原文

原文:FISH

Fish were the first animals to have bony internal skeletons, and therefore the first vertebrates. Since their appearance in the seas and oceans more than 500 million years ago, they have evolved into a dazzling diversity of forms, ranging from delicate seahorses to huge, powerful, predatory sharks.

译文:鱼

鱼是最早拥有骨骼的动物，因此也是最早的脊椎动物。自从它们在5亿多年前出现在海洋中以来，它们已经进化成各种令人眼花缭乱的形态，从精致的海马到巨大有力的食肉鲨鱼。

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原文

原文:16

WHAT IS AN INVERTEBRATE?

An invertebrate is any animal that does not have an internal jointed skeleton. The term includes a wide diversity of animals, ranging from microscopic worms to giant squid, with little in common except the lack of a vertebrate skeleton. Some have soft bodies and many others have protective shells. But the most abundant are the amazing variety of crustaceans, insects, spiders, and similar animals that have hard,

jointed external skeletons - the arthropods.

TYPES OF INVERTEBRATE

O

译文:16

什么是无脊椎动物?

无脊椎动物是任何没有内部关节骨骼的动物。这一术语包括各种各样的动物，从微小的蠕虫到巨型乌贼，除了缺乏脊椎动物的骨骼，它们几乎没有什么共同之处。一些有柔软的身体和许多其他有保护壳。但是最丰富的是各种各样的甲壳类动物，昆虫，蜘蛛和类似的动物，

关节外骨骼-节肢动物。

类型的无脊椎动物