Vertebrate explained to kids

A vertebrate is an animal that has a backbone. The backbone is made up of bones called vertebrae. Vertebrates include fish, amphibians, reptiles, birds, and mammals. There are about 55,000 species of vertebrates. Vertebrates are different from invertebrates, which are animals that do not have a backbone. Invertebrates include insects, worms, and crabs. There are about 1,000,000 species of invertebrates. The first vertebrates were fish. They appeared on Earth about 500 million years ago. Amphibians were the first animals to live on land. They appeared about 400 million years ago. Reptiles appeared about 300 million years ago. Birds appeared about 150 million years ago. Mammals appeared about 200 million years ago. All vertebrates have a nervous system, which helps them move and think. The nervous system is made up of the brain and the spinal cord. All vertebrates also have a skeleton, which helps them move and protects their internal organs. Most vertebrates have four limbs, or appendages. These are called arms and legs. Some vertebrates, such as snakes, do not have limbs. Vertebrates are warm-blooded, which means they can maintain a constant body temperature. Warm-blooded animals are different from cold-blooded animals, which cannot maintain a constant body temperature.