Physical Characteristics

Although there are many different shaped and many different sized dogs, there general characteristics are the same. Because dogs are predators they posses sharp teeth and very strong jaws, so that they can hold onto and tear through their food. A dog will always have strong, powerful muscles, which means they have good endurance, can sprint at high speeds. 

Most dogs will have excellent vision, however all dogs have color vision equivalent to red-green colour blindness in humans. The colour blindness doesn't affect the dog in any negative way,in fact some dogs have field vision of up to 270°, compared to a human who has field vision of 180°. 

Dogs also have super sensitive hearing. Their ears have at least 18 muscles in them, helping them rotate, raise or lower their ears. Dogs can identify the location of a sound much, much quicker than a human, and are able to hear sounds up to four times the distance a human can. 
A dogs sense of smell is probably it's most impressive characteristic. Some researchers believe that dogs can smell odours at concentrations one hundred times lower than humans. 
For further information on a dogs check out www.dogs.info.