M/C 1. When a biologist studies the way organisms interact with each other and with their environment, she is studying their a. Physiology b. Anatomy c. Morphology d. Genetics e. Ecology 2. In a deciduous oak forest of the American northeast, one example of an abiotic component of the ecosystem would be a. nematodes in the soil that feed on plant roots b. nematodes in the soil that feed on dead organic matter c. sunlight that filters through the canopy d. animals such as deer that migrate through the forest but do not eat in the forest e. the understory plant community Essay 3. An aquatic biologist is studying a lake in western Massachusetts in order to document the N cycle of the lake, and thus she is measuring inputs, turnover, and outputs of N. A second ecologist is studying a larger region of western Massachusetts that is forested, with several lakes, and is studying N transfers between the forest and the lakes. The first ecologist claims that her lake is an ecosystem; the second ecologist also claims that her forested region, with its many lakes, is an ecosystem. Which ecologist is correct, or are they both wrong or right? 4. Bacteria growing in a petri dish may grow rapidly and experience exponential growth. However, bacteria in the soil, measured as the number of organisms per gram of soil, usually do not increase in population size from one year to the next. Yet no new food is added to the petri dish after the initial addition of the bacterial innoculum, but new food sources are always added to the soil by way of plant detritus. How can this be true? 5. Although models of population structure in an ecosystem usually assume that populations reach a carrying capacity after time, in fact, population size may fluctuate around a mean from year to year. Using a population of mice in a grassland, give (1) an example of a density-independent factor that could cause population size to increase; (2) an example of a density-independent factor that could cause population size to decrease; (3) an example of a density-dependent factor that could cause population size to increase; (4) an example of a density-dependent factor that could cause population size to decrease. M/C 6. A complex interrelated network of organisms and the surrounding abiotic environment in a defined area is a(n): a. Community b. Ecosystem c. Population d. Biosphere e. Biome 7. All organisms that reside within an ecosystem and that can potentially interbreed are members of a(n) a. population b. community c. trophic level d. aggregation e. ecotope 8. The organisms that represent the different species within an ecosystem that interact in various ways comprise the a. population b. community c. trophic level d. aggregation e. ecotope 9. Environmental resistance may limit the size of populations by a. increasing both birth and death rates b. decreasing both birth and death rates c. increasing death rates and/or decreasing birth rates d. decreasing death rates and/or increasing birth rates e. changing the biotic potential 10. To determine the number of individuals that will be added to a population in a specified time we multiply the growth rate (r) by the ________. a. biotic potential b. original population size c. environmental resistance d. final population size e. number of immigrants 11. If a population of 100 birds increases to 120 birds the following year, r = ___________. a. 0.16 b. 0.20 c. 1.2 d. 2 e. 20 12. Which factor would not influence the size a population reaches over time? a. Number of individuals migrating b. Number of deaths c. Age of females at reproduction d. Distance travelled by migrants e. Number of births 13. Environmental resistance a. is limits imposed on population growth by the biotic environment (predators, competitors) b. is limits imposed on population growth by the abiotic environment c. is limits imposed on population growth by both the biotic and abiotic environment d. is a factor that decreases both death rates and birth rates e. is a factor that increases both death rates and birth rates 14. The biotic potential of a population a. directly affects environmental resistance b. causes changes in birth rates without affecting death rates c. causes changes in death rates without affecting birth rates d. is the maximum rate at which a population may increase e. both a and c 15. There are 150 spotted owls in an old-growth forest patch in western Oregon. A biologist tracking the birds saw that in one year, 25 new birds were hatched, and 5 died. Thus r = a. 170 b. 145 c. 2 d. 6 e. 20 16. Exponential growth occurs when a. there is a constant number of births each year and b > d b. the population grows by a fixed percentage each year c. immigration is greater than emigration d. the biotic potential increases each year e. environmental resistance declines each year T/F 17. Populations which have been relatively undisturbed by man normally grow unlimited by their environment. 18. According to the equation for population growth rate, of two populations with equal death rates the population with r = 2 will increase more rapidly than a population with r = 4. F/B 19. A measure of the ability of a population to grow under ideal circumstances is its _______________ _________________. 20. The sum of all factors that limit the ability of a population to grow are known as ________________ ________________. 21. In the equation "population growth = rN," the letter r stands for ____________________. 22. Many species of field mice are able to reproduce several times a year, and produce litters with multiple offspring. However, an ecologist noted that the population size of mice, as measured in a California grassland, did not change from year to year. The factors that keep natural populations from increasing are collectively called the __________. 23. How is a population growth rate expressed? Essay 24. Write an equation which describes a situation in which a population remains stable. 25. Explain what happens in exponential population growth. 26. In the United States today there is a trend toward women having their first child in their late 30's or early 40's. By contrast, a few years ago most women started having children in their early 20's. What effect would you expect this change to have on population growth in the USA? Would it have any effect if the number of children per woman is the same? Explain. 27. Why would a bacterial population living in an unrestricted environment grow much faster than an eagle population? M/C 28. When a population has inhabited an area for a long time and the population size has stabilized because of resource limitations: a. Carrying capacity has been reached b. Density dependence occurs c. Predation decreases d. Density independence occurs e. Environmental resistance declines 29. An insect population grows exponentially until an early winter freeze kills almost all of the insects. The next spring the population grows exponentially again. This type of population growth is known as a. Boom and bust b. Sigmoidal c. Density-dependent d. Density-independent e. Sustained 30. The human population is currently following a J-shaped curve. This means that the population is growing a. Arithmetically b. Sigmoidally c. At a decreasing rate d. By a boom and bust cycle e. Exponentially 31. An important density-independent factor limiting population size is __________. a. Predation b. Weather c. Environmental resistance d. Competition e. Food quantity 32. Which of these is not a density-dependent control of population size? a. Parasitism b. Predation c. Competition d. Biotic potential e. Shortage of food 33. Density-dependent factors such as predation have _________________ effect on population size. a. a long-term b. a short-term c. a negative feedback d. a positive feedback e. no 34. If a caterpillar eats a seedling in your garden, the caterpillar is acting as a a. Predator b. Parasite c. Competitor d. Density-independent factor e. Saprophyte 35. Predators and parasites are always harmful to their prey or host populations. a. True. b. False, because predators always harm the prey population, but parasites often do little or no harm. c. False, because parasites always harm their host populations but predators may be helpful. d. False, because parasites and predators kill their hosts and prey. e. False, because predators and parasites often help the host or prey population by attacking the weak. 36. In a maple forest in the spring the ground will often be covered with young maple seedlings which compete for light and nutrients. By fall, most of these have died, leaving only a few survivors. This is an example of ____________ competition. a. scramble b. contest c. dominance hierarchy d. interspecific e. social stress 37. Most parasites have evolved to _________ their host. a. kill b. only weaken c. have no effect on d. control e. all of these 38. What type of competition has occurred when one organism uses social or chemical interactions to limit the access of other individuals to resources? a. Contest competition b. Scramble competition c. Interspecific d. Intramural e. Social 39. A caribou dies because it was weakened by parasites (like tapeworms) passed from one individual to the next under crowded conditions during an unusually long, cold winter. What killed the caribou? a. Density-independent factors b. Density-dependent factors c. Abiotic factors d. Biotic factors e. Both density-dependent and density-independent factors 40. Some predators feed preferentially on the most abundant prey. This type of predation is: a. Density dependent b. Density independent c. Competitive d. Exponential e. Cyclical 41. Why do many non-native species, such as a prickly pear cactus brought to Australia from South America, rapidly become abundant when first introduced? a. The climate in the new site is more favorable than it's native site b. Non-native species increase their reproductive rate when introduced c. There are fewer predators and parasites capable of attacking the non-native species in the new site d. The carrying capacity at the new site is higher than at the native site e. Growth changes from an S-curve to a J-curve at the new site 42. An ecosystem's carrying capacity for a population is determined by all of the following factors except: a. Space b. Energy c. Water d. Food e. Competition 43. The carrying capacity of an ecosystem is determined by a. the number of ecotones in the ecosystem b. the availability of resources in the environment c. demand for space d. demand for space, water and light e. the intersection between environmental resistance and biotic potential 44. Parasites affect population sizes of their hosts a. in a density dependent fashion, and usually directly kill the hosts b. in a density dependent fashion, and do not usually directly kill the hosts c. in a density independent fashion, and usually directly kill the hosts d. in a density independent fashion, and do not usually directly kill the hosts e. in a density dependent fashion, and do not affect host death rates 45. During the winter of 1999, minimum temperatures did not get much below freezing in an Oregon pond, and the following summer large mosquito populations were observed. In the winter of 2000, frost came early, and most ponds froze for 3 months. In the following summer, very low mosquito populations were observed. This is an example of a. density independent regulation b. density dependent regulation c. ecosystem carrying capacity d. community carrying capacity e. exotic regulation 46. When mosquitoes are very abundant, purple martins flock to the area and specialize on them. When mosquito populations are not large, purple martins are similarly scarce and feed on other insects. This is an example of a. density independent regulation b. density dependent regulation c. ecosystem carrying capacity d. community carrying capacity e. exotic regulation 47. Juglans nigra, or the black walnut, releases an allelopathic (toxic to other plants) compound when its leaves decompose; the result is that few plants can live under the canopy of the tree. Thus the black walnut can be said to engage in a. parasitism b. scramble competition c. sociopathic competition d. allele-dependent competition e. contest competition T/F 48. Prey, such as lemmings, may have a density-dependent effect on predator populations, such as those of the snowy owl, by enabling the predator to increase the number of predator offspring at high prey densities. F/B 49. When predators and prey both have population cycles, the predator cycle will tend to _______________ the prey cycle. 50. Predation is considered to be a density __________ factor that controls the population size of prey. 51. Competition among individual members of the same species is referred to as __________ competition. Match these with the types of effects they might have on a lemming population: a. Density-dependent b. Density-independent 52. In a population of lemmings which followed a boom and bust cycle, a sudden freeze which caused many of the lemmings to die would be a _____________ factor. 53. When the lemmings ran out of food because there were so many of them, this would be a ________________ factor. 54. In this situation wolves which ate lemmings whenever they could find them would be a ________________ factor. 55. When a population stops growing because it has reached the maximum number that the environment can support, we say that the population has reached what? 56. Regular population cycles of rapid growth followed by massive die-off are known as what? Essay 57. Predation is considered to be a density dependent factor that controls the population size of prey species. Give two examples of ways in which predators act in density dependent ways in response to fluctuations in prey population sizes. 58. Parasites may often kill their hosts, although they do not directly benefit from host death. And yet, many ecologists believe that parasites may have beneficial effects on their host populations. Why might this be so? 59. In high elevation forested ecosystems of New Hampshire and Vermont, ecologists have noticed a serious decline in certain tree species such as red spruce. When the affected trees are studied, it often seems that parasitic beetles or microbes are involved. Other scientists have stated that acid rain might be the cause of red spruce decline. Yet a third group of scientists have argued that both factors are equally involved. How could this third possibility be true, and which cause is likely to be density dependent, and which is more likely to be density independent? 60. How do interspecific and intraspecific competition differ from each other? 61. Which tends to be more intense, intra or interspecific competition? Explain why. M/C 62. The distribution pattern associated with organisms that are grouped together because of availability of resources, for mating, or for protection from predators is a. Random b. Uniform c. Aggregated d. Social e. Linear 63. Cottonwood trees grow in groups only along streams and rivers in grasslands. This is an example of what kind of distribution? a. Random b. Uniform c. Aggregated d. Community e. Constant 64. Some desert plants (such as the creosote bush) secrete chemicals which inhibit the growth of nearby plants. This results in ________ distribution. a. random b. uniform c. aggregate d. density-independent e. density-dependent 65. When organisms (rainforest plants, for example) form no social groups and the resources they need are evenly distributed, they will often show _________ distribution. a. random b. uniform c. aggregate d. individual e. clumped 66. Species which are territorial, such as nesting Redwing Blackbirds, often show a/an _________ distribution pattern. a. random b. uniform c. aggregate d. temporal e. sigmoidal F/B 67. If the distance between individuals in a population is relatively constant the population is ____________ distributed. 68. If adults of reproductive age are having just enough children to replace themselves, then the population is said to have _______________ fertility. Essay 69. Animal species often show a clumped spatial pattern due to mating or cooperation; uniform patterns might arise from a competition for resources such as nesting space. Desert plants such as the perennial shrub Larrae tridentata often show uniform spatial patterns in extremely dry desert conditions, and random spatial patterns in more mesic deserts. Why might this be so? 70. Just after the Industrial Revolution, many countries in Europe saw expanding populations: infant mortality went down and family size increased. However, after World War II, many countries in Eastern Europe are actually declining in population as families choose to have either one or no children. Draw the 2 age-structure diagrams for a country such as Hungary, with first the post-Industrial Revolution scenario, and then the current scenario. Hint: number of individuals by age is represented on the x-axis, and age is represented on the y-axis. 71. The U.S. fertility rate in 1999 was 2.1 meaning that the average family had 2.1 offspring. Why is 2.1 considered to be replacement level fertility in developed countries, and not 2? Finally, if the U.S. has replacement level fertility, why is the population growing rapidly? M/C 72. If most of the individuals of a species die when they are young, that species will exhibit a ________ survivorship curve. a. convex b. constant c. concave d. sigmoid (S-shaped) e. declining 73. If the individuals of a species are very likely to live until old age, that species will exhibit a ________ survivorship curve. a. convex b. constant c. concave d. sigmoid (S-shaped) e. declining 74. If all the individuals of a species have an equal chance of dying at any age, that species will exhibit a ________ survivorship curve. a. convex b. constant c. concave d. sigmoid (S-shaped) e. declining 75. Which survivorship curve is characteristic of many large animals including humans? a. Early loss b. Concave c. Constant loss d. Late loss e. Uniform F/B 76. A graph which shows patterns of death or survivorship over time is known as what? Essay 77. What are the 3 shapes of survivorship curves, and what does each one tell about the population? M/C 78. Human populations have continued to grow because humans have increased the ____________ of the earth by agriculture, medicine, and technology. a. biotic potential b. evolutionary pressure c. environmental resistance d. fertility e. carrying capacity 79. In the 18th and 19th centuries people increased the capacity of the earth to support more humans by the discoveries of the _____________ revolution. a. cultural b. agricultural c. industrial-medical d. social e. demographic 80. At current rates of growth there will be about ____ million more people on the earth a year from now than there are today. a. 1 b. 4 c. 15 d. 65 e. 90 81. Which best describes the reason for the very rapid growth of the human population in the last 8,000 years? a. Humans have a late-loss survivorship curve. b. Environmental resistance does not apply to humans. c. Climatic change has allowed the human species to expand its range. d. Technology has allowed the species to overcome some environmental resistance. e. The biotic potential for humans has increased. 82. Population growth rates are high in less-developed countries because a. Medicines have lowered death rates. b. Wealth has not lowered birth rates. c. Children are often an important economic advantage. d. Social traditions support large families. e. All of these are important reasons why population growth is high in less-developed countries. 83. In areas with a stable population, the number of children is a. Increasing b. Decreasing c. Approximately equal to the number of adults d. Higher than the number of adults e. Lower than the number of adults 84. In countries such as Nigeria which have large numbers of children under age 15, the population is a. Becoming larger b. Becoming smaller c. Staying the same d. Hard to predict e. Able to expand their carrying capacity 85. If a population's age structure diagram looks like a pyramid, the: a. Population is expanding b. Population is remaining the same c. Population will expand for at least a generation d. Population is showing continuous exponential growth 86. In countries such as France in which the number of children below 15 is approximately equal to the number between 15 and 45, the population is a. Expanding slowly b. Stable c. Shrinking slightly d. Growing exponentially e. Declining drastically 87. Less-developed countries tend to have a(n) ________________ age diagram. a. rectangular-shaped b. inverted triangle c. pyramid-shaped d. square e. round 88. If people in less-developed countries reached replacement-level fertility immediately, their populations would a. Decline slowly. b. Decline rapidly. c. Become stable. d. Continue to grow for many years. e. Grow for a short time and then decline rapidly. 89. The population of the USA continues to grow as a result of a. Immigration b. Babies born to baby boom generation parents c. Increases in fertility d. The birth rate was above replacement level fertility during the 1940's through 1960's e. All of the above are causes of population growth in the USA 90. Americans use about ____ times as much energy as the world average. a. 2 b. 3 c. 4 d. 5 e. 6 91. The United Nations estimates that by 2150 the world's population may stabilize at about ______ billion. a. 7 b. 8.5 c. 11.5 d. 15 e. 20.5 92. If all people in the world were to live at the level which Americans live in terms of technology, wealth, education, etc., the population of the world would have to ___________________ in order to support them. a. double b. reduce by half c. reduce to a fourth of current levels d. reduce to less than a 10th of the current population e. decline by 90% 93. Which developed country has the fastest population growth rate today? a. France b. Denmark c. China d. USA e. Russia 94. At present, the earth's human population is: a. Stable b. Declining c. Increasing exponentially d. Increasing at a constant rate e. Increasing at about 10% per year 95. A population grows exponentially when: a. the birth rate and the death rate are equal b. the birth rate exceeds the death rate and there is no immigration or emigration c. emigration exceeds immigration and the birth rate equals the death rate d. the birth rate equals the death rate and immigration is equal to emigration e. the carrying capacity is exceeded F/B 96. Where do most of the people in the world live today, in developed or developing countries? Essay 97. Why has it been so hard to come up with an accurate measure of the carrying capacity of the earth? 98. What factors determine the earth's carrying capacity for humans? (c) 2002 Prentice-Hall, Inc. All rights reserved. M/C 1. e 2. c Essay 3. They both are correct. An ecosystem is a network of interrelated living things and their physical environment. The boundaries of an ecosystem may be drawn almost anywhere, depending on the scope of the study. 4. Bacteria in the petri dish grow exponentially when first added, but the population stabilizes (and will eventually decline) as space and food become limiting. In the field, bacterial populations have already reached equilibrium with food availability. New food is "added" with plant inputs, but old food has been consumed so there is not a net accumulation of food resources. 5. Density-independent factors may include a mild winter, which reduces death rates and thus causes a population to increase; the accidental spill of a pesticide might cause the population to decrease in a manner that is density-independent. The increase in a predator population would cause a density-dependent reduction in population; the reduction of a competitor species might cause a density-dependent increase in population size. M/C 6. b 7. a 8. b 9. c 10. b 11. b 12. d 13. c 14. d 15. e 16. b T/F 17. False 18. False F/B 19. biotic potential 20. environmental resistance 21. growth rate 22. environmental resistance 23. Changes per individual per unit of time. Essay 24. Birth + immigration = death + emigration 25. The population grows by a fixed percentage of its size during each time period so that the actual numbers of individuals being added to the population gets larger at an ever increasing rate. 26. Population growth will slow even if the number of offspring per woman remains the same. 27. A bacterial population can increase more rapidly than an eagle population because each bacterial cell can reproduce every 20 minutes, whereas eagles reproduce less often and begin reproducing at an older age. M/C 28. a 29. a 30. e 31. b 32. d 33. c 34. a 35. e 36. a 37. b 38. a 39. e 40. a 41. c 42. e 43. b 44. b 45. a 46. b 47. e T/F 48. True F/B 49. lag behind 50. independent 51. intraspecific 52. b 53. a 54. a 55. Its carrying capacity. 56. Boom and bust cycles. Essay 57. Predators may not only adjust the number of prey that they eat in response to prey abundance, but they might switch to alternate food sources when prey abundances are low or specialize in feeding on the prey when population sizes are high. In addition, predators may regulate the number of offspring that they produce in response to prey abundances. 58. Parasites and predators tend to destroy weaker and less fit prey, leaving the stronger or better-adapted prey to reproduce and pass genes to the next generation. Thus the prey population is regulated but very fit individuals are not eliminated. 59. Population size is a result of complex interactions between density dependent and density independent regulation. Many parasites will respond to trees in a density dependent way, but weaken the trees so that a density independent factor (acid rain) will kill them; the reverse may also be true. 60. Inter - between two species, intra - between members of the same species 61. Intraspecific, because the individuals of the same species all need very similar resources. M/C 62. c 63. c 64. b 65. a 66. b F/B 67. uniformly 68. replacement level Essay 69. The uniform pattern probably arises from intense competition for water as a resource; if 2 plants are too close together, either both will die or else the weaker one will die. Under less intense competition, random factors of plant dispersal will overcome the need for uniform spacing due to competition. 70. The diagrams should look like the expanding and the shrinking diagrams of figure 38-14. 71. RLF is 2.1 because parents must replace both themselves and children who die before reaching maturity. Immigration, and lag timing of the baby boom is causing the U.S. population to expand. M/C 72. c 73. a 74. b 75. d F/B 76. A survivorship curve Essay 77. Convex - Most individuals survive to old age Constant - Equal chance of dying at any age Concave - High infant mortality M/C 78. e 79. c 80. e 81. d 82. e 83. c 84. a 85. b 86. b 87. c 88. d 89. e 90. d 91. c 92. c 93. d 94. c 95. b F/B 96. In less-developed countries Essay 97. Because humans have the ability to increase their own carrying capacity by a series of revolutions in agriculture, industry, and medicine. 98. The amount of water, light, nutrients, and space available to sustain the maximum human population size indefinitely.