Section outline

  • General

    Collapse all Expand all

  • 鸟类结构和功能

    A flock of birds flying over a grassy landscape in a clear sky.

    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 is the ability to fly. Obviously, flight is a major evolutionary advantage. But together with the ability to fly must come a number of structural modifications. What do you think these might be?
    ::许多人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?

    Structure and Function in Birds
    ::鸟类的结构和功能

    Birds are endothermic tetrapod vertebrates . They are bipedal, which means they walk on two legs. Birds also lay amniotic eggs with hard, calcium carbonate shells. Although birds are the most recent class of vertebrates to evolve, they are now the most numerous vertebrates on Earth. Why have birds been so successful? What traits allowed them to increase and diversify so rapidly? Birds can vary considerably in size, as you can see from the world’s smallest and largest birds, pictured in Figure . The tiny bee hummingbird is just 5 centimeters (2 inches) long, whereas the ostrich towers over people at a height of 2.7 meters (9 feet). All modern birds have wings , feathers , and beaks . They have a number of other unique traits as well, most of which are adaptations for flight. Flight is used by birds as a means of in order to find food and mates and to avoid predators . Although not all modern birds can fly, they all evolved from ancestors that could.
    ::鸟类是末端热四面脊椎动物,它们是双腿双足动物。鸟类还用硬的碳酸钙罐头产出羊蛋。虽然鸟类是即将进化的脊椎动物中最新的一类,但现在它们却是地球上数量最多的脊椎动物。为什么鸟类如此成功?什么特征允许它们如此迅速增长和多样化?鸟类在大小上可以有很大差异,从世界最小和最大的鸟类中可以看到,如图所示。小蜜蜂蜂鸟只有5厘米(2英寸)长,而浮蜂塔则在2.7米高(9英尺)的人群之上。所有现代鸟类都有翅膀、羽毛和白鲸。它们还有许多其他独特的特征,其中多数是飞行适应性。飞行被鸟类用来寻找食物和伴侣以及避免捕食者。尽管并非所有现代鸟类都能飞翔,但它们都是从可能由祖先演变而来的。

    Comparison of a bee hummingbird and an ostrich, representing bird size variability.

    Range of Body Size in Birds. The bee hummingbird is the smallest bird. The ostrich is the largest.
    ::蜜蜂蜂鸟是最小的鸟。

    Wings and Feathers
    ::翼翼和羽毛

    Wings are an obvious adaptation for flight. They are actually modified front legs. Birds move their wings using in the chest. These muscles are quite large, making up as much as 35 percent of a bird’s body weight.
    ::翅膀是飞行的明显适应。 它们实际上是经过改装的前腿。 鸟类用胸前的翅膀移动翅膀。 这些肌肉非常大,占鸟类体重的35%。

    Feathers help birds fly and also provide insulation and serve other purposes. Birds actually have two basic types of feathers: flight feathers and down feathers . Both are shown in Figure . Flight feathers are long, stiff and waterproof. They provide lift and air resistance without adding weight. Down feathers are short and fluffy. They trap air next to a bird’s skin for insulation.
    ::羽毛可以帮助鸟类飞翔,也可以提供绝缘和为其他目的服务。鸟类实际上有两种基本羽毛类型:飞行羽毛和下羽毛。图中显示了这两种类型的羽毛。飞行羽毛长、僵硬和防水。它们提供升降和空气阻力而不增加重量。下羽毛短、毛毛。它们将鸟皮旁边的空气捕捉为绝缘。

    Comparison of flight feather and down feather, highlighting structural differences and functions.

    Types of Bird Feathers. These two types of bird feathers have different uses. How is each feather’s structure related to its function?
    ::鸟类羽毛类型。这两种鸟类羽毛有不同的用途。每种羽毛的结构如何与其功能相关?

    Organ Systems Adapted for Flight
    ::为飞行调整的机体系统

    Birds need a light-weight body in order to stay aloft. Even so, flying is hard work, and flight muscles need a constant supply of oxygen- and nutrient-rich . The organ systems of birds are adapted to meet these needs.
    ::鸟类需要轻量体重的身体才能保持高度。 即便如此,飞行是艰苦的工作,飞行肌肉需要不断的氧和营养丰富的供给。 鸟类的器官系统已经适应了这些需要。

    • Birds have light-weight that are filled with air. They also lack a jaw, which in many vertebrates is a dense, heavy bone with many teeth. Instead, birds have a light-weight keratin beak without teeth.
      ::鸟类的体重较轻,充斥着空气。它们也缺少下巴,在许多脊椎动物中,下巴是密度大、牙齿多的重骨头。 相反,鸟类的体重较轻,没有牙齿。
    • Birds have air sacs that store inhaled air and push it into the lungs like bellows. This keeps the lungs constantly filled with oxygenated air. The lungs also contain millions of tiny passages that create a very large surface area for gas exchange with the blood (see Figure ).
      ::鸟类有空气囊,将吸入的空气储存起来,并将它像钟头一样推入肺部。这使得肺部不断充满氧气。肺部还含有数百万小孔,形成与血液进行气体交换的巨大面积(见图 )。
    • Birds have a relatively large, four-chambered heart. The heart beats rapidly to keep oxygenated blood flowing to muscles and other tissues . Hummingbirds have the fastest heart rate at up to 1,200 beats per minute. That’s almost 20 times faster than the human resting heart rate!
      ::鸟类有相对大、四组的心脏。 心脏快速跳动,以保持氧化血液流向肌肉和其他组织。 蜂鸟的心脏速率最快,每分钟高达1 200节。 这比人类休息心率快近20倍!
    • Birds have a sac-like structure called a crop to store and moisten food that is waiting to be digested. They also have an organ called a gizzard that contains swallowed stones. The stones make up for the lack of teeth by grinding food, which can then be digested more quickly. Both structures make it easier for the to produce a steady supply of nutrients from food.
      ::鸟类有一种类似盐状结构,叫做作物,储存和湿润的食品,等待消化。它们还有一种器官,叫做雪沙,含有吞咽的石块。这些石块通过研磨食物来弥补牙齿的缺乏,然后可以更快地消化。 这两种结构使得从食物中产生稳定的营养供应更加容易。

    Diagrams of bird lung and digestive tract showing adaptations for flight and digestion.

    Organ System Adaptations for Flight. The intricate passageways in a bird’s lung are adapted for efficient gas exchange. Find the crop and gizzard in the digestive tract diagram. What are their functions? Bird Lung (left), Bird Digestive Tract (right)
    ::用于飞行的有机系统适应。 鸟类肺部的复杂通道适应了高效的气体交换。 在消化道图中找到作物和。 它们有什么功能? 鸟肺(左边), 鸟类消化轨迹(右边)

      

     

    Nervous System and Sense Organs
    ::神经系统和感官机构

    Birds have a large brain relative to the size of their body. Not surprisingly, the part of the brain that controls flight is the most developed part. The large brain size of birds is also reflected by their high level of intelligence and complex behavior. In fact, birds such as crows and ravens may be more intelligent than many mammals . They are smart enough to use objects such as twigs for tools. They also demonstrate planning and cooperation . Most birds have a poor sense of smell , but they make up for it with their excellent sense of sight . Predatory birds have especially good eyesight. Hawks, for example, have that is eight times sharper than human vision.
    ::鸟类的大脑与其身体大小相比是很大的。 毫不奇怪, 控制飞行的大脑部分是最发达的部分。 鸟类的大脑大小也反映在其高度智慧和复杂的行为中。 事实上, 乌鸦和乌鸦等鸟类可能比许多哺乳动物更聪明。 它们聪明到可以使用树枝等物体作为工具。 它们也表现出了规划和合作。 大多数鸟类的嗅觉很差, 但是它们以极好的视力来弥补它。 食用鸟类的视力特别好。 比如, 鹰的视力比人类的视力高八倍。

    Summary
    ::摘要

    • Birds are endothermic tetrapod vertebrates. They are bipedal and have wings and feathers.
      ::鸟类是末温四氟脊椎动物,是双翅动物,有翅膀和羽毛。
    • Bird organ systems are adapted for flight. For example, they have light-weight air-filled bones and a large four-chambered heart.
      ::鸟类器官系统适应飞行,例如,它们有轻量级充气骨头和四组心脏。
    • Birds also have relatively large brains and a high level of intelligence.
      ::鸟类的大脑也相对较大,智力水平也很高。

    Review
    ::回顾

    1. Why do birds fly?
      ::为什么鸟儿飞起来?
    2. List two functions of feathers in birds.
      ::列出鸟类羽毛的两个函数 。
    3. Describe the bird crop and gizzard. What are their functions?
      ::描述一下鸟的作物和灰熊 它们的功能是什么?
    4. How do birds keep their lungs filled with oxygenated air?
      ::鸟儿怎么让肺里充满氧气?
    5. Give an example of bird behavior that shows their relatively great intelligence.
      ::举一个鸟类行为的例子 展示了他们相当聪明的智慧