Pedigree dogs come in lots of different varieties. They may be different colours and sizes, but they are all still dogs. They are all still the same species. The different varieties of dog have been produced through deliberate selective breeding by dog-owners.
These are the steps taken to select a particular feature in an organism:
For example, suppose you wanted a variety of cow that produced a lot of milk. This is what you could do:
The key to success is to identify the feature you want, only breed from the individuals that have that feature, and do not allow individuals with undesirable features to breed. Here are some examples of what selective breeding can produce: