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  • 鸟类演变

    Comparison of an ostrich and a mononykus dinosaur, highlighting their structural similarities.

    Did birds really evolve from dinosaurs?
    ::鸟真的从恐龙进化了吗?

    One is an ostrich, the other is a mononykus dinosaur . The structural relationship is obvious. Mononykus moved about on two legs, was very nimble, and could run at high speeds, something that would have been useful in the open plains where they lived. It had a small skull, and its teeth were small and pointed, suggesting that it ate and small , such as lizards and mammals .
    ::一种是小蚂蚁,另一种是单龙恐龙。结构关系是显而易见的。莫诺尼库斯双腿移动,非常敏捷,可以高速运行,在他们居住的开阔平原上有用。它有一个小头骨,牙齿小,尖尖,表明它吃起来和小,如蜥蜴和哺乳动物。

    Evolution of Birds
    ::鸟类的演变

    are thought to have evolved from a group of bipedal dinosaurs called theropods . The ancestor of birds was probably similar to the theropod called Deinonychus, which is represented by the sketch in Figure . of Deinonychus were first identified in the 1960s. This was an extremely important discovery. It finally convinced most scientists that birds had descended from dinosaurs, which had been debated for almost a century.
    ::鸟儿的祖先可能与被称为Deinonychus的象类动物类似,这体现在1960年代首次发现的Deinonychus图中的草图中。这是一个极为重要的发现。它最终使大多数科学家相信鸟类是从恐龙中降生的,而恐龙已经辩论了近一个世纪。

    A detailed sketch of Deinonychus, an extinct theropod dinosaur believed to be a bird ancestor.

    Extinct Bird Relative: Deinonychus. Deinonychus shared many traits with birds. What similarities with birds to you see?
    ::灭绝鸟的相对:Deinonychus。Deinonychus与鸟类有许多共同特征。与鸟类有什么相似之处呢?

    What was Deinonychus ?
    ::迪诺尼琴是什么?

    Deinonychus is the genus name of an extinct dinosaur that is considered to be one of the closest non-bird relatives of modern birds. It lived about 110 million years ago in what is now North America. Deinonychus was a predatory carnivore with many bird-like features. For example, it had feathers and wings . It also had strong legs with clawed feet, similar to modern raptors . Its respiratory, circulatory, and digestive systems were similar to those of birds as well. The location of fossilized eggs near Deinonychus fossils suggests that it may have brooded its eggs. This would mean that it was endothermic . (Can you explain why?) On the other hand, Deinonychus retained a number of reptile-like traits, such as jaws with teeth, and hands with claws at the tips of its wings.
    ::Deinonichus 是一个灭绝的恐龙的基因名称,被认为是现代鸟类最接近的非鸟类亲戚之一。它大约在1亿1千万年前就生活在现在的北美。它是一种食肉动物,具有许多类似鸟类的特征。例如,它有羽毛和翅膀。它也有爪子般的长腿,与现代猛禽相似。它的呼吸、循环和消化系统也与鸟类相似。在Deinonichus化石化石附近化化卵的位置表明它可能已经孵化了它的蛋。这意味着它是异性动物。(你能解释原因吗? )另一方面,Deinonychus 保留了一些像爬虫一样的特征,例如牙齿的下巴和翅膀尖部的爪子。

    Evolution of Flight
    ::飞行的演变

    Scientists have long speculated about the evolution of flight in birds. They wonder how and why birds evolved wings from a pair of front limbs. Several hypotheses have been suggested. Here are just two:
    ::科学家早就对鸟类飞行的演进进行了猜测。他们想知道鸟类是如何和为什么从一对前肢进化翅膀的。他们提出了一些假设。这里只有两个:

    1. Wings evolved in a bird ancestor that leapt into the air to avoid predators or to capture prey . Therefore, wings are modified arms that helped the animal leap higher.
      ::翅膀在鸟类祖先身上进化,跳进空中以避免捕食者或捕食猎物。 因此,翅膀是改变的手臂,帮助动物跳得更高。
    2. Wings evolved in a bird ancestor that lived in trees. Thus, wings are modified arms that helped the animal glide from branch to branch.
      ::翅膀进化在一个生活在树木中的鸟类祖先身上。因此,翅膀是改变的手臂,帮助动物从树枝到树枝的滑翔。

    Scientists still don’t know how or why wings and flight evolved, but they continue to search for answers. In addition to fossils, they are studying living vertebrates such as bats that also evolved adaptations for flight.
    ::科学家们仍然不知道翅膀和飞行的演变方式和原因,但他们继续寻找答案。 除了化石,他们还在研究活的脊椎动物,比如蝙蝠,它们也进化了飞行的适应。

      

     

    Summary
    ::摘要

    • Birds are thought to have evolved from theropod dinosaurs around 150 million years ago.
      ::人们认为鸟类是从约1.5亿年前的 热带恐龙中进化而来的。
    • Bird ancestors may have been similar to the extinct theropod Deinonychus , whose fossils convinced most scientists that birds evolved from dinosaurs.
      ::鸟类祖先可能和灭绝的代诺尼琴人类似,后者的化石使大多数科学家相信鸟类是从恐龙中进化而来的。
    • Scientists still don’t know how or why wings and flight evolved, but they continue to search for answers.
      ::科学家仍不知道翅膀和飞行是如何或为什么演变的,

    Review
    ::回顾

    1. What was the bird ancestor?
      ::鸟的祖先是什么?
    2. What was Deinonychus ? What bird-like traits were evident in Deinonychus ?
      ::迪诺尼琴是什么?
    3. What are the two ideas associated with the evolution of flight?
      ::与飞行演变有关的两个想法是什么?