Canis lupus familiaris
Dogs are a domesticated subspecies of the Gray Wolf known by the scientific name Canis lupus familiaris. Dogs have been extensively trained by humans to perform a variety of tasks and make great pets. They have indeed grown to be the single most common and beloved domestic house pet to humankind.
Dogs have heavily differentiating characteristics. Size, color, shape and various other traits vary heavily and often rely on the dog's breed. Most breeds of dogs have strong jaws that are designed for eating meat, since they are carnivorous. There are two different shapes for the head, they can be long and narrow or they can be short and wide. The dog's skeleton is designed to run quickly and leap high. They have shoulder bones that are disconnected that help them run and leap. Dogs have four paws each with five toes. Out of the five toes one is observed to be useless, this claw is called the dewclaw. The dewclaw is often removed because it is practically useless. The removal of the dewclaw is illegal in a few countries. Dogs vary greatly to size from the tiny chihuahua to the large Great Dane. Scientists have found that the possible reason for this is a piece of DNA that is common to small dogs
The reproductive cycle begins when the female is in estrus. Estrus is a phase in which the female's estrogen levels rise high and when the female gets prepared for copulation. It occurs nearly every six months. The time in estrus is about 18 days or more. The female will only mate while in estrus. The males however are ready to mate anytime after puberty has taken place.
The reproductive cycle begins when the male attempts to copulate with the female. The male does this by attempting to mount the female. The female can respond by either accepting or rejecting the male. If th female rejects she will be uncooperative and begin moving around avoiding copulation. If she accepts then she will allow the male to copulate.
Once copulation is finished and the eggs are fertilized, the gestation period begins, gestation varies from 56 to 72 days. After gestation the female dog gives birth. Since dogs are mammals they give birth to live young. The number of puppies produced depends on half of the number of teats the mother has. When the offspring reach puberty, which occurs between the ages of six to twelve months, they are ready to reproduce and the reproductive cycle begins. 
A problem in America has been the overpopulation of dogs. Over 3 million dogs are killed in shelters every year because there is not enough space for them. Spaying and neutering helps control the population and helps prevent more dogs from getting killed.
Domestic dogs live in the homes of their owners. They are fed by them and have no need to hunt for food unlike their undomesticated brethren. Dogs are most often fed kibbles, which are dried pellets of flavored wheat, much like cereal. Dogs are also fed wet dog food.
Usefulness to humans
Since dogs can be trained to do various things, they have become very useful to humans. These are some examples of what dogs have been trained to do. Assistance dogs are dogs that have been trained to help those with physical imparities, such as blindness, deafness, etc. Guard dogs are dogs that have been trained to protect things. Therapy dogs are dogs used in psychology to help humans cope with disasters and personal problems. Dogs can also be trained to herd, hunt, assist in law enforcement, and much more.
- Information and facts on the anatomy of the dog. Author Unknown.
- Wikipedia. Multiple Authors.
- Reproduction & Breeding Information for Dogs. Dr. Foster & Dr.Smith.
- The Free Dictionary. Multiple Authors.