Question 1

When plants are initially exposed to elevated carbon dioxide levels most increase their rate of photosynthesis; how might plant communities be affected?

Accepted Answer

A) no changes other than increased NPP 
B) competition increases for other resources such as sunlight or phosphorus with the eventual disappearance of some community members 
C) community members decrease in size over time with the removal of the selection pressure for carbon dioxide acquisition 
D) Because carbon dioxide is never a limiting factor like water, nitrogen, or phosphorus, increased levels typically have no significant effects. 
A) no changes other than increased NPP 
B) competition increases for other resources such as sunlight or phosphorus with the eventual disappearance of some community members 
C) community members decrease in size over time with the removal of the selection pressure for carbon dioxide acquisition 
D) Because carbon dioxide is never a limiting factor like water, nitrogen, or phosphorus, increased levels typically have no significant effects. B

Question 2

The levels of carbon dioxide in the atmosphere

Accepted Answer

A) peaked around 1950 and have begun slowly decreasing since then. 
B) are high but not higher than the highest estimated levels in the last 420,000 years. 
C) are estimated to be higher than at any time in the past 420,000 years. 
D) began decreasing when the use of CFCs stopped. 
A) peaked around 1950 and have begun slowly decreasing since then. 
B) are high but not higher than the highest estimated levels in the last 420,000 years. 
C) are estimated to be higher than at any time in the past 420,000 years. 
D) began decreasing when the use of CFCs stopped. C

Question 3

Normally the major part of a polar bear's diet is composed of ____________________.

Accepted Answer

seals

Question 4

Humans are changing the way many chemicals ____________________ through ecosystems.

Accepted Answer

The answer of Humans are changing the way many chemicals...

Question 5

The amount of nitrogen that cycles among organisms is ____________________ than the amount that is in the atmosphere.

Accepted Answer

The answer of The amount of nitrogen that cycles among...

Question 6

Historically, an unusual aspect of the recent rise in CO₂ levels is that

Accepted Answer

A) there is no known mechanism for its occurrence. 
B) CO2 reacts so quickly with other compounds that it should not be occurring. 
C) it has occurred relatively slowly. 
D) it has occurred relatively rapidly. 
A) there is no known mechanism for its occurrence. 
B) CO2 reacts so quickly with other compounds that it should not be occurring. 
C) it has occurred relatively slowly. 
D) it has occurred relatively rapidly.

Question 7

Most plants can be considered carbon sinks; their net effect on atmospheric carbon is to reduce its concentration.

Accepted Answer

A) True 
 B)False

Question 8

Polar bears are threatened by a reduction in the amount of phytoplankton in the ocean because

Accepted Answer

A) polar bears are at the top of the food chain in which phytoplankton are the primary producers. 
B) polar bears use phytoplankton as an important source of vitamins. 
C) phytoplankton are bioindicators of the amount of ice in the polar bear's ecosystem. 
D) polar bears become covered with phytoplankton as camouflage when they forage on the tundra. 
A) polar bears are at the top of the food chain in which phytoplankton are the primary producers. 
B) polar bears use phytoplankton as an important source of vitamins. 
C) phytoplankton are bioindicators of the amount of ice in the polar bear's ecosystem. 
D) polar bears become covered with phytoplankton as camouflage when they forage on the tundra.

Question 9

One of the major effects of an increase in atmospheric carbon dioxide is

Accepted Answer

A) an increase in average global temperature. 
B) cooler average temperatures as carbon dioxide reflects sunlight back into space. 
C) an acceleration of the depletion of ozone. 
D) an increase in the pH of oceans and lakes. 
A) an increase in average global temperature. 
B) cooler average temperatures as carbon dioxide reflects sunlight back into space. 
C) an acceleration of the depletion of ozone. 
D) an increase in the pH of oceans and lakes.

Question 10

In recent years, the amount of nitrogen compounds fixed by human activities has

Accepted Answer

A) exceeded the amount of nitrogen compounds fixed by natural processes. 
B) been reduced to a level below the amounts fixed by natural processes. 
C) equaled the amount fixed by natural processes. 
D) fluctuated above and below the amounts fixed by natural processes. 
A) exceeded the amount of nitrogen compounds fixed by natural processes. 
B) been reduced to a level below the amounts fixed by natural processes. 
C) equaled the amount fixed by natural processes. 
D) fluctuated above and below the amounts fixed by natural processes.

Question 11

In comparison to past estimates, extinction rates are currently high. Which of the following is the most plausible explanation?

Accepted Answer

A) Natural fluctuations in climate causes extinctions. 
B) Continental drift is causing rapid changes in climate, which, in turn, causes extinctions. 
C) Previous extinctions make survival of contemporary species more difficult. 
D) Humans are affecting many aspects of the global environment. 
A) Natural fluctuations in climate causes extinctions. 
B) Continental drift is causing rapid changes in climate, which, in turn, causes extinctions. 
C) Previous extinctions make survival of contemporary species more difficult. 
D) Humans are affecting many aspects of the global environment.

Question 12

The effects of global warming have already been detected in both aquatic and terrestrial ecosystems.

Accepted Answer

A) True 
 B)False

Question 13

What will happen in the future if humans continue to impact natural systems at the same rates as today?

Accepted Answer

A) The environment is much too big and the human population much too small in comparison to have any serious consequences. 
B) Human societies may experience severe disruptions in the services ecosystems provide that human societies depend on. 
C) Some short-term changes may be experienced, but the magnitude will likely be no greater than those that have occurred naturally. 
D) Some beneficial and necessary reductions on population growth will occur. 
A) The environment is much too big and the human population much too small in comparison to have any serious consequences. 
B) Human societies may experience severe disruptions in the services ecosystems provide that human societies depend on. 
C) Some short-term changes may be experienced, but the magnitude will likely be no greater than those that have occurred naturally. 
D) Some beneficial and necessary reductions on population growth will occur.

Question 14

Biodeisel fuel is produced from oils synthesized by and harvested from living plants. How does the use of biodeisel fuel compare to the use of fossil fuels with respect to the amount of carbon dioxide released to the atmosphere?

Accepted Answer

A) There is no difference; the combustion of the fuel produces carbon dioxide regardless of its source. 
B) It is beneficial; converting plant material to biodeisel permanently traps carbon dioxide and prevents its entry to the atmosphere. 
C) It is detrimental; because biodeisel produces lower mileage, more must be burned, causing a proportional increase in carbon dioxide release. 
D) It is beneficial; because living plants are the source of the biodeisel, burning it simply represents nutrient recycling. 
A) There is no difference; the combustion of the fuel produces carbon dioxide regardless of its source. 
B) It is beneficial; converting plant material to biodeisel permanently traps carbon dioxide and prevents its entry to the atmosphere. 
C) It is detrimental; because biodeisel produces lower mileage, more must be burned, causing a proportional increase in carbon dioxide release. 
D) It is beneficial; because living plants are the source of the biodeisel, burning it simply represents nutrient recycling.

Question 15

Which of the following cycles appears to make the greatest contribution to climate change?

Accepted Answer

A) the phosphorus cycle 
B) the carbon cycle 
C) the sulfur cycle 
D) the nitrogen cycle 
A) the phosphorus cycle 
B) the carbon cycle 
C) the sulfur cycle 
D) the nitrogen cycle

Question 16

Humans have had little lasting impact on the physical appearance of Earth.

Accepted Answer

A) True 
 B)False

Question 17

Changes to the physical and biotic features of the Earth are called land and water transformations. Which of the following is an example of a water transformation?

Accepted Answer

A) Clearing land along an urban-growth boundary to allow a city to expand. 
B) Constructing a dam along a river so that an expanding city may increase the availability of drinking water. 
C) Clear-cutting a forest for the lumber needed to build the homes for an expanding city. 
D) Clear-cutting a forest to make cropland to grow the food for an expanding city. 
A) Clearing land along an urban-growth boundary to allow a city to expand. 
B) Constructing a dam along a river so that an expanding city may increase the availability of drinking water. 
C) Clear-cutting a forest for the lumber needed to build the homes for an expanding city. 
D) Clear-cutting a forest to make cropland to grow the food for an expanding city.

Question 18

Marine organisms with calcified structures, such as clams, are affected by increased atmospheric carbon dioxide levels because in the ocean these increases also cause an increase in ____________________.

Accepted Answer

The answer of Marine organisms with calcified structures, such as...

Question 19

Humans now use approximately 30-35 percent of the terrestrial net primary productivity (NPP). A result of this is that

Accepted Answer

A) human hunger has been virtually eliminated. 
B) the number of species on Earth has increased. 
C) humans are often in direct competition with other species for food and other natural resources. 
D) we have learned how to manage Earth's resources so that all species have the resources they need to survive. 
A) human hunger has been virtually eliminated. 
B) the number of species on Earth has increased. 
C) humans are often in direct competition with other species for food and other natural resources. 
D) we have learned how to manage Earth's resources so that all species have the resources they need to survive.

Question 20

The single most significant human-caused contribution (about 75 percent)to the worldwide increase in atmospheric carbon dioxide is

Accepted Answer

A) acid rain and the subsequent chemical reactions that release carbon dioxide from the soil. 
B) nitrogen supplements that accelerate decompositional activity and recycle carbon before it can become sequestered in the soil. 
C) the burning of fossil fuels and the subsequent emission of carbon dioxide. 
D) deforestation and the subsequent decline in photosynthesis. 
A) acid rain and the subsequent chemical reactions that release carbon dioxide from the soil. 
B) nitrogen supplements that accelerate decompositional activity and recycle carbon before it can become sequestered in the soil. 
C) the burning of fossil fuels and the subsequent emission of carbon dioxide. 
D) deforestation and the subsequent decline in photosynthesis.

Exam 25: Global Change

When plants are initially exposed to elevated carbon dioxide levels most increase their rate of photosynthesis; how might plant communities be affected?

The levels of carbon dioxide in the atmosphere

Normally the major part of a polar bear's diet is composed of ____________________.

Humans are changing the way many chemicals ____________________ through ecosystems.

The amount of nitrogen that cycles among organisms is ____________________ than the amount that is in the atmosphere.

Historically, an unusual aspect of the recent rise in CO₂ levels is that

Most plants can be considered carbon sinks; their net effect on atmospheric carbon is to reduce its concentration.

Polar bears are threatened by a reduction in the amount of phytoplankton in the ocean because

One of the major effects of an increase in atmospheric carbon dioxide is

In recent years, the amount of nitrogen compounds fixed by human activities has

In comparison to past estimates, extinction rates are currently high. Which of the following is the most plausible explanation?

The effects of global warming have already been detected in both aquatic and terrestrial ecosystems.

What will happen in the future if humans continue to impact natural systems at the same rates as today?

Biodeisel fuel is produced from oils synthesized by and harvested from living plants. How does the use of biodeisel fuel compare to the use of fossil fuels with respect to the amount of carbon dioxide released to the atmosphere?

Which of the following cycles appears to make the greatest contribution to climate change?

Humans have had little lasting impact on the physical appearance of Earth.

Changes to the physical and biotic features of the Earth are called land and water transformations. Which of the following is an example of a water transformation?

Marine organisms with calcified structures, such as clams, are affected by increased atmospheric carbon dioxide levels because in the ocean these increases also cause an increase in ____________________.

Humans now use approximately 30-35 percent of the terrestrial net primary productivity (NPP). A result of this is that

The single most significant human-caused contribution (about 75 percent)to the worldwide increase in atmospheric carbon dioxide is

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