Deck 42: Ecosystems and Energy

Question 1

The major role of detritivores in ecosystems is to

A)provide an organic nutritional resource for heterotrophic organisms.
B)recycle chemical matter to a form capable of being used by autotrophs.
C)prevent the buildup of the remains of organisms at all trophic levels.
D)convert organic matter to energy previously lost by the ecosystem.

Answer 1

B

Question 2

Which of the following refers to the amount of new biomass added in a given period of time?

A)net ecosystem production
B)net primary productivity
C)secondary productivity
D)trophic level efficiency
E)gross primary productivity

Answer 2

B

Question 3

Which of the following is an example of an ecosystem?

A)all of the brook trout in a 500-square-hectare river drainage system
B)the interactions between all plant and animal species in a savanna
C)the plants,animals,and decomposers that inhabit an alpine meadow
D)a pond and all of the various plant and animal species that live in it
E)the interactions between all organisms and their desert environment

Answer 3

E

Question 4

A cow's herbivorous diet indicates that it is a(n)

A)primary consumer.
B)secondary consumer.
C)chemotrophic animal.
D)autotrophic animal.
E)primary producer.

Question 5

How is it that the open ocean produces the highest net primary productivity of Earth's ecosystems,yet net primary productivity per square meter is relatively low?

A)Oceans contain more nutrients as compared to other ecosystems.
B)Oceans receive a lesser amount of solar radiation per unit area.
C)Oceans have the largest area of all the many ecosystems on Earth.
D)Ocean ecosystems are less diverse with more autotrophs per unit area.
E)Oceanic producers are generally much smaller than oceanic consumers.

Question 6

Approximately 1% of the solar radiation that strikes a plant is converted into the chemical bond energy of sugars.Why is this amount so low?

A)Approximately 99% of the incoming solar radiation is converted to heat energy.
B)Only 1% of visible light wavelengths are absorbed by photosynthetic pigments.
C)50% of the sun's energy strikes large bodies of water and barren land surfaces.
D)99% of the solar radiation is reflected,absorbed,or scattered in the atmosphere.
E)Only the green wavelengths of light are absorbed by plants for photosynthesis.

Question 7

Which of these ecosystems has the highest net primary productivity per square meter annually?

A)Nigerian savanna
B)Southern open ocean
C)Canada's boreal forest
D)Amazon rain forest
E)Asian temperate forest

Question 8

What percentage of visible light striking a plant is converted into chemical energy?

A)1%
B)10%
C)25%
D)50%
E)100%

Question 9

The availability of soil nutrients has a direct effect on primary productivity.Which of the following is most correct regarding non-limiting and limiting nutrients?

A)Only phosphorus acts as a limiting nutrient to global primary productivity.
B)Adding a limiting nutrient,such as nitrogen,would decrease primary production.
C)Increases in non-limiting nutrients result in increases in primary productivity.
D)Nitrogen is the limiting nutrient when considering global primary production.
E)Phosphorous is the only limiting nutrient in terrestrial primary productivity.

Question 10

Subtraction of which of the following will convert gross primary productivity into net primary productivity?

A)the energy contained in the standing crop
B)the energy used by heterotrophs in respiration
C)the energy used by autotrophs in respiration
D)the energy fixed by photosynthetic processes
E)the energy absorbed as solar or light energy

Question 11

Which of these ecosystems accounts for the largest amount of Earth's net primary productivity?

A)Antarctic tundra
B)African savanna
C)Florida salt marsh
D)Pacific open ocean
E)Bolivian rain forest

Question 12

The law of conservation of mass states that matter cannot be created,yet matter is sometimes gained or lost to an ecosystem.What is the reason for this seeming contradiction?

A)Chemosynthetic prokaryotes convert all organic matter to energy.
B)Matter can be moved between ecosystems as they are open systems.
C)Autotrophs convert simple sugars to complex organic molecules.
D)Matter can be lost to the environment as it is converted to energy.
E)Heterotrophs convert light energy to non-living organic matter.

Question 13

To recycle nutrients,an ecosystem must have,at a minimum,

A)producers.
B)producers and decomposers.
C)producers,primary consumers,and decomposers.
D)producers,primary consumers,secondary consumers,and decomposers.
E)producers,primary consumers,secondary consumers,top carnivores,and decomposers.

Question 14

Scientists use trophic cycles to study the flow of matter in an ecosystem by observing feeding relationships between organisms.Which of the following statements is most correct regarding the terminology used in trophic cycles?

A)It is incorrect to refer to an omnivore as a heterotroph.
B)The terms herbivore and autotroph mean the same thing.
C)Labeling a carnivore as a heterotroph would be correct.
D)Autotrophs can be correctly labeled as primary consumers.
E)Primary producers would include the heterotrophic species.

Question 15

Which of the following is most correct regarding the activity of detritivores?

A)They synthesize the organic molecules that are used by the primary producers.
B)They convert organic matter to inorganic,which is used by primary producers.
C)They are primary producers that convert organic matter into inorganic detritus.
D)They are autotrophs and heterotrophs that convert detritus to organic matter.

Question 16

If the sun were to suddenly stop providing energy to Earth,most ecosystems would vanish.Which of the following ecosystems would likely survive the longest after this hypothetical disaster?

A)Brazilian rain forest ecosystem
B)Antarctic tundra ecosystem
C)Pacific deep-sea vent ecosystem
D)African grassland ecosystem
E)California desert ecosystem

Question 17

In ecosystems,why is the term cycling used to describe the transfer of chemical elements,whereas the term flow is used for energy exchange?

A)Chemical elements are repeatedly used,but energy passes through and between ecosystems.
B)Photosynthesis results in transforming chemical elements with no effect on energy transfer.
C)Chemical elements flow between ecosystems,whereas energy stays within one ecosystem.
D)Photosynthesis alters system energy without a change in the number of chemical elements.

Question 18

Photosynthetic organisms are unique to most ecosystems because they

A)synthesize organic compounds they obtain from decaying heterotrophs.
B)synthesize inorganic compounds from decaying organic compounds.
C)use light energy to synthesize organic matter from inorganic matter.
D)use chemical energy to synthesize organic matter from decaying matter.
E)convert light and chemical energy into inorganic and organic matter.

Question 19

Which statement most accurately describes how matter and energy are used in ecosystems?

A)Matter flows through ecosystems;energy cycles within a single ecosystem.
B)Energy flows through ecosystems;matter cycles within and through ecosystems.
C)Energy can be converted into matter;matter cannot be converted into energy.
D)Matter can be converted into energy;energy cannot be converted into matter.
E)Matter is used in every ecosystem;energy is only used in some ecosystems.

Question 20

Primary producers support the primary consumers in an ecosystem.Which of the following is most correct regarding primary producers?

A)Primary producers occupy the trophic level that directly feeds all autotrophs.
B)Heterotrophs are able to thrive in an ecosystem without primary producers.
C)Chemoautotrophic prokaryotes near deep-sea vents are primary producers.
D)Detritivores have no interaction with the primary producers in an ecosystem.

Question 21

The number of trophic levels is typically limited to four or five.Which of the following is primarily responsible for this limitation?

A)Many primary and higher-order consumers are opportunistic feeders.
B)Decomposers compete with higher-order consumers for nutrients and energy.
C)Nutrient cycles involve both abiotic and biotic components of ecosystems.
D)Nutrient cycling rates tend to be limited by decomposition by detritivores.
E)Energy transfer between trophic levels tends to be of very low efficiency.

Question 22

Why is net primary production (NPP)a more useful measurement to an ecosystem ecologist than gross primary production (GPP)?

A)NPP can be expressed in energy per unit of area per unit of time [J/(m².yr].
B)NPP is expressed in terms of carbon fixed by photosynthesis for an ecosystem.
C)NPP represents the stored energy available to consumers in an ecosystem.
D)NPP is the same as the total biomass of the photosynthetic autotrophs present.
E)NPP shows the rate at which the total biomass is utilized by primary consumers.

Question 23

Assume that,over a period of time,an owl consumes 5000 J of animal matter.The owl loses 2000 J in feces and uses 100 J for cellular respiration.The remainder of the energy was used for growth and reproduction.What is the production efficiency based on the energy stored in assimilated food for this owl?

A)50%
B)40%
C)70%
D)30%
E)10%

Question 24

Which of the following lists of organisms is ranked in correct order from lowest to highest production efficiency?

A)bears,fish,mosquitos
B)mosquitos,fish,bears
C)fish,mosquitos,bears
D)mosquitos,bears,fish
E)bears,mosquitos,fish

Question 25

The measures of net primary production (NPP)and net ecosystem production (NEP)both can be used to quantify gross primary production (GPP).Which of the following most correctly explains a difference between these two measures?

A)NPP measures GPP minus the energy used by all heterotrophs.
B)NEP measures GPP minus the energy used by all autotrophs.
C)NPP measures GPP minus the energy used by primary producers.
D)NEP measures GPP minus the energy used by primary consumers.
E)NPP measures GPP minus the energy used by all detritivores.

Question 26

What is the primary limiting factor for aquatic primary production?

A)water pressure
B)lack of nutrients
C)light availability
D)primary consumers
E)invasive organisms

Question 27

A moderate-size lake in the American Midwest suddenly has succumbed to an algal bloom.What is the likely cause of eutrophication in this lake?

A)increased solar radiation during the summer season
B)the introduction of non-native tertiary consumer fish
C)excessive farm fertilizer runoff during a heavy rainfall
D)accidental introduction of a prolific culture of algae
E)iron dust blowing into the lake from area factories

Question 28

Which of the following ecosystems would likely have a larger net primary productivity per hectare (10,000 m²),and why?

A)the Atlantic open ocean due to the total biomass of photosynthetic autotrophs
B)the Asian temperate grasslands due to conditions suited for rapid decomposition
C)the Costa Rican rain forest due to high annual rainfall and moderate temperatures
D)the Alps underground caverns and caves due to the abundance of photoautotrophs
E)the Arctic tundra due to extreme growth patterns during the warm summer season

Question 29

It is well known that animals at higher trophic levels are vulnerable to extinction.Which of the following factors is most likely to increase the likelihood of extinction?

A)increased dry mass at higher trophic levels
B)increased energy transfer at higher levels
C)the same energy transfer at all levels
D)decreased energy transfer at higher levels
E)decreased dry mass at higher trophic levels

Question 30

Secondary production is

A)energy conversion by secondary consumers received from primary consumers.
B)solar energy that is converted to chemical energy by photosynthetic producers.
C)chemical energy in food that is converted to new biomass by consuming organism.
D)energy that is transferred when not used by consumers for growth and reproduction.
E)growth that takes place during the second year of life in heterotrophic consumers.

Question 31

Why does a vegetarian leave a smaller ecological footprint than a person who eats meat?

A)Fewer farm animals are slaughtered for human consumption.
B)There is an excess of plant biomass in all terrestrial ecosystems.
C)Vegetarians need to ingest less chemical energy than omnivores.
D)Vegetarians require less protein to sustain life than do omnivores.
E)Eating meat is an inefficient way to utilize autotrophic productivity.

Question 32

Aquatic primary productivity is most limited by which of the following?

A)light and nutrient availability
B)predation by primary consumers
C)increased pressure with depth
D)unregulated industrial pollution
E)global increases in temperature

Question 33

Energy transfer between trophic levels is typically only 10% efficient.Approximately how many kilograms of secondary consumer biomass can be supported by a field plot containing 1,000 kg of plant material?

A)10,000
B)1,000
C)100
D)10
E)1

Question 34

Gross primary production in aquatic ecosystems is most likely to be limited by decreases in which of the following nutrient pairs?

A)nitrogen and phosphorous
B)carbon and phosphorous
C)potassium and phosphorous
D)iron and phosphorous
E)molybdenum and phosphorous

Question 35

Climatic factors such as temperature and rainfall affect net primary production (NPP).Which of the following climate-related events led to an increase in NPP in terrestrial ecosystems?

A)severe droughts in the American Southwest
B)bark beetle infestations in white pine forests
C)wildfires in the Yellowstone National Park
D)decreased cloud cover in Amazon rain forests
E)increased phosphorous in the Atlantic Ocean

Question 36

Which trophic level is most vulnerable to extinction?

A)milkweed plants that conduct photosynthesis
B)monarch caterpillars that eat milkweed plants
C)goldfinches that eat monarch caterpillars
D)large golden eagles that eat goldfinches
E)inky cap fungus that breaks down detritus

Question 37

The amount of chemical energy in a consumer's food that is converted to its own new biomass during a given time period is known as which of the following?

A)tertiary production
B)quaternary production
C)primary production
D)secondary production

Question 38

Trophic efficiency basically measures the efficiency of energy transfer.Which of the following is most correct in illustrating a measurement of trophic efficiency?

A)9% of energy passed from a primary consumer to a tertiary consumer
B)5% of energy passed from a primary producer to a secondary consumer
C)12% of energy passed from a primary producer to a primary consumer
D)7% of energy passed from a tertiary consumer to a primary consumer
E)10% of energy passed from a primary consumer to a primary producer

Question 39

Some chemical energy is not converted to new biomass as energy is transferred between trophic levels.Which of the following best describes the fate of the unconverted energy?

A)It is all undigested and excreted as feces,so it is not passed on to higher trophic levels.
B)It is only used by organisms to maintain essential processes like cellular respiration.
C)It is converted during cellular respiration to heat helping the heterotroph to stay warm.
D)It is eliminated as feces or released as heat to satisfy the second law of thermodynamics.
E)It is recycled by decomposers to a form that is once again usable by primary producers.

Question 40

For most terrestrial ecosystems,pyramids composed of species abundances,biomass,and energy are similar in that they have a broad base and a narrow top.The primary reason for this pattern is that

A)secondary consumers and top-level carnivores require far less energy than producers.
B)at each step,energy is lost from the system because of the second law of thermodynamics.
C)as matter passes through ecosystems,some of the matter is lost to the environment as heat.
D)toxin accumulation in an animal's tissues limits the secondary consumers and top carnivores.
E)top carnivores and secondary consumers have a more general diet than primary producers.

Question 41

Figure 42.2 Diagram of a food web (arrows represent energy flow and numbers represent species)
If Figure 42.2 represents a terrestrial food web,the combined biomass of 3 + 4 would probably be

A)greater than the biomass of 1.
B)less than the biomass of 8.
C)greater than the biomass of 2.
D)less than the biomass of 1 + 2.
E)less than the biomass of 6.

Question 42

Which of the following locations is the main reservoir for nitrogen in Earth's nitrogen cycle?

A)atmosphere
B)solid rock
C)plant fossils
D)plant biomass
E)soil bacteria

Question 43

Corn production can be limited by nitrogen levels in the soil.Some farmers reduce the need to apply ammonia to their fields by rotating corn crops with nitrogen-fixing soybean crops.Using soybeans to add nitrogen to degraded soils is an example of

A)biological augmentation.
B)reducing fertilizer runoff.
C)production efficiency.
D)plant bioremediation.
E)trophic level efficiency.

Question 44

Nitrogen can be used by plants in the form of

A)nitrogen gas.
B)nitrite ions.
C)uric acid.
D)ammonia.
E)nitrate ions.

Question 45

How does phosphorus normally enter ecosystems?

A)from cellular respiration
B)from photosynthesis
C)from rock weathering
D)from the atmosphere

Question 46

The flow of energy in an arctic ecosystem goes through a simple food chain: phytoplankton to zooplankton to fish to seals to polar bears.Which of the following is most correct about this food chain?

A)Less energy is transferred from fish to seals than from seals to bears.
B)The total biomass of the fish population is lower than that of the seals.
C)Energy transfer is greater from zooplankton to fish than from fish to seals.
D)Seal populations are larger than zooplankton and phytoplankton populations.
E)There is equal energy transfer in joules between all organisms at all levels.

Question 47

After Hurricane Katrina,sunflowers and other plants were planted to selectively remove contaminants from the soil.Once the plants matured,they were pulled up by the roots and safely stored with other contaminated wastes.This is an example of

A)biological augmentation.
B)reducing primary production.
C)lowering production efficiency.
D)detoxification by phytoremediation.
E)obstruction of nutrient cycling.

Question 48

Which of the following statements about biogeochemical cycling is correct?

A)The phosphorus cycle includes the recycling of atmospheric phosphorus gas.
B)The phosphorus cycle involves the weathering of rocks of marine origin.
C)The carbon cycle incorporates carbon dioxide produced from photosynthesis.
D)The carbon cycle always maintains a constant level of atmospheric CO_2.

Question 49

Why do logged tropical rain forests typically have nutrient-poor soils?

A)Decomposition on the forest floor takes four to six years on average.
B)Logging results in soil temperatures that are lethal to nitrogen-fixing bacteria.
C)Most of the nutrients in the ecosystem are removed in the harvested timber.
D)Nutrients evaporate easily into the atmosphere in the post-logged forest.

Question 50

Which of the following is an example of bioremediation?

A)bulldozing the land around an abandoned strip mine to combat erosion
B)scraping a river bottom with a tool to remove contaminated sediments
C)reconfiguring a river channel to increase the flow of water down a river
D)using microorganisms to eat oil in marine waters after a tanker oil spill
E)selectively logging younger trees to leave older trees for woodpecker nests

Question 51

Figure 42.3
In the diagram of the nitrogen cycle in Figure 42.3,which number represents nitrogen gas?

A)1
B)2
C)3
D)4

Question 52

In Japan,seaweed and seagrass bed reconstruction included constructing a seafloor habitat,transplanting seaweeds and seagrasses,and hand seeding.Which of the following correctly pairs the specific task with the restoration strategy?

A)biological augmentation-transplanting seaweeds
B)biological augmentation-constructing seafloor habitat
C)bioremediation-hand seeding
D)bioremediation-transplanting seagrasses

Question 53

In the nitrogen cycle,which step depends exclusively on bacteria?

A)fertilizer runoff into waterways
B)sedimentation into lake bottoms
C)decomposition of detritus
D)nitrogen fixation in roots

Question 54

Consider the food chain grass → grasshopper → mouse → snake → hawk.How much of the chemical energy fixed by photosynthesis of the grass (100%)is available to the hawk?

A)0)01%
B)0)1%
C)1%
D)10%
E)60%

Question 55

Figure 42.2 Diagram of a food web (arrows represent energy flow and numbers represent species)
If Figure 42.2 represents a marine food web,the simplest organism might be

A)1)
B)6)
C)3)
D)9)
E)5)

Question 56

What is the first step in the restoration of an extremely degraded ecosystem?

A)to restore the physical structure
B)to restore the native species
C)to remove competitive invasive species
D)to identify the factors limiting producers
E)to remove toxic pollutants

Question 57

Which of the following locations is the largest reservoir for carbon in the carbon cycle?

A)atmosphere
B)sedimentary rocks
C)fossilized plants
D)plant biomass
E)soil bacteria

Question 58

In the nitrogen cycle,the organisms that convert nitrate to atmosphere N₂ are

A)detritivores.
B)nitrifying bacteria.
C)denitrifying bacteria.
D)nitrogen-fixing bacteria.
E)decomposers.

Question 59

Rain falls on a fertilized agricultural field after a farmer has harvested the corn.Which biogeochemical cycles are involved when runoff from the field flows into a nearby stream?

A)only carbon and water
B)only water and nitrogen
C)only carbon,nitrogen,and phosphorus
D)only water,nitrogen,and phosphorus

Question 60

What is the goal of restoration ecology?

A)to replace a ruined ecosystem with a more suitable ecosystem
B)to initiate or accelerate the restoration of a degraded ecosystem
C)to completely restore a disturbed ecosystem to its former state
D)to prevent further degradation by protecting an area with park status
E)to manage competition between species in human-altered ecosystems

Question 61

Suppose you are studying the nitrogen cycling in a pond ecosystem over the course of a month.While you are collecting data,a flock of 100 migrating Canada geese lands and spends the night.How could you quantify the effect of this event on the pond's nitrogen cycling?

A)Find out how much nitrogen is consumed in plant material by a Canada goose over about a 12-hour period,and add that amount to the total nitrogen.
B)Find out how much nitrogen is eliminated by a Canada goose over about a 12-hour period,and subtract that amount from the total nitrogen in the ecosystem.
C)Find out how much nitrogen is consumed and eliminated by a Canada goose over about a 12-hour period,and record the net value of nitrogen associated with the goose visitation.
D)Do nothing.The Canada geese visitation to the lake would have a negligible impact on the nitrogen budget of the pond.

Question 62

What is the dependent variable in the experiment shown in Figure 42.4?

A)net primary productivity
B)total biomass of heterotrophs
C)net secondary productivity
D)total biomass of autotrophs

Question 63

Figure 42.3
In the diagram of the nitrogen cycle in Figure 42.3,which number represents nitrogen-fixing bacteria?

A)5
B)6
C)7
D)1

Question 64

Figure 42.3
In the diagram of the nitrogen cycle in Figure 42.3,which number represents the ammonium ion (NH₄⁺)?

A)1
B)2
C)3
D)4

Question 65

Which of the following organisms is correctly paired with its trophic level?

A)cyanobacterium-primary consumer
B)grasshoppers-primary producers
C)zooplankton-primary consumer
D)detritivores-primary producers

Question 66

Which of these ecosystems has the lowest net primary production per square meter?

A)a salt marsh
B)an open ocean
C)a coral reef
D)a tropical rain forest

Question 67

Predict the fate of a phosphorus atom after a non-native earthworm consumes leaf litter in a forest.

A)It is incorporated into the earthworm as an energy-storing molecule.
B)It is excreted as ammonium ion by the non-native earthworm.
C)It is released during cellular respiration as a phosphate ion.
D)It is weathered into rocks as it is released from the soil and leaf litter.

Question 68

A porcupine eats 3000 J of plant material.Of this,2000 J are indigestible and are eliminated as feces,900 J are used in cellular respiration,and 100 J are used for growth and reproduction.What is the approximate production efficiency of this animal?

A)0)03%
B)3%
C)10%
D)5%
E)67%

Question 69

What is the production efficiency of the grasshopper?

A)70%
B)50%
C)30%
D)15%

Question 70

What is the net ecosystem production of this square meter of tundra?

A)100 g
B)85 g
C)15 g
D)1 g
E)0)15 g

Question 71

If the total amount of energy from light converted into chemical energy in this square meter of tundra is 200 g,what is the amount of autotrophic respiration?

A)200 g
B)100 g
C)85 g
D)15 g
E)0)5 g

Question 72

Please use the following information to answer the questions below.
A scientist conducts an experiment to quantify the effect of mycorrhizae and soil nitrogen levels on plant growth in a grassland.The experiment has four treatments: (1)mycorrhizae present and ambient levels of nitrogen, (2)mycorrhizae present and nitrogen added, (3)mycorrhizae absent and ambient levels of nitrogen,and (3)mycorrhizae absent and nitrogen added.After four weeks,the scientist removes the aboveground plant material for weighing.
Figure 42.4
Figure 42.4 shows the results of the experiment.What is (are)the independent variable(s)?

A)nitrogen treatment only
B)biomass of aboveground plant only
C)presence and absence of mycorrhizae
D)nitrogen treatment and whether mycorrhizae are present

Question 73

What is the amount of secondary production described in this scenario?

A)100 g
B)85 g
C)15 g
D)1 g
E)0)15 g

Question 74

What conclusion is best supported by Figure 42.4?

A)With ambient nitrogen levels,growth is limited even when mycorrhizae are present.
B)Mycorrhizal associations result in the highest NPP levels regardless of nitrogen level.
C)Interactions with mycorrhizae are always positive mutualistic fungal-plant interactions.
D)Mycorrhizae should be added to restore successfully grasslands with high soil nitrogen.

Question 75

Please use the following information to answer the questions below.
The tundra biome is rapidly changing as a result of global warming.Studying the energy budget of the tundra can help scientists to evaluate the magnitude of these changes.In a randomly selected square meter of tundra,the amount of plant biomass is 200 g.The amount of new plant biomass added in a year is 100 g.In the same square meter,the total biomass added in a year is 15 g.A grasshopper that eats 1 g of plant biomass is able to use 0.15 g of that biomass for growth.The grasshopper cannot assimilate 50% of the plant's biomass.
The 100 g of new plant biomass is the

A)net ecosystem production.
B)gross primary production.
C)total biomass production.
D)secondary production.
E)net primary production.

Question 76

You conduct an experiment to compare the nitrogen cycle in soils with and without non-native earthworms.Predict the results of your experiment.

A)The soils with earthworms will have a faster rate of nitrogen fixation.
B)The soils with earthworms will have a faster rate of ammonification.
C)The soils with earthworms will have a slower rate of denitrification.
D)The soils with earthworms will have a slower rate of nitrification.

Question 77

What is the maximum biomass of grasshoppers that could be supported by this square meter of tundra (i.e. ,if grasshoppers ate all the existing vegetation)?

A)100 g
B)50 g
C)20 g
D)15 g

Question 78

As big as it is,the ocean is nutrient-limited.If you wanted to investigate this,one reasonable approach would be to

A)follow whale migrations in order to determine where most nutrients are located.
B)observe Southern/Antarctic Ocean productivity from year to year to see if it changes.
C)enrich some areas of the ocean,and compare their productivity to that of untreated areas.
D)compare nutrient concentrations between photosynthetic and non-photosynthetic zones.
E)contrast nutrient uptake by autotrophs in marine locations with different temperatures.

Question 79

Figure 42.3
In the diagram of the nitrogen cycle in Figure 42.3,which number represents the activity of nitrifying bacteria converting ammonium to nitrate?

A)5
B)6
C)7
D)3

Question 80

Please use the following information to answer the questions below.
Starting with the European settlers,humans have introduced earthworms from Europe and Asia into North American forests.These introductions continue through the transport of soil that contains non-native earthworms,such as during construction and through the release of non-native earthworms used for fishing.The effects of non-native earthworms are especially large in forests that did not have any native earthworms.For example,forests of the Great Lakes region did not previously have earthworms until humans introduced them.When non-native earthworms are introduced,the thick layer of leaf litter disappears quickly,thereby altering biogeochemical cycles.
Which of the following correctly traces a carbon molecule in a Great Lakes forest that is invaded with non-native earthworms?

A)leaf litter → earthworm → soil → trees
B)trees → leaf litter → earthworm → atmosphere
C)bird → earthworm → soil → trees
D)earthworm → fungi → leaf litter → trees