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摘要:剑桥雅思9听力下载TEST1-Section4。剑桥雅思系列是官方指定的雅思考试复习资料,下面三立在线资料下载编辑为大家整理了剑桥雅思9听力在线,主要是剑9中Test1 section4的相关内容,还有音频,同学们可下载或在线练习。

  下面为大家整理了剑桥雅思真题9下载TEST1听力中Section1听力原文的详细内容,其中包含了雅思听力考试Section1的音频部分,同学们可在做剑桥雅思真题9下载TEST1听力(Section1)后,再听原文兑答案,另外,雅思听力原文中给出了答案的相关提示 ,供同学们进行下载练习。

剑桥雅思9听力下载TEST1
剑桥雅思9听力下载TEST1

  剑桥雅思9听力原文TEST1

  Section4

  Good afternoon everyone. Well, with some of you will go out on fieldwork it's timely that in this afternoon's session I'll be sharing some ideas about the reasons why groups of whales and dolphins sometimes swim ashore from the sea right onto the beach and, most often, die in what were known as "mass stranding".

  Unfortunately, this type of event is a frequent occurrence in some of the locations that you'll be travelling to, where sometimes the tide goes out suddenly, confusing the animals. However, there are many other theories about the causes of mass strandings.

  The first is that the behavior is linked to parasites. It's often found that stranded animals were infested with large numbers of parasites. For instance, a type of worm is commonly found in the ears of dead whales. Since marine animals rely heavily on their hearing to navigate, this type of infestation has the potential to be very harmful.

  Another theory is related to toxins, or poisons. These have also been found to contribute to the death of many marine animals. Many toxins, as I'm sure you're aware, originate from plants, or animals. The whale ingests these toxins in its normal feeding behavior but whether these poisons directly or indirectly lead to stranding and death, seems to depend upon the toxin involved.

  In 1988, for example, fourteen humpback whales exclaimed after stranding along the beaches of Cape Code were found to have been poisoned after eating tuna that contained saxitoxin, the same toxin that can be fatal to humans.

  Alternatively, it has also been suggested that some animals stranded accidentally by following their prey ashore in the confusion of the chase. In 1995 David Thurston monitored pilot whales that beached after following the squid ashore. However, this idea does not seem to hold true for the majority of mass strandings because examination of the animals' stomach contents reveal that most had not been feeding as they stranded.

  There were also some new theories, which link strandings to hunmans. A growing concern is that loud noises in the ocean cause stranings. Noises such as these caused by military exercises are of particular concern and have been pinpointed as the cause of some strandings of late.

  One of these, a mass stranding of whales in 2000 in the Bahamas conincided closely with experiments using a new submarine detection system. There are several factors that made this stranding stand out as different from previous strandings. This led researchers to look for a new cause. For one, all the stranded animals were healthy. In addition, the animals were spread out along 38 kilometers of coast, whereas it's more for the animals to be found in a group when mass strandings occur.

  A final theory is related to group behaviour, and sugests that sea mammals cannot distinguish between sick and healthy leaders and will follow sick leaders, even to an inevitable death. This is a particularly interesting theory since the whales that are thought to be most social-the toothed whaled- are the group that strand the most frequently.

  The theory is also supported by evidence from a dolphin stranding in 1994. Examination of the dead animals revealed that apart from the leader, all the others had been healthy at the time of their death.

  Without one consistent theory however it is very hard for us to do anything about this phenomenon except to assist animal where and when we can. Stranding networks have been established around the world to aid in rescuing animals and collecting samples form those that could not be helped. I recommended John Connor's Marine Mammals ashore as an excellent starting point if you're interested in finding out more about there networks, or establishing one yourself.

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