托福閱讀真題Official 45 Passage 3（七）

托福閱讀真題Official 45 Passage 3（七）

Feeding Strategies in the Ocean

In the open sea,animals can often find food reliably available in particular regions or seasons(e.g.,in coastal areas in springtime).In these circumstances,animals are neither constrained to get the last calorie out of their diet nor is energy conservation a high priority.In contrast,the food levels in the deeper layers of the ocean are greatly reduced,and the energy constraints on the animals are much more severe.To survive at those levels,animals must maximize their energy input,finding and eating whatever potential food source may be present.

In the near-surface layers,there are many large,fast carnivores as well as an immense variety of planktonic animals,which feed on plankton(small,free-floating plants or animals)by filtering them from currents of water that pass through a specialized anatomical structure.These filter-feeders thrive in the well-illuminated surface waters because oceans have so many very small organisms,from bacteria to large algae to larval crustaceans.Even fishes can become successful filter-feeders in some circumstances.Although the vast majority of marine fishes are carnivores,in near-surface regions of high productivity the concentrations of larger phytoplankton(the plant component of plankton)are sufficient to support huge populations of filter-feeding sardines and anchovies.These small fishes use their gill filaments to strain out the algae that dominate such areas.Sardines and anchovies provide the basis for huge commercial fisheries as well as a food resource for large numbers of local carnivores,particularly seabirds.At a much larger scale,baleen whales and whale sharks are also efficient filter-feeders in productive coastal or polar waters,although their filtered particles comprise small animals such as copepods and krill rather than phytoplankton.

Filtering seawater for its particulate nutritional content can be an energetically demanding method of feeding,particularly when the current of water to be filtered has to be generated by the organism itself,as is the case for all planktonic animals.Particulate organic matter of at least 2.5 micrograms per cubic liter is required to provide a filter-feeding planktonic organism with a net energy gain.This value is easily exceeded in most coastal waters,but in the deep sea,the levels of organic matter range from next to nothing to around 7 micrograms per cubic liter.Even though mean levels may mask much higher local concentrations,it is still the case that many deep-sea animals are exposed to conditions in which a normal filter-feeder would starve.

There are,therefore,fewer successful filter-feeders in deep water,and some of those that are there have larger filtering systems to cope with the scarcity of particles.Another solution for such animals is to forage in particular layers of water where the particles may be more concentrated.Many of the groups of animals that typify the filter-feeding lifestyle in shallow water have deep-sea representatives that have become predatory.Their filtering systems,which reach such a high degree of development in shallow-water species,are greatly reduced.Alternative methods of active or passive prey capture have been evolved,including trapping and seizing prey,entangling prey,and sticky tentacles.

In the deeper waters of the oceans,there is a much greater tendency for animals to await the arrival of food particles or prey rather than to search them out actively(thus minimizing energy expenditure).This has resulted in a more stealthy style of feeding,with the consequent emphasis on lures and/or the evolution of elongated appendages that increase the active volume of water controlled or monitored by the animal.Another consequence of the limited availability of prey is that many animals have developed ways of coping with much larger food particles,relative to their own body size,than the equivalent shallower species can process.Among the fishes there is a tendency for the teeth and jaws to become appreciably enlarged.In such creatures,not only are the teeth hugely enlarged and/or the jaws elongated but the size of the mouth opening may be greatly increased by making the jaw articulations so flexible that they can be effectively dislocated.Very large or long teeth provide almost no room for cutting the prey into a convenient size for swallowing;the fish must gulp the prey down whole.

Question 13 of 14

Look at the four squares[■]that indicate where the following sentence could be added to the passage.Such a passive approach requires those animals to develop specialized methods of acquiring food.Where would the sentence best fit?Click on a square[■]to add the sentence to the passage.

正確答案：B

題目詳解

題型分類：插入句子題

題干分析：考察句子和句子之間的銜接判斷，插入句開頭的Such a passive approach說明前文出現(xiàn)了消極的方式，結(jié)尾的specialized methods of acquiring food暗示后文會講獲得食物的方法。

選項分析：

B選項前一句說了await the arrival of food particles or prey對應(yīng)插入句的Such a passive approach，后一句說了a more stealthy style of feeding對應(yīng)插入句的specialized methods of acquiring food。插入句過渡了第二個空前后兩句話，填第二個空。

A選項是第五段開頭第一句話，前文沒有a passive approach，所以不填第一個空。

C選項前后一句話都是在說specialized methods of acquiring food，前面一句沒有提到a passive approach。

D選項后一句the fishes對應(yīng)前一句many animals，后一句在解釋前一句深海魚可以處理大的食物，中間不需要過渡句。

Question 14 of 14

Directions:An introductory sentence for a brief summary of the passage is provided below.Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage.Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage.This question is worth 2 points.

Ocean animals have developed various strategies for maximizing energy input from food.

Answer Choices:

A.

Large carnivores near the ocean surface feed mainly on organic matter left over after it passes through the filters of the filter-feeders.

B.

Near the surface of the water,many animals obtain food by using specialized body parts to filter plankton from the water.

C.

Even in deep ocean layers where prey is relatively hard to find,filter feeding is still the least energetically-demanding method of obtaining food.

D.

Filter-feeding is more common in shallow water,where there is a higher concentration of organic matter than there is in deeper water.

E.

Animals in deeper water have evolved strategies and body structures that allow them to use as little energy as possible in obtaining food.

F.

At deeper ocean levels plankton is relatively rare,requiring animals at those levels to actively search for their food sources.

正確答案：BDE

題目詳解

題型分類：文章總結(jié)題

題干分析：選擇概括性的正確選項

選項分析：

B選項為第二段重要信息，using specialized body parts to filter plankton對應(yīng)第二段第一句filtering them from currents of water that pass through a specialized anatomical structure。

D選項為第四段重要信息，F(xiàn)ilter-feeding is more common in shallow water對應(yīng)第二句forage in particular layers of water where the particles may be more concentrated，而由前文可知微粒更集中的地方是淺水區(qū)。

E選項為第五段重要信息，strategies對應(yīng)第二句a more stealthy style of feeding，body structure對應(yīng)第三句a tendency for the teeth and jaws to become appreciably enlarged。

A選項信息與第二段有關(guān)，但第二段沒有說Large carnivores以什么為食。matter left over無中生有。

C選項與第三段信息有關(guān)，但the least energetically-demanding method與第三段的第一句an energetically demanding method of feeding表述矛盾。

F選項與第五段信息有關(guān)，但actively search for their food sources與第一句animals to await the arrival of food particles or prey rather than to search them out actively矛盾。

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