What are Vertebrates?

One of the things that birds, snakes, fish, frogs, cows and men all have in common is a backbone, or vertebral column. It is made up of many small pieces of bone called "vertebrae". These forms of life are therefore called "vertebrates". Creatures that do not have a backbone such as crabs, snails, grasshoppers and sponges, are called "invertebrates".

True vertebrates also have a bony, boxlike structure at one end of  their backbone which contains the brain. Their nerves run together into large bundles which are carried in a cravity in the backbone to the brain. The nerves make contact with every part of the body in a vertebrate.

Vertebrate also have fine, hair-like blood vessels which carry food to every cell in the body. And they combine to form large arteries and veins which run the length of the body to heart. Another thing that distinguishes from boneless animals is their muscular system is well developed.

To the vertebrae of their backbone are attached the ribs and also the bones which carry the limbs.
Vertebrates never have more than four limbs. In fish, the two pairs of paired fins correspond to the limbs. In fish the two pairs of paired fins correspond to the limbs are entirely lacking.

In others such as birds, one pair of limbs has developed into wings. In man, one pair is arms, the other legs. Typical vertebrates have tails. But just as other vertebrates have lost their limbs during development, so man has lost his tail.

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