托福阅读真题+题目+答案：Shoaling Behavior

托福阅读真题+题目+答案：Shoaling Behavior

A shoal is any group of fish that remain together for social reasons. A shoal may be a school (a coordinated group with synchronized movements) at some times and a less organized mass at others. Shoaling is of considerable interest because of its prevalence, and various hypotheses have been put forward to explain it: increased efficiency of movement in water (hydrodynamic efficiency), increased efficiency of food finding, reproductive success, and reduced risk of predation.

1.The word “prevalence” in the passage is closest in meaning to

O success

O importance

O benefits

O commonness

The idea that shoaling increases the efficiency of swimming applies mainly to schooling. This idea is very appealing, both because of the regular spacing that seems to characterize fish in schools and because fish in shoals tend to be uniform in size. To gain hydrodynamic advantages, however, each fish must maintain rather precise positioning within a school to use the hydrodynamic lift created by its neighbors. ⬛ By and large, measurements of fish positions within schools in the laboratory have not found this to be true. ⬛ Nevertheless, the regular spacing of fish in schools observed in the wild indicates that being in a school probably does have a hydrodynamic advantage- -at least for fish that are behind other fish. ⬛ Some scientists argue that the leadership of a school is constantly changing, because while being immersed in a school incurs hydrodynamic advantages to individuals, leaders of schools are first to find food, which is also advantageous. ⬛

2.The word “appealing'' in the passage is closest in meaning to

O attractive

O appropriate

O significant

O widely held

Schooling by predators increases the probability of their detecting a school of prey, just as shoaling in planktivores (fish that feed on plankton, the very small plants and animals in the water) increases the probability of detecting suitable patches of plankton. The reason for this is the presence of many searching eyes over a large area. Fish in shoals share information by monitoring each other's behavior. Feeding behavior in one fish quickly stimulates food-searching behavior in others. For planktivores, however, this advantage may be decreased by having to share the patch with many other fish: fish in the rear of a school are likely to encounter much lower densities of plankton than those in the front as well as higher concentrations of waste products from their schoolmates.

3.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

A Planktivores decrease their advantage in finding food by sharing patches with many other schools of fish, and this lowers densities of plankton and increases concentrations of waste products.

B Planktivores in the rear of a school are likely to produce higher concentrations of waste products than those in the front, which decreases their advantage in finding food by lowering densities of plankton.

C Planktivores have an advantage in finding food because they share patches of plankton, with the fish in the front of a school locating dense patches and the fish in the rear disposing of waste products.

D Schooling provides less advantage for planktivores in finding food because fish in the rear of a school are likely to find less plankton and encounter more waste products than fish in the front.

For fish that shoal throughout their lifetimes, little energy has to be expended in finding a mate when spawning time comes. Presumably, shoaling also allows fish to closely synchronize their reproductive cycles (through behavioral and hormonal cues). In addition, for fish that migrate long distances to breed, schooling may increase the accuracy of finding the way home, because the average direction sought by fish in a school is likely to be a better choice than that chosen by an individual migrating alone. For tunas, with habitual migration routes, this means that groups of individuals may stay together for long periods.

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