Question 1

Addition of artificial nitrogen fertilizers to agricultural lands causes an increase in nitrification and denitrification by bacteria.These processes in turn release nitrous oxide (N₂O) into the atmosphere.What are the implications of additional nitrous oxide in the atmosphere? A) It is a harmless, inactive gas that has little or no effect. B) It increases smog and acts as a greenhouse gas. C) It lowers atmospheric temperatures. D) It remains near Earth's surface, causing smog but not climate change. E) It is fixed by soil bacteria and therefore can increase plant growth.

Accepted Answer

Nitrous oxide is a potent greenhouse gas, which means it has a significant impact on global warming and climate change. Additionally, it can also contribute to the formation of smog, which can have negative impacts on human health and the environment.

Question 2

Offshore oil drilling provides a natural resource for human use, that is, an ecosystem service.In 2010, oil drilling in the Gulf of Mexico led to the Deepwater Horizon oil spill, which caused serious impacts on marine life, beaches, and the fishing and tourism industries.Does the likelihood of such oil spills as a result of the production of oil products constitute an ecosystem service trade-off? Why or why not?
A) No; the oil spill did not affect other ecosystem services.
B) No; the oil spill had impacts, but the ecosystem will recover, so it did not really cause a trade-off.
C) No; oil is a necessary resource, so any effects it has are worth the risk and can be overlooked.
D) Yes; a provisioning service degraded both provisioning and cultural services.
E) Yes; a provisioning service degraded another provisioning service (industries); other factors are not ecosystem services.

Accepted Answer

The likelihood of oil spills as a result of oil production constitutes an ecosystem service trade-off because the oil spill degrades the provisioning service (oil production) but also degrades cultural services (fishing and tourism industries) that rely on the ecosystem. Therefore, the correct answer is D. Choices A, B, and C are incorrect since they do not acknowledge the trade-off between ecosystem services. Choice E is incorrect because it only considers the degradation of one provisioning service by another, ignoring the impacts on cultural services.

Question 3

Refer to the graph.  Which conclusion can be drawn from the graph about the value of sustainable ecosystems, compared with the value of those converted entirely to human use?
A) Their value is only slightly greater.
B) Their value is generally several times greater.
C) Their value is generally several times less.
D) The values shown are estimates and are therefore meaningless.
E) The values shown are meaningless because ecosystems have no dollar value.

Accepted Answer

The graph shows that the value of sustainable ecosystems is generally several times greater than the value of those converted entirely to human use. This can be seen by comparing the height of the bars representing the different ecosystem services. The bars for sustainable ecosystems are generally taller than the bars for converted ecosystems. Therefore, option B is the best choice as it accurately reflects the information presented in the graph.

Question 4

As a result of human agriculture and urbanization, and more recently large-scale phosphorus mining, the amount of phosphorus in Earth's freshwater and terrestrial ecosystems has nearly quadrupled.This suggests that recent increases in algal blooms in many lakes might be occurring because phosphorus
A) is no longer a limiting factor.
B) has become a limiting factor.
C) is no longer entering its major pools.
D) is no longer cycling through organisms.
E) levels on Earth have increased.

Accepted Answer

The increase in phosphorus due to human actions suggests that it is no longer a limiting factor for algal growth. This supports choice A as the best answer.

Question 5

A soil ecosystem has very low plant growth and is found to be deficient in nitrogen.To obtain the nitrogen it needs using natural processes (as opposed to fertilizers added by humans), this ecosystem would need more _______ bacteria.
A) nitrifying
B) denitrifying
C) nitrifying and denitrifying
D) nitrifying and nitrogen-fixing
E) nitrogen-fixing

Accepted Answer

Nitrogen-fixing bacteria convert atmospheric nitrogen into forms that plants can use, thus addressing the nitrogen deficiency in the soil ecosystem.

Question 6

Agriculture as it is practiced in the United States today is big business, which feeds and employs many people.Which of these is not a trade-off, in terms of ecological services, that results from the practice of large-scale, industrial agriculture?
A) Loss of pollinators
B) Eutrophication
C) Less clean water
D) More soil erosion
E) Improved pollution control

Accepted Answer

Improved pollution control is not a trade-off that results from the practice of large-scale, industrial agriculture. In fact, modern agricultural practices have led to an increase in pollution control measures and technologies to minimize environmental impacts. The other options - loss of pollinators, eutrophication, less clean water, and more soil erosion - are all trade-offs that result from industrial agriculture.

Question 7

Pollination is considered an important ecosystem service.People value pollination, and other ecosystem services, because they provide
A) essential services that people cannot provide or that would be difficult or costly to replace.
B) nonessential, but beneficial, services that simply enhance our lives.
C) frivolous, but fun, services such as recreational areas or beautiful vistas.
D) over-rated services that some people, such as environmentalists, consider important.
E) essential services that we could provide for ourselves with little trouble but prefer not to.

Accepted Answer

Pollination, and other ecosystem services such as air and water purification, soil fertility, and climate regulation, are essential services that are critical to human survival and well-being. These services are provided by natural ecosystems and would be difficult or costly to replace through artificial means. Hence, people value pollination and other ecosystem services for their essential nature.

Question 8

Which of these ecosystem services could be considered an example of a cultural service?
A) Flood control
B) Soil stabilization
C) Pollination
D) Climate regulation
E) A beautiful trail through a national park

Accepted Answer

A beautiful trail through a national park is an example of a cultural service, as it provides recreational and aesthetic value to humans. Choices A, B, C, and D are all examples of ecosystem services that benefit humans in more tangible ways, such as preventing damage from natural disasters or supporting crop production.

Question 9

In 2005, bleaching of coral reefs in the Caribbean killed half of the reefs.The National Ocean Service measured their temperature stress at 20 times higher than that of the previous 20 years combined.Also, many fewer coral larvae are settling in areas with higher-than-normal ocean acidity.From this information, what can be inferred about the effects on coral reefs of increased atmospheric CO₂? A) It has little effect in oceans; the only major effect is on land. B) It has a minor effect; some CO₂ enters the ocean and raises temperatures. C) It causes only temperature effects, as air temperatures cause the ocean to warm. D) It causes only acidity effects, as it dissolves in the water and forms acid. E) It causes both temperature and acidity effects; air temperature warms the ocean and dissolved CO₂ increases acidity.

Accepted Answer

The information provided suggests that increased atmospheric CO2 causes both temperature and acidity effects on coral reefs. The bleaching event in the Caribbean in 2005 was caused by high ocean temperatures, which were likely influenced by increased atmospheric CO2. Additionally, higher-than-normal ocean acidity is affecting the settlement of coral larvae. This suggests that dissolved CO2 is increasing the acidity of the ocean, which can have negative impacts on coral reefs.

Question 10

The flood control, wildlife habitat, and spawning grounds for marine organisms that coastal wetlands provide are
A) biogeochemical cycles.
B) ecosystem services.
C) environmental functions.
D) sustainable practices.
E) ecosystem evaluations.

Accepted Answer

The services provided by coastal wetlands, including flood control, wildlife habitat, and spawning grounds, are examples of ecosystem services. Ecosystem services are the benefits that humans receive from the natural environment.

Question 11

Currently, we can describe the general status of most ecosystem services in the United States as being
A) in excellent condition.
B) unchanged from the last century.
C) increasingly more degraded.
D) more functional than in the last century.
E) increasingly more sustainable.

Accepted Answer

Most ecosystem services in the United States are increasingly more degraded. This is due to human activities such as deforestation, pollution, and climate change. While there are some efforts to restore and protect ecosystem services, they often face significant challenges and are not keeping up with the rate of degradation.

Question 12

Refer to the figure.  The activities of the nitrogen cycle, as represented in the figure, are
A) nearly all initiated by human activities.
B) nearly all initiated by bacterial activities.
C) chemical, rather than biological, in nature.
D) biotic and relatively unimportant to the nitrogen cycle.
E) abiotic and relatively unimportant to the nitrogen cycle.

Accepted Answer

The figure shows various bacteria involved in different stages of the nitrogen cycle, indicating that nearly all activities are initiated by bacterial activities.

Question 13

DMSP, a chemical produced by ocean phytoplankton and seaweed, breaks down to produce the gas dimethyl sulfide.The fact that 70 percent of Earth's surface is covered with oceans suggests that the production of dimethyl sulfide is
A) relatively unimportant to the world sulfur cycle.
B) important to the sulfur cycle, but only within the oceans.
C) important only to the biotic portion of the sulfur cycle.
D) an essential part of the world sulfur cycle.
E) important when it breaks down and is taken up by plants.

Accepted Answer

The question specifically mentions that DMSP and its breakdown product, dimethyl sulfide, are important to the "world sulfur cycle." Additionally, the fact that it is produced by phytoplankton and seaweed suggests that it is involved in the biotic portion of the cycle, as these organisms are living and part of the ecosystem. Finally, the fact that 70 percent of the Earth's surface is covered in oceans suggests that the production of dimethyl sulfide is widespread and therefore an essential part of the overall sulfur cycle.

Question 14

The San Francisco Bay area was once surrounded by extensive tidal marshes, which were filled in for a variety of purposes, including building cities, factories, and other urban structures.These salt marshes once provided homes to many plants and animals and provided flood control and clean water to the human residents.These ecosystem services, lost when the marshes were drained and filled, belong to which ecosystem service category or categories?
A) Provisioning services only
B) Regulating services only
C) Supporting services only
D) Provisioning and regulating services
E) Regulating and supporting services

Accepted Answer

The salt marshes provided flood control and clean water (regulating services) and homes to many plants and animals (provisioning services).

Question 15

A major characteristic of the phosphorus cycle is that it
A) has been little affected by humans.
B) is not essential for life.
C) has its major pool in the atmosphere.
D) cycles rapidly through sediments and rocks.
E) cycles rapidly through organisms.

Accepted Answer

The phosphorus cycle involves the rapid cycling of phosphorus through organisms. It is an essential element for life and has been greatly affected by human activities such as fertilizer runoff and industrial waste. The major pool of phosphorus is found in rocks and sediments, not the atmosphere.

Question 16

Without microbes (primarily bacteria), what would most likely happen to the world's natural nitrogen cycle? A) Cycling would stop; most nitrogen would remain in the atmosphere as N₂ gas. B) The cycle would continue unchanged; chemical reactions would take over bacterial actions. C) Nitrogen cycling in the oceans, which does not involve bacteria, would become dominant. D) The cycle would continue unchanged; bacterial activity is not needed now that humans can fix nitrogen. E) Nitrogen fixation would not occur, but nitrification and denitrification would remain unchanged.

Accepted Answer

Bacteria play a crucial role in most steps of the nitrogen cycle, including nitrogen fixation, nitrification, and denitrification. Without bacteria, the majority of nitrogen in the environment would not be converted into usable forms for plants and animals, and would instead remain in the atmosphere as nitrogen gas. This would lead to a depletion of available nitrogen and a significant impact on ecological processes.

Question 17

A reduction in dimethyl sulfide production in the oceans would likely have what effect on global climate?
A) It would not affect climate; dimethyl sulfide remains in the oceans.
B) It acts as a greenhouse gas, so a reduction would increase global temperatures.
C) It acts as a greenhouse gas, so a reduction would decrease global temperatures.
D) It helps cloud formation, so a reduction would decrease incoming solar radiation.
E) It helps cloud formation, so a reduction would increase incoming solar radiation.

Accepted Answer

Dimethyl sulfide (DMS) produced in the oceans contributes to cloud formation by providing nuclei around which clouds can form. A reduction in DMS would lead to fewer clouds, thereby increasing the amount of incoming solar radiation reaching the Earth's surface, potentially warming the planet.

Question 18

Humans add to nitrogen fixation in two major ways.These are
A) burning fossil fuels and carrying out nitrification.
B) burning fossil fuels and carrying out denitrification.
C) producing artificial fertilizers and burning fossil fuels.
D) producing artificial fertilizers and carrying out nitrification.
E) producing artificial fertilizers and carrying out denitrification.

Accepted Answer

Humans contribute to nitrogen fixation primarily through the production of artificial fertilizers and the burning of fossil fuels. Artificial fertilizers add fixed nitrogen directly to the soil, enhancing plant growth. Burning fossil fuels releases nitrogen oxides into the atmosphere, which can eventually deposit as fixed nitrogen on the earth's surface.

Question 19

An important way sulfur is moved from its global pools into the active sulfur cycle is by
A) global wind currents.
B) human mining operations.
C) volcanic eruptions.
D) production of dimethylsulfoniopropionate (DMSP).
E) denitrification.

Accepted Answer

Volcanic eruptions release significant amounts of sulfur into the atmosphere, which can then contribute to the active sulfur cycle.

Question 20

Approximately 60 percent of Earth's ecosystem services are currently being degraded or are being used unsustainably.One ecosystem service that is probably not degrading, at least at present, is
A) agricultural soils.
B) atmospheric oxygen supply from photosynthesis.
C) the regulation of flooding.
D) the availability of clean water.
E) the ability to control pollution.

Accepted Answer

The atmospheric oxygen supply from photosynthesis is not degrading since it is a natural process that has been occurring for millions of years and is not being affected by human activities. Plants release oxygen into the atmosphere as a byproduct of photosynthesis, which is then used by animals, including humans, for respiration.

Quiz 57: Ecosystems

Addition of artificial nitrogen fertilizers to agricultural lands causes an increase in nitrification and denitrification by bacteria.These processes in turn release nitrous oxide (N₂O) into the atmosphere.What are the implications of additional nitrous oxide in the atmosphere?

Refer to the graph. Which conclusion can be drawn from the graph about the value of sustainable ecosystems, compared with the value of those converted entirely to human use?

As a result of human agriculture and urbanization, and more recently large-scale phosphorus mining, the amount of phosphorus in Earth's freshwater and terrestrial ecosystems has nearly quadrupled.This suggests that recent increases in algal blooms in many lakes might be occurring because phosphorus

A soil ecosystem has very low plant growth and is found to be deficient in nitrogen.To obtain the nitrogen it needs using natural processes (as opposed to fertilizers added by humans) , this ecosystem would need more _______ bacteria.

Agriculture as it is practiced in the United States today is big business, which feeds and employs many people.Which of these is not a trade-off, in terms of ecological services, that results from the practice of large-scale, industrial agriculture?

Pollination is considered an important ecosystem service.People value pollination, and other ecosystem services, because they provide

Which of these ecosystem services could be considered an example of a cultural service?

The flood control, wildlife habitat, and spawning grounds for marine organisms that coastal wetlands provide are

Currently, we can describe the general status of most ecosystem services in the United States as being

Refer to the figure. The activities of the nitrogen cycle, as represented in the figure, are

DMSP, a chemical produced by ocean phytoplankton and seaweed, breaks down to produce the gas dimethyl sulfide.The fact that 70 percent of Earth's surface is covered with oceans suggests that the production of dimethyl sulfide is

A major characteristic of the phosphorus cycle is that it

Without microbes (primarily bacteria) , what would most likely happen to the world's natural nitrogen cycle?

A reduction in dimethyl sulfide production in the oceans would likely have what effect on global climate?

Humans add to nitrogen fixation in two major ways.These are

An important way sulfur is moved from its global pools into the active sulfur cycle is by

Approximately 60 percent of Earth's ecosystem services are currently being degraded or are being used unsustainably.One ecosystem service that is probably not degrading, at least at present, is