TPO45阅读文本及答案解析

TPO45阅读文本3. Feeding Strategies in the Ocean

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

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

Filtering seawater for its particulate nutritional content can be anenergetically demanding method of feeding, particularly when the current ofwater to be filtered has to be generated by the organism itself, as is the casefor all planktonic animals. Particulate organic matter of at least 2.5micrograms per cubic liter is required to provide a filter-feeding planktonicorganism with a net energy gain This value is easily exceeded in most coastalwaters, but in the deep sea, the levels of organic matter range from next tonothing to around 7 micrograms per cubic liter. Even though mean levels maymask much higher local concentrations, it is still the case that many deep-seaanimals 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 thescarcity of particles. Another solution for such animals is to forage inparticular layers of water where the particles may be more concentrated. Manyof the groups of animals that typify the filter-feeding lifestyle in shallowwater have deep-sea representatives that have become predatory. Their filteringsystems, which reach such a high degree of development in shallow- waterspecies, are greatly reduced. Alternative methods of active or passive preycapture have been evolved, including trapping and seizing prey, entanglingprey, and sticky tentacles.

■ In thedeeper waters of the oceans, there is a much greater tendency for animals toawait the arrival of food particles or prey rather than to search them outactively (thus minimizing energy expenditure). ■ This has resultedin a more stealthy style of feeding, with the consequent emphasis on luresand/or the evolution of elongated appendages that increase the active volume ofwater controlled or monitored by the animal. ■ Another consequenceof the limited availability of prey is that many animals have developed ways ofcoping with much larger food particles, relative to their own body size, thanthe equivalent shallower species can process. ■Among the fishesthere is a tendency for the teeth and jaws to become appreciably enlarged. Insuch creatures, not only are the teeth hugely enlarged and/or the jawselongated but the size of the mouth opening may be greatly increased by makingthe jaw articulations so flexible that they can be effectively dislocated. Verylarge or long teeth provide almost no room for cutting the prey into aconvenient size for swallowing, the fish must gulp the prey down whole.

1.The word "severe" in the passage is closest in meaningto

O extreme

O complex

O basic

O immediate

2. What can be inferred from paragraph 1 about why energyconservation is not a high priority for ocean animals in coastal waters duringthe spring?

O Those animals are least active during the spring

O Those animals have a plentiful supply of food

O Those animals have to expend energy to avoid predators.

O Those animals store energy during the colder seasons.

3. What can be inferred from paragraph 2 about fish?

O Most fish feed on plankton.

O Fish tend to avoid well-illuminated areas.

O Most fish species are not filter-feeders.

O Few fish species are successful in the near-surface layers.

4. According to paragraph 2, how do sardines and anchovies obtainfood near the surface of the ocean?

O They rely on the large quantities of food resources also availableto local carnivores.

O They capture the larvae of some crustaceans.

O They feed on the organisms left over by commercial fisheries.

O They obtain algae by using their gills as filters.

5. In paragraph 1, the author compares pollen moved by wind withletters thrown off roofs in order to

O explain why there are relatively few species of trees that dependon wind pollination

O compare natural, biological processes with human social practices

O make a point about the probability of wind-blown pollen reaching atree of the same species

O argue against the common assumption that the tallest trees are themost likely to employ wind pollination

6. Paragraph 2 suggests that wind-pollinated plants do not havebright petals, nectar, and scent for which TWO of the following reasons? Toreceive credit, you must select TWO answers.

□ They interfere with pollination by wind

□ They are easily damaged by wind.

□ They are unnecessary.

□ They reduce the amount of pollen that can be produced.

7. The word "scarcity" in the passage is closest inmeaning to

O speed

O variety

O lack

O size

8. According to paragraph 4,deep-water filter-feeders have adoptedall of the following ways to obtain food EXCEPT

O      developing largerfiltering systems

O      capturing prey usingsticky tentacles

O      swimming up to thesurface at feeding time

O      searching in oceanlayers that contain a substantial amount of particles

9. Why does the author include the information that animals in thedeep ocean place an emphasis on lures" and have evolved "elongatedappendages”?

O To argue against the view that animals in the deep ocean use moreenergy to find food than do animals in shallow waters

O To emphasize the importance of an am mars ability to control alarge volume of water

O To identify some feeding strategies that animals have developed tominimize their energy expenditure

O To give examples of body structures that help those animals movequickly in deep ocean waters

10. The phrase "coping with" in the passage is closest inmeaning to

O Absorbing

O finding

O approaching

O managing

11. The word "flexible" in the passage is closest inmeaning to

O huge

O adaptable

O powerful

O precise

12. According to paragraph 5, why do some fish swallow their preywhole?

O Their teeth are too large to allow for cutting prey.

O They have no jaw muscles to allow chewing.

O Swallowing prey whole results in a higher net energy gain.

O Chewing can cause their jaws to dislocate.

13. Look at the four squares [■] that indicatewhere the following sentence could be added to the passage.

Such a passive approach requires those animals to developspecialized methods of acquiring food.

Where would the sentence best fit? Click on a square [■] to add thesentence to the passage.

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

Drag your answer choices to the spaces where they belong. To removean answer choice, click on it.

To review the passage, click VIEW TEXT

Ocean animals have developed various strategies for maximizing energyinput from food.

Answer Choices

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

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

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

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

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

Atdeeper ocean levels plankton is relatively rare, requiring animals at thoselevels to actively search for their food sources.

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