20.E: Ecosystems and the Biosphere (Exercises)
- Page ID
- 8098
20.1: Energy Flow through Ecosystems
Multiple Choice
Decomposers are associated with which class of food web?
A. grazing
B. detrital
C. inverted
D. aquatic
- Answer
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B
The producer in an ocean grazing food web is usually a ________.
A. plant
B. animal
C. fungi
D. plankton
- Answer
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D
Which term describes the process whereby toxic substances increase along trophic levels of an ecosystem?
A. biomassification
B. biomagnification
C. bioentropy
D. heterotrophy
- Answer
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B
Free Response
Compare grazing and detrital food webs. Why would they both be present in the same ecosystem?
- Answer
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Grazing food webs have a producer at their base, which is either a plant for terrestrial ecosystems or a phytoplankton for aquatic ecosystems. The producers pass their energy to the various trophic levels of consumers. At the base of detrital food webs are the decomposers, which pass their energy to a variety of other consumers. Detrital food webs are important for the health of many grazing food webs because they eliminate dead and decaying organic material, thus clearing space for new organisms and removing potential causes of disease.
20.2: Biogeochemical Cycles
Multiple Choice
The majority of the water found on Earth is:
A. ice
B. water vapor
C. fresh water
D. salt water
- Answer
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D
The process whereby oxygen is depleted by the growth of microorganisms due to excess nutrients in aquatic systems is called ________.
A. dead zoning
B. eutrophication
C. retrophication
D. depletion
- Answer
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B
Free Response
Why are drinking water supplies still a major concern for many countries?
- Answer
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Most of the water on Earth is salt water, which humans cannot drink unless the salt is removed. Some fresh water is locked in glaciers and polar ice caps, or is present in the atmosphere. The earth’s water supplies are threatened by pollution and exhaustion. The effort to supply fresh drinking water to the planet’s ever-expanding human population is seen as a major challenge in this century.
20.3: Terrestrial Biomes
Multiple Choice
Which of the following biomes is characterized by abundant water resources?
A. deserts
B. boreal forests
C. savanna
D. tropical wet forests
- Answer
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D
Which of the following biomes is characterized by short growing seasons?
A. deserts
B. tropical wet forests
C. Arctic tundra
D. savanna
- Answer
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C
Why is the tundra treeless?
A. lack of sufficient water
B. permanently frozen ground
C. winters too harsh
D. too many fires
- Answer
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B
Free Response
The extremely low precipitation of subtropical desert biomes might lead one to expect fire to be a major disturbance factor; however, fire is more common in the temperate grassland biome than in the subtropical desert biome. Why is this?
- Answer
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Fire is less common in desert biomes than in temperate grasslands because deserts have low net primary productivity, thus very little plant biomass to fuel a fire.
In what ways are the subtropical desert and the Arctic tundra similar?
- Answer
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Both the subtropical desert and the Arctic tundra have a low supply of water. In the desert, this is due to extremely low precipitation, and in the Arctic tundra, much of the water is unavailable to plants because it is frozen. Both the subtropical desert and the Arctic tundra have low net primary productivity.
20.4: Aquatic and Marine Biomes
Multiple Choice
Where would you expect to find the most photosynthesis in an ocean biome?
A. aphotic zone
B. abyssal zone
C. benthic realm
D. intertidal zone
- Answer
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D
A key feature of estuaries is
A. low light conditions and high productivity
B. salt water and fresh water
C. frequent algal blooms
D. little or no vegetation
- Answer
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B
Free Response
Describe the conditions and challenges facing organisms living in the intertidal zone.
- Answer
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Organisms living in the intertidal zone must tolerate periodic exposure to air and sunlight and must be able to be periodically dry. They also must be able to endure the pounding waves; for this reason, some shoreline organisms have hard exoskeletons that provide protection while also reducing the likelihood of drying out.