensing d. satellite monitoring ANSWER: a 15. When an animal eats fruit with hard seeds that cannot be digested and are excreted whole as a waste product, the seeds constitute _____ energy. a. assimilated b. egested c. respired d. kinetic ANSWER: b 16. Energy that an organism uses to add to its biomass is a. egested. b. respired. c. assimilated. d. secondary.

ANSWER: c 17. Which is the portion of energy that an organism uses to maintain its body temperature? a. primary b. secondary c. egested d. respired ANSWER: d Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 18. The rate of consumer biomass accumulation in a given area is called _____ productivity. a. gross secondary b. net secondary c. gross primary d. net primary ANSWER: b 19. Terrestrial secondary productivity is _____ correlated with primary productivity, and aquatic secondary productivity is _____ correlated with primary productivity. a. positively; positively b. positively; negatively c. negatively; negatively d. negatively; positively ANSWER: a 20. NPP varies with _____ around the world. a. elevation b. soil type c. longitude d. latitude ANSWER: d 21. Terrestrial NPP is greatest in _____ ecosystems, and aquatic NPP is greatest in _____ ecosystems. a. tropical; coastal b. tropical; open-water c. polar; tropical d. tropical; tropical ANSWER: a 22. Which of the following ecosystems has the lowest levels of primary productivity? a. desert scrub b. temperate grassland c. savanna d. tundra ANSWER: a 23. Which of the following ecosystems has the highest levels of primary productivity? a. coral reef b. swamp c. lake d. salt marsh Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 ANSWER: b 24. What are the major drivers of NPP? a. fertility and precipitation b. temperature and pH c. temperature and precipitation d. fertility and temperature ANSWER: c 25. Between latitudes of 30° N and 30° S, NPP is primarily constrained by a. temperature. b. fertility. c. pH. d. precipitation.

ANSWER: d 26. Experiments on how soil fertility limits terrestrial NPP demonstrate that _____ constrain(s) NPP. a. nitrogen b. phosphorus c. nitrogen and phosphorus d. micronutrients ANSWER: c 27. What is the primary reason that estuaries and coral reefs are so productive? a. high temperatures due to tropical location b. low levels of herbivory c. high light levels due to shallow waters d. high nutrient levels from runoff ANSWER: d 28. Aquatic NPP is primarily limited by a. fertility. b. light. c. temperature. d. salinity.

ANSWER: b 29. Which of the following is NOT a low-productivity aquatic ecosystem? a. open ocean b. coral reef c. forest stream Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 d. deep ocean ANSWER: b 30. Which of the following is NOT a high-productivity aquatic ecosystem? a. estuary b. coral reef c. salt marsh d. open ocean ANSWER: d 31. In fertilization experiments in a lake in Ontario, which of the following nutrients were shown to have the greatest limitation on productivity? a. nitrogen b. carbon c. phosphorus d. All three nutrients equally limited productivity.

ANSWER: c 32. Compilation of data from many experiments on nutrients and NPP in marine ecosystems shows that ecosystems with hard bottoms are generally limited by _____, while soft-bottomed ecosystems are generally limited by _____. a. nitrogen; phosphorus b. nitrogen; nitrogen and phosphorus c. phosphorus; nitrogen d. phosphorus; nitrogen and phosphorus ANSWER: b 33. In addition to nitrogen and phosphorus, what nutrients can limit productivity in the open ocean? a. silicon and magnesium b. silicon and iron c. manganese and iron d. molybdenum and manganese ANSWER: b 34. Silicon is used primarily by a. zooxanthellae. b. zooplankton. c. diatoms. d. algae.

ANSWER: c 35. Aquatic ecosystems can be limited by silicon because Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 a. there are few silicon organisms in the upper waters. b. many organisms compete for the silicon. c. silicon sinks slower than nitrogen or phosphorus. d. silicon sinks faster than nitrogen or phosphorus.

ANSWER: d 36. Iron is lost from oceans when it combines with _____ and precipitates. a. nitrogen b. silicon c. phosphorus d. carbon ANSWER: c 37. What accounts for the pyramid shape of the diagram that represents energy in trophic groups in an ecosystem? a. Energy produced by consumers is greater than energy stored by producers. b. Energy stored by consumers is greater than energy stored by producers. c. Energy is gained as it moves from one trophic level to the next. d. Energy is lost as it moves from one trophic level to the next.

ANSWER: d 38. In aquatic ecosystems, trophic pyramids of biomass are inverted because a. most biomass is found in the producers. b. the standing biomass of algae is lower than the standing biomass of consumers. c. the life span of producers is very long compared to that of consumers. d. consumers do not rapidly consume producers.

ANSWER: b 39. What is at the top level of a four-level, terrestrial trophic pyramid? a. quaternary consumers b. tertiary consumers c. secondary consumers d. producers ANSWER: b 40. The lowest level in marine trophic pyramids is a. phytoplankton. b. zooplankton. c. pelagic fish. d. periplankton.

ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 41. The percentage of energy or biomass in a trophic level that is consumed by the next higher trophic level is called _____ efficiency. a. consumption b. predation c. assimilation d. net production ANSWER: a 42. Consumption efficiency is calculated as a. consumed energy times net production energy of the next lower trophic level. b. net production energy of the next lower trophic level divided by consumed energy. c. consumed energy divided by net production energy of the next higher trophic level. d. consumed energy divided by net production energy of the next lower trophic level.

ANSWER: d 43. Assimilation energy is the percentage of consumed energy that is a. used for reproduction. b. digested and absorbed. c. used for growth. d. consumed by the next higher trophic level.

ANSWER: b 44. Net production energy divided by assimilation energy is _____ efficiency. a. consumption b. assimilation c. net assimilation d. net production ANSWER: d 45. Ecological efficiency is also called _____ efficiency. a. trophic pyramid b. food chain c. assimilation d. net production ANSWER: b 46. Food chain efficiency is the percentage of _____ from one trophic level compared to the next_____ trophic level. a. net production; higher b. net production; lower Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 c. consumed energy; higher d. consumed energy; lower ANSWER: b 47. As a rule of thumb, ecologists use _____ as a value for food chain efficiency. a. 10 percent b. 25 percent c. 15 percent d. 20 percent ANSWER: a 48. Aquatic ecosystems typically have _____ trophic levels, while terrestrial ecosystems typically have _____ trophic levels. a. two; three b. four; five c. three or four; six d. five; three or four ANSWER: d 49. The average energy residence time is calculated as a. energy in a trophic level times net productivity. b. net productivity times energy in a trophic level. c. energy in a trophic level divided by net productivity. d. net productivity divided by energy present in a trophic level.

ANSWER: c 50. Biomass residence time is the length of time that a. biomass takes to move through the food chain. b. energy takes to move through the food chain. c. energy spends in a given trophic level. d. biomass spends in a given trophic level.

ANSWER: d 51. A trophic level has a biomass residence time of 5 years and net productivity of 3 kg/m2/y. What is the biomass in the trophic level? a. 1.7 kg/m2 b. 15 kg/m2 c. 0.6 kg/m2 d. 2 kg/m2 ANSWER: b Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 52. In which ecosystem does leaf litter have the shortest residence time? a. humid tropical forest b. temperate forest c. dry tropical forest d. boreal forest ANSWER: a 53. The study of the balance of nutrients in ecological interactions is called a. ecosystem ecology. b. ecological stoichiometry. c. chemical ecology. d. stoichiometric biochemistry.

ANSWER: b 54. The decline of red-backed salamanders in some regions of eastern North America appears to be related to a. an increase in non-native earthworms. b. an increase in predatory songbirds like the ovenbird. c. a decrease in forest productivity. d. an increase in forest nutrient cycling by bacteria and fungi.

ANSWER: a 55. What term describes the total mass of trees, shrubs, herbaceous plants, and grasses present in a given forest on a given day? a. NPP, or net primary productivity b. GPP, or gross primary productivity c. primary productivity d. standing crop ANSWER: d 56. Using remote sensing, an ecosystem with high absorption of blue and red wavelengths and high reflectance of green reflectance would likely be found a. in the polar regions. b. in the tropical rainforest. c. in the desert. d. in the open ocean.

ANSWER: b 57. Researchers have found that whales consume approximately _____ of the ocean’s NPP (net primary productivity). a. 88 percent b. 50 percent Copyright Macmillan Learning. Powered by Cognero.

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Chapter 19 c. 12 percent d. 3 percent ANSWER: c 58. The 10 percent ecological efficiency rule of thumb has implications for humans in what way? a. The 10 percent rule can instruct humans as to which systems need the most protection. b. Understanding the 10 percent rule might protect species from extinction. c. Recognizing the 10 percent efficiency rule may provide insight into future human diets on an increasingly populated planet. d. The 10 percent ecological efficiency rule points to the open ocean as a means to increase worldwide food production.

ANSWER: c 59. In terms of NPP (net primary productivity), the most productive terrestrial systems are found in _____, while the most productive aquatic systems are found in _____. a. temperate forests; open ocean b. boreal forest; salt marshes c. savannas; coral reefs d. tropical forests; freshwater marshes ANSWER: d 60. When looking at net production efficiencies, we would likely a. see homeotherms having a higher efficiency than poikilotherms. b. see homeotherms having a lower efficiency than poikilotherms. c. see homeotherms and poikilotherms having the same net production efficiencies. d. not be able to determine since net production efficiencies cannot be quantified for poikilotherms.

ANSWER: b Essay 61. A terrestrial ecosystem has an NPP of 850 g C/m2/y and respiration of 1.25 kg C/m2/y. What is the ecosystem GPP in kilograms per meter squared per second?

ANSWER:

62.

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Chapter 19

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Chapter 19 The figure shows that as mean annual temperature increases, net primary productivity also increases. Net primary productivity increases with mean annual precipitation until approximately 3 meters of precipitation, after which productivity declines. Why does this decline occur?

ANSWER: After about 3 meters of annual precipitation, net primary productivity declines because the high levels of precipitation leach nutrients from the soil. The high levels of precipitation also waterlog soils, which reduces the amount of decomposition. Leaching and reduced decomposition cause a decline in availability of nutrients, which reduces productivity.

63. What nutrient fertilization has been discussed as a way to counteract global warming? How would the nutrient(s) affect global warming, and what are the drawbacks, if any?

ANSWER: Addition of iron may be a way to increase the primary productivity of phytoplankton in marine ecosystems. Phytoplankton populations have been shown to increase with iron fertilization, and increased phytoplankton populations would assimilate more atmospheric carbon dioxide via photosynthesis. Carbon dioxide is a greenhouse gas, so reductions in atmospheric carbon dioxide could counteract global warming. A drawback to this method is that sometimes increases in phytoplankton result in increases in zooplankton, which eat the phytoplankton. Since zooplankton are consumers, increases in their population increase carbon dioxide released to the atmosphere through respiration. This increase in respiration may cancel out the decreases in carbon dioxide from the phytoplankton.

64.

Energy (J) Net production available in lower trophic level Consumed energy Assimilated energy Net production energy

Terrestrial Ecosystem 1,500

Aquatic Ecosystem 1,500

375 260 84

826 550 210

Calculate in joules the four types of ecological efficiencies for the terrestrial and aquatic ecosystems from the table. Which ecosystem is more ecologically efficient?

ANSWER: The aquatic ecosystem is more ecologically efficient.

Calculations: Terrestrial ecosystem

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Chapter 19 Aquatic ecosystem

65. Red abalone (Haliotis rufescens) has a ratio of nitrogen to phosphorus of 45:1. The abalone consumes giant kelp (Macrocystis pyrifera), which has a ratio of nitrogen to phosphorus of 20:1. Would you expect this trophic level to have a high or low ecological efficiency? Why? ANSWER: This trophic level has low ecological efficiency because the abalone must consume more than twice as much kelp to meet its phosphorus requirements as to meet its nitrogen requirements and must excrete excess nitrogen. Since the assimilation of the abalone is low, the ecological efficiency of the trophic level is low.

66. Differentiate between gross primary productivity (GPP) and net primary productivity (NPP).

ANSWER: GPP is the rate at which energy is captured and assimilated by the producers in an area. NPP is the rate of energy that is assimilated by the producers and converted into producer biomass. Thus, the relationship between GPP and NPP can be seen in the following equation: NPP = GPP – respiration.

In this equation respiration refers to the energy that the producer uses itself, which is not available to subsequent trophic levels.

67. Why when measuring primary productivity is O2 uptake perhaps a more reliable technique than CO2 uptake?

ANSWER: Quantifying CO2 changes may be less reliable because CO2 in water may convert into bicarbonate, thus leading to erroneous results.

68. Why do aquatic systems tend to have more trophic levels than terrestrial systems?

ANSWER: In short, the differences in the number of trophic levels between terrestrial and aquatic systems are due to differences in ecological efficiencies. In terrestrial systems, much of the producer trophic level is unavailable for consumption by the herbivores (due to deterrents and unpalatable material— wood). Thus, a large fraction of the producer biomass becomes detritus. In aquatic systems, a larger percentage of the producers are consumed and digested by the herbivores, thus leading to higher efficiencies.

69. Why can plants use only a small portion of the light energy that strikes the surface of a leaf?

ANSWER: Photosynthetic pigments in plant leaves can use energy for photosynthesis only within a narrow band of wavelengths, 1 percent of the visible light spectrum, called the photosynthetically active region. Light energy within this range is absorbed for photosynthesis, and light energy outside this range is either reflected or transmitted.

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Chapter 20 Multiple Choice 1. The large dead zone that forms in the Gulf of Mexico each summer is caused by a. phytoplankton. b. zooplankton. c. algae. d. archaebacteria.

ANSWER: c 2. What is the largest pool of water on Earth? a. wetlands b. underground aquifers c. oceans d. lakes e. glaciers ANSWER: c 3. The energy required for evapotranspiration is provided by a. photosynthesis. b. the Sun. c. wind. d. plant respiration.

ANSWER: b 4. Chose a logical path for a molecule of water starting and ending in the atmosphere. a. precipitation, evaporation, infiltration, condensation b. infiltration, precipitation, condensation, evaporation c. evaporation, infiltration, condensation, precipitation d. precipitation, infiltration, evaporation, condensation ANSWER: d 5. In the hydrologic cycle, infiltration refers to a. water evaporating from the environment and condensing into water vapor. b. plants taking up water from the soil. c. the change of water from a liquid to a gas. d. the change of water from a gas to a liquid. e. water from precipitation becoming part of the groundwater.

ANSWER: e 6. Which statement is TRUE about the global hydrologic cycle? a. Precipitation is greater than evaporation in terrestrial ecosystems.

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Chapter 20 b. Evaporation is greater than precipitation in terrestrial ecosystems. c. Precipitation and evaporation are about equal in terrestrial ecosystems. d. Precipitation exceeds evaporation in aquatic ecosystems. e. Precipitation and evaporation are about equal in aquatic ecosystems.

ANSWER: a 7. In the hydrologic cycle, what is the final destination of liquid water falling on terrestrial environments? a. deep aquifers b. oceans c. lakes, rivers, and streams d. the atmosphere ANSWER: b 8. When terrestrial ecosystems are paved over, for example to construct a parking lot, how is the hydrologic cycle affected? a. Infiltration is decreased and runoff is increased. b. Infiltration is increased and runoff is decreased. c. Evapotranspiration is increased and runoff is decreased. d. Evapotranspiration is increased and precipitation is decreased.

ANSWER: a 9. What are the six types of transformations in the carbon cycle? a. photosynthesis, respiration, combustion, infiltration, sedimentation, burial b. combustion, precipitation, respiration, aeration, photosynthesis, exchange c. respiration, aeration, condensation, photosynthesis, exchange, extraction d. extraction, exchange, respiration, photosynthesis, sedimentation and burial, combustion e. sedimentation and burial, photosynthesis, respiration, exchange, mineralization, combustion ANSWER: d 10. The carbon cycle in ecosystems mostly follows the same paths as the movement of a. water. b. nitrogen. c. phosphorus. d. energy. e. heat.

ANSWER: d 11. In waterlogged conditions, anaerobic metabolism of carbon compounds can cause the production of the greenhouse gas a. hydrogen sulfide (H2S). b. methane (CH4).

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Chapter 20 c. ozone (O3). d. nitrous oxide (N2O). e. carbon dioxide (CO2).

ANSWER: b 12. Which of the following reactions describes how some species of archaea produce carbon dioxide under anaerobic conditions? a. 3 CH3OH  CO2 + 6 H2O + 3 CH4 b. 4 CH3OH  CO2 + 2 H2O + 3 CH4 c. CO2 + H2O + 3 CH4  2 CH3OH d. 3 CH3OH + O2  CO2 + H2O2 + 2 CH4 ANSWER: b 13. Carbon dioxide exchange between the atmosphere and aquatic ecosystems occurs a. unidirectionally from atmosphere to aquatic ecosystems, with net gain to aquatic ecosystems. b. unidirectionally from aquatic ecosystems to the atmosphere, with net gain to the atmosphere. c. bidirectionally, with net gain to aquatic ecosystems. d. bidirectionally and nearly equally. e. bidirectionally, with net gain to the atmosphere.

ANSWER: d 14. Current atmospheric carbon dioxide levels are approximately a. 256 ppm. b. 405 ppm. c. 394 ppm. d. 385 ppm.

ANSWER: b 15. From 1958 to 2017, atmospheric carbon dioxide measurements at Mauna Loa have risen approximately a. 35 percent. b. 10 percent. c. 15 percent. d. 28 percent. e. 55 percent.

ANSWER: d 16. Global climate change is primarily caused by increased levels of _____ in the atmosphere. a. ozone b. carbon dioxide Copyright Macmillan Learning. Powered by Cognero.

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Chapter 20 c. water vapor d. methane ANSWER: b 17. Choose the correct process of nitrogen fixation. a. N2  NO3–  NH3 or NH4+ b. N2  NH3  NH4 + or NO3– c. N2  NH4+  NH3 or NO3– d. NO3–  NH3 or NH4+  N2 e. NH4+ or NO3– ?NH3  N2 ANSWER: b 18. The chemical process NH4+  NO2–  NO3–, is known as a. assimilation. b. mineralization. c. nitrification. d. nitrogen fixation. e. ammonification.

ANSWER: c 19. Nitrogen mineralization is the process by which a. producers take up soil nitrogen and incorporate it into their tissues. b. primary consumers ingest producers in the soil and absorb or excrete nitrogen from their tissues. c. soil microbes produce organic nitrogen compounds from inorganic soil nitrogen. d. soil microbes break down organic nitrogen into inorganic nitrogen. e. nitrogen waste products in the soil are converted to atmospheric nitrogen by soil microbes.

ANSWER: d 20. Denitrification is described by a. NO  N2O  N2. b. N2O  NO  N2. c. NO → N2  N2O. d. N2  NO  N2O. e. N2  N2O  NO. ANSWER: a 21. Denitrification occurs under _____ conditions. a. aerobic Copyright Macmillan Learning. Powered by Cognero.

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Chapter 20 b. anaerobic c. both aerobic and anaerobic d. neither aerobic nor anaerobic ANSWER: b 22. Nitrogen fixation in the soil is carried out by a. anaerobic bacteria. b. aerobic bacteria. c. mycorrhizal fungi. d. cyanobacteria. e. archaebacteria.

ANSWER: d 23. Nitrogen mineralization in the soil is primarily carried out by a. producers. b. consumers. c. decomposers. d. cyanobacteria. e. nitrogen-fixing plants.

ANSWER: c 24. Nitrogen-fixing plants such as soybeans are able to convert a. soil nitrate and ammonium to gaseous nitrogen. b. atmospheric nitrogen to nitrate and ammonium. c. atmospheric nitric oxide to ammonium. d. ammonia gas to nitrate. e. soil ammonium to gaseous nitrogen.

ANSWER: b 25. What is the largest pool of nitrogen in the global nitrogen cycle? a. terrestrial biomass b. oceans c. the atmosphere d. soil ANSWER: c 26. Which is NOT an example of a major human alteration to the global nitrogen cycle? a. animal waste from agriculture b. combustion of fossil fuels c. production of nitrogen fertilizers d. planting of nitrogen-fixing crops Copyright Macmillan Learning. Powered by Cognero.

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Chapter 20 ANSWER: a 27. The burning of fossil fuels affects the nitrogen cycle by increasing atmospheric a. nitrous oxide. b. nitric oxide. c. nitrate. d. ammonia. e. nitrite.

ANSWER: b 28. What form of nitrogen reacts with water in the air to form nitrates that fall to the ground during precipitation? a. nitrous oxide b. ammonia c. nitric acid d. nitric oxide ANSWER: d 29. Where does phosphorus originate in the phosphorus cycle? a. the atmosphere b. ocean sediments c. wastewater d. rocks containing phosphate e. aqueous phosphate ANSWER: d 30. Which of the following is NOT a critical phosphorus-containing structure for organisms? a. bones b. nucleic acids c. ATP d. lipids e. teeth ANSWER: d 31. In what form does phosphorus move through the environment? a. Ca(H2PO4)2 b. H3PO4 c. PO33– d. PO43– e. PH3 Copyright Macmillan Learning. Powered by Cognero.

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Chapter 20 ANSWER: d 32. Phosphatizing bacteria convert phosphorus compounds into a. phosphate ions. b. phosphite ions. c. calcium phosphate. d. phosphoric acid.

ANSWER: a 33. What is the main avenue by which phosphorus returns to the ocean? a. dissolved in rainwater b. surface runoff c. wastewater d. dust ANSWER: b 34. Dead zones are formed when rivers that empty into oceans carry excess phosphorus and nitrate runoff.

These dead zones are caused by a. precipitates of nitrate and phosphorus forming in the water. b. bacterial blooms. c. algal blooms. d. nitrate and phosphorus poisoning. e. increased acidity due to nitrates and phosphorus.

ANSWER: c 35. Weathering is important to the input of a. nitrogen. b. carbon. c. phosphorus. d. water.

ANSWER: c 36. How do terrestrial ecosystems replace nongaseous nutrients lost to leaching and runoff? a. weathering of bedrock b. atmospheric fixation c. precipitation d. decomposition of organic matter ANSWER: a 37. Which organisms are primarily responsible for terrestrial decomposition? a. bacteria and insects Copyright Macmillan Learning. Powered by Cognero.

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Chapter 20 b. fungi and insects c. detritivores and fungi d. bacteria and fungi ANSWER: d 38. Which of the following does NOT significantly affect terrestrial decomposition rates? a. pH b. phosphorus content of litter c. moisture d. temperature ANSWER: b 39. Decomposition is more rapid in _____ forests because of _____. a. temperate; increased temperature and precipitation b. temperate; increased pH and elevated potassium levels c. tropical; increased temperature and precipitation d. tropical; lower nutrient contents and low pH ANSWER: c 40. The leaf decomposition in a tropical forest a. increases with increasing leaf solubility. b. decreases with increasing leaf solubility. c. is unaffected by leaf solubility. d. increases with soil pH. ANSWER: a 41. Leaf litter with a _____ lignin composition should _____ k (the daily rate of mass loss). a. high; increase b. high; decrease c. low; see no change in the value of d. low; decrease ANSWER: b 42. In the study of leaf decomposition in a stream in Germany using leaf litter enclosed in either fine- or largemesh bags, researchers found that decomposition was strongly affected by a. invertebrates and lignin content. b. vertebrates and lignin content. c. nitrogen and phosphorus. d. lignin and phosphorus.

ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 20 43. In aquatic ecosystems, most nutrients regenerate in a. surface waters. b. algal biomass. c. deep waters. d. sediments.

ANSWER: d 44. Stratification of lake waters is due to differences in a. salinity. b. temperature. c. pH. d. nutrients.

ANSWER: b 45. Stratification occurs in all of the following aquatic systems EXCEPT a. temperate oceans. b. tropical streams. c. polar lakes. d. coastal estuaries.

ANSWER: c 46. Where does most decomposition occur in aquatic systems? a. surface waters b. equally throughout the water levels c. sediments d. stream and river banks ANSWER: c 47. In the Hubbard Brook Experimental Forest, researchers found a 90 percent reduction in nitrates leaving the watershed over a 5-year period. To what did they attribute the majority of this reduction? a. changes in species composition b. recovery from past disturbances c. increased soil pH d. climate change ANSWER: b 48. When discussing nutrients within a stream ecosystem, those materials (i.e., leaves and other plant parts) that enter the stream from the surrounding terrestrial environment are termed a. regenerative. b. autochthonous. c. allochthonous.

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Chapter 20 d. biorestorative.

ANSWER: c 49. A summer algal bloom observed in a lake due to excessive agricultural runoff of nutrients would be considered an example of a. cultural eutrophication. b. nutrient cycling. c. biomagnification. d. nutrient precipitation.

ANSWER: a 50. In dead zones, fish species are at risk when the water shows signs of decreased oxygen levels called a. the facilitation threshold. b. hypoxia. c. the photosynthetic minimum. d. the aerobic reduction zone.

ANSWER: b 51. The issue associated with the Ogallala Aquifer is a. the annual dead zones are increasing in size, threatening aquatic life. b. the increase in the amount of human-made toxins entering the aquifer. c. the rate of extraction of the water has exceeded the rate of replenishment. d. the aquifer is seeing a greater infiltration of salt water.

ANSWER: c 52. Potential impacts of an increased atmospheric CO2 level may include all of the following EXCEPT a. altering the length of plant growing seasons. b. reducing the size of the polar ice sheets and glaciers. c. changing the timing of plant and animal life histories. d. increasing the rate of cultural eutrophication.

ANSWER: d 53. When looking at the atmospheric CO2 concentrations collected from ice core layers over the last 500,000 years, what does one see? a. an ever-increasing level of CO2 from 500,000 years before the present (BP) to today b. an ever-decreasing level of CO2 from 500,000 years BP until 150,000 years BP and then a steady rise until today c. a varying level of CO2 from 500,000 years BP to today d. no change in the level of CO2 from 500,000 years BP until just recently (the last 100 years of human history) Copyright Macmillan Learning. Powered by Cognero.

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Chapter 20 ANSWER: c 54. What did researchers find in the 2012 Canadian study of 21 small watersheds in Quebec? a. The rate of weathering changed with the size of the watershed. b. The rate of weathering changed with the age of the watershed. c. The rate of weathering changed due to differences in temperature, precipitation, and soil conditions. d. The rate of weathering at all sites was influenced largely by factors associated with climate change.

ANSWER: c Essay 55. Describe the process by which solar radiation drives the hydrologic cycle.

ANSWER: Solar radiation drives the hydrologic cycle by heating up water from a liquid to a gas through evaporation and evapotranspiration. This water vapor enters the atmosphere, where it condenses into clouds that result in precipitation, which returns water to terrestrial and aquatic systems.

56. A common pesticide used to control insect herbivory of crops is found in an aquifer. Using what you know about the hydrologic cycle, describe how the pesticide could have contaminated the water.

ANSWER: Precipitation rinsed the pesticide from crop plants and the pesticide infiltrated the soil with the rainwater.

57. Using what you know about the global carbon cycle, describe two ways that deforesting in tropical forests by burning affects atmospheric carbon dioxide levels.

ANSWER: Burning of forest biomass directly releases carbon dioxide into the atmosphere through combustion of organic molecules. Reduction in the amount of forested area decreases uptake of atmospheric carbon dioxide by plants through photosynthesis.

58. How does ice core sampling help scientists learn what atmospheric carbon dioxide levels were in the past?

ANSWER: As ice forms, air bubbles are trapped in it. Since new ice is formed every year, an ice core contains the oldest air bubbles at the deepest portion and newer air at the upper portion. Scientists can measure the carbon dioxide concentrations of the air in the air bubbles to determine past carbon dioxide levels.

59. Describe the path of nitrogen as it moves from the atmosphere to the soil, plants, animals, and back to the atmosphere. Describe each process and the location and the form of nitrogen (including chemical formula) at each step.

ANSWER: [Multiple possible answers] Nitrogen starts in the atmosphere as nitrogen gas (N2), which is converted by cyanobacteria in the soil to ammonium (NH4+; fixation). The ammonium (NH4+) is converted to nitrate (NO2–) and then to nitrite (NO3–; nitrification) in the soil by nitrifying bacteria.

The nitrite (NO3–) is taken up by plants (assimilation), and the nitrogen in plant biomass is further assimilated into consumer biomass. The nitrogen in consumer biomass is returned to the soil through waste products or by the death of the consumer and eventually mineralized to ammonia (NH3) or ammonium (NH4+) by decomposers. Ammonia or ammonium in the soil is again nitrified to nitrate (NO2–) and then to nitrite (NO3–) by nitrifying bacteria. The nitrite (NO3–) is then denitrified by bacteria and returned to the atmosphere as gaseous nitrogen (N2).

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Chapter 20 60.

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Chapter 20

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Chapter 20 61. Why is the phosphorus cycle described as less complicated than the nitrogen cycle?

ANSWER: Phosphorus, unlike nitrogen, does not have a gas phase and can enter the atmosphere only in the form of dust. Also, phosphorus usually moves through the environment as phosphate (PO43–), while nitrogen has many chemical forms.

62. A lake in New York State is fed by a watershed consisting of a single river on its northern end. For many decades this watershed has been forested. However, recently all of the trees on the northern end of the lake were logged. The roots were also removed, and all that remains is bare soil. What effect will this logging have on the watershed’s hydrology over the next few decades? How will these effects influence the concentrations of nitrogen and phosphorus in the lake?

ANSWER: Removal of the trees and roots will decrease the amount of water that is stored in the watershed.

This will increase the concentrations of soluble nitrogen (nitrate) and nutrients bound to soil (ammonium and phosphate) in the runoff and also the quantity of runoff entering the lake.

63. Decomposition can be modeled using the following equation: where mt is the mass of leaf litter that remains at a particular time, m0 is the initial mass of leaf litter, k is the daily decomposition rate, and t is time in days.

Using a decomposition rate (k) of 0.15, how long would it take for 100 g of leaf material to degrade 75 percent?

ANSWER: mt = m0 e–kt 25 g = 100 g × e–(0.15)(t) 0.25 g = e–(0.15)(t) ln 0.25 g = –(0.15)(t) t = 21.5 days 64. How do scientists use watersheds to study nutrient inputs and outputs?

ANSWER: A watershed is an aquatic system that drains into a single stream or river. This facilitates quantification of inputs, outputs, and movements of nutrients.

65. What are two ways that vertical mixing of waters in lakes and oceans affects primary production?

ANSWER: Mixing brings deep, nutrient-rich water to the surface, where phytoplankton can use it. Conversely, mixing can carry the phytoplankton down to deep waters, where they cannot survive because there isn’t enough light.

66. During autumn in Ontario, Canada, you are walking by a tree near a deep lake when you see two leaves fall.

One leaf drops on the ground near your feet and the other is blown out into the middle of the lake, where it sinks. Assuming that these leaves have identical physical and chemical composition, compare the rate and processes by which the nutrients in the two leaves will be recycled and used again by producers.

ANSWER: For both leaves, the first step in decomposition will be leaching of soluble nutrients into soil or water. Also, both leaves will be shredded into smaller pieces by detritivores, after which bacteria and fungi will decompose the small fragments and convert nutrients in the leaves to compounds that can be taken up by producers. The process on land is relatively rapid, because the decomposition takes place in an aerobic environment; however, the leaf that falls into the lake will decompose Copyright Macmillan Learning. Powered by Cognero.

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Chapter 20 slowly because its environment is anaerobic. Further, once the leaf on land decomposes, producers can quickly take up the nutrients. The nutrients from the leaf that decomposes on the bottom of the lake are far from producers and will either never be used or will be used only once the water mixes and the nutrients are brought to the surface where producers live.

67. How did logging in the Hubbard Brook Experimental Forest affect water and nutrient cycling in the watershed?

ANSWER: When the forest was logged, the amount of water movement from the watershed to the stream increased because there were no plants to take it up. The water leaving the watershed also contained more nutrients, especially nitrate, because the plants were not there to take it up.

68. Explain why the Hubbard Brook Experimental Forest was an ideal location for a study dealing with nutrient flow in a watershed.

ANSWER: The Hubbard Brook Forest sits atop a layer of impenetrable bedrock. Thus, all water (and the nutrients held by/transported by the water) will either be taken up by plants or run off/percolate into nearby streams. This allowed researchers to accurately monitor the amount of water and nutrients leaving the watershed.

69. Define what allochthonous inputs are and the role they play in a stream.

ANSWER: Allochthonous inputs are nutrients that enter the stream from outside the stream (as opposed to autochthonous sources). For streams, allochthonous inputs typically take the form of leaves that fall into the stream from nearby trees at the end of the growing season. These leaves represent a major source of the stream’s energy and nutrients as a result of the breakdown of these leaves by means of the dissolving of soluble nutrients, the action of detritivores, and the breakdown by decomposers.

70. In terms of nutrient loss and nutrient input, how are nutrient levels maintained within a terrestrial ecosystem, thus maintaining a stable level of productivity?

ANSWER: Terrestrial ecosystems see a constant loss of nutrients by the processes associated with leaching from the soil and erosion (transport) from the ecosystem via streams and rivers. Nutrients are regenerated into the ecosystem by a number of processes, including fixation from the atmosphere (nitrogen) as well as weathering of parent bedrock material (phosphorus among others).

71. How does phosphorus lead to eutrophication of aquatic ecosystems?

ANSWER: Excess phosphorus alone or in combination with nitrate can run off into aquatic ecosystems, causing increased productivity of algae, which leads to algal blooms and eventually dead zones.

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Chapter 21 Multiple Choice 1. Which field considers the spatial arrangement of habitats at different scales? a. community ecology b. landscape ecology c. ecosystem ecology d. population ecology ANSWER: b 2. A long-lasting influence of historical processes on the current ecology of an area is called a _____ effect. a. retention b. landscape c. legacy d. spatial ANSWER: c 3. Eskers are legacy effects of a. volcanic eruptions. b. asteroid strikes. c. glaciers. d. floods.

ANSWER: c 4. Researchers studying soil conditions and plant species between 0 and 500 meters from former Roman settlements found that sites closer to settlements had a. lower soil pH. b. more available nitrogen. c. greater species richness. d. less species richness.

ANSWER: c 5. As habitat _____, species diversity _____. a. homogeneity decreases; decreases b. homogeneity increases; increases c. heterogeneity decreases; increases d. heterogeneity increases; increases ANSWER: d 6. The number of species in a relatively small area of homogeneous habitat is called a. regional diversity. b. local diversity.

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Chapter 21 c. regional species pool. d. gamma diversity.

ANSWER: b 7. Local species diversity is also called _____ diversity. a. gamma b. beta c. alpha d. delta ANSWER: c 8. All of the species in all of the habitats that constitute a large geographic area are called a. regional diversity. b. alpha diversity. c. local diversity. d. regional species pool.

ANSWER: a 9. Regional species diversity is also called _____ diversity. a. beta b. alpha c. delta d. gamma ANSWER: d 10. A regional species pool is the collection of species a. that occur within a region. b. that occur between two habitats. c. in a relatively small area of homogeneous habitat. d. in a large area of homogeneous habitat.

ANSWER: a 11. Arranging species in the regional pool among localities according to their adaptations and interactions is called _____ sorting. a. biodiversity b. species c. gamma d. alpha ANSWER: b 12. A classic study by MacArthur and Wilson demonstrated that as the size of islands increases, species Copyright Macmillan Learning. Powered by Cognero.

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Chapter 21 a. richness increases. b. richness decreases. c. population size increases. d. population size decreases.

ANSWER: a 13. In species–area curves, S represents a. number of species. b. area of the site. c. species diversity. d. a constant fitted to the data.

ANSWER: a 14. Which of the following equations describes the species–area curve? a. S = cAz b. A = cSz c. S = czA d. SA = cz ANSWER: a 15. Which of the following describes the log-log form of the species area curve? a. log S + log c = z log A b. log S = log c × z log A c. log S = log c + z log A d. log S + z log A = log c ANSWER: c 16. In the log-log form of the species–area curve, the slope of the relationship, z, is typically a. 0.5 to 1. b. 0.2 to 0.35. c. 0.1 to 0.15. d. 1 to 2.

ANSWER: b 17. Which of the following is NOT an effect of fragmentation of a large contiguous habitat? a. The amount of edge habitat decreases. b. The total amount of habitat decreases. c. The number of habitat patches increases. d. Patch isolation increases.

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Chapter 21 18. Which is NOT a way that edge habitat differs from interior habitat? a. Edge habitat has more sunlight. b. Edge habitat has warmer temperatures. c. Edge habitat has higher soil moisture. d. Edge habitat has higher rates of evaporation.

ANSWER: c 19. When habitat is fragmented, a(n) _____ forms along the edges. a. ecotone b. biome c. mesocosm d. microhabitat ANSWER: a 20. Small intervening patches that dispersing organisms can use to move between large favorable habitats are called a. habitat corridors. b. stepping stones. c. glades. d. matrix pathways.

ANSWER: b 21. A graph of the number of species observed in relation to the number of individuals sampled is called a species _____ curve. a. increase b. accretion c. accumulation d. area ANSWER: c 22. MacArthur and Wilson’s theory of island biogeography considers both species–area relationships and a. biomes. b. productivity. c. isolation. d. environment.

ANSWER: c 23. The equilibrium theory of island biogeography states that the number of species on an island reflects a balance between a. emigration of existing species and extinction of existing species. b. colonization of new species and extinction of existing species.

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Chapter 21 c. evolution of new species and emigration of existing species. d. colonization of new species and emigration of existing species.

ANSWER: b 24. In the equilibrium theory of island biogeography, equilibrium occurs where extinction _____ colonization. a. is greater than b. equals c. is less than d. None of the above ANSWER: b 25. Smaller islands at equilibrium contain fewer species than larger islands at equilibrium because smaller islands have a. less colonization. b. greater extinction. c. greater isolation. d. greater emigration.

ANSWER: b 26. Islands at equilibrium that are farther from the mainland contain fewer species than nearer islands at equilibrium because farther islands have a. less colonization. b. greater emigration. c. less isolation. d. greater extinction.

ANSWER: a 27. Based on the theory of island biogeography, which statement about reserve designs is TRUE? a. Small reserves are better than large reserves. b. Oval reserves are better than circular reserves. c. One large reserve is better than many small reserves. d. Remote reserves are better than nearby reserves.

ANSWER: c 28. In the Northern Hemisphere, the number of species of plants generally a. decreases from east to west. b. increases from east to west. c. decreases from north to south. d. increases from north to south.

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Chapter 21 29. In North America, the number of species of mammals generally a. increases from north to south. b. decreases from north to south. c. increases from east to west. d. decreases from east to west.

ANSWER: c 30. For marine organisms, the highest diversity is seen at _____ and the lowest diversity is seen at _____. a. low longitudes; high longitudes b. high longitudes; low longitudes c. low latitudes; high latitudes d. high latitudes; low latitudes ANSWER: c 31. In North America, amphibian diversity is greatest in the a. northeast. b. northwest. c. southeast. d. southwest.

ANSWER: c 32. In North America, reptile diversity is greatest in the a. south. b. east. c. west. d. north.

ANSWER: a 33. Which of the following is NOT associated with low terrestrial diversity? a. recent glaciation b. variation in vegetation c. high temperature d. low precipitation ANSWER: d 34. Given average temperature and humidity, potential evapotranspiration is the amount of water that could be a. evaporated from the soil. b. transpired by plants. c. evaporated from the habitat. d. evaporated from the soil and transpired by plants.

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Chapter 21 35. PET is a measurement that combines the amount of solar radiation and a. temperature. b. precipitation. c. transpiration. d. evaporation.

ANSWER: a 36. According to the _____ hypothesis, sites with higher amounts of energy are able to support more species. a. energetic–diversity b. energy–diversity c. energy–biodiversity d. bioenergetics–diversity ANSWER: b 37. Marine environments are most diverse in _____ environments and most productive in _____ environments. a. tropical; tropical b. tropical; temperate c. temperate; tropical d. temperate; temperate ANSWER: b 38. The movement of landmasses across the surface of Earth is called a. tectonic spread. b. Pangaea. c. continental drift. d. continental divide.

ANSWER: c 39. Landmass movement occurs because islands of _____ rock are moved by _____ currents of semi-molten material. a. high-density; convection b. low-density; convection c. high-density; conduction d. low-density; conduction ANSWER: b 40. About 250 million years ago, all of Earth’s landmasses were joined as a single landmass called a. Pangaea. b. Gondwana. c. Laurasia.

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Chapter 21 d. Indomalaysia.

ANSWER: a 41. About 150 million years ago the single landmass separated into northern and southern landmasses called a. Laurasia and Gondwana. b. Gondwana and Afrotropica. c. Pangaea and Laurasia. d. Nearctica and Palearctica.

ANSWER: a 42. Eventually _____ split into North America, Europe, and Asia. a. Gondwana b. Pangaea c. Laurasia d. Neotropica ANSWER: c 43. Eventually _____ split into South America, Africa, Antarctica, Australia, and India. a. Gondwana b. Pangaea c. Indomalaysia d. Laurasia ANSWER: a 44. When the continents divided 60 million years ago, there was a land bridge between a. Africa and Europe. b. India and Asia. c. North America and South America. d. Asia and North America.

ANSWER: d 45. North and South America were joined by the Isthmus of Panama a. 3 million to 6 million years ago. b. 10 million to 12 million years ago. c. 5 million to 8 million years ago. d. 1 million to 2 million years ago.

ANSWER: a 46. Which of the following is NOT a Southern Hemisphere biogeographic region? a. Afrotropical b. Indomalayan Copyright Macmillan Learning. Powered by Cognero.

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Chapter 21 c. Nearctic d. Neotropical ANSWER: c 47. In which biogeographic region is Egypt? a. Neotropical b. Afrotropical c. Indomalayan d. Palearctic ANSWER: d 48. In which biogeographic region is the United States? a. Neotropical b. Nearctic c. Palearctic d. Indomalayan ANSWER: b 49. Which biogeographic region is also called the Oriental region? a. Indomalayan b. Afrotropical c. Australian d. Palearctic ANSWER: a 50. Which of the following is NOT true with regard to the species–area relationship? a. The relationship only holds for terrestrial environments and not aquatic (i.e., wetlands). b. The species–area curve is represented by the equation S = cAz. c. The relationship is not always represented as a linear relationship. d. The relationship is found among various taxa.

ANSWER: a 51. The reduction in habitat size resulting from fragmentation causes a decline in species diversity for what reason? a. Fragments are more diverse, leading to greater specialization. b. Fragments are more diverse, leading to greater generalization. c. Fragments support smaller populations that are more prone to extinction. d. Fragments tend to have more predators than unfragmented areas.

ANSWER: c 52. The bronzed cowbird is a species of bird that thrives in edge habitat. This species is a nest parasite, which Copyright Macmillan Learning. Powered by Cognero.

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Chapter 21 means what? a. The female of the species takes over the nests built by other species and incubates and raises its young in these nests. b. The male of the species steals nest materials from the nests of other species to be used in building its own nests. c. The male and female of the species destroy the nests of other birds and then claim the location as their own to build their own nest. d. The female of the species lays her eggs in the nests of other species and then departs, leaving the eggs to be incubated by the other species and the young to be raised by the other species.

ANSWER: d 53. According to researchers, how has forest fragmentation led to the potential higher rate of exposure to Lyme disease? a. Forest fragmentation has led to a decrease in population size of the bird species that feed on ticks. b. Forest fragmentation has led to a warmer and drier environment that is not suitable for tick growth. c. Forest fragmentation has led to increased white-footed mice populations that serve as hosts for ticks. d. Forest fragmentation has led more human contact with the smaller parcels of forests.

ANSWER: c 54. Based on MacArthur and Wilson’s equilibrium theory of island biogeography at Ŝ, a. the rate of colonization exceeds the rate of extinction. b. the number of species on the island stays the same though the actual species present on the island may be changing. c. the rate of extinction exceeds the rate of colonization. d. the number of species on the island stays the same and the actual species present on the island is unchanging.

ANSWER: b 55. On which type of island should we expect to see the lowest level of biodiversity when equilibrium is reached? a. a small island located far from the source of colonizing species b. a small island located nearer to the source of colonizing species c. a large island located far from the source of colonizing species d. a large island located nearer to the source of colonizing species ANSWER: a 56. Why are nature reserves that are more circular more likely to be preferred than nature reserves that are more oval in shape? a. Oval-shaped nature reserves act more like corridors; thus, species are less likely to reside in them as compared to circular-shaped nature reserves. b. Oval-shaped nature reserves have more edge and less interior than do more circular-shaped nature reserves; thus, oval-shaped nature reserves will favor edge species.

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Chapter 21 c. In circular-shaped nature reserves, edge species are all equidistant to the center of the reserve. d. There is no difference between oval-shaped and circular-shaped nature reserves based solely on their geometric shape.

ANSWER: b Essay 57. How does fire cause habitat heterogeneity?

ANSWER: When an area has a fire, not all portions are burned or burned to the same degree. After the fire there are patches of bare ground, unburned vegetation, and partially burned vegetation.

58. What do studies of Roman Empire settlements tell us about the legacy effects of humans on the landscape?

How do human settlements cause legacy effects?

ANSWER: Researchers have found that sites closer to Roman Empire settlements have higher soil pH, more available phosphorus, and greater plant species richness than elsewhere. These legacy effects were caused by the slow breakdown of ancient building materials contributing to calcium and phosphorus in the soil and the introduction of many plant species by the Romans.

59. How does habitat fragmentation increase the total edge habitat? Describe the effect of habitat fragmentation on a 600-meter by 600-meter forest plot that has been divided into nine 200-meter by 200-meter sections using calculations of edge size.

ANSWER: Although the unfragmented and fragmented forest plots have the same area (360,000 square meters), the unfragmented plot has a total edge of 2,400 square meters (600 meters by 4 edges), while the fragmented plot has a total edge of 7,200 square meters (200 meters by 4 edges by 9 plots).

60.

Species Betula lenta Acer saccharum Acer pensylvanicum Fagus grandifoia Tilia Americana Quercus rubra Prunus serotina Robinia pseudoacacia Acer rubrum Prunus pensylvanica

Community A 42 33 12 10 1 9 1 3 1 2

Community B 29 35 20 1 8 2 1 8 2 0

The table lists tree species observed in communities A and B. Based on these data, calculate the estimated number of species in each community. How does the number of species represented by single individuals affect the estimated number of species in the community?

ANSWER: Community A

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Chapter 21 Community B

Based on the observed species in communities A and B, community A is estimated to have 11.5 species and community B is estimated to have 9.3 species. The more species represented by single individuals, the higher the estimate becomes.

Based on the observed species in communities A and B, community A is estimated to have 11.5 species and community B is estimated to have 9.3 species. The more species represented by single individuals, the higher the estimate becomes.

61. Researchers in the Florida Keys fumigated islands to remove most arthropods and then observed colonization of species over time. The fumigated islands were near other islands, far from other islands, or at intermediate distances from other islands. What did their results show?

ANSWER: At the end of the experiment, the near islands showed most species, followed by intermediate islands and then far islands. The numbers of species for near islands and intermediate islands were close to the numbers prior to fumigation, while far islands had species numbers lower than the original.

62. How can we apply the theory of island biogeography to determine which characteristics might give a nature reserve the highest probable success rate in preserving a region’s biodiversity? Discuss size, number, proximity, spatial arrangement, connectivity, and shape of the reserve.

ANSWER: The ideal size would be large rather than small. Fewer large reserves are more beneficial than multiple small reserves. With multiple reserves, it is better for them to be close together than far apart. The spacing of reserves is better when multiple reserves are clustered rather than strung out in a line. Connectivity between reserves is better than isolation. Finally, square or circular reserves are better than oval or rectangular ones, because square and circular reserves have lower ratios of edge to area.

63. Time since glaciation is one possible predictor of species diversity. Explain how time since glaciation leads to differences in terrestrial diversity between polar and tropical regions.

ANSWER: Higher diversity in tropical versus polar regions is partially explained by time since glaciation. As the world’s temperate and polar regions cycled between advancing and retreating glaciation, species living in these regions have gone extinct or have been driven toward unglaciated regions closer to the equator. Tropical regions did not undergo glaciation; therefore, habitats in these areas have remained stable for a much longer time and have had more time to accumulate species.

64.

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Chapter 21

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Chapter 21 65. Why does Australia have a wide variety of unique animals and plants? Give examples.

ANSWER: Australia has long been isolated from other landmasses. This led to reduced dispersal between Australia and other landmasses along with independent evolution. This has led to animals (most marsupials) and plants (eucalyptus trees) that are not seen elsewhere.

66.

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Chapter 21

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What caused changing tree distributions seen in the figure? As global warming increases temperatures, what can be expected to happen to tree distributions of spruce, hemlock, and oak?

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Chapter 21 67. Discuss the confounding issue that areas are losing species while at the same time increasing in biodiversity.

ANSWER: Answers will vary. Many areas of the world are seeing a loss of native species while at same time seeing an increase in biodiversity. This increase in biodiversity is the result of an increase in the numbers of non-native species introduced to the areas in question and becoming naturalized. A question to address is whether increased biodiversity is a “good thing,” and whether it is necessarily “bad” if native species are lost but the overall number of species increases by the addition of nonnative species.

68. You own a small backyard lot behind your home that you have fertilized and mowed consistently over the years as a lawn. You decide you want to refocus your backyard lot and emphasize species diversity. What might you do to your backyard lot to enhance species diversity?

ANSWER: Answers will vary. The simplest approach would be to do nothing at all. If you stopped maintaining the lawn (mowing, etc.), you would see the lawn revert over time to a field that would likely have greater species diversity of insects, wildflowers, and so forth. If allowed to progress (through successional stages), you would see eventually shrubs and trees taking hold in the area. A more proactive approach might be to plant different areas of the lot in trees and shrubs of varying types, creating a variety of microhabitats that would, as a result of habitat heterogeneity, lead to greater diversity.

69. Discuss what MacArthur and Wilson meant by the species–area curve. What implications does this curve have for the management of nature centers/reserves?

ANSWER: MacArthur and Wilson studied the relationship of species diversity found on islands of varying sizes. MacArthur and Wilson found that as an island increased in size, the level of biodiversity of various taxa also increased. In terms of nature centers or preserves (answers may vary), if a fundamental mission of a nature center is to educate the public about issues regarding biodiversity/provide experiences for the public to witness biodiversity, then nature centers/preserves should opt for larger areas if possible. For example, if a nature center/preserve is adjacent to land that is undeveloped and available (i.e., for sale) and if the nature center can acquire such a contiguous parcel, then in theory, based on the species–area curve, one might expect greater species diversity will be found on this larger nature center/preserve with the newly acquired parcel.

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Chapter 22 Multiple Choice 1. Biodiversity hotspots throughout the world contain _____ percent of the world’s plant species. a. 75 b. 40 c. 80 d. 50 ANSWER: d 2. A focus on the economic value a species can provide is called the a. intrinsic value of biodiversity. b. instrumental value of biodiversity. c. provisioning service of biodiversity d. regulating service of biodiversity ANSWER: b 3. Which of the following is NOT a category of instrumental values? a. cultural b. regulating c. consumer d. supporting ANSWER: c 4. Provisioning services are those that a. support ecosystems, such as primary production, soil formation, and nutrient cycling. b. include climate regulation, flood control, and water purification. c. humans use, including lumber, fur, meat, crops, water, and fiber. d. provide aesthetic, spiritual, or recreational value.

ANSWER: c 5. Cultural services are those that a. humans use, including lumber, fur, meat, crops, water, and fiber. b. allow ecosystems to exist, such as primary production, soil formation, and nutrient cycling. c. include climate regulation, flood control, and water purification. d. provide aesthetic, spiritual, or recreational value.

ANSWER: d 6. A supporting service provides benefits of biodiversity that a. have aesthetic, spiritual, or recreational value. b. humans use. c. include climate regulation, flood control, and water purification.

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Chapter 22 d. allow ecosystems to exist.

ANSWER: d 7. What is NOT an example of a regulating service? a. climate regulation b. nutrient cycling c. flood control d. water purification ANSWER: b 8. The cancer drug Taxol, which originally came from the Pacific yew tree (Taxus brevifolia), is an example of a _____ service. a. provisioning b. cultural c. supporting d. regulating ANSWER: a 9. Drinking water is an example of a _____ service. a. cultural b. provisioning c. supporting d. regulating ANSWER: b 10. The carbon-sequestering ability of tropical rainforests is an example of a _____ service. a. regulating b. provisioning c. cultural d. supporting ANSWER: a 11. Nutrient cycling is an example of a _____ service. a. regulating b. cultural c. supporting d. provisioning ANSWER: c 12. The beauty of a national park is an example of a _____ service. a. supporting Copyright Macmillan Learning. Powered by Cognero.

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Chapter 22 b. provisioning c. regulating d. cultural ANSWER: d 13. Flood control is an example of a _____ service. a. provisioning b. cultural c. regulating d. supporting ANSWER: c 14. Which of the following describes intrinsic values of biodiversity? a. aesthetic b. cultural c. inherent d. economic ANSWER: c 15. How many total species have been named? a. 2.3 million b. 1.3 million c. 13 million d. 3.5 million ANSWER: b 16. A mass extinction event is one in which _____ percent of the existing species go extinct within a 2-millionyear period. a. 75 b. 95 c. 55 d. 25 ANSWER: a 17. How many mass extinctions have occurred? a. 5 b. 15 c. 10 d. 3 ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 22 18. The mass extinction that occurred 443 million years ago was caused by a. global warming. b. an asteroid. c. volcanism. d. an ice age.

ANSWER: d 19. The most recent mass extinction event occurred a. 65 million years ago. b. 200 million years ago. c. 35 million years ago. d. 450 million years ago.

ANSWER: a 20. The period of the last _____ may be a sixth mass extinction. a. 100,000 years b. 10 million years c. 1,000 years d. 10,000 years ANSWER: d 21. Extinction rates over the past 50 years are _____ times higher than the historic rate. a. 100 b. 1,000 c. 10 d. 10,000 ANSWER: b 22. Scientists hypothesize that losses of large mammals between 11,500 and 500 years ago were caused by a. humans. b. climate change. c. pollution. d. invasive species.

ANSWER: a 23. The International Union for Conservation of Nature (IUCN) defines the term extinct as pertaining to a species that was alive in the wild in the a. past but no individuals remain alive today. b. year 1000 but no individuals remain alive today. c. year 1500 but no individuals remain alive today. d. year 1900 but no individuals remain alive today.

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Chapter 22 ANSWER: c 24. Which of the following is NOT an IUCN category relating to species assessment? a. threatened b. least concern c. near-threatened d. endangered ANSWER: d 25. Of the 607 species of conifers, how many have gone extinct? a. 42 percent b. 20 percent c. 5 percent d. No conifers have gone extinct.

ANSWER: d 26. During the past 500 years, _____ of mammal species have gone extinct. a. 10 percent b. 0.2 percent c. 5 percent d. 1.5 percent ANSWER: d 27. A review of research in Europe demonstrated that species richness is a. positively related to aboveground biomass. b. negatively related to aboveground biomass. c. positively related to genetic diversity. d. negatively related to genetic diversity.

ANSWER: a 28. Which of the following is NOT a cause of declining genetic diversity? a. inbreeding depression b. declining population sizes c. bottleneck effect d. mutation ANSWER: d 29. Declines in genetic diversity can a. increase the probability that a population will survive changing environmental conditions. b. reduce the probability that a population will survive changing environmental conditions. c. decrease the probability of speciation.

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Chapter 22 d. increase the rate of evolution.

ANSWER: b 30. The Svalbard facility on an island north of the Norwegian mainland was constructed to store a. plants. b. seeds. c. animals. d. embryos.

ANSWER: b 31. Tropical forests are being logged at a rate of _____ million hectares per year. a. 20 b. 5 c. 50 d. 10 ANSWER: d 32. The largest cause of declining biodiversity is a. habitat loss. b. overharvesting. c. introduced species. d. global climate change.

ANSWER: a 33. The Sumatran tiger (Panthera tigris sumatrae) has become critically endangered as a result of a. pollution. b. invasive species. c. habitat loss. d. climate change.

ANSWER: c 34. All species of moas (Dinornis) in New Zealand have gone extinct as a result of a. habitat loss. b. overharvesting. c. invasive species. d. pollution.

ANSWER: b 35. The collapse of the Atlantic cod fishery in the early 1990s was the result of a. pollution. b. climate change.

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Chapter 22 c. introduced species. d. overharvesting.

ANSWER: d 36. Biotic _____ is the process by which unique species compositions originally found in different regions slowly become more similar as a result of the movement of people, cargo, and species. a. normalization b. confluence c. magnification d. homogenization ANSWER: d 37. Which of the following is NOT a way that pesticides may decrease biodiversity? a. by killing nontarget species b. through the process known as biomagnification c. by altering food webs d. by shortening the growing season ANSWER: d 38. Which chemical caused declines in predatory bird populations in the 1950s and 1960s in the United States? a. DDT b. Alar c. organophosphates d. pyrethroids ANSWER: a 39. What is the process by which the concentration of a contaminant increases as it moves up the food chain? a. bioexpansion b. bioconcentration c. biomagnification d. bioaccumulation ANSWER: c 40. The pesticide DDT in a body of water increases about _____ in concentration when it binds to particles such as algae. a. 10-fold b. 5-fold c. 50-fold d. 30-fold ANSWER: a Copyright Macmillan Learning. Powered by Cognero.

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Chapter 22 41. In a food chain that undergoes biomagnification of a pesticide, which organism can be expected to have the highest pesticide concentration? a. algae b. carnivorous fish c. zooplankton d. herbivorous fish ANSWER: b 42. The time required for a chemical to break down to half of its original concentration is called its a. decomposition coefficient. b. retention time. c. half-life. d. decontamination time.

ANSWER: c 43. The half-life of a contaminant is calculated as a. Ln (N0 ÷ Nt) ÷ t ln (2). b. Ln (N0 × Nt) ÷ t ln (2). c. t ln (2) ÷ ln (N0 × Nt). d. t ln (2) ÷ ln (N0 ÷ Nt).

ANSWER: d 44. In the calculation of half-life, N0 represents the a. final amount of the contaminant. b. initial amount of the contaminant. c. elapsed time. d. half-life.

ANSWER: b 45. From 1880 to 2013, Earth’s temperatures have increased an average of a. 0.2°C. b. 2°C. c. 4°C d. 0.8°C. ANSWER: d 46. Global climate change is predicted to lead to all of the following except a. causing extreme weather events. b. altering precipitation patterns. c. shifting distributions of species. d. changing day length patterns Copyright Macmillan Learning. Powered by Cognero.

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Chapter 22 ANSWER: d 47. Over the past 20 years, sea levels have been rising at a rate of _____ millimeters per year. a. 5 b. 1 c. 10 d. 3 ANSWER: d 48. The goal in protecting a habitat is commonly the preservation of a large enough area to support a _____ population. a. maximum sustaining b. minimum sustaining c. maximum viable d. minimum viable ANSWER: d 49. Protecting habitat for buffalo and wildebeests is challenging because of all of the following except a. they have a very large range. b. they undergo large-scale movements. c. there may not be enough contiguous habitat to meet their requirements. d. they are prone to many parasitic diseases originating in their habitats.

ANSWER: d 50. A minimum viable population is the _____ population of a species that can _____. a. smallest; persist in the face of environmental variation b. ideal; persist in increasing global temperatures c. smallest; maintain genetic variability d. ideal; return a population from threatened status ANSWER: a 51. The northern elephant seal (Mirounga angustirostris) was saved from extinction by a. captive breeding. b. species reintroduction. c. habitat protection. d. reduced harvesting.

ANSWER: d 52. The California condor (Gymnogyps californianus) was saved from extinction by a. habitat protection. b. reduced harvesting.

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Chapter 22 c. captive breeding and species reintroduction. d. the banning of pesticides.

ANSWER: c 53. The environmental organization called Conservation International describes a(n) _____ as an area that contains at least 1,500 endemic plant species and that has experienced at least a 70 percent vegetation loss due to human activity. a. ecologically critical area b. critically endangered habitat c. critical species intervention site d. biodiversity hotspot ANSWER: d 54. An endemic species is one that a. has no intrinsic value. b. has no instrumental value. c. has a relatively restricted distribution. d. is found in all biogeographic regions yet is still endangered.

ANSWER: c 55. Instrumental values of biodiversity differ from intrinsic values of biodiversity in which ways? a. Society can place a clear dollar value on instrumental values. b. Society can place a clear dollar value on intrinsic values. c. Intrinsic values include those that allow ecosystems to exist. d. Instrumental values are those that are based (or not) on one’s belief system.

ANSWER: a 56. According to the IUCN (2017), which group of species is the most threatened or near-threatened with the risk of future extinction globally? a. birds b. amphibians c. reptiles d. mammals ANSWER: b 57. The IUCN has defined categories to be applied to species based on their conservation status. The category “extinct in the wild” refers to a species that a. was known to exist in the year 1500 but no individuals remain alive today. b. was known to exist in the year 1900 but no individuals remain alive today. c. can be found only in zoos or facilities that might be conducting captive breeding. d. are found only in less than 1 percent of their original documented native habitat Copyright Macmillan Learning. Powered by Cognero.

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Chapter 22 ANSWER: c 58. An introduced species tends to have a greater impact (leading to the decline or extinction of native species) if they a. are accidentally introduced. b. are intentionally introduced. c. compete with native species. d. act as predators or pathogens on native species.

ANSWER: d 59. The concept known as minimum viable population (MVP) refers to a. the species whose role in a community is the most important and if its habitat is lost will have cascading effects through the entire community. b. the smallest population size of a species that can persist even if environmental conditions change. c. the smallest, single contiguous habitat that can hold a species. d. the historical size of a species habitat that is required for its survival prior to the impacts of human harvesting, introduced species, and global climate change.

ANSWER: b Essay 60. Why are regulating services considered instrumental values? Give examples.

ANSWER: Regulating services are benefits of biodiversity, such as flood control, water purification, and climate regulation. These values may be difficult to define, but they are still economic values. For instance, if water purification were no longer provided as an ecosystem service, to preserve public health the government would have to replace the ecosystem service with infrastructure such as a water purification plant or transport potable water into an area. These costs of replacing the service are how economic values are ascribed to regulating services.

61. What is the difference between instrumental and intrinsic values of biodiversity? Give examples for each.

ANSWER: Instrumental values of biodiversity focus on the economic value a species can provide. For instance, some trees have economic value as lumber. The economic value for other instrumental benefits, such as water purification, could be determined by looking at replacement cost. For example, how much would it cost to build infrastructure to purify water if the ecosystem did not already do so?

What is the cost of building flood controls or rebuilding after a flood if the ecosystem does not provide flood control? Intrinsic values of biodiversity are more difficult to quantify. Intrinsic values do not have an economic value. An example of an intrinsic value is the inherent value of biodiversity that makes people feel a moral or spiritual obligation to preserve biodiversity.

62. Why has it been challenging to determine the declines in species diversity of amphibians?

ANSWER: Amphibians are not as visible as other types of animals, such as birds and mammals, and scientists are discovering new species of amphibians at a rapid rate. Since little is known about the populations of these new species and scientists are not close to knowing how many species of amphibians actually exist, it is difficult to estimate how amphibian diversity is changing over time.

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Chapter 22 63. How has agriculture led to losses of genetic diversity? Why is this a problem?

ANSWER: Modern livestock operations favor relatively few breeds of animals. Crop diversity has declined: Most people’s diets consist of just 12 species of plants. Commercial agriculture favors topproducing varieties rather than diversity. Loss of diversity can be a problem when a new pathogen or environmental challenge occurs for which the crops or livestock do not have resistance or adaptations.

64. Methylmercury is an organic mercury compound that is a waste product of industrial processes and also results from the burning of fossil fuels. Methylmercury has been shown to increase up food chains by biomagnification. Bigeye tuna (Thunnus obesus) can have tissue concentrations of methylmercury of 0.69 ppm (parts per million). Assuming a food web that starts with phytoplankton (0.00069 ppm) and a 10-fold biomagnification from each level in the food chain to the next level, calculate the concentration of methylmercury at each level in the food chain. How many levels are there in the food chain, including the phytoplankton and the tuna?

ANSWER: Phytoplankton are assumed to be the first level in the food chain.

Level 2, 0.00069 ppm × 10 = 0.0069 ppm Level 3, 0.0069 ppm × 10 = 0.069 ppm Level 4, 0.069 ppm × 10 = 0.69 ppm (tuna) There are four levels in this food chain.

65. You measure 1,000 mg of the pesticide DDT in the soil, and 30 days later the amount in the soil is 998.1 mg. What is the half-life (in years) of DDT in this soil?

ANSWER:

66. The California condor (Gymnogyps californianus) reintroduction was very successful in increasing natural populations of condors. In addition to reintroduction, what strategies were used to conserve this species?

ANSWER: Prior to reintroduction of condors, all known wild condors were captured and bred in captivity to increase their numbers. Biologists were able to increase the egg output of females and raise chicks in large numbers for release. Large areas of habitat were also preserved in southern California.

Awareness of the importance of protecting the species was raised among the residents near condor habitat.

67. The reintroduction of wolves to Yellowstone National Park has had effects beyond the conservation of wolves. What are other benefits of the reintroduction?

ANSWER: Reintroduction of wolves had cascading effects on the prey species that the wolves consume. Elk have changed their behavior to reduce predation, which has increased populations of aspens and cottonwoods that elk grazed. The populations of coyotes, a mesopredator, have declined because of competition with and predation by wolves. Scavenger populations have benefited from increased predation by wolves. The reintroduction of wolves has brought the ecosystem to more closely resemble its earlier condition when its fauna was intact.

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Chapter 22 68. Briefly describe what is known about the causes of the five past mass extinctions and the possible sixth mass extinction that may be under way.

ANSWER: The cause of the first mass extinction (443 mya) is thought to have been an ice age that caused sea levels to drop and ocean chemistry to change. The cause of the second mass extinction (359 mya) is unclear, though it is known that much of the ocean lacked oxygen. The cause of the third mass extinction (248 mya) is likewise uncertain. The cause of the fourth mass extinction (200 mya) is believed to have been increased volcanic activity, an asteroid collision with Earth, and climate change. The cause of the fifth mass extinction (65 mya) is also thought to have been volcanic eruptions, an asteroid strike, and climate change, specifically an extended period of cooling. It is hypothesized that the possible sixth mass extinction under way (over the course of the past 10,000 years) is driven by increasing human population.

69. Explain how an insecticide like DDT, which was found in low concentrations in water after its application for insect control, nearly caused the loss of species like the bald eagle in some places in the United States during the 1960s.

ANSWER: DDT is a fat-soluble chemical that is biomagnifiable as one proceeds up the food chain. Starting with low concentrations in the water after insecticide application, the DDT was taken up by phytoplankton (algae) in levels 10 times greater than that found in the water. The phytoplankton were then consumed by zooplankton and further magnification was observed as the DDT accumulated in the fat molecules of the zooplankton. This magnification continued through the various predator fish, ending at the top-level carnivore, the bald eagle. At each step (small fish, larger fish, and bald eagle) the DDT level increased as the chemical was stored in the fatty tissue of each species in the succeeding trophic levels. At the highest level (bald eagle), the level of DDT was problematic and caused a physiological impairment in eggshell formation. The eggshells were too thin and when adult eagles attempted to incubate their eggs, the thin-shelled eggs broke, killing the embryo inside. This biomagnifiable chemical nearly led to the loss of bald eagles during the 1960s.

70. It has been documented (see Figure 23.12) that forest cover has declined in many regions of the world for nearly the past 20 years. In other parts of the world, forest cover has increased during this time. Why do conservation biologists see both of these developments as potentially problematic for biodiversity?

ANSWER: The loss of forest cover in many regions of the tropics (the Amazon, Southeast Asia, etc.) has led to a large number of species becoming critically endangered. In addition, in some regions (the United States, Europe, etc.) that have seen an increase in forest cover during the last 20 years, the original level of biodiversity/species composition has been lost because the trees being replanted are often a single or a few species with high economic value as opposed to a more naturally diverse forest structure.

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