RC doubt of big book

[Viral]

The deep sea typically has a sparse fauna dominatedby tiny worms and crustaceans, with an even sparser dis-tribution of larger animals. However, near hydrothermalvents, areas of the ocean where warm water emergesfrom subterranean sources, live remarkable densities ofhuge clams, blind crabs, and fish. Most deep-sea faunas rely for food on particulatematter, ultimately derived from photosynthesis, fallingfrom above. The food supplies necessary to sustain thelarge vent communities, however, must be many timesthe ordinary fallout. The first reports describing'vent 'faunas proposed two possible sources of nutrition: bac-terial chemosynthesis, production of food by bacteriausing energy derived from chemical changes, and advec-tion, the drifting of food materials from surroundingregions. Later, evidence in support of the idea of intenselocal chemosynthesis was accumulated: hydrogen sul-fide was found in vent water; many vent-site bacteriawere found to be capable of chemosynthesis; and ex-tremely large concentrations of bacteria were found insamples of vent water thought to be pure. This finalobservation seemed decisive. If such astonishing concen-trations of bacteria were typical of vent outflow, thenfood within the vent would dwarf any contribution fromadvection. Hence, the widely quoted conclusion wasreached that bacterial chemosynthesis provides the foun-dation for hydrothermal-vent food chains—an excitingprospect because no other communities on Earth areindependent of photosynthesis. There are, however, certain difficulties with this inter-pretation. For example, some of the large sedentaryorganisms associated with vents are also found at ordi-nary deep-sea temperatures many meters from thenearest hydrothermal sources. This suggests that bacte-rial chemosynthesis is not a sufficient source of nutritionfor these creatures. Another difficulty is that similarlydense populations of large deep-sea animals have beenfound in the proximity of "smokers"—vents wherewater emerges at temperatures up to 350° C. No bacteriacan survive such heat, and no bacteria were found there (45) (10) (60) Unless smokers are consistently located near more hos-pitable warm-water vents, chemosynthesis can accountfor only a fraction of the vent faunas. It is conceivable,however, that these large, sedentary organisms do in fafeed on bacteria that grow in warm-water vents, rise inthe vent water, and then rain in peripheral areas to nourist animals living some distance from the warm-watervents. Nonetheless, advection is a more likely alternativefood source. Research has demonstrated that advectiveflow, which originates near the surface of the oceanwhere suspended particulate matter accumulates, trans-ports some ofthat matter and water to the vents'. Esti-mates-suggest that for every cubic meter of vent dis-charge, 350 milligrams of particulate organic materialwould be advected into the vent area. Thus, for anaverage-sized vent, advection could provide more than30 kilograms of potential food per day. In addition, it ilikely that small live animals in the advected water miglbe killed or stunned by thermal and/or chemical shockthereby contributing to the food supply of vents.
16. The passage provides information for answeringwhich of the following questions? (A) What causes warm-water vents to form? (B) Do vent faunas consume more than do deep-si faunas of similar size? (C) Do bacteria live in the vent water of smokers7 (D) What role does hydrogen sulfide play in chemosynthesis? (E) What accounts for the locations of deep-sea smokers?
17. The information in the passage suggests that themajority of deep-sea faunas that live in nonventhabitats 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.
18. The primary purpose of the passage is to (A) describe a previously unknown natural phenomenon (B) reconstruct the evolution of a natural phenomenon (C) establish unequivocally the accuracy of a hypothesis (D) survey explanations for a natural phenomenon and determine which is best supported byevidence (E) entertain criticism of the author's research and provide an effective response
19. Which of the following does the author cite as aweakness in the argument that bacterial chemosyn-thesis provides the foundation for the food chains atdeep-sea vents? (A) Vents are colonized by some of the same ani- mals found in other areas of the ocean floor. (B) Vent water does not contain sufficient quanti- ties of hydrogen sulfide. (C) Bacteria cannot produce large quantities of food quickly enough. (D) Large concentrations of minerals are found in vent water. (E) Some bacteria found in the vents are incapable of chemosynthesis.
20. Which of the following is information supplied inthe passage that would support the statement thatthe food supplies necessary to sustain vent commu-nities must be many times that of ordinary fallout? I. Large vent faunas move from vent to vent in search of food.II. Vent faunas are not able to consume food pro-duced by photosynthesis.III. Vents are more densely populated than are otherdeep-sea areas. (A) I only. (B) III only (C) I and II only (D) II and III only (E) I, II, and III
21. The author refers to "smokers" (line 3 most prob-ably in order to (A) show how thermal shock can provide food for some vent faunas by stunning small animals (B) prove that the habitat of most deep-sea animals is limited to warm-water vents (C) explain how bacteria carry out chemosynthesis (D) demonstrate how advection compensates for the lack of food sources on the seafloor (E) present evidence that bacterial chemosynthesis may be an inadequate source of food forsome vent faunas 22. Which of the following can be inferred from the pas-sage about the particulate matter that is earneddown from the surface of the ocean? (A) It is the basis of bacterial chemosynthesis in- the vents. (B) It may provide an important source of nutrition for vent faunas.(Q- It may cause the internal temperature of the. vents to change significantly. (D) It is transported as large aggregates of particles. (E) It contains hydrogen sulfide.