2014年3月16日托福阅读真题+题目+答案：Costs and Benefits of Social Life
Many think that the reason so many animals live with others of their species is that social creatures are higher up the evolutionary scale and so are better adapted and leave more offspring than do animals that live solitary lives. However, in each and every species, generation after generation, relatively social and relatively solitary types compete unconsciously with one another in ways that determine who leaves more offspring on average. In some species, the more social individuals have won out, but in a large majority, it is the solitary types that have consistently left more surviving descendants on average.
But how can living alone ever be superior to living together? Under some conditions, a cost-benefit comparison favors solitary life over a more social existence. For example, among most social species, animals have to expend time and energy competing for social status. Those that do not occupy the top positions regularly have to signal their submissive state to their superiors if they are to be permitted to remain in the group. This can take up a major share of a social subordinate's life. In fact, even in small social groups there are both subtle competition and not-so-subtle competition.
Social groups also offer opportunities for reproductive interference. Breeding males that live in close association with more attractive rivals may lose their mates to these individuals. In addition, sociality has two other potential disadvantages. The first is heightened competition for food, which occurs in animals as different as colonial fieldfares (a kind of songbird) and groups of lions, whose females are often pushed from their food by hungry males. The second is increased vulnerability to parasites and disease, which plague social species of all sorts. While it is true that some social animals have evolved special responses designed to combat parasites and disease, those responses can only reduce, but cannot totally eliminate, the damage caused by those threats, and the responses may even carry their own costs. Thus, honeybees warm their hives in response to an infestation by a fungal pathogen, which apparently helps kill the heat-sensitive fungus, but at the price of time and energy expended by the heat-producing workers.
If social living carries a heightened risk of infection, then the larger the group, the greater the risk. This prediction holds for cliff swallows, which pack their nests side by side in colonies composed of anywhere from a handful of birds to several thousand pairs. The more swallows nesting together, the greater the chance that at least one bird will be infested with swallow bugs, which can then readily spread from one nest to another.
The parasites and fungi that make life miserable for swallows and other social creatures demonstrate that if sociality is to evolve, the asorted costs of living together must be outweighed by compensatory benefits. Cliff swallows may join others to take advantage of the improved foraging that comes from following companions to good feeding sites, while other animals, such as male imperial penguins, save thermal energy by huddling shoulder to shoulder during the brutal Antarctica winter. Still others, such as lionesses, join forces to fend off enemies of their own species.
The most widespread fitness benefit for social animals, however, probably is improved protection against predators. Many studies have shown that animals in groups gain by reducing the individual risk of being captured, or by spotting danger sooner, or by attacking their enemies in groups. Males in nesting colonies of bluegill sunfish cooperate in driving egg-eating bullhead catfish away from their nests at the bottom of a freshwater lake. While bluegills have adopted social behavior to avoid predation, closely related species that nest alone have evolved means to protect themselves while nesting alone. Thus, the solitary pumpkinseed sunfish, a member of the same genus as the bluegill, has powerful biting jaws and so can repel egg-eating enemies on its own, whereas bluegills have small, delicate mouths good only for inhaling small, soft-bodied insect larvae. Pumpkinseed sunfish are in no way inferior to or less well adapted than bluegills because they are solitary; they simply gain less through social living, which makes solitary nesting the adaptive tactic for them.
1. Which of the following can be inferred from paragraph 2 as a reason for saying that under some conditions a solitary life is superior to a more social life?
A. Solitary animals can compete more successfully against animals of other species than social animals can.
B. Solitary animals can hide from predators more easily than groups of animals can.
C. Solitary animals do not need to spend time and energy competing for social status.
D.Solitary animals do not need large quantities of food to survive.
2. The word "potential" in the passage is closest in meaning to
3. Which of the following is associated in paragraph 3 with reproductive interference in social animals
A.Females being pushed away from their food by hungry males
B. Breeding males losing their mates to more attractive males
C.Parasites and disease infecting the eggs of breeding females
D. Females warming their habitats to care a fungal pathogen
4. According to paragraph 3 which of the following is likely to increase when animals live with other members of their species rather than alone
B.unpredictable behavior among males
C. resistance to disease
D. competition for food
5. In paragraph 3 why does author discuss "honeybees warming their hives in response to an infestation by a fungal pathogen"?
A.To give an example of how living in groups benefits animals
B. To illustrate how social species combat parasites and disease
C. To indicate that worker bees are the most active in fighting parasites and disease
D.To demonstrate that avoiding a disadvantage of social living can carry its own costs
6. The word "heightened" in the passage is closest in meaning to
7. Paragraphs 4 and 5 support all of the following statements about cliff swallows EXCEPT
A. They feed primarily on bugs found in their nests.
B.They sometimes live in groups of only a few birds.
C. They sometimes locate good feeding sites by following other cliff swallows.
D. They build their nests close to the nests of other cliff swallows.
8. The word "assorted" in the passage is closest in meaning to
9. Which of the following is NOT identified in paragraph 5 as a need that some animals can better satisfy when they live with other members of their species?
A.The need to find food
B.The need to locate breeding sits
C. The need to preserve body heat
D.The need to protect themselves from attackers
10. In paragraph 6, why does the author compare the bluegill sunfish to the pumpkinseed sunfish?
A. To show that nesting has different costs and benefits for solitary organisms than it has for organisms living with other members of the same species
B. To provide evidence that social nesting is usually superior to solitary nesting
C.To argue that, in closely related species, the feeding organs of solitary organisms usually differ from those of social organisms
D. To show that closely related species can be social or solitary depending on which behavior better enables them to fight off predators
Paragraph 6 is marked with an arrow [→]
11. The word “tactic” in the passage is closet in meaning to
Paragraph 3 Social groups also offer opportunities for reproductive interference. Breeding males that live in close association with more attractive rivals may lose their mates to these individuals. In addition, sociality has two other potential disadvantages. The first is heightened competition for food, which occurs in animals as different as colonial fieldfares (a kind of songbird) and groups of lions, whose females are often pushed from their food by hungry males. ■The second is increased vulnerability to parasites and disease, which plague social species of all sorts. ■While it is true that some social animals have evolved special responses designed to combat parasites and disease, those responses can only reduce, but cannot totally eliminate, the damage caused by those threats, and the responses may even carry their own costs. ■Thus, honeybees warm their hives in response to an infestation by a fungal pathogen, which apparently helps kill the heat-sensitive fungus, but at the price of time and energy expended by the heat-producing workers.■
12. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Likewise, termites can reduce their risk of some infectious diseases by associating with other termites, but only at the expense of decreased physiological functioning.
Where would the sentence best fit? Click on a square [■] to add the sentence to the passage.
13. 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 answer choices 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. Drag your choices to the spaces where they belong. To review the passage, click on View Text.
There are costs and benefits associated with living in groups. ●
1，Solitary animals are sometimes thought to be higher up the evolutionary scale because they leave more surviving descendants on average than social animals do.
2，Social animals have evolved fewer mechanisms for reducing the costs of competing for social status than they have for reducing the risks of exposure to disease and parasites.
3，The need for pr has advantages such as making it possible for animals to become more successful at locating food, but it also has risks such as increased competition for mates.
4，The numerous disadvantages of living together lead animals to adopt social living only when the benefits are greater than the costs.
5，Animals that live alone such as pumpkinseed fish need to evolve a special mouth or some other special organ to help them combat predators.
托福阅读真题答案 CABDD BACBD AD 345