章节大纲

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  • 节肢动物

    A close-up of a pink crab-like arthropod on a rocky ocean floor.

    What has more species than any other animal phylum?
    ::还有什么比任何其他动物植物 更多的物种呢?

    Arthropods are not only the largest phylum of invertebrates . They are by far the largest phylum of the . Roughly 80 percent of all animal living on Earth today are arthropods. Obviously, arthropods have been extremely successful. What accounts for their success?
    ::节肢动物不仅是无脊椎动物中最大的植物,也是迄今为止最大的植物。今天,地球上所有动物中大约有80%是节肢动物。很显然,节肢动物非常成功。它们的成功原因何在?

    Arthropods
    ::节肢动物

    There are more than a million known species of arthropods. There may actually be ten times that many. Arthropods include , spiders, lobsters, and centipedes. The arthropods pictured in Figure give just a hint of the phylum’s diversity. 
    ::已知的节肢动物种类超过100万种。 事实上,可能有十倍之多。 亚节肢动物包括蜘蛛、龙虾和。 图中描绘的节肢动物只是植物多样性的提示。

    Diverse arthropods including dust mites, spider crabs, barnacles, millipedes, wasps, and scorpions.
    Arthropod Diversity. Dust mites are among the smallest of arthropods. Japanese spider crabs are the largest. Besides size, what other differences among arthropods do you see in these photos?

    Structure and Function of Arthropods
    ::甲类动物的结构和功能

    Arthropods range in length from about 1 millimeter to 4 meters (about 13 feet). They have a segmented body with a hard exoskeleton . They also have jointed appendages . The body segments are the head, thorax, and abdomen (see Figure ). In some arthropods, the head and thorax are joined together as a cephalothorax .
    ::甲草胺的长度从大约1毫米到4米(约13英尺)不等。它们有一个有硬外骨骼的分块体。它们也有连接的附着物。身体的部位是头部、胸部和腹部(见图 )。在一些节肢动物中,头部和胸部被结合为头部和腹部。

    The body segments of various arthropods: head, thorax, and abdomen.
    Arthropod Body Plan. Notice the three body segments of each organism.

    The arthropod exoskeleton consists of several layers of cuticle . The exoskeleton prevents loss and gives support and protection. It also acts as a counterforce for the contraction of . The exoskeleton doesn’t grow as the animal grows. Therefore, it must be shed and replaced with a new one periodically through life. This is called molting .
    ::节肢动物的外骨骼由几层外科动物组成。 外骨骼可以防止损失并提供支持和保护。 它也可以作为抗缩的力量。 外骨骼动物的生长不会随着动物的生长而成长。 因此, 必须在生命中定期产卵, 代之以新的。 这被称为“ 摩擦 ” 。

    The jointed appendages of arthropods may be used as legs for walking. Being jointed makes them more flexible. Try walking or climbing stairs without bending your knees, and you’ll see why are helpful. In most arthropods, the appendages on the head have been modified for other functions. Figure shows some of head appendages found in arthropods. Sensory organs such as are also found on the head.
    ::节肢动物的连接附着物可以用作行走的腿。 被连接后,它们更灵活。 尝试走路或爬上楼梯而不弯下膝盖,你会看到为什么有用。 在大多数节肢动物中,头部的附着物已经为其他功能做了修改。图显示了节肢动物中发现的一些头部附着物。头部器官,如头部。

    Arthropod head with sensory organs and specialized appendages for various functions.
    Arthropod Head. Arthropods have evolved a variety of specialized appendages and other structures on their head.

    Some arthropods have special excretory structures. They are called coxal glands and Malpighian tubules . Coxal glands collect and concentrate liquid waste from . They excrete the waste from the body through a pore. Malpighian tubules carry waste from the digestive tract to the anus. The waste is excreted through the anus.
    ::一些节肢动物有特殊的排泄结构,称为科克斯腺和马尔皮吉亚管状体; 毒性腺从体内收集和浓缩液体废物; 将废物从身体通过孔隙排出; 马尔皮吉亚管状体将废物从消化道运到肛门; 废物通过肛门排出。

    Like and , arthropods may have gills to exchange gases with the water (discussed below). arthropods, on the other hand, have special respiratory structures to exchange gases with the air. These are described in Figure .
    ::例如,节肢动物可能有与水交换气体(下文讨论)。 另一方面,节肢动物有特殊的呼吸结构与空气交换气体。

    Book lungs and trachea in terrestrial arthropods for gas exchange.
    How Terrestrial Arthropods Breathe Air. Terrestrial arthropods have respiratory structures that let them breathe air.

    Underwater Spiders
    ::水下蜘蛛

    In the ponds of northern Europe lives a tiny brown spider that spends its entire life underwater. But just like land spiders, it needs oxygen to breathe. So, how does this spider breath? Does it use book lungs ? No. In fact, aquatic spiders, known as "diving bell spiders," have gills. Every so often, the spider leaves its underwater web to visit the surface and bring back a bubble of air that sticks to its hairy abdomen. It deposits the bubble into a little silk air tank. This "diving bell" is a gill that sucks oxygen from the water, allowing the spider to stay underwater for up to 24 hours.  
    ::在北欧的池塘里, 一只小棕色蜘蛛生活在水下, 整个生命都花在水下。 但是就像陆地蜘蛛一样, 它需要氧气呼吸。 那么, 蜘蛛呼吸如何? 它使用书本肺吗? 不。 事实上, 水生蜘蛛, 被称为“ 潜水钟蜘蛛 ” , 有刺。 蜘蛛经常离开水下网络, 查看表面, 并带回一个气泡, 将气泡粘在毛发的腹部。 它把气泡放入一个小丝质空气箱里。 这个“ 潜水钟” 是一个从水中吸氧的刺, 让蜘蛛在水下停留长达24小时。

     

     

    Arthropod Reproduction
    ::Arthropod 生殖

    Arthropods have a with . Most species go through larval stages after hatching. The larvae are very different from the adults. They change into the adult form in a process called metamorphosis . This may take place within a cocoon . A familiar example of metamorphosis is the transformation of a caterpillar (larva) into a butterfly (adult). Other arthropod species, in contrast, hatch young that look like small adults. These species lack both larval stages and metamorphosis.
    ::甲状腺动物与甲状腺动物有着相似之处。大多数物种在孵化后经历幼年阶段。幼虫与成年人大相径庭。幼虫与成年人大不相同。它们以被称为变形的过程改变成成人形态。这可以在锥形中发生。一个常见的变形例子是毛虫(幼虫)变成蝴蝶(成年),而其他的节肢动物则像小成人一样孵化成幼虫。这些物种既缺乏幼年阶段,也缺乏变形。

    Evolution of Arthropods
    ::亚热带动物的演变

    The oldest known arthropods are trilobites . A trilobite is shown in Figure . Trilobites were arthropods. They had many segments with paired appendages for walking. As arthropods continued to evolve, segments fused. Eventually, arthropods with three major segments evolved. Appendages were also lost or modified during the course of .
    ::已知最古老的节肢动物是三叶虫,图中显示三叶虫。三叶虫是节肢动物,它们有许多部分配有配对辅助行走的附着物。正如节肢动物继续进化,各部分融为一体。最后,有三个主要部分的节肢动物演变成节肢动物。在进化过程中,还丢失或修改附着物。

    A fossil trilobite showing segmented body structure of ancient marine arthropods.
    Trilobite Fossil. This trilobite fossil represents the earliest arthropods. Trilobites first appeared more than 500 million years ago. They lived for at least 200 million years before going extinct. They left behind large numbers of fossils.

    Arthropods were the first animals to live on land. The earliest terrestrial arthropods were probably millipedes. They moved to land about 430 million years ago. Early land arthropods evolved adaptations such as book lungs or trachea to breathe air. The exoskeleton was another important adaptation. It prevents an animal from drying out. It also provides support in the absence of buoyant water.
    ::最早的陆生节肢动物可能是毫升的,它们迁移到大约4亿3千万年前的陆地上。早期的陆生节肢动物发展了肺部或气管等用于呼吸空气的适应措施。外骨骼是另一个重要的适应措施。它防止了动物干涸。在没有浮水的情况下,它也提供了支持。

    Classification of Arthropods
    ::类人类动物分类

    Living arthropods are divided into four subphyla. They are described in Table . The Hexapoda subphylum includes mainly insects. There are so many insects and they are so important that they are described in greater detail below.
    ::活节肢动物分为4个亚植物类,表1对此作了说明。六甲二醇亚植物类主要包括昆虫,昆虫数量众多,它们非常重要,下文将更详细地加以说明。

    Subphylum (includes) Description Example
    Myriapoda (centipedes, millipedes) terrestrial; herbivores or predators ; 10–400 walking legs; centipedes possess poison claws for hunting

    centipede
    ::百分点e

    Centipede displaying multiple legs, found in a terrestrial environment.

    Chelicerata (spiders, scorpions, mites, ticks, horseshoe crabs, sea spiders) mainly terrestrial; predators or parasites ; 8 walking legs; appendages called chelicerae for grasping prey ; poison fangs for killing prey; no mandibles, maxillae, antennae; two body segments

    spider
    ::蜘蛛蜘蛛蜘蛛

    A spider displaying eight legs, chelicerae, and a distinct body structure.

    Crustacea (lobsters, crabs, shrimp, barnacles, krill) mainly aquatic, predators, scavengers , or filter feeders ; two pairs of antennae and claws for hunting; unique larval stage (called “nauplius”) with head appendages for swimming

    lobster
    ::龙虾

    A lobster underwater, showcasing its claws and long antennae, with surrounding aquatic scenery.

    Hexapoda (ants, flies, grasshoppers, beetles, butterflies, moths, bees, springtails) mainly terrestrial or aerial; herbivores, predators, parasites, scavengers, or decomposers ; 6 walking legs; many modified appendages, such as wings for flying

    beetle
    ::甲酸甲酯

    A ladybug on a green leaf, illustrating a common type of Hexapoda.

    Summary
    ::摘要

    • Arthropods are the largest phylum in the animal kingdom.
      ::动物王国中最大的类动物
    • Most arthropods are insects. The phylum also includes spiders, centipedes, and crustaceans.
      ::大部分节肢动物是昆虫,植物也包括蜘蛛、和甲壳类动物。
    • The arthropod body consists of three segments with a hard exoskeleton and jointed appendages.
      ::节肢动物身体由三部分组成,有硬外骨骼和结合附着物。
    • Terrestrial arthropods have adaptations for life on land, such as trachea or book lungs for breathing air.
      ::地面节肢动物适应陆地上的生活,如气管或呼吸空气的书写肺。
    • The earliest arthropods were trilobites. The earliest land arthropods were millipedes.
      ::最早的节肢动物是三叶虫,最早的陆地节肢动物是毫克。

    Review
    ::回顾

    1. Identify the distinguishing trait of arthropods.
      ::辨别节肢动物的特征
    2. What is molting? Why does it occur?
      ::什么是磨衣,为什么会发生?
    3. What are the Malpighian tubules?
      ::马尔皮吉亚管子是什么?
    4. Describe two structures that allow arthropods to breathe air.
      ::描述允许节肢动物呼吸空气的两个结构。
    5. Assume you see a “bug” crawling over the ground. It has two body segments and lacks antennae. Which arthropod subphylum does the “bug” belong to? Explain your answer.
      ::假设你看到一个“ 虫子” 爬过地面。 它有两个身体部位, 缺少天线。 “ 虫子” 属于哪个节肢动物子植物? 请解释您的答案 。