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新托福口语Task4题目解析:动物成年之后回家繁殖

2017-09-18 15:14:15来源：网络

　　2017年9月9日托福口语考试有哪些内容呢？新东方在线托福网为大家带来新托福口语Task4题目解析:动物成年之后回家繁殖一文，更多精彩尽请关注新东方在线托福网（http://toefl.koolearn.com）!

　　新托福口语Task4题目回忆版本一:

　　Reading

　　natal homing，动物成年之后回到自己出生的地方进行繁殖

　　Listening

　　green sea turtle回到出生地繁殖因为温度合适且没有天敌

　　新托福口语Task4题目回忆版本二:

　　Task 4 阅读 标题：natal homing

　　定义：一些特殊物种在繁殖的时候会回到自己的原栖息地寻求更佳适合的条件。

　　听力例子：举出一种绿色海龟，在繁殖产卵的时候就会回到原来的栖息地海滩，因为温度更适合，而且能够有效抵御天敌攻击，保护幼崽等。

　　新托福口语Task4题目回忆版本三:

　　natal homing:一些特殊物种在繁殖的时候会回到自己的原栖息地寻求更佳适合的条件。

　　举出一种绿色海龟，在繁殖产卵的时候就会回到原来的栖息地海滩，因为温度更适合，而且能够有效抵御天敌攻击，保护幼崽等。

　　新托福口语Task4知识补充；

　　Natal homing, or natal philopatry, is the homing process by which some adult animals return to their birthplace to reproduce. This process is primarily used by aquatic animals, such as sea turtles and Pacific salmon. Scientists believe that the main cues used by the animals are geomagnetic imprinting and olfactory cues. The benefits of returning to the precise location of an animal's birth may be largely associated with its safety and suitability as a breeding ground. When seabirds, like the Atlantic puffin, return to their natal breeding colony, which are mostly on islands, they are assured of a suitable climate and a sufficient lack of land-based predators.

　　Sea turtles born in any one area differ genetically from turtles born in other areas. The newly hatched young head out to sea and soon find suitable feeding grounds, and it has been shown that it is to these feeding areas that they return rather than to the actual beach on which they started life. Salmon start their lives in freshwater streams and eventually travel down-river and are washed out to sea. Their ability to travel back, several years later, to the river system in which they were spawned is thought to be linked to olfactory cues, the "taste" of the water. Atlantic bluefin tuna spawn on both the east and west shores of the Atlantic Ocean but intermingle as they feed in mid-ocean. Juvenile tuna that have been tagged have clearly shown that they almost invariably return to the side of the Atlantic on which they were spawned.

　　Various theories have been put forward as to how the animals find their way home. The geomagnetic imprinting hypothesis holds that they are imprinted with the unique magnetic field that exists in their natal area. This is a plausible theory but has not been proven to occur. Pacific salmon are known to be imprinted on the water chemistry of their home river, a fact that has been confirmed experimentally. They may use geomagnetic information to get close to the coast and then pick up the olfactory cues. Some animals may make navigational errors and end up in the wrong location. If they successfully breed in these new sites, the animal will have widened its breeding base which may ultimately increase the species' chances of survival. Other, unknown means of navigation may be involved, and further research is needed.

　　以上就是新东方在线托福网为你带来的新托福口语Task4题目解析:动物成年之后回家繁殖，更多精彩敬请关注新东方在线托福网（http://toefl.koolearn.com）。

本文关键字: 20170909托福口语 托福口语解析

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