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  • 鸟类 - 高级

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    Why is flight so important to birds?
    ::为什么飞行对鸟儿如此重要?

    One of the defining traits of many birds is the ability to fly. Obviously, flight is a major evolutionary advantage. But with the ability to fly must come a number of structural modifications. What do you think these might be?
    ::许多鸟类的特征之一是飞行能力。很明显,飞行是一个主要的进化优势。但飞行能力必须带来一些结构性的改变。你认为这些可能是什么?

    Characteristics of Birds
    ::鸟类的特点

    What is a bird? Birds are bipedal, endothermic, amniotic vertebrates that lay eggs . There are around 10,000 living of birds, making them the most numerous tetrapod vertebrates on Earth. They live in across the globe, from the to the Antarctic. Birds range in size from the 5 cm (2in) bee hummingbird to the 2.7m (9ft) ostrich, which is shown in  Figure .
    ::鸟是什么?鸟是产卵的双翅、端温、羊角脊椎动物。大约有1万只鸟类,它们成为地球上数量最多的四面脊椎动物。它们生活在从地球到南极的地球各地。鸟类大小从5厘米(2英寸)蜂蜂鸟到2.7米(9英尺)食鸟不等,图中显示了这一点。

    Modern birds are characterized by feathers , a beak with no teeth, the laying of hard-shelled eggs, and a high metabolic rate. Feathers are the only distinguishing feature that only birds posses. Other vertebrates have beaks, lay hard-shelled eggs, and have a high metabolic rate.
    ::现代鸟类的特征是羽毛、没有牙齿的嘴、硬壳蛋的产卵以及高代谢率。 羽毛是唯一只有鸟类才能捕捉的显著特征。 其他脊椎动物有嘴、硬壳蛋和高代谢率。

    Birds also have a four-chambered heart and a lightweight, but strong, skeleton. All birds have forelimbs that are modified as wings , and most birds can fly. There are some exceptions; birds such as the ratites, penguins, and kakapos have lost the ability to fly. Birds also have unique digestive and respiratory systems that are highly adapted for flight.
    ::鸟类也有四分形的心脏和轻量级但坚固的骨骼。所有鸟类都有作为翅膀而变形的骨,大多数鸟类可以飞翔。 有一些例外,如老鼠、企鹅和卡卡波斯等鸟类失去了飞行能力。 鸟类还拥有独特的消化和呼吸系统,这些系统非常适合飞行。

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    Characteristics of birds. (left-right) The Rufous Hummingbird (Selasphorus rufus) is a small hummingbird, about 8 cm long, that is native to North America. Hummingbirds are some of the smallest bird. Ostriches (Struthio camelus) are the largest birds, at about 2.7m tall. Ostriches are native to Africa. Ostriches and hummingbirds have feathers, toothless beaks, a four-chambered heart, and lay eggs, which are the characteristics of birds.

    Summary
    ::摘要

    • Modern birds are characterized by feathers, a beak with no teeth, the laying of hard-shelled eggs, and a high metabolic rate.
      ::现代鸟类的特点是羽毛、没有牙齿的嘴、硬壳蛋的铺设和高代谢率。

    Review
    ::回顾

    1. Can all birds fly?
      ::所有的鸟都能飞吗?
    2. What structures contribute to a bird's ability to fly?
      ::什么样的结构能提高鸟的飞行能力?