新GRE阅读36篇 Exercise11 第6与第7题

KevinButtUID：2468098

请问下新GRE阅读36篇 Exercise11 第6与第7题为何选B和"For  example,  some  of  the  large
sedentary"。我第6题选的是D,因为感觉第2段整个讲的是依靠chemosynthesis取得食物的途径，而第7题我选的句子是Another difficulty is that similarly dense populations...因为个人感觉这句更具体到题目中some of the same animal (similarly dense populations of large deep-sea animals) found in other areas of the ocean floor (vents)。请高人指点，非常感谢！

KevinButtUID：2468098

自己顶，请高人解答，谢谢！

cinkieUID：2933620

麻烦LZ把文章和题贴出来~~

KevinButtUID：2468098

The deep sea typically has a sparse fauna dominated
by tiny worms and crustaceans, with an even sparser
distribution of larger animals. However, near
Line  hydrothermal vents, areas of the ocean where warm water
emerges from subterranean sources, live remarkable
densities of huge clams, blind crabs, and fish.
Most deep-sea faunas rely for food on particulate
matter, ultimately derived from photosynthesis, falling
from above. The food supplies necessary to sustain the
large vent communities, however, must be many times
the ordinary fallout. The first reports describing vent
faunas proposed two possible sources of nutrition:
bacterial chemosynthesis, production of food by bacteria
using energy derived from chemical changes, and
advection, the drifting of food materials from surrounding  
regions. Later, evidence in support of the idea of intense
local chemosynthesis was accumulated: hydrogen sulfide
was found in vent water; many vent-site bacteria were
found to be capable of chemosynthesis; and extremely
large concentrations of bacteria were found in samples of
vent water thought to be pure. This final observation
seemed decisive. If such astonishing concentrations of
bacteria were typical of vent outflow, then food within the
vent would dwarf any contribution from advection.
Hence, the widely quoted conclusion was reached that
bacterial chemosynthesis provides the foundation for
hydrothermal-vent food chains—an exciting prospect
because no other communities on Earth are independent
of photosynthesis.
  There are, however, certain difficulties with this
interpretation. For example, some of the large sedentary
organisms associated with vents are also found at
ordinary deep-sea temperatures many meters from the
nearest hydrothermal sources. This suggests that bacterial
chemosynthesis is not a sufficient source of nutrition for
these creatures. Another difficulty is that similarly dense
populations of large deep-sea animals have been found in
the proximity of ―smokers‖ –vents where water emerges
at temperatures up to 350° C. No bacteria can survive such
heat, and no bacteria were found there.  Unless smokers
are consistently located near more hospitable warm-water
vents, chemosynthesis can account for only a fraction of
the vent faunas. It is conceivable, however, that these
large, sedentary organisms do in fact feed on bacteria that
grow in warm-water vents, rise in the vent water, and then
rain in peripheral areas to nourish animals living some
distance from the warm-water vents.
Nonetheless, advection is a more likely alternative
food source. Research has demonstrated that advective
flow, which originates near the surface of the ocean
where suspended particulate matter accumulates,
transports some of that matter and water to the vents.
Estimates suggest that for every cubic meter of  vent
discharge, 350 milligrams of particulate organic
material would be advected into the vent area. Thus, for
an average-sized vent, advection could provide more
than 30 kilograms of potential food per day. In addition,
it is likely that small live animals in the advected water
might be killed or stunned by thermal and/or chemical
shock, thereby contributing to the food supply of vents.

6. The information in the passage suggests that the
majority of deep-sea faunas that live in nonvent
habitats have which of the following characteristics?
(A) They do not normally feed on particles of food
in the water.
(B) They are smaller than many vent faunas.
(C) They are predators.
(D) They derive nutrition from a chemosynthetic
food source.
(E) They congregate around a single main food
source.

7. Select the sentence in the passage in which the author
implies that  vents are colonized by some of the same
animal found in other areas of the ocean floor, which
might be a weakness for the bacterial chemosynthesis
model.

Leon-WangUID：2772364

KevinButt 发表于 2013-9-24 22:57
The deep sea typically has a sparse fauna dominated
by tiny worms and crustaceans, with an even sp ...

第六题抓住下面这两句话：
Most deep-sea faunas(nonvent faunas) rely for food on particulate
matter, ultimately derived from photosynthesis, falling
from above. The food supplies necessary to sustain the
large vent communities(vent faunas), however, must be many times
the ordinary fallout.
第七题抓住题干的关键词：
Select the sentence in the passage in which the author
implies that vents are colonized by some of the same
animal found in other areas of the ocean floor, which
might be a weakness for the bacterial chemosynthesis
model.
正文
This suggests that bacterial
chemosynthesis is not a sufficient source of nutrition for
these creatures.
再说你选的那句的重心是在谈细菌这么高温度生存不了的矛盾，而非谈那些大动物。

KevinButtUID：2468098

好的，谢谢楼上的解答！