Unit 8 Progress Check Review

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.

Yellowstone National Park annual wolf population from 1995 to 2016

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).

Which behaviors decreased in the presence of wolves?

• Rest

• Travel

• Hunt

• Feeding on Carcasses

• Vigilance

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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.

Yellowstone National Park annual wolf population from 1995 to 2016

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).

Which behaviors increased in the presence of wolves?

• Rest

• Travel

• Hunt

• Feeding on Carcasses

• Vigilance

Answer explanation

Although the mean proportion of time spent on travel increases in the presence of wolves, the error bars overlap, showing that the difference is not statistically significant.

Tags

NGSS.MS-LS2-1

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* 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.

Yellowstone National Park annual wolf population from 1995 to 2016

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).

Which behaviors were not effected by the presence of wolves?

• Rest

• Travel

• Hunt

• Feeding on Carcasses

• Vigilance

Answer explanation

Although the mean proportion of time spent on travel increases in the presence of wolves, the error bars overlap, showing that the difference is not statistically significant.

Tags

NGSS.MS-LS2-1

NGSS.MS-LS2-4

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?

• Reforestation efforts in Britain near this section of the river have caused changes in the plant community structure.

• Increased fertilizer use near this section of the river has led to increased runoff of phosphates into the river.

• Spiked water-milfoil adapted to lower phosphorous conditions has been observed to outcompete fennel-leaved pondweed in this section of the river.

• Measured levels of SRP in this section of the river have remained constant over a period of time.

Answer explanation

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.

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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.

Identify possible explanations for the discrepancies in the Kelp density between Alaid Island and Adak Island.

• Adak Island has more fertilizer runoff allowing for more kelp growth

• The reintroduction of otters in Adak Island limits the herbivory of Kelp by Sea Urchins

• Alaid Island has more fertilizer runoff limiting Kelp growth

• The absence of otters in Alaid Island resulted in Sea Urchins feeding on Kelp without limits

Answer explanation

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.

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* 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?

• Increased rainfall on land leads to increased nutrient runoff into the ocean and increased food resources for marina iguanas.

• Warm surface water contains fewer nutrients needed by red and green algae than cooler surface waters does.

• Warm surface water shortens the incubation time of marine iguana embryos.

• Cool surface water decreases the metabolic rate of marine iguanas, so they need more food to compensate for the lowered metabolic rate.

Answer explanation

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.

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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.

Increased rainfall could lead to increased nutrient runoff into the ocean which will, in turn, increase the red and green algae. How will this increased nutrient runoff effect the iguanas?

• Iguanas will increase

• Iguanas will decrease

• Iguana populations would remain stable

Tags

NGSS.MS-LS2-1

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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.

What are some of the effects of El Niño?

• Cool surface water

• Warm surface water

• Increased rainfall

• Decreased rainfall

Tags

NGSS.MS-ESS2-6

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* 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?

• The light, moist environment is the most ideal environment for plants.

• The most diverse environment is the dark, dry environment because plants are best able to protect themselves from drying out during the summer months.

• Based on the data, there is no statistical difference between the species diversity of plants in the light, moist environment and in the dark, moist environment.

• Based on the data, there is no statistical difference between the species diversity of plants in light, dry and dark, dry environments.

Answer explanation

Because the error bars overlap, the light, moist and dark, moist environments show no significant statistical difference in diversity.

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* 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.

Yellowstone National Park annual wolf population from 1995 to 2016

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.

• The presence of wolves

• The proportion of time

• Coyote behavior

• The study area

Answer explanation

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.

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