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Feeding Strategies in the Ocean
In the open a,animals can often find food reliably available in particular regions or asons(e g.,in coastal areas in springtime).In the circumstances,animals are neither constrained to get the last calorie out of their diet nor is energy conrvation 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 vere.To survive at tho levels,animals must maximize their energy input,finding and eating whatever potential food source may be prent.
In the near-surface layers,there are many large,fast carnivores as well as an immen 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.The filter-feeders thrive in the well-illuminated surface waters becau 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 hig
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灯带h productivity the concentrations of larger phytoplankton(the plant component of plankton)are sufficient to support huge populations of filter-feeding sardines and anchovies.The small fishes u 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 abirds.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 compri small animals such as copepods and krill rather than phytoplankton.
交友的成语故事 Filtering awater 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 itlf,as is the ca 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 a,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 ca that many deep-a animals are expod to conditions in which a normal filter-feeder would starve.
凤毛济美 There are,therefore,fewer successful filter-feeders in deep water,and some of tho that are there h
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酒后驾驶ave 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-a reprentatives 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 izing prey,entangling prey,and sticky tentacles.
■A 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 arch them out actively(thus minimizing energy expenditure).■B This has resulted in a more stealthy style of feeding,with the conquent emphasis on lures and/or the evolution of elongated appendages that increa the active volume of water controlled or monitored by the animal.■C Another conquence 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.■D Among the fishes there is a tendency for the teeth and jaws to become appreciably enlarged.In such creatures,are the teeth hugely enlarged and/or the jaws elongated but the size of the mouth opening may be greatly increas
ed 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.
Paragraph 1
In the open a,animals can often find food reliably available in particular regions or asons(e g.,in coastal areas in springtime).In the circumstances,animals are neither constrained to get the last calorie out of their diet nor is energy conrvation 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 vere.To survive at tho levels,animals must maximize their energy input,finding and eating whatever potential food source may be prent.
1.The word"vere"in paragraph 1 is clost in meaning to
A.extreme
B.complex
C.basic
D.immediate
2.What can be inferred from paragraph 1 about why energy conrvation is not a high priority for ocean animals in coastal waters during the spring?