Passage 34
Coral reefs are one of the most fragile, biologically
complex, and perse marine1 ecosplayystem2 on Earth. This
ecosplayystem is one of the fascinating paradoxes3 of the bio-
sphere: how do clear, and thus nutrient4-poor, waters sup-
port such prolific5 and productive communities? Part of the
answer lies within the tissues of the corals themselves.
Symbiotic6 cells of algae7 known as zooxanthellae carry out
photosynthesis using the metabolic8 wastes of the coral
thereby9 producing food for themselves, for their corals,
hosts, and even for other members of the reef community.
This symbiotic process allows organisms in the reef com-
munity to use sparse10 nutrient resources efficiently11.
Unfortunately for coral reefs, however, a variety of
human activities are causing worldwide degradation12 of
shallow marine habitats by adding nutrients13 to the an increasing abundance of algae and filter-feeding
animals.
Declines in reef communities are consistent with observa-
tions that nutrient input14 is increasing in direct proportion to
growing human populations, thereby threatening reef com-
munities sensitive to subtle changes in nutrient input to
their waters.
213. The passage is primarily concerned with
describing the effects of human activities on algae in coral reefs
explaining how human activities are posing a threat to coral reef communities
discussing the process by which coral reefs deteriorate15 in nutrient-poor waters
explaining how coral reefs produce food for themselves
describing the abundance of algae and filter-feeding animals in coral reef areas
214. The passage suggests which of the following about coral reef communities?
Coral reef communities may actually be more likely to thrive in waters that are relatively16 low in nutrients.
The nutrients on which coral reef communities thrive are only found in shallow waters.
Human population growth has led to changing ocean temperatures, which threatens coral reef communities.
The growth of coral reef communities tends to destabilize underwater herbivore populations.
Coral reef communities are more complex and perse than most ecosplayystems17 located on dry land.
215. The author refers to filter-feeding animals in order to
provide an example of a characteristic sign of reef deterioration
explain how reef communities acquire sustenance18 for survival
identify a factor that helps herbivore populations thrive
indicate a cause of decreasing nutrient input in waters that reefs inhabit
identify members of coral reef communities that rely on coral reefs for nutrients
216. According to the passage, which of the following is a factor that is threatening the survival of coral reef communities?
The waters they inhabit contain few nutrient resources.
A decline in nutrient input is disrupting their symbiotic relationship with zooxanthellae
The degraded waters of their marine habitats have reduced their ability to carry out photosynthesis
They are too biologically complex to survive in habitats with minimal19 nutrient input.
Waste by-products result in an increase in nutrient input to reef communities.
217. It can be inferred from the passage that the author describes coral reef communities as paradoxical most likely for which of the following reasons?
They are thriving even though human activities have depleted20 the nutrients in their environment.
They are able to survive in spite of an overabundance of algae inhabiting their waters.
They are able to survive in an environment with limited food resources.
Their metabolic wastes contribute to the degradation of the waters that they inhabit.
They are declining even when the water sur-rounding them remains21 clear.
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