1 Vertebrates-Low

Vertebrates Written by Kira Freed

Introduction Knock on your head. The hard thing you feel inside your head is bone. Bones hold up your body. They also protect your brain, heart, and other organs. We can sort animals into two groups. Vertebrates have backbones. Invertebrates do not have backbones. Let's learn about the five groups of vertebrates.

What Are 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. The bones inside your body are alive. Some bone cells help your bones heal if one breaks. Other bone cells make blood cells. These bone cells are found in special tissue in the middle of some large bones.

The skeleton supports and protects a vertebrate's body. All vertebrates have a spine, or backbone. The spine is like a chain of bones. At the top of the spine is the skull. It holds and protects the brain. Your skeleton has 206 bones. Other kinds of vertebrates have different numbers of bones.

The ends of many bones are covered with cartilage. Cartilage is soft tissue that keeps bones from rubbing against each other. Other body parts have cartilage, too. Your nose and ears are made of cartilage. Joints are the places where bones meet. Different joints move in different ways. Cartilage helps all these joints to move.

Different bones have different jobs. Leg bones hold up an animal while it walks or runs. Most flying vertebrates have hollow bones that do not weigh much. The small bones in feet and hands help animals to use tools and get food.