托福閱讀tpo2theoriginsofcetaceans鯨類起源原題解析-文庫(kù)吧資料
2025-04-01 00:30本頁(yè)面
【正文】 yte, a plete hind leg that features a foot with three tiny toes. Such legs would have been far too small to have supported the 50footlong Basilosaurus on land. D選項(xiàng)是同義改寫(xiě)，正確。D反。A反。BCD都不能推出。根據(jù)sea otters定位原文，找到：unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like。D錯(cuò)誤，沒(méi)有提到。A錯(cuò)誤，反了。毫無(wú)疑問(wèn)，鯨魚(yú)是連接著陸地生命和海洋生命的物種。大的后肢通常被當(dāng)作是水中前行的發(fā)動(dòng)機(jī)。雖然 Ambulocetus natans保留了尾巴，但它們?nèi)鄙佻F(xiàn)代水生鯨類動(dòng)物用于行動(dòng)的主要身體部位——尾片。它的后肢很強(qiáng)壯，底部有長(zhǎng)足，非常像現(xiàn)在的鰭足類動(dòng)物。比Pakicetus晚大約 300萬(wàn)年，比Basilosaurus早 900萬(wàn)年左右。因 此，Basilosaurus必定是完全水生的鯨魚(yú)，它們的后肢已經(jīng)不起任何作用，或者說(shuō)已經(jīng)退化.An even more exciting find was reported in 1994, also from Pakistan. The now extinct whale Ambulocetus natans (the walking whale that swam) lived in the Tethys Sea 49 million years ago. It lived around 3 million years after Pakicetus but 9 million before Basilosaurus. The fossil luckily includes a good portion of the hind legs. The legs were strong and ended in long feet very much like those of a modern pinniped. The legs were certainly functional both on land and at sea. The whale retained a tail and lacked a fluke, the major means of lootion in modern cetaceans. The structure of the backbone shows, however, that Ambulocetus swam like modern whales by moving the rear portion of its body up and down, even though a fluke was missing. The large hind legs were used for propulsion in water. On land, where it probably bred and gave birth, Ambulocetus may have moved around very much like a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea.1. Fluke: the two parts that constitute the large triangular tail of a whale2. Blowhole: a hole in the top of the head used for breathing1994年，巴基斯坦報(bào)道了一個(gè)更令人興奮的發(fā)現(xiàn)。盡管發(fā)現(xiàn)的這些骨骼并不完整，但這是專家們 第一次在原始動(dòng)物身上發(fā)現(xiàn)完整的后肢，它有三個(gè)小腳趾作為的足部特征。人們?cè)诠诺刂泻埩舻某练e物中發(fā)現(xiàn)了另一類早期鯨魚(yú)Basilosaurus的一些骨骸，這些骨骸如今暴露在撒哈 拉大沙漠上。它們很有可能在陸地進(jìn)行生育繁殖。 然而，專家認(rèn)為Pakicetus的其它特征表明它們是已滅絕的食肉哺乳動(dòng)物（中獸科動(dòng)物）和鯨類動(dòng)物的過(guò)渡型。Pakicetus的主 人可能會(huì)像陸生哺乳動(dòng)物那樣通過(guò)張開(kāi)的耳朵來(lái)探測(cè)聲音。盡管只是個(gè)頭蓋骨，但它卻提供了研究原始鯨類動(dòng)物起源的珍貴信息。這塊化石被 官方命名為 Pakicetus，以紀(jì)念人們發(fā)現(xiàn)它的地方。Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans. In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale. The fossil was officially named Pakicetus in honor of the country where the discovery was made. Pakicetus was found embedded in rocks formed from river deposits that were 52 million years old. The river that formed these d
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