人教版九全unit13拯救鲨鱼原文
人教版九全unit13拯救鲨鱼原文
鲨鱼，生活在海洋中，是海洋中的鱼类。接下来学习啦小编为你整理了人教版九全unit13拯救鲨鱼原文，一起来看看吧。
人教版九全unit13拯救鲨鱼原文
Many have heard of shark’s fi n soup. Th is famous and expensive dish is especially popular in southern China. But do you realize that you’re killing a whole shark each time you enjoy a bowl of shark’s fi n soup?
学习啦在线学习网 When people catch sharks, they cut off their fi ns and throw the shark back into the ocean. Without a fi n, a shark can no longer swim and slowly dies. Th is method is not only cruel, but also harmful to the environment. Sharks are at the top of the food chain in the ocean’s ecosystem. If their numbers drop too low, it will bring danger to all ocean life. Many believe that sharks can never be endangered because they are the strongest in their food chain. But in fact, around 70 million sharks are caught and traded in this industry every year. Th e numbers of some kinds of sharks have fallen by over 90 percent in the last 20 to 30 years.
Environmental protection groups around the world, such as WildAid and the WWF, are teaching the public about “fi nning”. Th ey have even asked governments to develop laws to stop the sale of shark’s fi ns. So far, no scientifi c studies have shown that shark’s fi ns are good for health, so why eat them? Help save the sharks!
学习啦在线学习网 Many have heard of shark’s fin soup. This famous and expensive dish is especially popular in southern China. But do you realize that you’re killing a whole shark each time you enjoy a bowl of shark’s fin soup?When people catch sharks, they cut off their fins and throw the shark back into the ocean. Without a fin, a shark can no longer swim and slowly dies. This method is not only cruel, but also harmful to the environment. Sharks are at the top of the food chain in the ocean’s ecosystem. If their numbers drop too low, it will bring danger to all ocean life. Many believe that sharks can never be endangered because they are the strongest in their food chain. But in fact, around 70 million sharks are caught and traded in this industry every year. The numbers of some kinds of sharks have fallen by over 90 percent in the last 20 to 30 years.Environmental protection groups around the world, such as WildAid and the WWF, are teaching the public about “finning”. They have even asked governments to develop laws to stop the sale of shark’s fins. So far, no scientific studies have shown that shark’s fins are good for health, so why eat them? Help save the sharks!
人教版九全unit13拯救鲨鱼翻译
拯救鲨鱼!
学习啦在线学习网 很多人听说过鱼翅汤。这道著名且昂贵的菜肴在中国南方尤其流行。但是你们意识到每次你享受一碗鱼翅汤时，你都在杀死一整只鲨鱼?
人们捕捉鲨鱼时，他们砍掉它们的鱼翅，然后再把鲨鱼放在海里。这个方式不仅残忍，还对环境非常有害。没有了鱼翅，鲨鱼在也游不动，会慢慢死掉。鲨鱼在海洋的生态系统中处于食物链的顶端，如果它们的数量降至过低，会给所有海洋生命带来危险。很多人相信鲨鱼不会陷入危险中，因为它们是食物链中最强大的，但事实上，每年在这个产业中大约有7000万鲨鱼被捕捉和交易。在过去20到30年中，有些种类的数量已经减少百分之九十以上。 世界各地的环保团体，例如野生救援会和世界自然基金会，教育公众有关“猎翅”的行为。它们甚至已经要求政府部门制定切当的法律来销售鲨鱼翅。到目前为止，没有科学研究显示鲨鱼翅对于健康的好处，因此为什么要吃它们呢?帮忙拯救鲨鱼吧!
鲨鱼的自然生长
和多数动物一样，鲨鱼是有性繁殖。鲨鱼的交配行为非常复杂，不同种类的雄性和雌性鲨鱼在交配前的例行程序也有很大的分别。结伴同游，撕咬和颜色变化等行为模式是共有的。姥鲨等种类的鲨鱼采用复杂的成群环游的行为，还不了解这一行为的目的。
学习啦在线学习网 在雌雄鲨鱼成功交配、同时雌性鲨鱼体内的卵子完成受精之后，这一种属鲨鱼的受精卵就会以下列三种方式中的某一种继续发育：
学习啦在线学习网 1.卵生：卵生鲨鱼产下带有厚厚的卵鞘的卵，使它们能够附着在岩石或者海藻上，并抵抗捕食者。一般是大型鲨鱼采用。鲨鱼的卵很大，营养供应不虞匮乏。大多数的卵鞘呈宽广的矩形。排出的卵包在扁平的垫形鞘内，而垫形鞘是卵在通过输卵管时四周加上去的，鞘的外皮于进入水中后会变硬，鞘的每个角落都有一个短而中空的角状物，海水能由此进入，使卵获得氧气。母鲨鱼每次排卵数目有限。卵呈布袋状或螺旋状，产出后被固定于珊瑚礁、海底植物或石缝中。被冲上海岸的短吻棘鲛的空卵囊，则被昵称为“美人鱼的小钱包”。这些卵在几天或几星期后孵出，鲨鱼就会离开幼仔让它们独立生存。
学习啦在线学习网 2.卵胎生(非胎盘型胎生)：此类鲨鱼也养护体内的胚胎，然后产出活的幼仔，但它们不能向它们的后代提供任何直接的营养。某些种类的鲨鱼，如鲭鲨使用“奥佛吉(oophagy)”的方式，即鲨鱼妈妈产出一串小的没有受精的卵，被生长中的胚胎吃掉。受精卵在子宫中发育，以卵黄囊或由卵巢排入子宫的卵为营养来源，在子宫中并不形成胎盘。除鲸鲨每次可产300尾以上外，其余每次顶多数十尾，最少的是狐鲛(长尾鲨)，每次只产两尾。相反，孕育中的鲨鱼依赖于卵的卵黄囊维持生计。
3.假胎生(胎盘型胎生)：外包角质壳的受精卵于子宫中发育，成长所需的营养由卵黄囊胎盘得，后期在雌性鲨鱼的子宫内通过胎盘或一种称为子宫液的分泌物吸取营养物质，直到幼鲨几乎完全成形才产出，每次产数十尾。胎生确保幼仔在生长期间得到很好的孕育，因此出生后能够立刻在严酷的大海中生存。远洋的大部分鲨鱼都是胎生。大部分鲨鱼每年按照季节进行繁殖，一些大型鲨鱼隔年繁殖。大部分鲨鱼怀孕期达8～9个月，白斑角鲨的怀孕期甚至高达24个月。一般而言，大型鲨一次生产较多小鲨，小型鲨则相反。鲨鱼的生长也异常缓慢，直到5～10岁才算性成熟。鲨鱼是地球上最早的通过两性交配体内受精孕育繁殖的动物。
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