All things evolve not just a selected few. Many examples include eyesight, hearing , along with various other features. One particular example is the dog. It evolved from the wolf a long time ago because certain traits about it were desirable, such as speed, strength, and agility. Because these traits were so desirable, the animals that presented these traits the most were bred and their desirable traits were passed on to the next generation and so on, continually evolving so that it could survive, like many animals do. It's just survival of the fittest.

Why do only certain things evolve?