Deck 42: Ecosystems and Energy

Question 1

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 solar radiation is converted to heat energy.
B) Only 1% of the wavelengths of visible light is absorbed by photosynthetic pigments.
C) Most solar energy strikes water and land surfaces.
D) Approximately 99% of the solar radiation is reflected.
E) Only the green wavelengths are absorbed by plants for photosynthesis.

Answer 1

B

Question 2

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 flows through and out of ecosystems.
B) Photosynthesis and feeding relationships result in transforming chemical elements, but not energy.
C) Chemical elements are transferred into ecosystems from other ecosystems, but energy is only transferred within a single ecosystem.
D) In an ecosystem, the total amount of chemical elements does not change, whereas the total amount of energy can change.

Answer 2

A

Question 3

The major role of detritivores in ecosystems is to

A) provide a nutritional resource for heterotrophs.
B) recycle chemical nutrients to a form capable of being used by autotrophs.
C) prevent the buildup of the organic remains of organisms, feces, and so on.
D) return energy lost to the ecosystem by other organisms.

Answer 3

B

Question 4

Photosynthetic organisms are unique to most ecosystems because they

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

Question 5

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

A) tundra
B) savanna
C) salt marsh
D) open ocean
E) tropical rain forest

Question 6

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) tropical rain forest
B) tundra
C) deep-sea hydrothermal vent community
D) grassland
E) desert

Question 7

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

A) Matter flows through ecosystems; energy cycles within ecosystems.
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 ecosystems; energy is not.

Question 8

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 greater concentrations of nutrients compared to other ecosystems.
B) Oceans receive a lesser amount of solar energy per unit area.
C) Oceans have the largest area of all the ecosystems on Earth.
D) Ocean ecosystems have less species diversity.
E) Oceanic producers are generally much smaller than oceanic consumers.

Question 9

Which of the following statements is true?

A) The trophic level that ultimately supports all others consists of detritivores.
B) Consumers can exist in an ecosystem without primary producers.
C) Chemoautotrophic prokaryotes near deep-sea vents are primary producers.
D) No losses of energy occur from primary producers in an ecosystem.

Question 10

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 11

Which of the following terms encompasses all of the others?

A) heterotrophs
B) herbivores
C) carnivores
D) primary consumers
E) secondary consumers

Question 12

Which of the following is true of detritivores?

A) They synthesize organic molecules that are used by primary producers.
B) They convert organic materials from all trophic levels to inorganic compounds usable by primary producers.
C) They secrete enzymes that convert the organic molecules of detritus into CO₂ and H₂O.
D) Some species are autotrophic, whereas others are heterotrophic.

Question 13

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) Chemoautotrophic organisms can convert matter to energy.
B) Ecosystems are open systems; therefore, matter can be moved in/out of an ecosystem from/to another ecosystem.
C) Photosynthetic organisms convert sugars to more complex organic molecules.
D) Detritivores convert matter to energy.
E) Heterotrophs convert heat to energy.

Question 14

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 plants, animals, and decomposers that inhabit an alpine meadow
C) a pond and all of the plant and animal species that live in it
D) the intricate interactions of the various plant and animal species on a savanna during a drought
E) all of the organisms and their physical environment in a tropical rain forest

Question 15

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

A) primary consumer.
B) secondary consumer.
C) decomposer.
D) autotroph.
E) producer.

Question 16

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

A) savanna
B) open ocean
C) boreal forest
D) tropical rain forest
E) temperate forest

Question 17

The total biomass of photosynthetic autotrophs present in an ecosystem is known as

A) gross primary productivity.
B) standing crop.
C) net primary productivity.
D) secondary productivity.
E) trophic efficiency.

Question 18

What percentage of solar radiation striking a plant is converted into chemical energy?

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

Question 19

Which of the following is a true statement regarding mineral nutrients in soils and their implication for primary productivity?

A) Globally, only phosphorus availability is most limiting to primary productivity.
B) Adding a non-limiting nutrient will stimulate primary productivity.
C) Adding more of a limiting nutrient will increase primary productivity regardless of other nutrient availability.
D) Phosphorus is sometimes unavailable to producers due to leaching.
E) Alkaline soils are more productive than acidic soils.

Question 20

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 photosynthesis
E) all solar energy

Question 21

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) pollution
E) temperature

Question 22

A 3-hectare 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
B) introduction of non-native tertiary consumer fish
C) nutrient-rich runoff
D) accidental introduction of a prolific culture of algae
E) iron dust blowing into the lake

Question 23

How is it that satellites can detect differences in primary productivity on Earth?

A) Photosynthetic organisms absorb more visible light in the 350- to 750-nm wavelengths.
B) Satellite instruments can detect reflectance patterns of the photosynthetic organisms of different ecosystems.
C) Sensitive satellite instruments can measure the amount of NADPH produced in the summative light reactions of different ecosystems.
D) Satellites detect differences by comparing the wavelengths of light captured and reflected by photoautotrophs to the amount of light reaching different ecosystems.
E) Satellites detect differences by measuring the amount of water vapor emitted by transpiring producers.

Question 24

How does inefficient transfer of energy among trophic levels result in the typically high endangerment status of many top-level predators?

A) Top-level predators are restricted to small populations that are sparsely distributed.
B) Predators have relatively large population sizes.
C) Predators are more disease-prone than animals at lower trophic levels.
D) Predators have short life spans and short reproductive periods.
E) Top-level predators are more likely to be stricken with parasites.

Question 25

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

A) mammals, fish, insects
B) insects, fish, mammals
C) fish, insects, mammals
D) insects, mammals, fish
E) mammals, insects, fish

Question 26

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 carnivores require 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 it is lost to the environment.
D) the accumulation of toxic materials in tissues of animals limits the secondary consumers and top carnivores.
E) top carnivores and secondary consumers have a more general diet than primary producers.

Question 27

Aquatic ecosystems are most likely to be limited by which of the following nutrients?

A) nitrogen
B) carbon
C) potassium
D) iron
E) zinc

Question 28

Trophic efficiency is

A) the ratio of net secondary production to assimilation of primary production.
B) the percentage of production transferred from one trophic level to the next.
C) a measure of how nutrients are cycled from one trophic level to the next.
D) usually greater than production efficiencies.
E) about 90% in most ecosystems.

Question 29

Which of the following ecosystems would likely have a larger net primary productivity/hectare, and why?

A) open ocean, because of the total biomass of photosynthetic autotrophs
B) a temperate grassland, because of the small standing crop biomass that results from consumption by herbivores and rapid decomposition
C) tropical rain forest, because of the long growing season and large amount of leaf surface area
D) a cave, due to the lack of photosynthetic autotrophs
E) tundra, because of the incredibly rapid period of growth during the summer season

Question 30

What is secondary production?

A) energy converted by secondary consumers from primary consumers
B) solar energy that is converted to chemical energy by photosynthesis
C) chemical energy in food that is converted to new biomass by consumers
D) energy that is not used by consumers for growth and reproduction
E) growth that takes place during the second year of life in consumers

Question 31

How is net ecosystem production (NEP) typically estimated in ecosystems?

A) the ratio of producers to consumers
B) the amount of heat energy released by the ecosystem
C) the net flux of CO₂ or O₂ in or out of an ecosystem
D) the rate of decomposition by detritivores
E) the annual total of incoming solar radiation per unit of area

Question 32

Owls eat rats, mice, shrews, and small birds. Assume that, over a period of time, an owl consumes 5,000 J of animal material. The owl loses 2,300 J in feces and owl pellets and uses 2,600 J for cellular respiration. What is the production efficiency of this owl?

A) 0.02%
B) 1%
C) 4%
D) 10%
E) 40%

Question 33

Which trophic level is most vulnerable to extinction?

A) milkweed plants
B) monarch caterpillars that eat milkweed plants
C) goldfinches that eat monarch caterpillars
D) golden eagles that eat goldfinches
E) inky cap fungus that breaks down plant material

Question 34

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) biomass
B) standing crop
C) primary production
D) secondary production

Question 35

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 36

Which statement best describes what ultimately happens to the chemical energy that is not converted to new biomass in the process of energy transfer between trophic levels in an ecosystem?

A) All of it is undigested and winds up in the feces and is not passed on to higher trophic levels.
B) It is only used by organisms to maintain their life processes through the reactions of cellular respiration.
C) Heat produced by cellular respiration is used by heterotrophs to thermoregulate.
D) It is eliminated as feces or is dissipated into space as heat in accordance with the second law of thermodynamics.
E) It is recycled by decomposers to a form that is once again usable by primary producers.

Question 37

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.
B) NPP can be expressed in terms of carbon fixed by photosynthesis for an entire ecosystem.
C) NPP represents the stored chemical energy that will be available to consumers in the ecosystem.
D) NPP is the same as the standing crop.
E) NPP shows the rate at which the standing crop is utilized by consumers.

Question 38

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

A) Fewer 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 than do omnivores.
E) Eating meat is an inefficient way of acquiring photosynthetic productivity.

Question 39

Which of the following is primarily responsible for limiting the number of trophic levels in most ecosystems?

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.
E) Energy transfer between trophic levels is almost always less than 20% efficient.

Question 40

What is the primary limiting factor for aquatic productivity?

A) pressure
B) lack of nutrients
C) light availability
D) presence of herbivores
E) competition

Question 41

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

A) atmosphere
B) sedimentary rocks
C) fossilized plant and animal remains (coal, oil, and natural gas)
D) plant and animal biomass

Question 42

Figure 42.1 Food web for a particular terrestrial ecosystem (arrows represent energy flow and numbers represent species)
Examine the food web for a particular terrestrial ecosystem in Figure 42.1. Which species is most likely a decomposer in this food web?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 43

Figure 42.1 Food web for a particular terrestrial ecosystem (arrows represent energy flow and numbers represent species)
Examine the food web for a particular terrestrial ecosystem in Figure 42.1. Species C is toxic to predators. Which species is most likely to benefit from being a mimic of C?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 44

In Japan, seaweed and seagrass bed reconstruction includes constructing suitable seafloor habitat, transplanting seaweeds and seagrasses from natural beds using artificial substrates, and hand seeding. Which of the following correctly classifies the techniques by the major restoration strategies?

A) biological augmentation-transplanting seaweeds and seagrasses, hand seeding
B) biological augmentation-hand seeding and constructing seafloor habitat
C) bioremediation-constructing seafloor habitat and using artificial substrates
D) bioremediation-transplanting seaweeds and seagrasses, hand seeding

Question 45

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

A) to restore the physical structure
B) to restore native species that have been extirpated due to disturbance
C) to remove competitive invasive species
D) to identify the limiting factors of the producers
E) to remove toxic pollutants

Question 46

Figure 42.1 Food web for a particular terrestrial ecosystem (arrows represent energy flow and numbers represent species)
Examine the food web for a particular terrestrial ecosystem in Figure 42.1. Which species is autotrophic?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 47

Which of the following statements about biogeochemical cycling is correct?

A) The phosphorus cycle involves the recycling of atmospheric phosphorus.
B) The phosphorus cycle involves the weathering of rocks.
C) The carbon cycle is a localized cycle that primarily involves the burning of fossil fuels.
D) The carbon cycle has maintained a constant atmospheric concentration of CO₂ for the past million years.
E) The nitrogen cycle involves movement of diatomic nitrogen between the biotic and abiotic components of the ecosystem.

Question 48

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 49

Which of the following is an example of bioremediation?

A) using a bulldozer to reshape the land around an abandoned strip mine to change erosion patterns
B) dredging a river bottom to remove contaminated sediments
C) reconfiguring the channel of a river to increase the flow of water down a river
D) raising chromium-accumulating plants to extract chromium from contaminated soil
E) selectively harvesting younger trees in a forest to leave older trees for woodpecker nesting habitat

Question 50

In the nitrogen cycle, the organisms that replenish the atmosphere with N2 are

A) mycorrhizal fungi.
B) nitrifying bacteria.
C) denitrifying bacteria.
D) nitrogen-fixing bacteria.

Question 51

What is the goal of restoration ecology?

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

Question 52

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

A) runoff into waterways
B) sedimentation into lake bottoms
C) decomposition of detritus
D) fixation in root nodules

Question 53

Nitrogen is available to plants mostly in the form of

A) N2 in the atmosphere.
B) nitrite ions in the soil.
C) uric acid from animal excretions.
D) nucleic acids from decomposing plants and animals.
E) nitrate and ammonium ions in the soil.

Question 54

To selectively remove soil toxins from regions affected by Hurricane Katrina, some residents are growing sunflowers and other plants in their yards. Once mature, the plants are pulled and safely stored with other contaminated wastes. This is an example of

A) biological augmentation.
B) reducing primary production.
C) lowering production efficiency.
D) bioremediation.
E) arresting nutrient cycling.

Question 55

Rain falls on an 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 56

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

A) Tropical bedrock contains little phosphorus.
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 57

If the flow of energy in an arctic ecosystem goes through a simple food chain, perhaps involving humans, moving from phytoplankton to zooplankton to fish to seals to polar bears, then which of the following could be true?

A) Polar bears can provide more food for humans than seals can.
B) The total biomass of the fish is lower than that of the seals.
C) Seal meat probably contains the highest concentrations of fat-soluble toxins.
D) Seal populations are larger than fish populations.
E) The fish can potentially provide more food for humans than the seal meat can.

Question 58

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

A) atmosphere
B) sedimentary bedrock
C) fossilized plant and animal remains (coal, oil, and natural gas)
D) plant and animal biomass
E) soil

Question 59

How does phosphorus normally enter ecosystems?

A) as a product from cellular respiration
B) as a product from photosynthesis
C) from rock weathering
D) as atmospheric phosphorus gas

Question 60

Corn production in many states of the Midwest is limited by nitrogen levels in the soil. Some farmers reduce the need to apply expensive anhydrous 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) the biomass pyramid.
C) promoting leaching efficiency.
D) bioremediation.
E) trophic efficiency.

Question 61

Please use the following information to answer the question(s) 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.
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 62

Please use the following information to answer the question(s) 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 biomass only
C) presence and absence of mycorrhizae
D) nitrogen treatment and whether mycorrhizae are present

Question 63

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 64

Please use the following information to answer the question(s) 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.
What is the production efficiency of the grasshopper?

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

Question 65

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 account for 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, multiply this number by 100, and add that amount to the total nitrogen in the ecosystem.
B) Find out how much nitrogen is eliminated by a Canada goose over about a 12-hour period, multiply this number by 100, 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 multiply this number by 100; enter the net value of nitrogen associated with the goose visitation into the nitrogen budget of the ecosystem.
D) Do nothing. The Canada geese visitation to the lake would have a negligible impact on the nitrogen budget of the pond.
E) Put a net over the pond so that no more migrating flocks can land on the pond and alter the nitrogen balance of the pond.

Question 66

Please use the following information to answer the question(s) 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.
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 67

Please use the following information to answer the question(s) 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.
Predict the fate of a phosphorus atom after a non-native earthworm consumes leaf litter in a forest.

A) It becomes incorporated into the earthworm as an energy-storing molecule.
B) It is excreted as ammonium.
C) It is released during cellular respiration as PO43-.
D) It is weathered into rocks.

Question 68

A porcupine eats 3,000 J of plant material. Of this, 2,100 J are indigestible and are eliminated as feces, 800 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) 11%
D) 27%
E) 33%

Question 69

Please use the following information to answer the question(s) 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

Question 70

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 71

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 72

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

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

Question 73

Figure 42.1 Food web for a particular terrestrial ecosystem (arrows represent energy flow and numbers represent species)
Examine the food web for a particular terrestrial ecosystem in Figure 42.1. Which pair of species acquire energy from more than one trophic level?

A) 1 and 2
B) 1 and 4
C) 2 and 3
D) 3 and 4
E) 3 and 5

Question 74

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 smallest organism might be

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

Question 75

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 Ocean (Antarctic Ocean) productivity from year to year to see if it changes.
C) experimentally enrich some areas of the ocean and compare their productivity to that of untreated areas.
D) compare nutrient concentrations between the photic zone and the benthic zone in various marine locations.
E) contrast nutrient uptake by autotrophs in marine locations that are different temperatures.

Question 76

Please use the following information to answer the question(s) 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.
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 77

Please use the following information to answer the question(s) 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.
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 78

Figure 42.3
In the diagram of the nitrogen cycle in Figure 42.3, which number represents nitrite (NO₂)?

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

Question 79

Please use the following information to answer the question(s) 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) standing crop.
D) secondary production.
E) net primary production.

Question 80

Please use the following information to answer the question(s) 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.
What is the maximum biomass of grasshoppers that could be supported by this square meter of tundra (i.e., if grasshoppers ate all of the existing vegetation)?

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