章节大纲

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  • 无脊椎动物分类

    A Monarch caterpillar with distinctive yellow and black stripes on a green leaf.

    Invertebrate, arthropod or insect?
    ::无脊椎动物、节肢动物还是昆虫?

    This Monarch caterpillar is an invertebrate . It is also an insect and an . Of all the , it is estimated that well over 90% are invertebrates. Of all invertebrates, the are by far the most numerous. There are so many species of insects that scientists have yet to discover them all, let alone name or count them. Estimates of the total number of insect species fall in the range of 1 to 30 million. So, it helps if there are methods to classify not just the insects, but all invertebrates.
    ::这只毛虫是无脊椎动物。它也是昆虫和无脊椎动物。据估计,90%以上是无脊椎动物。在所有无脊椎动物中,有90%以上是无脊椎动物。在所有无脊椎动物中,有最多。有如此多的昆虫物种科学家尚未全部发现它们,更不要说它们的名字或数量了。昆虫物种总数估计在100万到3000万之间。因此,如果有方法不仅对昆虫,而且对所有无脊椎动物进行分类,则有帮助。

    Classification of Invertebrates
    ::无脊椎动物分类

    Eight major phyla contain the majority of invertebrate species.
    ::八大主要植物含有大多数无脊椎物种。

    Major Invertebrate Phyla
    ::主要无脊椎动物

    Table gives an overview of the eight invertebrate phyla with the greatest number of species.
    ::表格概述了8种物种数量最多的无脊椎植物。

    Phylum (includes) Notable Characteristics Example
    Porifera (sponges) multicellularity, specialized but no tissues , asymmetry, incomplete digestive system
    Cnidaria (jellyfish, corals) radial symmetry , true tissues, incomplete digestive system jellyfish
    Platyhelminthes ( , tapeworms, flukes) cephalization , bilateral symmetry , mesoderm , incomplete digestion with some exceptions flatworm
    Nematoda (roundworms) pseudocoelom , complete digestive system roundworm
    Mollusca (snails, clams, squids) true coelom , organ systems , some with primitive brain snail
    Annelida ( earthworms , leeches , worms) segmented body, primitive brain earthworm
    Arthropoda (insects, spiders, , centipedes) segmented body, jointed appendages , exoskeleton , brain insect (dragonfly)
    Echinodermata (sea stars, sea urchins, sand dollars, sea cucumbers) complete digestive system, coelom, spiny internal skeleton sea urchin

    Protostomes and Deuterostomes
    ::蛋白质和双子体

    Most invertebrates (and higher animals) can be placed in one of two groups based on how they develop as embryos . The two groups are called protostomes and deuterostomes . As shown in Figure , organisms in the two groups have different ways of forming the coelom and mouth, among other differences.
    ::多数无脊椎动物(和较高层动物)可按胚胎的发育方式分为两类之一,这两类动物称为蛋白质和离子体,如图3所示,两种生物的卵巢和口腔形成方式不同,其他差异也不同。

    , , and arthropods are protostomes. and are deuterostomes. This distinction is important. Why does it matter? It shows that echinoderms are more closely related to chordates than are the other invertebrate phyla. This is not apparent based on other, more obvious traits.
    ::, 节肢动物是原代物, 并且是离子体。 这种区分很重要。 为什么重要? 它表明, 电离层与其他无脊椎植物相比, 更密切地与染色体相关。 这一点在其他更加明显的特性上并不明显。

    Comparison of protostomes and deuterostomes illustrating embryonic development differences.
    Protostomes vs. Deuterostomes. In protostomes such as mollusks, the coelom forms within the mesoderm. In deuterostomes such as echinoderms, the coelom forms from a pouch of endoderm. How does the formation of the mouth differ in these two groups of animals?

    Science Friday: Isn't this Octopus Adorabilis?
    ::科学周五:难道这不是章鱼阿多拉比利斯吗?

    What do you call a tiny octopus with big , gelatinous skin and is cute as a button? Nobody knows quite yet! In this video by Science Friday, Stephanie Bush aims to classify and name this presently undescribed deep-sea cephalopod .
    ::如何称呼小章鱼的皮肤大而有凝胶的皮肤,又可爱又像按钮一样?谁还不知道呢?在科学周五的这段视频中,斯蒂芬妮·布什的目的是为这个目前尚未被描述的深海头目分类和命名。

     

     

     

     

     

    Summary
    ::摘要

    • Eight invertebrate phyla contain most invertebrate species.
      ::八种无脊椎植物含有大多数无脊椎物种。
    • Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as embryos.
      ::无脊椎动物(和较高级的动物)也可以根据胚胎发育的方式,将其分为两类之一。

    Review
    ::回顾

    1. What are protostomes?
      ::什么是原质?
    2. Describe evidence showing that echinoderms are more closely related to chordates than are other invertebrate phyla.
      ::描述证据表明,与其他无脊椎植物相比,脑电介质与染色体的关系更为密切。
    3. Assume you have discovered a new invertebrate. It has a segmented body, a brain, and jointed appendages. In which phylum would you place it? Why?
      ::假设你已经发现了一个新的无脊椎动物。它有一块被分割的躯体,一个大脑, 和一个被连接的附着物。你会把它放在哪个植物里呢?为什么?