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Flashcards in Chapter 23 Deck (45)
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1
Q

During the past century, the concentration of carbon dioxide in the earth’s atmosphere has
increased rapidly from its pre‐industrial level of about __________ to its present level of about
385 ppm.
A) 0 ppm B) 100 ppm C) 280 ppm D) 350 ppm

A

C) 280 ppm

2
Q

Characterize the pre‐industrial atmospheric carbon dioxide concentration in the context of the
earth’s geologic history.
A) It was probably at the highest level in the earth’s geologic history.
B) It was probably at an average level in the earth’s geologic history.
C) It was probably at the lowest level in the earth’s geologic history.

A

C) It was probably at the lowest level in the earth’s geologic history.

3
Q

Some chemical transformations of elements in ecosystems take place in abiotic contexts. Which
of the following is an example of such a transformation?
A) weathering of bedrock
B) production of reduced nitrogen (in ammonia) by lightning
C) precipitation of calcium carbonate in the oceans
D) all of the above

A

D) all of the above

4
Q

Most biochemical energy transformations are associated with the oxidation and reduction of
which of the following elements?
A) sodium, potassium, calcium, and magnesium
B) copper, iron, aluminum, and manganese
C) carbon, oxygen, nitrogen, and sulfur
D) nickel, cadmium, and zinc

A

C) carbon, oxygen, nitrogen, and sulfur

5
Q

Energy transformations in biological systems typically link assimilatory and dissimilatory
processes. Which of the following is necessary for such transformations to occur?
A) The dissimilatory process must release less energy than that required by the assimilatory
process.
Chapter 23: Pathways of Elements in Ecosystems
Page 66
B) The dissimilatory process must release at least as much or more energy than that required
by the assimilatory process.
C) The energy released by the dissimilatory process must exactly balance the energy required
by the assimilatory process.

A

B) The dissimilatory process must release at least as much or more energy than that required
by the assimilatory process.

6
Q

Which of the following is by far the largest reservoir of water on earth?
A) the oceans D) lakes and rivers
B) polar ice caps and glaciers E) soil moisture
C) underground aquifers

A

A) the oceans

7
Q

What percentage of solar energy striking the earth provides the energy required to drive the
global water cycle?
A) 1% B) 2% C) 10% D) 25% E) 100%

A

D) 25%

8
Q

Each year, the input (as water vapor) and output (as precipitation) of water to and from the
earth’s atmosphere is balanced. The inputs and outputs each amount to 65 cm of water, if this
water were spread evenly over the earth’s surface. The amount of water in the atmosphere at
any time would amount to 2.5 cm if spread evenly over the earth’s surface. What is the
approximate residence time (in years) of water in the atmosphere?
A) 40 years B) 26 years C) 4 years D) 0.4 years E) 0.04 years

A

E) 0.04 years

9
Q

How many times longer is the residence time of water in soils, rivers, lakes, and oceans
(combined) compared to its residence time in the atmosphere?
A) 10 times longer D) 10,000 times longer
B) 100 times longer E) 100,000 times longer
C) 1000 times longer

A

E) 100,000 times longer

10
Q

The global assimilation rate of carbon by photosynthesis is approximately 85 gigatons per year,
balanced by an equivalent rate of dissimilation by respiration. Given a global organic carbon
pool (excluding fossil carbon) of 2650 gigatons, what is the average residence time of carbon in
this pool?
A) 0.032 years B) 0.32 years C) 3.1 years D) 31 years

A

D) 31 years

11
Q

In aquatic systems, there is a small net removal of soluble carbon from the water column,
primarily through precipitation of insoluble calcium carbonate. What balances this small net
loss?
A) inputs from rivers, which tend to carry dissolved carbonate sediments
B) inputs from wind‐blown dust carried from terrestrial limestone deposits
C) inputs from dissolution of insoluble aquatic calcium phosphate deposits

A

A) inputs from rivers, which tend to carry dissolved carbonate sediments

12
Q

Geologist Gregory Retallack has studied fossilized Antarctic soils that formed during the
Devonian. His findings suggest that declining atmospheric carbon concentrations during the
Devonian were prompted by which of the following processes?
A) extensive fires in Devonian forests
B) cessation of soil development in the Devonian
C) increased weathering of calcium and magnesium from soils during the Devonian
D) increased respiration by soil invertebrates during the Devonian

A

C) increased weathering of calcium and magnesium from soils during the Devonian

13
Q

The atmosphere contained vastly more carbon dioxide at the beginning of the Devonian (417
Mya) than it did toward the end of the Devonian (354 Mya). What was the ultimate fate of this
atmospheric carbon?
A) It was incorporated into carbonate sediments in the ocean basins.
B) It was incorporated into solid methane deposits in the ocean basins.
C) It was incorporated into the living biomass of the earth’s rapidly developing forests.
D) It was bound to clay minerals in paleosols.

A

A) It was incorporated into carbonate sediments in the ocean basins.

14
Q

When Jack Morgan and colleagues exposed plots of Colorado grassland to an elevated
concentration of atmospheric carbon dioxide, they noted an increase in biomass accumulation
at the community level. When they investigated contributions of three dominant grass species
to this increase, what did they find?
A) All three species contributed equally to this increase.
B) Two of the three species actually declined in biomass, but the third more than
compensated for these declines.
C) Two of the three species showed little change in biomass accumulation, but the third
increased substantially.

A

C) Two of the three species showed little change in biomass accumulation, but the third
increased substantially.

15
Q

In Morgan’s study of Colorado grassland exposed to an elevated concentration of atmospheric
carbon dioxide (previous question), what was an unexpected finding related to production of
needle grass?
A) Production of needle grass declined substantially, but digestibility increased.
B) Production of needle grass remained constant, but digestibility increased.
C) Production of needle grass remained constant, but digestibility declined.
D) Production of needle grass increased substantially, but digestibility declined.

A

D) Production of needle grass increased substantially, but digestibility declined.

16
Q
Which of the following abiotic processes can result in the transformation of atmospheric
nitrogen gas (N2) to ammonia (NH3) available to plants and microorganisms?
A) landslides B) acidification of lakes C) lightning D) none of the above
A

C) lightning

17
Q

What kinds of organism are capable of carrying out ammonification?
A) plants B) animals C) fungi D) microbes E) all organisms

A

E) all organisms

18
Q

Is biological nitrogen fixation an assimilatory or dissimilatory process?
A) assimilatory B) dissimilatory C) neither of the above

A

A) assimilatory

19
Q

How do free‐living bacteria, such as Azotobacter, obtain the energy necessary to reduce
atmospheric nitrogen gas (N2) to ammonia (NH3)?
A) photosynthesis C) metabolism of organic detritus
B) parasitism of plant roots D) none of the above

A

C) metabolism of organic detritus

20
Q

How do free‐living cyanobacteria obtain the energy necessary to reduce atmospheric nitrogen
gas (N2) to ammonia (NH3)?
A) photosynthesis C) metabolism of organic detritus
B) parasitism of plant roots D) none of the above

A

A) photosynthesis

21
Q

Aside from that produced by biological nitrogen fixation, biologically available nitrogen is
abundantly available in various rocks and minerals, which can be mined for fertilizer.
A) True B) False

A

B) False

22
Q

Nitrification:
A) is carried out only by fungi.
B) can proceed in waterlogged, anaerobic soils and sediments.
C) results in the oxidation of nitrogen.
D) releases nitrogen gas (N2) to the atmosphere.
E) produces a form of nitrogen unavailable to plants.

A

C) results in the oxidation of nitrogen.

23
Q

You are asked to identify a sample of microorganisms responsible for nitrification in aerobic
soils. Which of the following would be a likely candidate?
A) Methanosomonas D) Thiobacillus
B) Hydrogenomonas E) Ferrobacillus
C) Nitrosomonas

A

C) Nitrosomonas

24
Q

Denitrification is an important biological process because:
A) it results in the release of nitrogen in a form unavailable to plants.
B) it can proceed in waterlogged, anaerobic soils and sediments.
C) it results in the breakdown of organic matter in soils and sediments.
D) it is carried out by certain bacteria.
E) All of the above are true.

A

E) All of the above are true.

25
Q

Which of the following elements lacks a form that circulates readily (as a gas) through the
atmosphere?
A) nitrogen B) phosphorus C) carbon D) sulfur E) oxygen

A

B) phosphorus

26
Q

The phosphorus cycle is not of particular interest to ecologists because phosphorus is not an
essential element.
A) True B) False

A

B) False

27
Q

Which of the following statements correctly characterizes the phosphorus cycle?
A) Phosphorus undergoes relatively few oxidation and reduction reactions.
Chapter 23: Pathways of Elements in Ecosystems
Page 70
B) Phosphorus is typically limiting in aquatic habitats.
C) Phosphorus is relatively unavailable in both basic and acidic soils.
D) All of the above are true.

A

D) All of the above are true

28
Q

Following the spring overturn, phosphorus is relatively abundant in the surface waters of
temperate lakes. However, during the summer months, phosphorus becomes increasingly
scarce, leading to a situation of imbalanced stoichiometry. Herbivores, in particular, egest
material that is much __________ in C:P ratio than the foods they consume.
A) lower
B) higher

A

B) higher

29
Q

Under certain environmental conditions, bacteria may use sulfate as an oxidizing agent for
organic carbon, much as they use nitrate under similar conditions. Under what conditions
would you expect such use of sulfate to occur?
A) aerobic conditions B) anaerobic conditions C) either of the above

A

B) anaerobic conditions

30
Q

Sulfides are commonly associated with coal deposits. When mine wastes are exposed to oxygen
and water, the resultant reactions can lead ultimately to the formation of:
A) hydrogen sulfide. C) sulfuric acid.
B) elemental sulfur. D) organic forms of sulfur.

A

C) sulfuric acid.

31
Q

Chemoautotrophic organisms use carbon dioxide as their source of inorganic carbon, but obtain
energy for reduction of carbon from:
A) sunlight.
B) heat extracted from the atmosphere or water.
C) oxidation of inorganic substrates.
D) oxidation of carbohydrates.

A

C) oxidation of inorganic substrates.

32
Q

Chemoautotrophic organisms are almost exclusively:

A) higher plants. B) fungi. C) protists. D) bacteria and archaebacteria.

A

D) bacteria and archaebacteria.

33
Q

You are asked to identify a sample of microorganisms responsible for chemoautotrophic
oxidation of reduced forms of sulfur. Which of the following would be a likely candidate?
A) Methanosomonas D) Thiobacillus
B) Hydrogenomonas E) Ferrobacillus
C) Nitrosomonas

A

D) Thiobacillus

34
Q

The high productivity of areas surrounding deep‐sea hydrothermal vents contrasts sharply with
that of the surrounding ocean floor. What is the base of the food chain of these productive
habitats?
A) primary productivity by chemoautotrophic sulfur bacteria
B) primary productivity by photoautotrophic sulfur bacteria
C) detritus filtering down from the ocean surface
D) carbohydrates emitted by the hydrothermal vents

A

A) primary productivity by chemoautotrophic sulfur bacteria

35
Q

Pogonophoran worms of deep‐sea hydrothermal vents occupy which trophic level in the vent
ecosystem?
A) first (primary producer) C) third (secondary consumer)
B) second (primary consumer)

A

B) second (primary consumer)

36
Q

When an atom gives up electrons, it is said to be __________.

A

oxidized

37
Q

Dissimilatory biological processes typically involve ___________ of an organic compound.

A

oxidation

38
Q

Ecologists use __________ models to organize their thinking about elemental cycling and
processing of energy in ecological systems.

A

compartment

39
Q

Most of the earth’s carbon is locked up in __________.

A

sedimentary rocks

40
Q

__________ involves the hydrolysis of proteins into their constituent amino acids, followed by
oxidation of the carbon in the amino acids, which releases ammonia.

A

ammonification

41
Q

Species with __________‐fixing capabilities typically dominate on land first exposed to
colonization by living things.

A

nitrogen

42
Q

Plants assimilate phosphorus in the form of __________.

A

phosphate

43
Q

Under aerobic conditions, chemoautotrophic bacteria, such as Thiobacillus, can oxidize reduced
sulfur to __________.

A

sulfate

44
Q

Organisms broadly referred to as __________ obtain carbon in reduced (organic) form by
consuming other organisms or organic detritus.

A

heterotrophs

45
Q

Bacteria at the base of the food chain in ecosystems surrounding deep‐sea vent communities
are __________.

A

chemoautotrophs