Many aspects of coral reefs remain puzzling to scientists

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Many aspects of coral reefs remain puzzling to scientists. One mystery concerns the relationship between Scleractinia, the coral type whose colonization produces reefs, and their symbiotic partners, a unicellular algae present in the coral's endodermic tissues. It is known that both organisms play an integral part in the formation of a reef's foundation by together secreting and depositing calcium carbonate, which reacts with sea salt to form a hard limestone underlayer. Scientists also know that, because of algal photosynthesis, the reef environment is oxygen-rich, while similarly high amounts of carbon dioxide are removed rapidly. All of this accounts for the amazing renewability of coral reefs despite the erosion caused by waves. The precise manner in which one symbiotic organism stimulates the secretion of calcium carbonate by the other, however, remains unclear.

In addition to the above unanswered question, scientists have proposed various theories to explain the transformation of "fringing reefs" (those connected above sea level to land masses) into "barrier reefs" (those separated from shorelines by lagoons) and finally into island atolls. Although Darwin's view of the transformation is considered partially correct, some scientists feel that the creation of reef formations has more to do with the rise in sea level that occurred at the end of the last Ice Age than with a gradual submergence of the volcanic islands to which fringing reefs were originally attached. However, recent drillings at one atoll have revealed a substantial underlayer of volcanic rock, which suggests that Darwin's explanation may be largely correct. The term "coral reef" is something of a misnomer. The Scleractiniathemselves generally comprise only 10 percent of the total mass of life forms of an average reef community: algae, along with foraminifera, annelid worms and assorted molluscs, can account for up to 90 percent of the reef mass. Moreover, the conditions under which reef growth occurs are determined by the needs of the algae, not those of the coral. Reefs flourish only in shallow, highly saline waters above 70° F, because the algae require such an environment. Non-reef-building coral, meanwhile, occur worldwide.


It can be inferred from the passage that Darwin
A. believed that reefs became atolls through the sinking of volcanoes.
B. should have expanded his studies of reefs to include those found at atolls
C. theorized that each reef was formed by an entirely different process.
D. is less persuasive on the topic of reef formation in light of recent discoveries
E. was more interested in algae and coral than in other organisms living at reefs

OA A

How am I suppose to know the word atolls? How can we infer the Darwin theory from above esp when nothing has been mentioned directly regarding his theory?

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by MartyMurray » Sat Jan 02, 2016 7:39 am
Mechmeera wrote:How am I suppose to know the word atolls?
As is often the case with words in RC passages and questions, you don't need to know the exact meaning of the word atolls in order to answer the question correctly. You merely have to notice that the passage is discussing theories related to the formation of atolls, whatever atolls are.
How can we infer the Darwin theory from above esp when nothing has been mentioned directly regarding his theory?
The passage states "Although Darwin's view of the transformation is considered partially correct, some scientists feel that the creation of reef formations has more to do with the rise in sea level that occurred at the end of the last Ice Age than with a gradual submergence of the volcanic islands".

From this one can deduce that since those who feel that the creation of reef formations differs from Darwin's view in that the creation has more to do with something other than a gradual submergence of volcanic islands, then Darwin's view must have something to do with gradual submergence of volcanic islands.

Further, the passage says that recent drillings have revealed volcanic rock, and that that discovery "suggests that Darwin's explanation may be largely correct."

So, it seems from the second point that Darwin's view has something to do with volcanic rock and from the first that his view has something to do with the submergence, or sinking, of volcanic islands.

While the sinking of volcanoes themselves is not discussed in the passage, choice A is, basically, supported by the passage, and at least choice A is supported more than is any of the other choices.
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