2019年12月14日托福阅读真题+题目+答案+译文：Models of Egg Development

2019年12月14日托福阅读真题+题目+答案+译文：Models of Egg Development

1. Several different theories have been put forward to explain how the hard-shelled eggs of land-dwelling reptiles (e.g. lizards) evolved from the soft eggs that amphibians (e.g. frogs and toads) lay in water. The Romer model of egg development is named after the late Alfred Romer, a paleontologist who also became director of the Harvard University Museum of Comparative Zoology. His specialty was early reptiles because, he felt, they were the key to understanding the great reptile diversification seen in the Late Paleozoic and Mesozoic Eras (around 230 million years ago). Romer's hypothesis was that some aquatic amphibians¨Cthat is, amphibians living in water¨Ccalled anthracosaurs began to lay their eggs on land at about the time that they were evolving reptile-like skeletal features. Indeed, some of these early amphibians and earliest reptiles are so similar in their skeletons that the exact transition point from one to the other is still difficult to determine. Eventually, though, the transition was made, but these early reptiles remained aquatic. The advantage for laying eggs on land was primarily to avoid the aquatic larval (pre-adult) stage during which immature amphibians live exclusively in water with its inherent risk of predators and drying of ponds. However, the land has its own set of dangers, not least of which is the drying effect of the atmosphere. To cope with these problems, a series of protective membranes developed around the egg, including a hard shell. Only later did the reptiles completely abandon an aquatic lifestyle.

关于陆栖爬行动物(如蜥蜴)的硬壳卵如何从两栖动物(如青蛙和蟾蜍)产在水里的软卵进化而来，人们已经提出几种不同的理论来对其进行解释。“罗默式卵发展模式”就是根据古生物学家阿尔弗雷德·罗默( Alfred Romer)的姓命名的，他同时也是哈佛大学比较动物学博物馆的董事。他专门从事早期爬行动物研究，因为他认为它们是弄明白为什么晚古生代(Late Paleozoic)和中生代(Mesozoic Eras)时期(大约2.3亿年前)会出现多种大型爬行动物的关键。罗默的设想是，一些水生的两栖动物，即生活在水里的、被称作“暴龙”的两栖动物，大约在它们进化成具有爬行动物骨骼特征的生物时，开始将它们的卵产在陆地上。事实的确如此，这些早期两栖动物中的一部分，和最早的爬行动物的骨骼是如此相似，以至于很难确定这些两栖动物进化成爬行动物时确切的转折点。最后，尽管转变是完成了，但是这些早期的爬行动物仍保持水栖的习性。最开始，在陆地上产卵的好处是可以避免其幼体(长成前)阶段在水中进行，在这个阶段，这些不成熟的两栖动物幼体只生活在水中，要面对随之而来的天敌捕杀和池塘干涸的风险。然而，陆地上也存在着固有的危险，尤其是气候干燥带来的影响。为了应对这些困难，卵的周身发展出了一系列保护膜，包括一层坚硬的壳。爬行动物完全摈弃水里的生活方式，还是一段时间之后的事情。

2. Another hypothesis was proposed by German paleontologist Rolf Kohring, whose specialty is fossil eggs. In Kohring's model, amphibians during the Mississippian epoch (360¨C320 million years ago) spread into nutrient-poor or cooler water. Because of the harsher conditions, eggs were produced with larger yolks, that is, more nutrients for the embryo. With larger yolks, the eggs were bigger, and fewer of them could be produced by the female¨Chundreds rather than thousands. To keep the larger egg intact, one or more membranes were developed, including one that surrounded and protected the egg. This outer membrane provided a place to safely store calcium ions, which are poisonous. Accumulating the calcium in a hard shell then made it possible for the egg to be laid on land (it was pre-adapted to be laid there.)

专门从事化石蛋研究的德国(German)古生物学家罗尔夫·科林(Rolf Kohring)提出了另一个假说。科林认为，密西西比纪(Mississippian epoch)(距今3.2亿年至3.6亿年间)时期的两栖动物扩张到食物匮乏或者水温更低的水域里生活。由于生存条件更加恶劣，它们的卵的卵黄变得更大，意味着可以为胚胎提供更多的营养。因为卵黄变大，整个卵也随之变大，而雌性一次生产的数量也减少，每次生产几百颗而不是几千颗。为了保持卵完好无损，更多的细胞膜发展出来，包括包裹和保护整个卵的硬壳。这层外膜为储存有毒的钙离子提供了安全的空间。硬壳里不断积累的钙质使卵被产在陆地上成为可能(为其得以被产在陆地上作了前期准备)。

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托福阅读真题题目：

1..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. During the period that early amphibians changed into reptiles, their skeletons were exactly the same.

B. It is difficult to identify the time that early amphibians changed to reptiles because their skeletons look so much alike.

C. The skeletons of some early amphibians and reptiles are so similar that it is difficult to say which are amphibians and which are reptiles.

D. Early amphibians and reptiles had the same kind of skeleton at the same point in time.

2..The word exclusively in the passage is closest in meaning to

A. only

B. initially

C. primarily

D. temporarily

3..According to paragraph 1, aquatic amphibians laid their eggs on land in order to

A. enable young amphibians to benefit from a dry atmosphere

B. ensure the rapid development of a hard shell

C. enable young amphibians to evolve features necessary for living on land

D. protect young amphibians from the dangers associated with life in the water

4..The word Accumulating in the passage is closest in meaning to

A. Forcing

B. Collecting

C. Distributing

D. Isolating

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