Fish are an extremely old species of animal. They first appeared around five hundred and ten million years ago. At this time, there were no living creatures on land, only in the seas. However, about three hundred and fifty million years ago, insects and plants had begun taking control of the land. This meant that there was plenty of food for venturesome fish to feed on. Through evolution some fish started to develop smaller fins which eventually turned into short, stubby legs. They also developed lungs so that they could breathe air. The take over of land begun. From here, different groups of animals evolved which included dinosaurs, reptiles, birds and ​mammals.