There is a great diversity in shape in pedigree dog breeds, and in a lesser degree, a wide range of tempers. Some breeds are not common and probably more expensive, while others are usually seen, and the price is often an indication of the pedigree. This fact is very important for those interested in exhibitions. Generally, there are around 300 different dog breeds accepted; some of them not admitted in exhibitions but with a great tradition of work in their native countries.
Most known breeds: Each dog has his time, there are changing interests in the dog's world; therefore while some breeds increase their number, others decrease, simply due to fashion.
Why is there such diversity in size and shape of dogs? This is a result of selective reproduction. It's been suggested than only 20 mutations, as the shortened legs, would have been necessary to originate the wide range of present breeds.
Directory of Breed of Dog
There have been almost 4,000 generations of dogs
since the beginning of domestication, and each generation increases probabilities of mutations
. Through selective mutations some outlines have been fostered, and therefore, the present diversity of breeds has been created.If two breeds with very different physical characteristics, like length of extremities, length of hair, and head shape, are coupled, their descendants will have a mixture of around half way between both parents. Explanation is, that for some reason, mechanisms existing in most of species to limit variations within them, does not work anymore. Presumably, this might be caused by years of selective reproduction for different types of dogs
Frequently, new characteristics in shape have been developed, and maybe the dog has been the major target for selective reproduction compared with other domestic animals, like cows or cats. In theory, species could even reach a wider diversity. But recently some strict standards have been enacted to identify breeds, with the predominant criteria that present variations are enough.