单选题
Small dogs generally live longer than big dogs so that a small Yorkshire terrier (猎狐狗) next door could be around for a long time. But body size isn't the only factor that 18 how long dogs survive. Personality influences life span, too, according to a new study that might help explain how animal 19 evolve. Study on animals from ants to apes has found that different 20 have different personalities. Some are timid, others 21 . Biologists have proposed that temperaments (性情) evolved along with life history. Bold, violent animals use a lot of energy fast in 22 short lives, the thinking goes, whereas calmer animals last longer, saving themselves to 23 later in life. But it's hard to run evolutionary researches on these personalities in anything longer lived than a fruit fly. So evolutionary biologist Vincent from Canada 24 an idea about dogs. 'All these breed differences reflect an experiment on artificial selection,' says Vincent. The huge diversity of dogs resulted not from natural selection, but from generations of humans selecting animals with traits they wanted—the ability to chase foxes into holes, or herd sheep, or sit 25 on a sofa. But evolutionary physiologist Joseph Williams of Ohio State University in Columbus isn't 26 that what happened in dogs has anything to do with evolution in nature. 'For me, it still remains to be seen. Dogs are contrary to what you would expect in nature 27 longevity,' he says. Elephants can live for decades, whereas a mouse might make it through only for several seasons. On the other hand, a Chihuahua will generally outlast a Saint Bernard.
问答题
【正确答案】determines
【答案解析】[听力原文] Small dogs generally live longer than big dogs so that a small Yorkshire terrier (猎狐狗) next door could be around for a long time. But body size isn't the only factor that determines how long dogs survive. Personality influences life span, too, according to a new study that might help explain how animal characters evolve. Study on animals from ants to apes has found that different individuals have different personalities. Some are timid, others aggressive. Biologists have proposed that temperaments (性情) evolved along with life history. Bold, violent animals use a lot of energy fast in relatively short lives, the thinking goes, whereas calmer animals last longer, saving themselves to reproduce later in life. But it's hard to run evolutionary researches on these personalities in anything longer lived than a fruit fly. So evolutionary biologist Vincent from Canada came up with an idea about dogs. 'All these breed differences reflect an experiment on artificial selection,' says Vincent. The huge diversity of dogs resulted not from natural selection, but from generations of humans selecting animals with traits they wanted—the ability to chase foxes into holes, or herd sheep, or sit attractively on a sofa. But evolutionary physiologist Joseph Williams of Ohio State University in Columbus isn't convinced that what happened in dogs has anything to do with evolution in nature. 'For me, it still remains to be seen. Dogs are contrary to what you would expect in nature in terms of longevity,' he says. Elephants can live for decades, whereas a mouse might make it through only for several seasons. On the other hand, a Chihuahua will generally outlast a Saint Bernard.