托福听力lecture并列型分析

之前我们介绍了lecture的并列型结构，一般是围绕某一个主题并列平行展开去讲解。这类结构没有之前我们见到的直线型结构那么好区分，因为他没有明显的表示时间地点人物的信号词，但是这种结构类型是我们TPO和考试中出现的比较多的结构类型。我们这次分析一篇按并列结构分层的文章。

今天我们以TPO30-L2为例，给大家讲解一下。

As we’ve discussed, birds are apparently descendants of dinosaurs and shared many commonalities with some dinosaur species, like…um…feathers and maybe even flight and of course egg laid. OK.

So, many paleontologists, myself included, have wondered about other similarities between dinosaurs and birds. Since adult dinosaur fossils have sometimes been discovered near or on top of nests, we’ve been looking at the dinosaur parenting behavior. 首先我们先引出一个常见的观点

Student

Parenting behavior, well, that sounds so gentle and caring. But dinosaurs were ferocious reptiles and reptiles don’t take care of their young, do they?一般我们认为因为恐龙是凶猛的爬行动物，所以是没有养育行为的

Professor

Well, some reptiles incubate their eggs, crocodiles do. And as for popular attitudes towards dinosaurs…well, take the Oviraptor for instance.

In the 1920s, a paleontologist discovered the fossil remains of a small dinosaur near a nest containing eggs. He assumed the dinosaur was stealing the eggs, so he named it Oviraptor that means egg thief in Latin, which fueled the generally negative public image of such dinosaurs. 但是随后就提出了相反的证据，Overaptor就是跟我们所想相反的一种动物，它其实是在照顾恐龙蛋。

But by the 1990s, other experts had convincingly made the case that instead of robbing the nest; the Oviraptor was probably taking care of the eggs. You see, dinosaurs’ closest living relatives – birds and crocodiles – display nesting behavior. And dinosaur fossils have been found in postures that we now believe to indicate brooding behavior, that is, sitting on the eggs until they hatch.

So we are curious about the type of care dinosaurs gave to their young. And we’d like to figure out which dinosaur parent, the male or the female gave the care. 进一步开始研究，既然他们会照顾后代，那么到底是雄性还是雌性呢?

Student

Shouldn’t the behavior of crocodiles and birds give us some clues then?

Professor

Well, with crocodiles, it is the female who guards the nest, and with birds, it depends on the species, it can be the male or the female that takes care the eggs, or both. In over 90 percent of all bird species, both parents take care of the eggs and the young birds. 首先按常理来说基本是雌性照顾幼崽的，或者是同时照顾。

Student

But sometimes it’s just the male?

Professor

Well, exclusive care by the male parent is much less common, but it does occur. Now, for animals other than birds, the care of young by both parents is pretty unusual in the animal kingdom. Males contribute to parental care in fewer than five percent of all mammalian species. It’s even less frequent among reptiles. And exclusive care by the male is very rare. So researchers have wondered about the evolution of male parenting behavior in birds for quite some time. And now there’s research showing that for some of the birds’ dinosaur relatives, it’s likely that the male parent was also in charge of taking care of the eggs. 但是之后又提出了不同的观点，其实有时雄性也会参与到照顾幼崽的行为中

Student

How did they figure that out?

Professor

Well, first they looked at clutch volume, that’s the number of eggs in the nest of crocodiles, birds and three types of dinosaurs, including Oviraptors that are thought to be closely related to the dinosaur ancestors of birds.

So when researchers examined fossilized remains of nests, they found that the dinosaurs had larger clutch volumes, more eggs in the nests that is, than most of the crocodiles and birds that were studied. But, and this is important , their clutch volumes matched those of birds that have only male parental care. You see, bird species in which only the males take care of the nest tend to have the largest clutches of eggs. 后面提出了有力的证据clutch volume，来证明了之前的观点。

Student

So what’s the connection between bird and dinosaur behavior?

Professor

Well, researchers now believe, because of this study, that the male parenting behavior of these birds might have its origins in the behavior of dinosaurs.

Student

Based only on evidence of clutch volume size, the number of eggs?

Professor

No, there’s more. They also examined the fossilized bones of those three types of dinosaurs that were found on or near nests to determine their sex. You see, adult female birds during egg production produce a layer of spongy bone tissue inside certain long bones. And so did female dinosaurs of the kinds that were investigated. This spongy tissue serves as a source of calcium for eggshell formation. But when the dinosaur fossils were examined, there were no spongy bone deposits. 最后又提出了另一个有利的证据spongy bone tissue来支持我们的观点。

Student

Meaning that those dinosaurs on the nests were probably adult males who wouldn’t have needed calcium for making eggshells.

Professor

Exactly. And then there’s this: birds like the kiwi, the ostrich and the emu; they share certain physical characteristics with these dinosaurs. And interestingly, they also show a consistent pattern of nest care by the male.

所以整篇文章为了证明雄性会照顾幼崽，一步步的提出证据进行论证，最终证实观点。

当然，在课程当中，老师会给大家针对这种并列型结构做充分的讲解，如果有同学自己复习效果不是很好，可以通过的方式，找专业的老师来对大家的这部分进行训练和提升。在这里小编祝大家在当中取得优异的成绩。如果同学们对我们的感兴趣，或是托福复习过程中遇到了问题，都可以

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