The following information was found on Dog Anatomy Wikipedia.
In 1986, researchers discovered that domestic dogs and wolf-like canids are morphologically very different. In fact, the shape of domestic dogs has changed dramatically from their ancestors. Since humans, through breeding, have modified their characteristics, they have also changed their head shape which have resulted in the change in skull type.
Dogs vary a lot in height and weight. The smallest dog known was a Yorkshire Terrier which weighed only 111grams. On the other side, the largest dog was an English Mastiff which weighed 144.5kg. Also, the tallest dog known was a Great Dane. Researchers found a specific gene responsible for size. A regulatory sequence was found next to the gene Insulin-like growth factor 1 (IGF1). Together, the regulatory sequence and the gene are responsible of body size of small dogs.
The coat of an domestic dog is the hair that covers their body. Often, hair and fur are used interchangeably. Some dogs might have a double coat which is made of an undercoat and a top coat. The undercoat serves as insulation and the top coat serves to repel water and shield from dirt. Dog’s fur varies in colors and patterns just like their size and shape.
Dogs are mammals which have two types of cone photoreceptors. They are dichromats. Their visual world might be consisted of yellows, blues and grays. They have huge difficulties making the difference between red and green. Often, if an object is red to humans, it will appear yellow to dogs.
Dogs’ frequency range of hearing is between 16-40 Hz. They can detect sounds that we cannot since out frequency range of hearing is between 20-70 Hz. In fact, dogs can hear sounds beyond our upper limit of auditory spectrum.