2 Vertebrates-Mid

Vertebrates Written by Kira Freed

脊椎动物作者:基拉·弗里德

Introduction Knock on your forehead. The hard thing you feel inside your head is bone. Bones hold up your body and protect organs such as your brain and heart. Scientists sort animals into two groups. Vertebrates have backbones. Invertebrates do not have backbones. Let's learn about the five groups of vertebrates. Think about what the groups have in common and how they are different.

敲敲你的额头。 你脑袋里硬的东西是骨头。 骨骼支撑着你的身体，保护着你的大脑和心脏等器官。 科学家把动物分成两类。 脊椎动物有脊骨。 无脊椎动物没有脊椎。 让我们来了解一下这五类脊椎动物。 想想这些群体有什么共同之处，又有什么不同之处。

A Closer Look at Bones All bones are made of a hard kind of body tissue. (Skin and muscles are other kinds of tissue.) Without bone tissue, your body would just be a big, soft blob. If you've ever seen a bone, you may think it looks dry and lifeless. But the bones inside your body are alive! Some bone cells help to mend broken bones. Others make blood cells. These bone cells are found in bone marrow, a special tissue in the middle of some larger bones.

所有的骨头都是由一种坚硬的身体组织构成的。 (皮肤和肌肉是另外两种组织。)没有骨组织，你的身体就只是一个又大又软的一团。 如果你见过骨头，你可能会认为它看起来干燥而没有生命。 但是你身体里的骨头是活的!一些骨细胞有助于修复骨折。 其他的则制造血细胞。这些骨细胞存在于骨髓中，骨髓是一些较大骨骼中间的一种特殊组织。

The skeleton is the strong frame that supports and protects a vertebrate's body. The spine, or backbone, is the special feature of vertebrates. The spine is made up of a chain of bones. At the top of the spine is the skull. It holds and protects the body's control center— the brain. Your skeleton has 206 bones. Other kinds of vertebrates have different numbers of bones.

骨骼是支撑和保护脊椎动物身体的坚固框架。 脊椎是脊椎动物的特殊特征。 脊椎是由一串骨头组成的。 脊椎的顶部是头骨。 它控制并保护身体的控制中心——大脑。 你的骨骼有206块骨头。 其他种类的脊椎动物有不同数量的骨头。

The ends of many bones are covered with cartilage. Cartilage is soft, rubbery tissue that keeps bones from grinding against each other. Other body parts have cartilage, too. Your nose and ears are made of cartilage. Joints are the places where bones meet. Joints let vertebrates move in different ways. Some joints, such as your knees, only bend one way. Other joints, such as your shoulders, rotate. The joints in your spine can twist and turn. Cartilage helps all these joints to move smoothly.

许多骨头的末端都覆盖着软骨。 软骨是一种柔软的橡胶组织，可以防止骨头相互摩擦。 身体的其他部位也有软骨。 你的鼻子和耳朵是由软骨组成的。 关节是骨头接合的地方。 关节让脊椎动物以不同的方式活动。 有些关节，比如你的膝盖，只能向一个方向弯曲。 其他关节，比如肩膀，也会旋转。 脊椎的关节可以扭曲和转动。 软骨帮助所有的关节活动顺畅。

Different bones have different jobs. Leg bones support the weight of an animal while it walks or runs. Most flying vertebrates have hollow bones so they weigh less in the air. The bones in feet, hands, flippers, and wings help animals to move their bodies or handle food.

不同的骨头有不同的功能。 当动物行走或奔跑时，腿骨支撑着动物的重量。 大多数会飞的脊椎动物都有中空的骨骼，所以它们在空中的重量较轻。 脚、手、鳍和翅膀上的骨头帮助动物移动身体或处理食物。