Unit 8 - AP Biology

In an experiment, three different animals were exposed to a series of environmental temperatures and their body temperatures were assessed at multiple temperature points between 10 and 40 degrees Celsius. Ten different individuals of each type of animal were included in the study to produce an average body temperature profile for each type of animal. Figure 1 shows the data collected. Which of the following statements is most consistent with the data in Figure 1 ? A - Armadillos tend to be more metabolically active than either gerbils or snakes are. B - Armadillos cannot survive at environmental temperatures over 30°C. C - Snakes are found in terrestrial rather than aquatic environments. D - Snakes display behaviors that allow them to absorb or radiate heat as required.

D - Snakes display behaviors that allow them to absorb or radiate heat as required. (Correct. Figure 1 shows that snakes cannot control their internal temperatures through metabolic processes. In low temperatures, snake will bask on rocks and flatten their profiles to absorb heat to raise their body temperatures above ambient temperature.)

In an experiment to determine the effect of light availability on species richness in an environment, a grassland was divided into 26 plots that were assigned to one of two treatment groups: 1. Clipped - plots were mowed to simulate the grazing of herbivores that maintain the low height of grasses. 2. Enclosure - plots were enclosed in fences, and grasses were allowed to grow undisturbed to their maximum height. After eight years, data was collected on the amount of light penetration to the soil (bottom light density) and the number of species in the two treatment groups. Figure 1 shows the averaged light penetration measurements, and Figure 2 shows the averaged number of species per plot type. Which of the following statements is consistent with the data shown in the figures? A - Grazing activity in a field decreases the species richness of the field. B - Different patterns of energy availability in ecosystems will affect species richness. C - Forests that develop a closed canopy with a shaded floor will exhibit increased species richness. D - The enclosed plots are more efficient at capturing and distributing energy than the clipped plots.

B - Different patterns of energy availability in ecosystems will affect species richness. (Correct. When light energy is allowed to reach the soil surface of an ecosystem, species richness is greater than when most of the light is absorbed before it can reach the soil surface.)

In the Florida Everglades, Burmese pythons are an invasive species. They were introduced into southern Florida in 1992. These pythons feed on many of the native Florida species, establishing the pythons as the top predator in the environment. By the year 2000, their population had increased dramatically. Figures 1 and 2 display data collected by ecologists studying the results of the Burmese python invasion. Figure 1 shows counts of animals collected from nighttime road surveys in southern Florida, which are used to estimate population size. Figure 2 shows data collected from mosquitoes captured from the wild. DNA sequencing was used to identify the species of blood that the mosquitoes had in their stomachs, identifying various hosts used by the mosquitoes. In 1996, the native Culex cedecei mosquitoes in southern Florida preferentially took blood meals from white-tailed deer and raccoons. It was predicted that changes in host population size would alter these host preferences. Additionally, it is known that cotton rats are often infected by the Everglades virus, which normally exists in animals, but is capable of infecting humans. Ecologists predict that increased feeding on cotton rats by C. cedecei may significantly increase the tendency of this virus to infect humans. Which of the following most accurately explains an impact of Burmese pythons on the Everglades community in southern Florida using the data provided? A - Python parasitism has reduced the population of white-tailed deer and raccoons. B - Python predation has caused a trophic cascade that changed the mosquitoes' niche. C - Pythons have a mutual symbiosis with cotton rats, allowing their population to increase. D - Intraspecific competition for food between white-tailed deer and raccoons has increased due to pythons.

B - Python predation has caused a trophic cascade that changed the mosquitoes' niche. (Correct. Since predation by invasive Burmese pythons has decreased the number of white-tailed deer and raccoons, the mosquitoes are forced to use alternative hosts, including cotton rats.)

Bt corn varieties are genetically modified to produce a toxin that specifically kills corn borers, a type of insect that eats and damages corn crops. Insects that are not closely related to corn borers are not affected by the toxin. Figure 1 shows the increasing production of Bt corn varieties and the change in the use of broad-spectrum pesticides that were the primary means of killing corn borers before the invention of Bt corn. How do the data in Figure 1 support the alternative hypothesis that increased use of Bt corn reduces the impact of corn farming on the natural environment? A - The increased use of Bt corn will result in rapid mutation in corn borers. B - The toxin in Bt corn kills only the corn pests, leaving other insects unharmed. C - Other insect species will replace corn borers and require additional applications of insecticides. D - Since Bt corn is not natural like non-Bt corn, it will not interact with the rest of the environment.

B - The toxin in Bt corn kills only the corn pests, leaving other insects unharmed. (Correct. Bt corn is modified to be toxic to certain insects; thus, it doesn't require as much insecticide. The graph shows this trend.)

The marine iguana, Amblyrhynchus cristatus, is endemic to the Galápagos Islands and is especially vulnerable to El Niño events. These iguanas feed on red and green algae. During an El Niño climate event, surface waters and their currents in the central and eastern Pacific Ocean become significantly warmer than usual. Also during El Niño years, land masses experience increased rainfall. A researcher suggests that El Niño conditions cause a significant decrease in the size of the Galápagos marine iguana population. Which of the following would best support this alternative hypothesis? A - Increased rainfall on land leads to increased nutrient runoff into the ocean and increased food resources for marina iguanas. B - Warm surface water contains fewer nutrients needed by red and green algae than cooler surface waters does. C - Warm surface water shortens the incubation time of marine iguana embryos. D - Cool surface water decreases the metabolic rate of marine iguanas, so they need more food to compensate for the lowered metabolic rate.

B - Warm surface water contains fewer nutrients needed by red and green algae than cooler surface waters does. (Correct. Upwelling brings cold, nutrient-rich waters to the surface. During El Niño years this is inhibited, so algae populations decrease because nutrients are limiting, resulting in decreased marine iguana populations.)

Meerkats live together in groups to help raise and protect their offspring. Meerkat pups are most vulnerable when they are away from their burrow foraging for food. Adult meerkats exhibit sentinel behavior, standing upright and making alarm calls to warn other members in the group that predators are nearby. In a study of meerkat behaviors, scientists observed meerkat foraging groups and recorded the presence or absence of pups along with the frequency of adult sentinel behavior. The scientists determined that sentinel behavior increased when pups were present in the foraging group. Which of the following correctly identifies the dependent and independent variables in the described study? A - The frequency of sentinel behavior is the independent variable, and the presence of pups is the dependent variable. B - The presence of pups is the independent variable, and the frequency of sentinel behavior is the dependent variable. C - The number of predators is the independent variable, and the presence of pups is the dependent variable. D - The distance from the burrow is the independent variable, and the number of predators is the dependent variable.

B - The presence of pups is the independent variable, and the frequency of sentinel behavior is the dependent variable. (Correct. The scientists are studying the relationship between the presence of pups (independent variable) and the frequency of sentinel behavior (dependent variable).)

A study recorded changes in the distribution of some commercial marine species off the East Coast of the United States over a period of several decades. The results of the study are summarized in Figure 1. Some researchers link changes in the distribution of these species to warming of the oceans due to climate change. Which of the following pieces of data best supports this alternative hypothesis? A - Decreased acidity of ocean water in the more southern latitudes caused a migration of these species northward. B - These species evolved new adaptations over time, allowing them to survive in warmer ocean environments. C - The prey of these species require colder waters to survive, and owing to warming in the oceans, they are moving farther north, to higher latitudes, where the water is colder. D - Diseases devastated the prey of these species, forcing them to move northward as insufficient food was available in their original range.

C - The prey of these species require colder waters to survive, and owing to warming in the oceans, they are moving farther north, to higher latitudes, where the water is colder. (Correct: Global increases in average temperature are associated with global climate change. This would produce warming in the oceans, so the prey these fish depend on can survive only by moving to more northern latitudes with colder waters. The fish would move with their food sources.)

In a study of energy flow, the following data were collected: Each human requires 55 grams of protein per day. An acre of soybeans produces 200,000 grams of protein per year. A cow grazing on one acre of land produces 19,000 grams of protein per year. Based on these data, an acre of land would support: 10 humans per year on a diet of soy, or 0.9 human per year on a diet of beef. Which of the following statements best explains these relationships in terms of energy transfer? A - Humans are better adapted to make efficient use of soy protein than beef protein, so they can extract more energy from a gram of soy protein than from a gram of beef protein. B - A cow can harvest energy only at a certain rate, so adding another cow to the acre of land would double the number of humans supported by the acre. C - Preparing meat for human consumption takes more energy per gram of protein than preparing soy for consumption. D - Only 10% of the energy on each level of the trophic pyramid is available for use by the next level. The rest is lost as heat or used for growth and repair.

D - Only 10% of the energy on each level of the trophic pyramid is available for use by the next level. The rest is lost as heat or used for growth and repair. (Correct. The 10% rule states that approximately 90% of the energy at any trophic level is lost to heat, growth, and repair of the organisms, and only 10% is available for harvesting by the next trophic level.)

In the mid-1920s, gray wolves, Canis lupus, were eliminated from Yellowstone National Park in the northwestern United States. Over the course of 1995 and 1996, 31 wolves from Canada were relocated to the park. Researchers have tracked the growth of the wolf population from 21 in 1995 to 108 at the end of the study in 2016 (Figure 1). The wolves prey on large herbivores, primarily elk. The carcasses of wolf kills are a valuable food source for coyotes, Canis latrans. When coyotes are feeding on carcasses, they may be chased off the carcass and/or killed by wolves. Coyotes also hunt small mammals for food. Researchers were studying the effect of wolves' presence on the behavior of coyotes. Researchers observed coyotes in a specific area of Yellowstone National Park and recorded the proportion of the coyotes' time spent on five different activities when wolves were present in the study area and when wolves were absent (Figure 2). Based on information in Figure 1, which of the following is closest to the annual growth rate of the wolf population in Yellowstone National Park from 1996 to 2004 ? A - 4 wolves per year B - 17 wolves per year C - 87 wolves per year D - 135 wolves per year

B - 17 wolves per year (Correct. The equation for calculating a rate is dY/dt, which is the difference in the variable on the y-axis divided by the difference in the variable on the x-axis. In this case, that equation becomes annual population growth rate = (final population size - initial population size)/(number of years). According to Figure 1, in 1996 the population was 36 wolves, and 8 years later, in 2004, the population was 171 wolves. Therefore, 171−368=16.875, which can be rounded to 17 wolves per year.)

Researchers were studying species diversity in a savanna rangeland community in southwest Queensland, Australia. Researchers counted the numbers of plants species in four different categories at two nearby sites within the savanna rangeland; one lightly grazed by herbivores and one heavily grazed by herbivores (Figure 1). Which of the following best predicts the results of a drought in the savanna research area with regards to community resilience to this environmental change? A - The heavily grazed area is more likely to recover more quickly from the drought due to reduced competition between species. B - The lightly grazed area is likely to recover more quickly from the drought due to greater biodiversity. C - The lightly and heavily grazed areas are likely to recover at equal rates due to the overlapping categories of plant species. D - The lightly and heavily grazed areas are likely to recover at equal rates due to the similar climates and locations.

B - The lightly grazed area is likely to recover more quickly from the drought due to greater biodiversity. (Correct. As shown in Figure 1, the lightly grazed area has a greater number of species of grasses, herbaceous flowering plants, and subshrubs. Higher levels of biodiversity in an ecosystem are associated with the greater ability of an ecosystem to respond to environmental changes. After a drought, some species will recover more quickly than others and the greater the biodiversity, the faster the ecosystem is likely to recover.)

In the Florida Everglades, Burmese pythons are an invasive species. They were introduced into southern Florida in 1992. These pythons feed on many of the native Florida species, establishing the pythons as the top predator in the environment. By the year 2000, their population had increased dramatically. Figures 1 and 2 display data collected by ecologists studying the results of the Burmese python invasion. Figure 1 shows counts of animals collected from nighttime road surveys in southern Florida, which are used to estimate population size. Figure 2 shows data collected from mosquitoes captured from the wild. DNA sequencing was used to identify the species of blood that the mosquitoes had in their stomachs, identifying various hosts used by the mosquitoes. In 1996, the native Culex cedecei mosquitoes in southern Florida preferentially took blood meals from white-tailed deer and raccoons. It was predicted that changes in host population size would alter these host preferences. Additionally, it is known that cotton rats are often infected by the Everglades virus, which normally exists in animals, but is capable of infecting humans. Ecologists predict that increased feeding on cotton rats by C. cedecei may significantly increase the tendency of this virus to infect humans. Based on the data, which of the following most accurately matches a potential change with its predicted effects on the southern Florida ecosystem? A - Introduction of a new top predator species that preys solely on Burmese pythons would cause an increase in the raccoon population. B - If the population of Burmese pythons were to decrease, then the cotton rat population would increase. C - If more Burmese pythons are introduced in the Everglades, then mosquitoes will begin feeding on white-tailed deer frequently again. D - Introduction of a new snake species that competes with the Burmese python for food would lead to an increase in the white-tailed deer population.

A - Introduction of a new top predator species that preys solely on Burmese pythons would cause an increase in the raccoon population. (Correct. If the Burmese python population were reduced, then there would be less predation on raccoons, and the raccoon population would be able to grow larger. The same would be true of the white-tailed deer population.)

Zebra mussels, Dreissena polymorpha, were introduced into the Great Lakes on shipping vessels, first appearing in Lake St. Clair in the 1980s. Since that time, they have rapidly expanded in range, as shown in Figure 1. Which of the following best supports the alternate hypothesis that zebra mussels display characteristics of an invasive species? A - Lacking natural predators and able to outcompete native species of mussels and other freshwater species for food, zebra mussels have experienced exponential population growth and rapid expansion into new habitats. B - Since their arrival, zebra mussels have undergone rapid adaptive radiation, producing new species in many different habitats. C - Throughout their current range, zebra mussels coexist with native mussel species, whose populations have been unaffected by the arrival of zebra mussels. D - Zebra mussels can crossbreed with native mussels, producing hybrids that are better adapted in the range shown in Figure 1.

A - Lacking natural predators and able to outcompete native species of mussels and other freshwater species for food, zebra mussels have experienced exponential population growth and rapid expansion into new habitats. (Correct. Because invasive species typically do not have natural predators in the habitats into which they are introduced, they can experience rapid exponential population growth. In addition, because these mussels are able to outcompete native species, zebra mussel range has expanded rapidly.)

Climate change can affect oceanic ecosystems and their food webs. In the East China Sea (ECS), three major climactic events were considered: the Pacific Decadal Oscillation (PDO), the East Asia winter monsoon (EAWM), and the El Niño Southern Oscillation. Figure 1 shows the relationships among these climactic events, surface sea temperature (SST), amount of phytoplankton, and copepod abundance. Copepods are important primary consumers in this ecosystem, and many species of fish depend on copepods as a food source. Solid arrows on the diagram indicate a statistically significant effect. The thicker the arrow, the greater the effect. Dashed arrows indicate statistically insignificant relationships. What do the data in Figure 1 suggest about a null hypothesis that the East China Sea ecosystem is unaffected by climactic events? A - The null hypothesis is rejected since there are significant effects of EAWM and PDO on surface sea temperature and copepod abundance. B - The null hypothesis is rejected because the El Niño Southern Oscillation has a significant impact on the abundance of copepods in the ECS. C - The null hypothesis is rejected because the EAWM and PDO do not have significant effects on the abundance of copepods and phytoplankton in the ECS. D - The null hypothesis is rejected because the El Niño Southern Oscillation does not have a significant impact on the abundance of copepods in the ECS.

A - The null hypothesis is rejected since there are significant effects of EAWM and PDO on surface sea temperature and copepod abundance. (Correct. The null hypothesis should be rejected because the data indicate that the EAWM and the PDO have significant effects on surface sea temperature as well as copepod abundance.)

Bison in Yellowstone National Park have a food-limited carrying capacity that determines how their population grows. If the population grows too large, some bison will either starve or migrate to search for more food. The park is able to support a maximum population of 4,500 bison. Park conservation officials must watch the population and prevent the bison from overpopulating, since they would migrate to nearby farms, causing agricultural damage and creating hazards to drivers. The bison begin to migrate when the population reaches 4,000 because of competition for food. If the current population size of bison is 3,652 and the maximum growth rate of the population is 0.28, calculate the population size after one year and determine whether the park will need to take measures to control the population. A - The population will be 3,845 after a year. The bison will not pose a problem until the following year, and no conservation action will need to take place. B - The population will be 4,675 after a year. Some bison will need to be removed to prevent migration, since they will surpass the resource availability. C - The population will be 1,023 after a year, since the growth rate is too low. Conservation efforts will need to focus on increasing the bison population. D - The population will be 4,500 after a year. The bison cannot exceed the carrying capacity, so they will stop reproducing. Some bison will need to be removed.

A - The population will be 3,845 after a year. The bison will not pose a problem until the following year, and no conservation action will need to take place. (Correct. dN/dt=rmaxN(K−NK) should be used to determine the one-year change in population size: 0.28×3,652(4,500−3,6524,500)=193. Adding 193 to 3,652 projects a population of 3,845, so the population will not reach the point at which bison migration occurs. However, it will reach a level to initiate migration the following year.)

In the mid-1920s, gray wolves, Canis lupus, were eliminated from Yellowstone National Park in the northwestern United States. Over the course of 1995 and 1996, 31 wolves from Canada were relocated to the park. Researchers have tracked the growth of the wolf population from 21 in 1995 to 108 at the end of the study in 2016 (Figure 1). The wolves prey on large herbivores, primarily elk. The carcasses of wolf kills are a valuable food source for coyotes, Canis latrans. When coyotes are feeding on carcasses, they may be chased off the carcass and/or killed by wolves. Coyotes also hunt small mammals for food. Researchers were studying the effect of wolves' presence on the behavior of coyotes. Researchers observed coyotes in a specific area of Yellowstone National Park and recorded the proportion of the coyotes' time spent on five different activities when wolves were present in the study area and when wolves were absent (Figure 2). Based on the data in the figure, a student claimed that since 2007, the carrying capacity of wolves in Yellowstone National Park has been 100 wolves, and the maximum annual per capita growth rate of gray wolves is 0.6 wolves per wolf per year. Which of the following is closest to the calculated wolf population size in 2017 based on the student's claim? A - 100 B - 103 C - 113 D - 173

B - 103 (Correct. According to the logistic growth model, the change in population size (dN/dt) can be calculated using the equation dN/dt=rmaxN(K−NK). According to the student's claim, rmax=0.6wolves/year and K=100K=100 wolves. From Figure 1, N=108N=108 wolves in 2016. Therefore, dN/dt=0.6×108×(100−108100)=−5.184. The -5.184 needs to be added to the 2016 population size to get the population size for 2017: 108+(−5.184)=102.816, which is rounded to 103 to get the final answer.)

Soluble reactive phosphate (SRP) is a term used to describe the amount of phosphate available for uptake by living things. A study of river plants species and water phosphate levels was completed in Great Britain. Recently, in a section of one of the rivers studied, a population of fennel-leaved pondweed was replaced by spiked water-milfoil, even though these two plants are associated with different environmental conditions as indicated in the table below. A group of researchers suggest that the concentration of available phosphate in this particular section of the British river does not have a significant impact on which plant species grow. Alternatively, another group of researchers hypothesize that levels of available phosphate do affect which plant species grow at this location. Which of the following observations would best support this alternative hypothesis? A - Reforestation efforts in Britain near this section of the river have caused changes in the plant community structure. B - Increased fertilizer use near this section of the river has led to increased runoff of phosphates into the river. C - Spiked water-milfoil adapted to lower phosphorous conditions has been observed to outcompete fennel-leaved pondweed in this section of the river. D - Measured levels of SRP in this section of the river have remained constant over a period of time.

B - Increased fertilizer use near this section of the river has led to increased runoff of phosphates into the river. (Correct. Human activities such as the addition of organic or chemical fertilizers to lawns, golf courses, and agricultural lands and the observed increase in runoff of the phosphorus in these fertilizers into the rivers is the most likely contributor to the increased SRP level in the water that resulted in the change in plant species.)

In the Florida Everglades, Burmese pythons are an invasive species. They were introduced into southern Florida in 1992. These pythons feed on many of the native Florida species, establishing the pythons as the top predator in the environment. By the year 2000, their population had increased dramatically. Figures 1 and 2 display data collected by ecologists studying the results of the Burmese python invasion. Figure 1 shows counts of animals collected from nighttime road surveys in southern Florida, which are used to estimate population size. Figure 2 shows data collected from mosquitoes captured from the wild. DNA sequencing was used to identify the species of blood that the mosquitoes had in their stomachs, identifying various hosts used by the mosquitoes. In 1996, the native Culex cedecei mosquitoes in southern Florida preferentially took blood meals from white-tailed deer and raccoons. It was predicted that changes in host population size would alter these host preferences. Additionally, it is known that cotton rats are often infected by the Everglades virus, which normally exists in animals, but is capable of infecting humans. Ecologists predict that increased feeding on cotton rats by C. cedecei may significantly increase the tendency of this virus to infect humans. Scientists hypothesize that the invasive Burmese pythons are responsible for recent increases in human Everglades virus infections. Evaluate this alternate hypothesis using the data provided. A - The alternate hypothesis is supported because invasive Burmese pythons caused an increase in the mosquito population. This enabled them to transmit the Everglades virus at a higher frequency if they were infected. B - The alternate hypothesis is supported because the invasive Burmese pythons caused mosquitoes to switch to feeding on cotton rats. This means that mosquitoes are more likely to carry the Everglades virus when they bite humans. C - The alternate hypothesis is refuted because humans are used as hosts for only a small percentage of mosquito feedings. Humans therefore will not have an increase in Everglades virus infection. D - The alternate hypothesis is refuted by the data because the population of cotton rats increased. Since there are more cotton rats, they will contain the Everglades virus and prevent it from infecting humans.

B - The alternate hypothesis is supported because the invasive Burmese pythons caused mosquitoes to switch to feeding on cotton rats. This means that mosquitoes are more likely to carry the Everglades virus when they bite humans. (Correct. As mosquitoes change hosts from white-tailed deer and raccoons to cotton rats, they will more frequently be carriers of the Everglades virus. Thus, interactions with humans are more likely to result in transmission of the Everglades virus.)

Potatoes as a food crop originated in South America. There are over 4,000 variations of potato grown there. Potatoes were brought to Europe by Spanish colonists in the late 1500s. One variety became the chief crop grown in much of Ireland by the early 1800s. Table 1 summarizes the spread of potatoes as a food crop. The Irish Lumper variety of potato was introduced into Ireland in the early 1800s. The Lumper soon became the only variety of potato grown in much of Ireland. The potato blight destroyed most of the Lumper crop between 1845 and 1852 resulting in the death of about 1 million Irish from starvation. A researcher suggests that the Irish monoculture (growing a single crop) of the Lumper potato did not significantly change the overall resistance of the potato crop in Ireland to diseases. Which of the following observations best refutes this null hypothesis? A - Before the arrival of the potato blight, there were already two other potato plant diseases in Ireland. B - The number of fatalities from the Irish potato famine was greater than the rest of the European countries combined. C - During the early nineteenth century, the vast majority of people in Ireland depended on the Lumper potato for food. D - Growing more varieties of potatoes increases competition for available resources, which may yield fewer potatoes.

B - The number of fatalities from the Irish potato famine was greater than the rest of the European countries combined. (Correct. Table 1 shows that twelve different varieties of potatoes were grown across Europe, as compared to the Lumper variety in Ireland. This suggests that the European potato crop, with more varieties, was less affected by the potato blight. This observation would support the alternative hypothesis that the variability of potato crops did affect the impact of the potato famine in Europe compared to Ireland.)

A group of biologists were investigating the effects of light color on phototropism (growing toward the light source) in tomato plants. Four groups of tomato plants were grown in the same greenhouse under identical conditions. Each group was then placed in a different room, each room having a different color of light, exposed to that single color of light from different directions for one week at a time. After each week, the biologists counted the number of tomato plants in the groups that were showing evidence of phototropism. The results are summarized in Table 1. Which of the following correctly identifies the dependent and independent variables in this experiment? A - The color of the light is the dependent variable, and the percentage of plants showing phototropism is the independent variable. B - The percentage of plants showing phototropism is the dependent variable, and the color of the light is the independent variable. C - The direction of the light is the dependent variable, and the percentage of plants showing phototropism is the independent variable. D - The color of the light is the dependent variable, and the direction of the light is the independent variable.

B - The percentage of plants showing phototropism is the dependent variable, and the color of the light is the independent variable. (Correct. The dependent variable is a variable whose value depends on that of another. For this experiment, this would be the percentage of plants showing phototropism. The independent variable represents the potential reason or cause for a given outcome. In this case, it is the color of the light.)

The population of Japanese sika deer in central Japan was determined each year from 2005 to 2014. The sika deer population underwent logistic growth starting at 26,000 deer in 2005 and stabilized at 58,000 deer between 2012 and 2014. Based on these data, the rmax for this population was determined to be 0.57. Central Japan contains a variety of habitats, including forests and grasslands. Sika deer benefit from the resources in grasslands more than forests; if deforestation occurred, producing more grasslands in the region, the carrying capacity for sika deer population would increase. What would the population size of sika deer be one year after the carrying capacity increased to 70,000 as a result of deforestation? Assume rmax does not change. A - The population would grow to 70,000 deer in a year, because they would occupy the entire environmental niche. B - The population would grow to 91,060 deer in a year, but then they would die off from a lack of resources. C - The population would grow to 63,667 deer in a year, and the growth rate would decrease the following year. D - The population would remain at 58,000 deer, since it had already stabilized.

C - The population would grow to 63,667 deer in a year, and the growth rate would decrease the following year. (Correct. dN/dt=rmaxN(K−NK)should be used to calculate the increase in the population size after a year: 0.57×58,000×(70,000−58,00070,000)=5,6670. The new population size would be 5,667+58,000=63,667. The growth rate would decrease the following year because the population would be closer to the new carrying capacity and (K−NK) would get smaller.)

A biologist was investigating the effects of herbivory on the amount of nicotine produced by the leaves of tobacco plants (Nicotiana rustica). Six groups of plants were grown from seed in the same greenhouse with identical environmental conditions. Three groups were then each exposed for a different interval of time to tobacco hornworms (Maduca sexta), which feed on the foliage of tobacco plants. The amount of nicotine present in the leaves was measured at the beginning and end of each time interval. As a control, the other three groups were not exposed to hornworms. The results of the experiment are summarized in Table 1. Which of the following correctly identifies the dependent variable and the independent variable for the experiment? A - The dependent variable is the time interval the plants were exposed to the hornworms and the independent variable is the percent change in the amount of nicotine. B - The dependent variable is the absence or presence of hornworms, and the independent variable is the initial amount of nicotine. C - The dependent variable is the initial amount of nicotine, and the independent variable is the final amount of nicotine. D - The dependent variable is the percent change in the amount of nicotine, and the independent variable is the time interval the plants were exposed to the hornworms.

D - The dependent variable is the percent change in the amount of nicotine, and the independent variable is the time interval the plants were exposed to the hornworms. (Correct. The change in the concentration of nicotine is the factor being studied and is therefore the dependent variable. The time interval the plants were exposed to the hornworms is changed by the biologist and therefore the independent variable.)

Scientists are studying the two primary vocalizations made by Belding's ground squirrels (Urocitellus beldingi). The trill call consists of a series of medium-pitched notes given rapidly, while the whistle call consists of a single high-pitched note. The objective of the experiment is to determine the function of each vocalization. Recordings of the calls were played to four different groups of squirrels, and the response of each individual squirrel was documented. The responses are summarized in Table 1. Which of the following correctly identifies the dependent variable and the independent variable for the experiment? A - The independent variable is the percent of squirrels responding, and the dependent variable is the type of alarm call. B - The independent variable is the percent of squirrels responding, and the dependent variable is the type of response. C - The independent variable is the group of squirrels, and the dependent variable is the percent of squirrels responding. D - The independent variable is the type of alarm, and the dependent variable is the percent of squirrels responding.

D - The independent variable is the type of alarm, and the dependent variable is the percent of squirrels responding. (Correct. The type of alarm is the independent variable because it is the factor manipulated by the scientists. The response of the squirrels is being studied to determine how it is affected by the nature of the alarm and is therefore the dependent variable.)

Figure 1 shows the population fluctuations of phytoplankton and zooplankton in the eastern Pacific Ocean over the course of six years. The major dip in phytoplankton was attributed to a lack of nutrients for phytoplankton. Of the following, which explains why the zooplankton also dipped during the same year and then seemed to cycle over the next three years? A - The zooplankton rely on the same nutrients for energy harvesting as the phytoplankton, so their population was also unable to acquire the necessary energy to maintain their population level. After that major dip there were enough nutrients for both categories of plankton. B - Zooplankton are more temperature-sensitive than the phytoplankton, so the annual seasonal changes will affect their population sizes in a cyclical fashion. There was a sudden, extreme temperature change in the first dip that also affected the phytoplankton. C - A migration of whales was blown off course by a storm one year and ate most of the phytoplankton and zooplankton. In the following years the whales returned to their normal migration route. D - The reduction in the phytoplankton population meant that the zooplankton's energy source was drastically reduced, leading to the decrease in the zooplankton population size. After the dip, the phytoplankton provided a steady energy source, and the zooplankton population fluctuated around its carrying capacity.

D - The reduction in the phytoplankton population meant that the zooplankton's energy source was drastically reduced, leading to the decrease in the zooplankton population size. After the dip, the phytoplankton provided a steady energy source, and the zooplankton population fluctuated around its carrying capacity. (Correct. The energy source of zooplankton is the carbon compounds fixed by phytoplankton. Without the proper inorganic nutrients, the phytoplankton population is limited in its photosynthetic activity, leading to an energy deficit in the zooplankton populations. It is also correct that the annual fluctuations in zooplankton represent a stable population cycling around its carrying capacity.)

Sea otters living along the Pacific coast were hunted to near extinction in the nineteenth century. After being protected from hunting in the early 1900s, a remnant population of otters near Adak Island, Alaska, recovered rapidly. Otters did not return to the environmentally similar nearby island, Alaid Island. Sea otters eat sea urchins, which eat kelp, a brown alga. Researchers surveyed both islands in 1988, to measure sea urchin biomass and kelp density. The data are presented in Table 1. In 1991, researchers at Adak Island observed the first attack by a killer whale on a sea otter in historical times. The researchers hypothesized that the population sizes of the larger marine mammals that the killer whales normally prey on declined, so the killer whales were starting to prey on different prey, including the smaller sea otters. Which of the following best predicts the effects of an increase in killer whale predation on sea otters on the Adak Island ecosystem? A - Both the sea urchin population and the kelp population will increase, leading to greater total biomass and diversity in the Adak Island ecosystem. B - Both the sea urchin population and the kelp population will decrease, leading to reduced total biomass and diversity in the Adak Island ecosystem. C - The sea urchin population will increase and the kelp population will decrease, leading to greater total biomass and diversity in the Adak Island ecosystem. D - The sea urchin population will increase and the kelp population will decrease, leading to reduced total biomass and diversity in the Adak Island ecosystem.

D - The sea urchin population will increase and the kelp population will decrease, leading to reduced total biomass and diversity in the Adak Island ecosystem. (Correct. Increased predation by killer whales will lead to a decrease in the sea otter population at Adak Island. A decline in the sea otter population will allow the sea urchin population to increase without predation as a limiting factor. An increasing sea urchin population will lead to overgrazing and reduced kelp densities. Kelp forests provide important habitat and food for many other organisms, and their decline would cause the entire ecosystem to decline. Due to this cascade effect, sea otters are described as a keystone species because when they are removed from an ecosystem, the ecosystem declines rapidly.)

Which of the following best describes opportunistic, or r-strategy, organisms? A - They reach sexual maturity rapidly. B - They reach their adult size slowly. C - They attain a large body size. D - They live for a long time. E - The size of their population remains fairly constant.

A - They reach sexual maturity rapidly.

A fish population of 250 in a pond has a maximum annual rate of increase of 0.8. If the carrying capacity of the pond is 1,500 for this species, what is the expected population size after one year? A - 167 B - 417 C - 450 D - 500

B - 417 (Correct. Using the formula for logistic growth, dN/dt=rmaxN(K−NK), the increase in population is calculated: 8×250(1,500−2501,500)=166.7 Adding 166.7 to 250 (the current population) provides a predicted population of 417 after one year.)

A population of 250 birds inhabit the canopy of a tropical rain forest that has a carrying capacity of 400 birds. What is the maximum population growth rate (rmax) if the population grows to 283 in one year? A - 0.12 B - 0.13 C - 0.35 D - 0.39

C - 0.35 (Correct. This calculation uses the correct population size of N=250 and includes consideration of the carrying capacity (K=400) as part of the logistical growth pattern, as described by dN/dt=(283−250)=rmaxN(K−NK): 33=rmax×250×(400−250400)33=rmax×250×(400−250/400) and rmax=0.35rmax=0.35.)

Which of the following communities is likely to be most stable? A - One where a keystone predator has been removed B - One with uniformly spaced vegetation C - One with high species diversity D - One that lacks decomposers

C - One with high species diversity

In the process of succession, which of the following is true of K-selected plant species? A - They keep their carrying capacity at a minimum level. B - They usually reproduce early in life. C - They are usually found in climax stages of succession. D - They are the dominant species in early stages of succession. E - They have a short lifespan.

C - They are usually found in climax stages of succession.

A researcher is investigating the relationship between the existing species diversity in a community and the ability of an introduced nonnative species to destabilize the community. Which of the following graphs is most consistent with the claim that communities with high diversity are more resistant to change than are communities with low diversity?

Species diversity decreases steadily

In the mid-1920s, gray wolves, Canis lupus, were eliminated from Yellowstone National Park in the northwestern United States. Over the course of 1995 and 1996, 31 wolves from Canada were relocated to the park. Researchers have tracked the growth of the wolf population from 21 in 1995 to 108 at the end of the study in 2016 (Figure 1). The wolves prey on large herbivores, primarily elk. The carcasses of wolf kills are a valuable food source for coyotes, Canis latrans. When coyotes are feeding on carcasses, they may be chased off the carcass and/or killed by wolves. Coyotes also hunt small mammals for food. Researchers were studying the effect of wolves' presence on the behavior of coyotes. Researchers observed coyotes in a specific area of Yellowstone National Park and recorded the proportion of the coyotes' time spent on five different activities when wolves were present in the study area and when wolves were absent (Figure 2). Identify the independent variable for the experimental results shown in Figure 2. A - The presence of wolves B - The proportion of time C - Coyote behavior D - The study area

A - The presence of wolves (Correct. The independent variable is selected by the researchers, and the researchers test its effect on the dependent variable. In this experiment, the researchers were looking at the effect of wolves' presence on the behavior of coyotes. Therefore, the presence of wolves is the independent variable, and the behavior of coyotes is the dependent variable.)

In the mid-1920s, gray wolves, Canis lupus, were eliminated from Yellowstone National Park in the northwestern United States. Over the course of 1995 and 1996, 31 wolves from Canada were relocated to the park. Researchers have tracked the growth of the wolf population from 21 in 1995 to 108 at the end of the study in 2016 (Figure 1). The wolves prey on large herbivores, primarily elk. The carcasses of wolf kills are a valuable food source for coyotes, Canis latrans. When coyotes are feeding on carcasses, they may be chased off the carcass and/or killed by wolves. Coyotes also hunt small mammals for food. Researchers were studying the effect of wolves' presence on the behavior of coyotes. Researchers observed coyotes in a specific area of Yellowstone National Park and recorded the proportion of the coyotes' time spent on five different activities when wolves were present in the study area and when wolves were absent (Figure 2). Following the reintroduction of wolves to Yellowstone National Park, researchers measured the mean height of young aspen trees in upland and streamside areas. Which of the following is the most likely cause of the change in mean aspen height from 1998 to 2010 ? A - The reintroduction of wolves led to a decrease in the population of elk, allowing aspen trees to grow taller. B - The reintroduction of wolves led to a decrease in the population of small mammals, allowing aspen trees to grow taller. C - The reintroduction of wolves led to an increase in the number of carcasses that provided fertilizer for young aspen trees. D - The reintroduction of wolves led to an increase in the number of carcasses, so coyotes no longer ate young aspen trees.

A - The reintroduction of wolves led to a decrease in the population of elk, allowing aspen trees to grow taller. (Correct. Top carnivores are keystone species, meaning they have a larger role in maintaining an ecosystem than would be expected by their population size. After wolves were eliminated from Yellowstone National Park, the population of elk rose dramatically. The high elk population led to the overgrazing of plant species, including aspen. With the reintroduction of wolves, the elk population has declined, allowing plant species to recover.)

Students in a class were divided into five groups to analyze community structure. Each group of students assessed the species of plants in four environments and determined the Simpson's Diversity Index for each environment. The Simpson's Diversity Index takes into account the number of species present as well as the abundance of each species. The index values are shown in Figure 1. Based on the data in Figure 1, which of the following statements is most accurate about the species diversity of the four different environments that the students analyzed? A - The light, moist environment is the most ideal environment for plants. B - The most diverse environment is the dark, dry environment because plants are best able to protect themselves from drying out during the summer months. C - Based on the data, there is no statistically significant difference between the species diversity of plants in the light, moist environment and in the dark, moist environment. D - Based on the data, there is no statistically significant difference between the species diversity of plants in light, dry and dark, dry environments.

C - Based on the data, there is no statistically significant difference between the species diversity of plants in the light, moist environment and in the dark, moist environment. (Correct. Because the error bars overlap, the light, moist and dark, moist environments show no significant statistical difference in diversity.)