The most advanced organisms on Earth are vertebrates. They are the smartest creatures like dolphins,chimpanzees, elephants and humans. But when the first vertebrates evolved about 525 million years ago, they were simple creatures. Later, reptiles comprised the majority of vertebrates,birds and f then dinosaurs, inally mammals. All vertebrates have muscles and skeletons. Also, they usually have two pairs of limbs. In humans, this is represented by arms and legs while birds have wings and legs. Of course, fish do not have limbs, but they use two sets of fins for steering through the water. All of this means that vertebrates were able to move to a new environment when conditions changed. By being mobile, they could choose where to live more easily than other types of animals.