陈虎平36套第11套第6题
The information in the passage suggests thatthe majority of deep-sea faunas that live in nonvent habitats have which of thefollowing characteristics?.(L14——15 The food supplies necessary
to sustain the large vent communities, B直接对应)
A. They do not normally feed onparticles of food in the water.
B.They are smaller than many vent faunas
C. They are predators.
D. They derive nutrition from achemosynthetic food source.
E. They congregate around asingle main food source.
答案：(B)
原文：Thedeep sea typically has a sparse
fauna dominated by tiny worms and
(5) crustaceans, with an even sparser
distribution of larger animals. However,
near hydrothermal vents, areas of the
ocean where warm wateremerges from
subterranean sources,live remarkable
(10) densities of huge clams, blind crabs,
and fish. Most deep-sea faunasrely for
food on particulate matter, ultimately
derived from photosynthesis, falling
from above. The food supplies necessary
(15)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
(20)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
(25) support of the idea of intense local
chemosynthesis wasaccumulated:
hydrogen sulfied was found in vent
water; many vent-site bacteria were
found to be capable of chemosynthesis;
(30)and extremely large concentrations of
bacteria were found in samples of vent
water thought to be pure.This final
observation seemeddecisive. If such
astonishing concentrations ofbacteria (35) were typical of ventoutflow, then food within the vent would dwarfany contribution from advection.Hence, the widely quoted conclusion was reached that bacterialchemosynthesis (40) provides the foundation for hydrothermal- vent food chains—an exciting prospect because noother communities on Earth areindependent of photosynthesis.
(45)
There are, however, certaindifficul-
ties with thisinterpretation.For example,
some of the large sedentary organisms
associated with vents are alsofound at
ordinary deep-sea temperaturesmany
(50)meters from the nearest hydrothermal
sources. This suggests thatbacterial
chemosynthesis is not asufficient
source of nutrition for thesecreatures.
Another difficulty is thatsimilarly
(55)dense populations of large deep-sea
animals have been found in the
proximity of "smokers"–ventswhere
water emerges at temperatures upto
350°C. No bacteria can survivesuch
(60)heat, and no bacteria were found there.
Unless smokers are consistently
located near more hospitablewarm-water
vents, chemosynthesis can accountfor
only a fraction of thevent faunas.
(65)It is conceivable, however, that
these large, sedentary organismsdo
in fact feed on bacteria thatgrow in
warm-water vents, rise in the vent
water, and then rain inperipheral areas
(70)to nourish animals living some distance
from the warm-water vents.
Nonethelessadvection is a more likely
alternative foodsource. Researchhas
demonstrated that advective flow,which
(75)originates near the surface of the ocean
where suspended particulatematter
accumulates, transports some ofthat
matter and water to the vents.Estimates
suggest that matter and water tothe
(80)vents. Estimates suggest that for every
cubic meter of vent discharge,
milligrams of particulateorganic
material would be advected intothe
vent area. Thus, for anaverage-sized
(85)vent, advection could provide more
than 30kilograms of potential food per
day. In addition, it is likelythat small
live animals in the advectedwater might
be killed or stunned by thermaland/or
(90)chemical shock, thereby contributing to
the food supply of vents.
我 选的是C，我的根据是这句话：“ 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
(70) to nourish animals living some distance
from the warm-water vents.”
好心人 指点一下嘛作者: 苏梳眠 时间: 2012-1-15 23:15:15